How much does frame size matter

[Graham]

I have 4 bikes all with 73.5 degree seat tube angles and 55.5cm effective horizontal top tube lengths. I have the saddles set centred on the rails with 90mm stems. I now have the opportunity of aquiring a very nice frame which has a 74.5 degree seat tube angle and an effective horizontal top tube length of 53.5 degrees. There are also comenserate reductions in head tube height and wheelbase althought these are both within 2cm.

Given the steeper seat tube angle then setting the saddle back about 1cm and using a 100mm stem should give me the same cockpit geometry so should I expect any problems particularly with handling. If not why does this particular manufacturer produce this frame with another one size up identical to my existing bikes.

Graham.

[Duane]

On 10/18/2013 11:59 AM, Graham wrote:
> I have 4 bikes all with 73.5 degree seat tube angles and 55.5cm effective horizontal top tube lengths. I have the saddles set centred on the rails with 90mm stems. I now have the opportunity of aquiring a very nice frame which has a 74.5 degree seat tube angle and an effective horizontal top tube length of 53.5 degrees. There are also comenserate reductions in head tube height and wheelbase althought these are both within 2cm.
>
> Given the steeper seat tube angle then setting the saddle back about 1cm and using a 100mm stem should give me the same cockpit geometry so should I expect any problems particularly with handling. If not why does this particular manufacturer produce this frame with another one size up identical to my existing bikes.
>

I don't think you want to move the seat back to adjust reach. This
should be adjusted with the stem size. Seat fore/aft adjustment changes
the reach but it also changes the weight distribution and the hip angle.
I think that if you can't adjust the reach with the stem then the bike
is not the right size.

[Graham]

"Duane" <duane....@group-upc.com> wrote in message news:l3rpms$v6q$1...@dont-email.me...

Agreed I only suggested moving the seat back to compensate for the steeper seat tube angle.

[Frank Krygowski]

On Friday, October 18, 2013 1:04:26 PM UTC-4, Duane wrote:
>
> I don't think you want to move the seat back to adjust reach. This
> should be adjusted with the stem size. Seat fore/aft adjustment changes
> the reach but it also changes the weight distribution and the hip angle.

The new bike has a seat tube angle that's a degree steeper. Sliding the seat back a centimeter should give almost exactly the same hip angle as the older bike. NOT sliding it back would change the hip angle. Reach can be addressed separately.

Without data on chainstay lengths, front center dimensions, etc. we really can't say anything about weight distribution. But if the frames are otherwise similar, I really doubt there will be a practical change in weight distribution, i.e. one that has a measurable effect on riding.

- Frank Krygowski

[datakoll]

LESS CLIMBING POWER, sharper turn in/response....ergomeasures doahn change the geometry's on road performance, per se, yet gives a different leg power stroke, energy capacity moderated by the first sentence.

you won't notice it

it'll make you puke.

who knows ?

maybe the factory has a readout sez 50% buyers in this category have longer/shorter arms.

The Redline cyclocrosser here has a waaaay back Ritchey (4 bolt main) seatpost/seat mechanism...caws I'm larger than the larger size. IMHO, the waaay back is a less satisfactory solution poss diluting handling some. You know like enough to be annoying.

[Duane]

Well he's talking about moving the seat just enough to compensate for
the different angle. It's probably ok if everything else is equal but I
would set the seat based on pedal and leg angles and then look at the
stem to take care of the reach. Or I am not understanding what you mean.

Anyway, Sheldon Brown has some good information here about seats,
including adjusting them:
http://www.sheldonbrown.com/saddles.html
And also
http://sheldonbrown.com/kops.html

[Graham]

"Frank Krygowski" <frkr...@gmail.com> wrote in message news:294a4cd4-401b-44cb...@googlegroups.com...

Chain stays are the same length with the wheelbase being 1cm shorter on the smaller frame.

Graham.

[Jay Beattie]

The frame has a steep headtube and will take less input to initiate a turn, although the longer stem will mitigate that -- and the fork offset may do the same. At the end of the day it may or may not feel like your other bikes while seated depending on how the stem length/offset plays out. If your saddle has to go way back to give you proper position over your pedals, you'll be popping wheelies on seated climbs and really feeling bumps.

For me, frame size difference are more apparent riding out of the saddle, both in terms of frame flex and handling. A small frame with a lot of stem (not your case, I'm talking 130mm) makes me feel like a hood ornament -- way out in front of the bike, more flex in the front end and an odd, slow caster-like steering feel.

-- Jay Beattie.

[Duane]

Why not just take a few minutes and do the adjustments? The most
important thing when you change a bike is the fit.

[James]

Does the front wheel overlap your toes? Something I try to avoid.

--
JS

[(PeteCresswell)]

Per Duane:

>Why not just take a few minutes and do the adjustments? The most
>important thing when you change a bike is the fit.

Which begs a question that I keep asking myself...

What's wrong with this approach to saddle placement:
-------------------------------------------------------
Ride along in a spinning gear.

Shift up a few gears as if you were approaching bumps.

Pedal hard enough so that your butt floats an inch or two above the
saddle's surface.

Ease back off on the pedaling until your butt settles back on the
saddle.

Wherever your sit bones are now is where the sit bone area of the saddle
should be.
-------------------------------------------------------

I *think* it works for me. I get some pretty weird saddle placements.
But I've got pretty weird body geometry.

But nobody else ever mentions it, so I'm looking for the fatal flaw in
the reasoning.
--
Pete Cresswell

[Duane]

Check your knees, calves, hamstrings, lower back etc after a 100k or so.
Adjust as necessary. Time consuming and painful when you can get pretty
close by measuring.

What I mean is things start to hurt after a longer distance. Then if you
adjust you have to try again over that distance.

--
duane

[Graham]

"Duane" <duane....@group-upc.com> wrote in message news:l3s27a$h0m$1...@dont-email.me...

I asked the question as I have the opportunity of aquiring this frame. It is not yet in my possession. I am just working from the geometry given on the manufacturers website. Clearly if I had it as a made up bike it would not take me very long to answer my original question.

[Frank Krygowski]

On Friday, October 18, 2013 4:49:42 PM UTC-4, (PeteCresswell) wrote:
>
> Which begs a question that I keep asking myself...
> What's wrong with this approach to saddle placement:
>
> -------------------------------------------------------
>
> Ride along in a spinning gear.
>
> Shift up a few gears as if you were approaching bumps.
>
> Pedal hard enough so that your butt floats an inch or two above the
> saddle's surface.
>
> Ease back off on the pedaling until your butt settles back on the
> saddle.
>
> Wherever your sit bones are now is where the sit bone area of the saddle
> should be.
>
> -------------------------------------------------------
>
> I *think* it works for me. I get some pretty weird saddle placements.
> But I've got pretty weird body geometry.
>
> But nobody else ever mentions it, so I'm looking for the fatal flaw in
> the reasoning.

Well, it sounds pretty reasonable to me. I'll have to remember to try it out.

- Frank Krygowski

[John B.]

I've been tinkering with an old hard tail mountain bike frame. The
telescoping forks had rusted solid so I took them off and made a fork
the same length from the underside of the fork crown to the drop-outs
as the telescope forks. It rode all right but the was nearly six
inches of clearance above the tire so I bought a manufactured fork
that was somewhat shorter and installed that. I have no idea what the
top tube length is and adjusted the seat so that it "feels right" have
recently changed to "cow horn" handle bars to change my hand position.

And the point of this rambling discourse is that nothing I did seem to
change the feeling of riding the bike. It isn't any more stable, no
more unstable, doesn't turn better or worst, in any of its now four
configurations.

I'd say go for it.
--
Cheers,

John B.

[Frank Krygowski]

On Friday, October 18, 2013 7:40:32 PM UTC-4, John B. wrote:
>
> And the point of this rambling discourse is that nothing I did seem to
> change the feeling of riding the bike. It isn't any more stable, no
> more unstable, doesn't turn better or worst, in any of its now four
> configurations.

Did your modifications keep the original trail value? Many say that's the dimension that most affects handling.

Not that I know the trail values for my bikes. Four of mine were bought ready-made, and two of them were custom built, but on none did I specify or even give a lot of thought to the trail measurement.

Admittedly, I don't tend to be a connoisseur of such matters. I like some bikes' handling better than others, but I'm happy on a wide range of bikes. I'd fail as a road tester for "Buy This Bike" magazine. Those road testers, as we know, can [*] discern minute differences that ordinary humans could never detect.

[* pretend to]

- Frank Krygowski

[Dan]

The bike will handle quicker than what you're used to.
That could be a good thing, but it can also freak you
out and spit you off. It might be your soul mate, but
give it some time before you wring it out all the way.

[John B.]

On Fri, 18 Oct 2013 16:54:33 -0700 (PDT), Frank Krygowski
<frkr...@gmail.com> wrote:

>On Friday, October 18, 2013 7:40:32 PM UTC-4, John B. wrote:
>>
>> And the point of this rambling discourse is that nothing I did seem to
>> change the feeling of riding the bike. It isn't any more stable, no
>> more unstable, doesn't turn better or worst, in any of its now four
>> configurations.
>
>Did your modifications keep the original trail value? Many say that's the dimension that most affects handling.
>

No, I gave "trail" some thought but after looking at the usual
telescope mountain bike forks it appears that due to the long fork
legs trail is far more then what we see in the usual road bike frame.
The first set of forks I made were slightly shorter then the telescope
forks and after riding them for a while I came across a set of
aluminum forks that are about as long as a 700C road bike fork but
with brake studs for 26" wheels. None of the various forks seemed to
vary greatly in steering feel.

>Not that I know the trail values for my bikes. Four of mine were bought ready-made, and two of them were custom built, but on none did I specify or even give a lot of thought to the trail measurement.

The problem with most of these frame measurements is that they are
interrelated. Trail is supposed to be an indication of how "quick" the
bike steers but dropping the bottom bracket, and C.G., makes the bike
more stable so a bike with X" of trail and a low bottom bracket may
well steer very differently then a bike with X" trail and a higher
bottom bracket.

>Admittedly, I don't tend to be a connoisseur of such matters. I like some bikes' handling better than others, but I'm happy on a wide range of bikes. I'd fail as a road tester for "Buy This Bike" magazine. Those road testers, as we know, can [*] discern minute differences that ordinary humans could never detect.
>
>[* pretend to]
>
>- Frank Krygowski

Yes, I've read those tests. and then I read the double blind test
where a frame maker made two identical frames, excepting they were
made from different materials. Painted one pink and one blue and gave
them to a bloke to test. The bloke and his mate couldn't decide which
frame was better and the both guessed wrong when it came to material.

I also read the test where several "road racers" tested some of the
traditional down tube shifter bikes like they used to race and were
afraid to reach down to shift.

I now save money by not buying these magazines.

--
Cheers,

John B.

[datakoll]

waaaal, the factory is eating here not diddling with an extra frame for the garage so think the saddle goes right dab on the posts center as equipped. If you want a different post then figure off the stock setup for starters.

Asking the front carcass for extra weight support with same handling as no weight support...more or less the stock design planned toward. I would guess there are ongoing discussions there.

If ura gonna design for whatever reasons...a good quantity buy in water pipe ?...for 8 pounds on the front then you gotta go find a 8 pound tire...over at WHEELCHAIR. Any weight beyond as is is is downhill.

JB sez wheelies up hill...that's OK for JB but we mainly walk up hills so what the hey right ? Hill climbing seats tend toward long bodies and rear lips. Use at your discretion. Yawl do get up and lean forward sometimes on urway up Pike's ?

I dunno Cwell. here we have Spec pro road's with gell and a very sharp turnin to cencenter following the ischial connections. I am fatless. After level comfort placement relating to That's where the seat goes to the angle where muh skin doahn rub against the saddle past the sitbones.

all else is kinda brazed in.

but urine the same position I was. There's the longest top tube ad wera gonna buy if there's an available awaaay back stem. I could use another 10mm. But like you, the Redline Monodog comes in $500 less and is rock solid steel. I can compensate.

Now abt Windows 8 at $200 less when muh 1705e blew the AC ID......


eeeyaiiiiiiiiiiii ! no damn I doahn wannah know the time I gotta....

[datakoll]

btw, IGNORING Sheldon advice, a new Spec was tilted down past the recommended 2mm, limited for tissue (mine) adjustment.

I tilted maybe 20 degrees thinking a brief ride..uh 10 mles...wouldn;lt hurt. I stretch and am in shape.

My pudendum developed a tear and MF it was painful for months like 2-3 levels down from serious stabbing pain.

AVOID

I assume the farther back the seat rails go from stock the greater seat angle avoiding gluteal rub past the ischials.

........................

[Frank Krygowski]

On Saturday, October 19, 2013 7:57:41 AM UTC-4, John B. wrote:

> On Fri, 18 Oct 2013 16:54:33 -0700 (PDT), Frank Krygowski wrote:
>
> >Did your modifications keep the original trail value? Many say that's the dimension that most affects handling.
>
> No, I gave "trail" some thought but after looking at the usual
> telescope mountain bike forks it appears that due to the long fork
> legs trail is far more then what we see in the usual road bike frame.
> The first set of forks I made were slightly shorter then the telescope
> forks and after riding them for a while I came across a set of
> aluminum forks that are about as long as a 700C road bike fork but
> with brake studs for 26" wheels. None of the various forks seemed to
> vary greatly in steering feel.
>
> >Not that I know the trail values for my bikes. Four of mine were bought ready-made, and two of them were custom built, but on none did I specify or even give a lot of thought to the trail measurement.
>
> The problem with most of these frame measurements is that they are
> interrelated. Trail is supposed to be an indication of how "quick" the
> bike steers but dropping the bottom bracket, and C.G., makes the bike
> more stable so a bike with X" of trail and a low bottom bracket may
> well steer very differently then a bike with X" trail and a higher
> bottom bracket.

I'm a little skeptical of the idea that a lower center of gravity (or bottom bracket) confers more stability. Again, I'm not a connoisseur of bike handling, but regarding C.G. height, I've ridden the extremes: recumbents with very low C.G., and "Ordinaries" or antique "Penny-Farthings" with extremely high C.G.

The difference was clear. My first recumbent ride (Avatar 2000) had me swerving all over the pavement to balance, until I relaxed and settled in, so to speak. But during my very first ride on an Ordinary, I was able to pedal at less than walking speed. It was _extremely_ easy to balance.

It seems very similar to balancing a 12" ruler vs. a 36" yardstick on end. The taller object has much more polar moment of inertia about the balancing point, so it gives you much more time to correct any unwanted lean. The difference would of course be smaller for a centimeter or so difference in BB height, but why would the affect be in the opposite direction?

The main advantage I see to lower BB height is the possibility of greater standover clearance. But with currently fashionable frames with slanted top tubes, even that's not an issue.

Just curious...

- Frank Krygowski

[Dan]

Frank Krygowski <frkr...@gmail.com> writes:

> On Saturday, October 19, 2013 7:57:41 AM UTC-4, John B. wrote:
>> On Fri, 18 Oct 2013 16:54:33 -0700 (PDT), Frank Krygowski wrote:
>>
>> >Did your modifications keep the original trail value? Many say that's the dimension that most affects handling.
>>
>> No, I gave "trail" some thought but after looking at the usual
>> telescope mountain bike forks it appears that due to the long fork
>> legs trail is far more then what we see in the usual road bike frame.
>> The first set of forks I made were slightly shorter then the telescope
>> forks and after riding them for a while I came across a set of
>> aluminum forks that are about as long as a 700C road bike fork but
>> with brake studs for 26" wheels. None of the various forks seemed to
>> vary greatly in steering feel.
>>
>> >Not that I know the trail values for my bikes. Four of mine were bought ready-made, and two of them were custom built, but on none did I specify or even give a lot of thought to the trail measurement.
>>
>> The problem with most of these frame measurements is that they are
>> interrelated. Trail is supposed to be an indication of how "quick" the
>> bike steers but dropping the bottom bracket, and C.G., makes the bike
>> more stable so a bike with X" of trail and a low bottom bracket may
>> well steer very differently then a bike with X" trail and a higher
>> bottom bracket.
>
> I'm a little skeptical of the idea that a lower center of gravity (or bottom bracket) confers more stability. Again, I'm not a connoisseur of bike handling, but regarding C.G. height, I've ridden the extremes: recumbents with very low C.G., and "Ordinaries" or antique "Penny-Farthings" with extremely high C.G.
>
> The difference was clear. My first recumbent ride (Avatar 2000) had me swerving all over the pavement to balance, until I relaxed and settled in, so to speak. But during my very first ride on an Ordinary, I was able to pedal at less than walking speed. It was _extremely_ easy to balance.
>

> It seems very similar to balancing a 12" ruler vs. a 36" yardstick on end. The taller object has much more polar moment of inertia about the balancing point,so it gives you much more time to correct any unwanted lean.
>

Reminds me of those TV ads about getting rid of your "unwanted
gold" :-)

> The difference would of course be smaller for a centimeter or so difference in BB height, but why would the affect be in the opposite direction?
>

Because there's more to stability than not tipping over, and
because you're not running as fast as you can while balancing
that yardstick on your hand (?)

> The main advantage I see to lower BB height is the possibility of greater standover clearance. But with currently fashionable frames with slanted top tubes, even that's not an issue.
>
> Just curious...
>

I'll give you a general hint: "Stay vertical" is bad advice.

[Jay Beattie]

You're dealing with annoying wheel flop on recumbents.

You have to compare DF bikes -- ones with higher or lower BBs. I have both high (cyclocross) and low (racing), and the difference in BB height is totally lost in the noise of weight, tire cross section, wheelbase, etc. I would have to defer to someone with princess and the pea sensitivities to divine the difference due solely to BB height.

-- Jay Beattie.

[datakoll]

yeah butbutbut a mm here a mm there and soon ura downhill thru the gravel pile no hands whereas with standard Japanese touring-sport geometery ura on ur face.

they spouteth

https://www.google.com/webhp?hl=en&tab=nw#hl=en&q=bicycle+center+of+gravity+lower+bottom+bracket+BB

and on p. 7 DISTRIBUTTED CG !

AHHH let see how many kinds of CG ?

please remember all above the CG weighs on that point.

[datakoll]

spout spout

" If I lowered the bottom bracket on a touring frame, it was to lengthen the tubes to make a more comfortable ride. It had nothing to do with stability. "

betcha canna say that with a 'straight face'

[datakoll]

ohhh no
itsa UTUBE and the ususual

http://www.youtube.com/watch?v=eHPD7lu3ou4

avoiding more serious considerations all stating that Yes Virginia, a lower CG gives more what ?

[Dan]

Pedal strikes?

[datakoll]

cudbe some conjure CG as a static device but itsnot. One powers thru CG to the contac patchs forward and behind while mooooving the system forward waaaay up there atop the saddle.

to stipulate CG as 3.5 inches or 4 inches above ground then suggest CG has no exceptional variable effects on the system for given height draws conclusions from mid air.

[(PeteCresswell)]

Per Frank Krygowski:

>Well, it sounds pretty reasonable to me. I'll have to remember to try it out.

I would be interested to hear how it works out for a normal person who
knows what they're doing.

Other schemes seem to presuppose that the saddle can determine where
other parts of your body wind up. That might be true for the first
five seconds of riding, but it seems to me like, from then on, the butt
goes where it wants to go as soon as the rider stops thinking about it.
--
Pete Cresswell

[(PeteCresswell)]

Per Frank Krygowski:

>the idea that a lower center of gravity (or bottom bracket) confers more stability

Having moved from FS MTBs to a rigid frame with much lower BB, I can
attest that stability suffers considerably when one forgets and takes a
full pedal stroke when crossing tree roots..... -)
--
Pete Cresswell

[Frank Krygowski]

I agree with you that the differences in DF bikes are minor. But I don't think that the problem with the recumbents I've ridden has been wheel flop. For one thing, I've ridden DF bikes with geometries that should have induced similar wheel flop (antiques with low head tube angles, for example) and had no such problems.

Recumbents tend to tip faster, just as a 6" (15 cm) ruler tends to tip faster than a yardstick (meter stick). And the first recumbent I tried, the Avatar 2000, was a long wheelbase design. That means corrective action through steering reacts more slowly than with a DF bike.

On that first ride, a spotter was running along, just as when parents first teach a kid to ride. The spotter kept yelling "Lean back! Relax! Lean back!" as I weaved badly. When I did what he said, the bike immediately settled down and tracked perfectly well. So part of the problem may have been a lack of coupling or connection between my body mass and the bike.

I've ridden several recumbents since, and while I don't recall having that weaving problem again, I still think they're quicker to tip than a DF bike.

- Frank Krygowski

[Frank Krygowski]

On Saturday, October 19, 2013 9:26:47 PM UTC-4, (PeteCresswell) wrote:
>
> Having moved from FS MTBs to a rigid frame with much lower BB, I can
> attest that stability suffers considerably when one forgets and takes a
> full pedal stroke when crossing tree roots..... -)

Yep, a higher BB makes a big difference there.

One big technical mistake I made once: We got a quite nice rigid MTB frame on an unbeatable deal from Nashbar, back when it was a hometown business and two family members worked there.

Anyway, the intent was to build it up for my wife. The frame size (BB to top tube) was just what she needed. But when I put it all together, she couldn't straddle it. I'd completely lost sight of the fact that the BB would be so high, and so would the top tube.

The result was I had to buy her a different mountain bike. I kept the one I built for her, since it was much nicer than the mountain bike I had at the time.

Of course, it's now desperately out of fashion, being rigid with relatively few cogs. Last week, I was doing some volunteer work with the guys in the local IMBA chapter, and I rode that bike to the bridge we were repairing in the woods. I'm sure they felt sorry for me, riding such a primitive machine.

- Frank Krygowski

[John B.]

On Sat, 19 Oct 2013 09:30:06 -0700 (PDT), Frank Krygowski
<frkr...@gmail.com> wrote:

>On Saturday, October 19, 2013 7:57:41 AM UTC-4, John B. wrote:
>> On Fri, 18 Oct 2013 16:54:33 -0700 (PDT), Frank Krygowski wrote:
>>
>> >Did your modifications keep the original trail value? Many say that's the dimension that most affects handling.
>>
>> No, I gave "trail" some thought but after looking at the usual
>> telescope mountain bike forks it appears that due to the long fork
>> legs trail is far more then what we see in the usual road bike frame.
>> The first set of forks I made were slightly shorter then the telescope
>> forks and after riding them for a while I came across a set of
>> aluminum forks that are about as long as a 700C road bike fork but
>> with brake studs for 26" wheels. None of the various forks seemed to
>> vary greatly in steering feel.
>>
>> >Not that I know the trail values for my bikes. Four of mine were bought ready-made, and two of them were custom built, but on none did I specify or even give a lot of thought to the trail measurement.
>>
>> The problem with most of these frame measurements is that they are
>> interrelated. Trail is supposed to be an indication of how "quick" the
>> bike steers but dropping the bottom bracket, and C.G., makes the bike
>> more stable so a bike with X" of trail and a low bottom bracket may
>> well steer very differently then a bike with X" trail and a higher
>> bottom bracket.
>
>I'm a little skeptical of the idea that a lower center of gravity (or bottom bracket) confers more stability. Again, I'm not a connoisseur of bike handling, but regarding C.G. height, I've ridden the extremes: recumbents with very low C.G., and "Ordinaries" or antique "Penny-Farthings" with extremely high C.G.
>

I've got an article written by Chris Kvale regarding rake, trail, etc.
in which he rates the characteristics of some six bikes and then
measures them. Two, a Cinelli and a Masi road bikes were rated as
stable although they had 48 and 46 mm trail while the other four bikes
all had over 60 mm trail. He reckons that the BB drop of 70 and 73 mm
on the Italian frames as compared to BB drop in the 60's for the other
frames was the reason.

In fact the Italian bikes had steep head angles, a lot of rake and low
trail which should have made them very flighty, but they weren't and
the only major difference was the BB drop.

>The difference was clear. My first recumbent ride (Avatar 2000) had me swerving all over the pavement to balance, until I relaxed and settled in, so to speak. But during my very first ride on an Ordinary, I was able to pedal at less than walking speed. It was _extremely_ easy to balance.
>

But that is pretty much what happens with any short coupled light
weight "racing" bike. You hop on and "Whee, doesn't it turn quick!"
but after an afternoon's ride it seems normal.

>It seems very similar to balancing a 12" ruler vs. a 36" yardstick on end. The taller object has much more polar moment of inertia about the balancing point, so it gives you much more time to correct any unwanted lean. The difference would of course be smaller for a centimeter or so difference in BB height, but why would the affect be in the opposite direction?
>

I think you are ignoring C.G.

>The main advantage I see to lower BB height is the possibility of greater standover clearance. But with currently fashionable frames with slanted top tubes, even that's not an issue.
>
>Just curious...
>
>- Frank Krygowski

--
Cheers,

John B.

[Dan]

Frank Krygowski <frkr...@gmail.com> writes:

> On Saturday, October 19, 2013 9:26:47 PM UTC-4, (PeteCresswell) wrote:
>>
>> Having moved from FS MTBs to a rigid frame with much lower BB, I can
>> attest that stability suffers considerably when one forgets and takes a
>> full pedal stroke when crossing tree roots..... -)
>
> Yep, a higher BB makes a big difference there.
>
> One big technical mistake I made once: We got a quite nice rigid MTB frame on an unbeatable deal from Nashbar, back when it was a hometown business and two family members worked there.
>

(Polite note: Your story is digressing into material that adds nothing
but gratuitous self-aggrandizement.)

> Anyway, the intent was to build it up for my wife. The frame size (BB to top tube) was just what she needed. But when I put it all together, she couldn't straddle it. I'd completely lost sight of the fact that the BB would be so high, and so would the top tube.
>

Doh!

> The result was I had to buy her a different mountain bike. I kept the one I built for her, since it was much nicer than the mountain bike I had at the time.
>
> Of course, it's now desperately out of fashion, being rigid with relatively few cogs. Last week, I was doing some volunteer work with the guys in the local IMBA chapter, and I rode that bike to the bridge we were repairing in the woods. I'm sure they felt sorry for me, riding such a primitive machine.
>

Maybe, but if it's anything like my full-rigid, six-speed rear
Stumpjumper, any of them with real taste would have been envious.

(Why do you say, "doing some volunteer work"? Why not just, "I
rode that bike out in the woods"? More self-aggrandizement,
perhaps? Do you see where we get this sense? Your posts are
*rife* with it.)

[(PeteCresswell)]

Per Phil W Lee:
>But if you're already stretching to reach, standing up then sitting
>will have you sitting on the rivet every time, and if you are normally
>a bit cramped, you'll find yourself hanging off the back.
>Neither means that thee's necessarily anything wrong with the saddle
>position.

Bar extension is what everybody seems to point to. But, by virtue of
flat bars with curved handles on the ends, I can vary my effective bar
extension by over six inches just by changing my grip. When I
experiment with that, the place on the saddle where my sit bones wind up
does not seem to vary by more than a quarter inch.

Seems like the body wants to find some balance point and that point does
not vary that much even when reaching far forward or not. All I can
think of is that the butt gets stuck out backward to compensate for the
arms going forward. My guess is that the feet on the pedals are at
the root of it all. Move the pedals forward, the balance point moves
forward. Move them back and...
--
Pete Cresswell

[Frank Krygowski]

On Sunday, October 20, 2013 2:29:04 AM UTC-4, John B. wrote:

> On Sat, 19 Oct 2013 09:30:06 -0700 (PDT), Frank Krygowski wrote:
>
>
> >I'm a little skeptical of the idea that a lower center of gravity (or bottom bracket) confers more stability. Again, I'm not a connoisseur of bike handling, but regarding C.G. height, I've ridden the extremes: recumbents with very low C.G., and "Ordinaries" or antique "Penny-Farthings" with extremely high C.G.
>
> I've got an article written by Chris Kvale regarding rake, trail, etc.
> in which he rates the characteristics of some six bikes and then
> measures them. Two, a Cinelli and a Masi road bikes were rated as
> stable although they had 48 and 46 mm trail while the other four bikes
> all had over 60 mm trail. He reckons that the BB drop of 70 and 73 mm
> on the Italian frames as compared to BB drop in the 60's for the other
> frames was the reason.
>
> In fact the Italian bikes had steep head angles, a lot of rake and low
> trail which should have made them very flighty, but they weren't and
> the only major difference was the BB drop.

I'd be interested in all the details. I think that regarding bike handling (as with many other technical things in bicycling) there's LOTS of "myth and lore" as Jobst would say.

Jan Heine, who publishes _Bicycle Quarterly_ magazine, is a big fan of bikes with low trail. He claims that the longer trail on modern road frames (compared to frames of the 1950s) is a mistake. Admittedly, this seems to be based primarily on his and his assistants' judgment of handling during (extended) road tests; and judgment isn't as reliable as measured data. But Heine's idea certainly seems consistent with the article you described.

Also: One of the first books on bicycling I purchased was _DeLong's Guide to Bicycles and Bicycling_, c 1974. Page 78 of this edition has a computer-calculated graph, in which one can input fork offset and head angle to read a "stability index." Superimposed is a plot from a formula supposedly used by "bicycle engineers" to give "satisfactory steering":

Fork Offset = (wheel radius) * Tan ((90 - head angle)/2)

The formula's plot yields "stability indexes" ranging from 3.8 to 5.2. Perhaps that means that wide variations in stability can be acceptable for various uses.

To corroborate that idea: DeLong also mentions investigating the effect of trail by use of a custom fork with elongated dropout slots that allowed him to set and test trail values.

The next page has a sort of "soft" graph showing "one rider's evaluation of the handling characteristics of his bicycle." (I assume that rider was the author.) In any case, the X axis is trail value, and the Y axis is marked "Poor ... Fair ... Good ... Excellent" so it's entirely judgment. According to this rider's judgment, "Snaking" & "Hands Off" & "High Speed" & "Gravel Road" all have peak "Excellent" values at different values of trail. For "High Speed," his peak is about 35 mm trail, falling off sharply past about 41 mm.

>
>
> >The difference was clear. My first recumbent ride (Avatar 2000) had me swerving all over the pavement to balance, until I relaxed and settled in, so to speak. But during my very first ride on an Ordinary, I was able to pedal at less than walking speed. It was _extremely_ easy to balance.
>
> But that is pretty much what happens with any short coupled light
> weight "racing" bike. You hop on and "Whee, doesn't it turn quick!"
> but after an afternoon's ride it seems normal.

Right, people can get used to a variety of handling characteristics, at least if they're experienced at riding.

I do recall one friend, though, who surprised his new wife with a gift of a bike sometime in the early 1980s. I don't recall the brand (except that it was well known Japanese one - perhaps Fuji?). It was from the lower end of the line, but as I recall, pretty decent equipment for the time: QR hubs, alloy rims, alloy most everything else but steel frame, etc.

He called me over because she couldn't ride the thing. When I tried it out, the steering seemed amazingly quick, into "twitchy." That surprised me, because it seemed to me that most bikes toward the bottom of the product lines were more stable feeling.

> >It seems very similar to balancing a 12" ruler vs. a 36" yardstick on end. The taller object has much more polar moment of inertia about the balancing point, so it gives you much more time to correct any unwanted lean. The difference would of course be smaller for a centimeter or so difference in BB height, but why would the affect be in the opposite direction?
>
> I think you are ignoring C.G.

C.G. and polar moment of inertia about the ground are very closely related for a bike. You can't lower the C.G. without decreasing the polar moment of inertia. And a higher polar moment means more time to regain balance when disturbed.

And I don't see why physics would say a lower C.G. would be more stable on a two-wheeled vehicle. On something with four wheels (or three wheels), sure. But why with two wheels?

- Frank Krygowski

[John B.]

On Sun, 20 Oct 2013 08:23:55 -0700 (PDT), Frank Krygowski
<frkr...@gmail.com> wrote:

>On Sunday, October 20, 2013 2:29:04 AM UTC-4, John B. wrote:
>> On Sat, 19 Oct 2013 09:30:06 -0700 (PDT), Frank Krygowski wrote:
>>
>>
>> >I'm a little skeptical of the idea that a lower center of gravity (or bottom bracket) confers more stability. Again, I'm not a connoisseur of bike handling, but regarding C.G. height, I've ridden the extremes: recumbents with very low C.G., and "Ordinaries" or antique "Penny-Farthings" with extremely high C.G.
>>
>> I've got an article written by Chris Kvale regarding rake, trail, etc.
>> in which he rates the characteristics of some six bikes and then
>> measures them. Two, a Cinelli and a Masi road bikes were rated as
>> stable although they had 48 and 46 mm trail while the other four bikes
>> all had over 60 mm trail. He reckons that the BB drop of 70 and 73 mm
>> on the Italian frames as compared to BB drop in the 60's for the other
>> frames was the reason.
>>
>> In fact the Italian bikes had steep head angles, a lot of rake and low
>> trail which should have made them very flighty, but they weren't and
>> the only major difference was the BB drop.
>
>I'd be interested in all the details. I think that regarding bike handling (as with many other technical things in bicycling) there's LOTS of "myth and lore" as Jobst would say.
>
>Jan Heine, who publishes _Bicycle Quarterly_ magazine, is a big fan of bikes with low trail. He claims that the longer trail on modern road frames (compared to frames of the 1950s) is a mistake. Admittedly, this seems to be based primarily on his and his assistants' judgment of handling during (extended) road tests; and judgment isn't as reliable as measured data. But Heine's idea certainly seems consistent with the article you described.

A friend in Singapore has built some frames according to the "low
trail" theories and likes them but how much of his "liking them" is
due to having first read the theory and how much is due to actual
better performance is perhaps doubtful :-)

>Also: One of the first books on bicycling I purchased was _DeLong's Guide to Bicycles and Bicycling_, c 1974. Page 78 of this edition has a computer-calculated graph, in which one can input fork offset and head angle to read a "stability index." Superimposed is a plot from a formula supposedly used by "bicycle engineers" to give "satisfactory steering":
>
>Fork Offset = (wheel radius) * Tan ((90 - head angle)/2)
>
>The formula's plot yields "stability indexes" ranging from 3.8 to 5.2. Perhaps that means that wide variations in stability can be acceptable for various uses.
>
>To corroborate that idea: DeLong also mentions investigating the effect of trail by use of a custom fork with elongated dropout slots that allowed him to set and test trail values.
>
>The next page has a sort of "soft" graph showing "one rider's evaluation of the handling characteristics of his bicycle." (I assume that rider was the author.) In any case, the X axis is trail value, and the Y axis is marked "Poor ... Fair ... Good ... Excellent" so it's entirely judgment. According to this rider's judgment, "Snaking" & "Hands Off" & "High Speed" & "Gravel Road" all have peak "Excellent" values at different values of trail. For "High Speed," his peak is about 35 mm trail, falling off sharply past about 41 mm.
>>
>>
>> >The difference was clear. My first recumbent ride (Avatar 2000) had me swerving all over the pavement to balance, until I relaxed and settled in, so to speak. But during my very first ride on an Ordinary, I was able to pedal at less than walking speed. It was _extremely_ easy to balance.
>>
>> But that is pretty much what happens with any short coupled light
>> weight "racing" bike. You hop on and "Whee, doesn't it turn quick!"
>> but after an afternoon's ride it seems normal.
>
>Right, people can get used to a variety of handling characteristics, at least if they're experienced at riding.
>
>I do recall one friend, though, who surprised his new wife with a gift of a bike sometime in the early 1980s. I don't recall the brand (except that it was well known Japanese one - perhaps Fuji?). It was from the lower end of the line, but as I recall, pretty decent equipment for the time: QR hubs, alloy rims, alloy most everything else but steel frame, etc.
>
>He called me over because she couldn't ride the thing. When I tried it out, the steering seemed amazingly quick, into "twitchy." That surprised me, because it seemed to me that most bikes toward the bottom of the product lines were more stable feeling.
>
>> >It seems very similar to balancing a 12" ruler vs. a 36" yardstick on end. The taller object has much more polar moment of inertia about the balancing point, so it gives you much more time to correct any unwanted lean. The difference would of course be smaller for a centimeter or so difference in BB height, but why would the affect be in the opposite direction?
>>
>> I think you are ignoring C.G.
>
>C.G. and polar moment of inertia about the ground are very closely related for a bike. You can't lower the C.G. without decreasing the polar moment of inertia. And a higher polar moment means more time to regain balance when disturbed.
>
>And I don't see why physics would say a lower C.G. would be more stable on a two-wheeled vehicle. On something with four wheels (or three wheels), sure. But why with two wheels?
>
>- Frank Krygowski

I can't give you a reference to download the article as it is one of
those things that I read and then saved for future reference but the
title is

A FRESH LOOK AT STEERING GEOMETRY
by Chris Kvale with technical and mathematical assistance by John
Corbett
Reprinted in December, 2006 from a copy marked, with Kvale\u2019s
corrections, Original Draft - Copy

Perhaps if you do a search on that you can locate it.

Part of the article reads, "One of the other experiments Corbett
performed
was to build and ride a fork with an adjustable
wheel position (Figures 3 & 4). By fixing the head
angle and changing the fork rake, he was able to
ride one of his bikes with trail from -21mm to
110mm in 20mm increments and evaluate its
steering characteristics. He found that the steering
characteristics fit into the pattern described above,
i.e., with trail in the low forties the bike felt nervous, with a
trail of 55mm it had the sort of hands-
off stability which seems desirable yet still turns
easily, and with a trail of 74mm it was very heavy feeling"

--
Cheers,

John B.

[Graham]

"John B." <sloc...@gmail.com> wrote in message news:65p869t93oacti86e...@4ax.com...

> On Sun, 20 Oct 2013 08:23:55 -0700 (PDT), Frank Krygowski
> <frkr...@gmail.com> wrote:
>
>>On Sunday, October 20, 2013 2:29:04 AM UTC-4, John B. wrote:
>>> On Sat, 19 Oct 2013 09:30:06 -0700 (PDT), Frank Krygowski wrote:

[Snip]

> A FRESH LOOK AT STEERING GEOMETRY
> by Chris Kvale with technical and mathematical assistance by John
> Corbett
> Reprinted in December, 2006 from a copy marked, with Kvale\u2019s
> corrections, Original Draft - Copy

[Snip]

As the OP I must first say how pleasing it is that this discussion as so far remained OT.

I decided not to risk buying the smaller frame in the end however the discussion got me to thinking about the performance of my 4 bikes which have almost identical top tube lengths and are set up to give the same cockpit dimensions. The frames range from a 50+ year old steel frame of unknown provenance set up as a fixie, through a 1978 Peugeot made out of Reynolds 531 and two modern CF steeds, a Raleigh and BMC. Under normal riding they all feel very similar providing they are being ridden regularly. If one remains in the garage unridden for a few months then as soon as I get on it it feels strange but, as another poster has commented, that feeling disappears after a couple of hours of riding. So clearly under such circumstances our brains make the necesary accomodations for the individual bikes's characteristics.

The differences do, however, become apparent in high speed technical decents. Clearly this is not relevent to the fixie for obvious reasons but with regard to the others they do feel different. I can descend faster on the Raleigh than the BMC or the Peugeot as it feels more stable, as some say as if it is on rails, whereas to varying degrees the other two feel progressively more skittish. This ability to be able to descend faster could go some way to explaining why the Raleigh is measurably faster than the BMC on rides over 50 miles over the same mixed terrain routes. They both weigh about the same with the same wheels and groupsets. This can translate into 10-15 minutes over a century. The same comparison cannot be made with the Peugeot as it is 10lbs heavier with winter training wheels and tyres.

Having found the frame reference given by John B:

http://www.johnforester.com/Articles/BicycleEng/Kvale%20Geometry.pdf

its time to go away and do some detailed measuring and see if my findings above agree with those in the paper.

Graham.

[Dan]

"Graham" <h2gt2g42-mi...@yahoo.co.uk> writes:

<snip>

>
> ... the discussion got me to thinking about the performance of my 4 bikes which have almost identical top tube lengths and are set up to give the same cockpit dimensions. The frames range from a 50+ year old steel frame of unknown provenance set up as a fixie, through a 1978 Peugeot made out of Reynolds 531 and two modern CF steeds, a Raleigh and BMC. Under normal riding they all feel very similar providing they are being ridden regularly. If one remains in the garage unridden for a few months then as soon as I get on it it feels strange but, as another poster has commented, that feeling disappears after a couple of hours of riding. So clearly under such circumstances our brains make the necesary accomodations for the individual bikes's characteristics.

>
> The differences do, however, become apparent in high speed technical decents. Clearly this is not relevent to the fixie for obvious reasons but with regard to the others they do feel different. I can descend faster on the Raleigh than the BMC or the Peugeot as it feels more stable, as some say as if it is on rails, whereas to varying degrees the other two feel progressively more skittish. This ability to be able to descend faster could go some way to explaining why the Raleigh is measurably faster than the BMC on rides over 50 miles over the same mixed terrain routes. They both weigh about the same with the same wheels and groupsets. This can translate into 10-15 minutes over a century. The same comparison cannot be made with the Peugeot as it is 10lbs heavier with winter training wheels and tyres.
>

This guy has removed his training wheels for the technical descent:

http://news.bbcimg.co.uk/media/images/56475000/jpg/_56475369_zoobomb_640.jpg

(He's also chosen a relatively small frame - so we're still on-topic.)

<snip>

[Jay Beattie]

So how does the geometry differ between the two bikes?

-- Jay Beattie.

[datakoll]

uh Frank ura pinning CG to handling characteristics or vice versa...snot a valid relationship...eg on my van with Bils, Hellwig bar, and 10 ply Toyo tires, handling is btter grade family sedan lika an old Chevy with the suspension upgrade...F11 ?

but the CG is waaay above a sedan so when balanced tires adhesion reaches its upper levels, the higher van CG begins playing into the balance equation, as the inside tires bear less, outsides more.

the recumbent has a lower CG, OBVIOUSLY, than a sports-tourer useable if handling characteristics are properly applied to the surface by rider ? are recumbents riding or lame ?

[Jay Beattie]

http://www.youtube.com/watch?v=u-DdSdi2LOs Same idea, except Zoobombing Timberline road. You can go really fast on tiny bikes if you want.

[Frank Krygowski]

On Monday, October 21, 2013 12:58:02 PM UTC-4, datakoll wrote:
> uh Frank ura pinning CG to handling characteristics or vice versa.

You misunderstand. I'm saying, first, that I believe changes in bottom bracket height (or bike+rider center of gravity) have very little effect on handling of DF bikes.

And I'm saying secondly that if there is an effect, I'd expect it be in the opposite direction that "conventional wisdom" predicts. Other things being equal, bikes (and other objects) with higher centers of gravity are generally easier to balance. So I'd call them more stable.

But most people seem to say a lower C.G. makes a bike more stable. I don't see why that should be so, based on the physics.

- Frank Krygowski

[John B.]

Well, all I can say is that many of the guys that build frames seem to
believe that lower bottom brackets result in a more stable bike and
attribute it to a lower C.G.

Tim Paterek, for example, says, "says, "... a tourist may even desire
a lower bottom bracket. A lower bottom bracket would lower the load on
the bike by as much as 2 cm. and hence lower the center of gravity
significantly. This would produce a more stable bike that would
"cruise" down the road more comfortably".

This of course does not a prove a thing but it does seem to
demonstrate popular thinking regarding BB height.
--
Cheers,

John B.

[datakoll]

AHH Frank's giving us a load....

1/8th more trail, an 1/8th lower bracket, 78% more stability on transient surfaces.

has FK ridden bare ased in Seattle ?

I hadda laugh.....scheded for a nice day....eyehhahahhah like 45 minutes sun followed with 35 days cold fog with occasional drizzzzle then an extensive fungus outbreak.

drives people nuts

this year Washingtonians ride stoned.

look for the pics..

[James]

A consequence of a higher BB is less likelihood of pedal strike and more
difficulty putting a foot down while remaining seated (assuming the seat
is adjusted to give the same leg extension).

--
JS

[Dan]

http://cycleseven.org/bicycle-stability-and-centre-of-gravity-or-mass

A nice mix of theory and subjective impressions (with no flaming!)

"Perhaps handling and stability are two separate things."

And I would add that stability exists independently in multiple
perspectives, some of which may be tradeoffs.

[Frank Krygowski]

On Monday, October 21, 2013 9:54:04 PM UTC-4, James wrote:
> On 22/10/13 11:02, John B. wrote:
>
> > Well, all I can say is that many of the guys that build frames seem to
> > believe that lower bottom brackets result in a more stable bike and
> > attribute it to a lower C.G.

Yes, I know that belief is common. I'm trying to examine whether it's accurate, based on physics.

> > Tim Paterek, for example, says, "says, "... a tourist may even desire
> > a lower bottom bracket. A lower bottom bracket would lower the load on
> > the bike by as much as 2 cm. and hence lower the center of gravity
> > significantly. This would produce a more stable bike that would
> > "cruise" down the road more comfortably".
>
> >
>
> > This of course does not a prove a thing but it does seem to
> > demonstrate popular thinking regarding BB height.

True.

> A consequence of a higher BB is less likelihood of pedal strike and more
> difficulty putting a foot down while remaining seated (assuming the seat
> is adjusted to give the same leg extension).

Agreed. And it makes sense for touring bikes to have lower BBs based on those points, since tourists don't really need to worry about losing a pedal stroke while in a corner.

I'll note that a lower CG does make a bike more stable (or actually, less unstable) while it's stationary. The C.G. has (microscopically) less tipping moment arm for a given displacement from vertical. But that's never how the supposed advantage is described.

- Frank Krygowski

[John B.]

On Tue, 22 Oct 2013 12:54:04 +1100, James <james.e...@gmail.com>
wrote:

Yes. the "..." at the beginning of my quotation was intended to imply
that I had taken it from a larger statement, which was a discussion of
why one would want a higher BB. He goes into quite some detail about
why road and track racers will want a higher BB - "1 or 2 degrees more
lean when cornering". He also explains why pedal strike is generally
something to be avoided - "Scraping the ground (with the inner pedal)
at such a time could be totally disastrous".
--
Cheers,

John B.

[John B.]

Often times the explanation of why such and such is beneficial is
described in terms that seem logical to the bulk of the listeners. The
description that a low BB "lowers the C.G." certainly sounds likely
and fits most people's pre-conceptions although the actual effect may
be that with a lower C.G. the lateral displacement of the C.G. is less
for at angle of lean than with a high BB.

(You will remember the long and drawn out discussion of how/why a bike
turns :-).
--
Cheers,

John B.

[John B.]

On Mon, 21 Oct 2013 19:17:52 -0700, Dan <d...@t23.daisyheadmayzie.net>
wrote:

Well, the usual description of a stable, or well handling, bike is
usually that it feels safe hands off. While stability can probably be
described, or measured, in detail it may be that there are other
things involved in how we rate a bike.

For example, a good heavy single speed bike, preferably with two top
tubes, and the wide handle bars (streamers are optional) always felt a
lot more stable then one of those skinny, lightweight, things with the
funny bent handlebars. Sheesh, look over your shoulder and you just
turned onto Elm Street.

But I'm not sure whether that is a subjective or objective judgment
:-)
--
Cheers,

John B.

[Duane]

I wonder how much the bike's ability to balance affects stability to
begin with. I mean if I'm doing a track stand maybe I care about that
but under power not so much.

For me a test of stability is how the bike rides when it's bent over
into a steep twisty descent. Here it seems a lower center of gravity is
making it more stable.

[Frank Krygowski]

On Tuesday, October 22, 2013 8:23:42 AM UTC-4, John B. wrote:
>
> For example, a good heavy single speed bike, preferably with two top
> tubes, and the wide handle bars (streamers are optional) always felt a
> lot more stable then one of those skinny, lightweight, things with the
> funny bent handlebars.

A few years ago, I repaired one of those old "balloon tired bombers" for some folks down the street. I hadn't been on such a bike since I was a kid. After doing the repair I rode it back to them, and I was amazed at how stable it felt - that is, how much it insisted on maintaining a straight line instead of a turn, and how very easy it was to ride no-hands.

I'm betting the difference was front end geometry, though.

- Frank Krygowski

[Frank Krygowski]

On Tuesday, October 22, 2013 8:30:46 AM UTC-4, Duane wrote:
>
> For me a test of stability is how the bike rides when it's bent over
> into a steep twisty descent. Here it seems a lower center of gravity is
> making it more stable.

To be able to determine whether that were true, ISTM you'd need to try two bikes that were reasonably identical except for C.G. height.

Now in terms of physics (torque, moment of inertia, etc.), why do you think a lower C.G. would give you that feeling?

- Frank Krygowski

[Dan O]

It shifts less in space when you lean the bike, and has less
leverage to affect the maneuver.

A sixteen ton cube of granite is very stable, but not much fun
to ride :-)

[Duane]

On 10/22/2013 2:32 PM, Dan O wrote:
<snip>

>
> It shifts less in space when you lean the bike, and has less
> leverage to affect the maneuver.

My Bianchi (similar frame to a Roubaix) has a higher BB than my Tarmac
and the Tarmac seems more stable in the turns (as long as the pedal is
up <g>) Of course the Tarmac has a compact frame, better wheels, is
much lighter and if CF instead of steel so it's not a very good test.

couple things:

Talking about balancing a pencil as opposed to a broom we're presumably
not sitting on top of either.

Talking about the height of the BB WRT the center of gravity, on a bike
with a rider on it, the center of gravity is going to be near the seat.
How does the smallish difference in BB heights affect this overall?
And wouldn't the rider position make the most difference?

And my original question was why would the balance of the bike affect
the stability that much when the bike was moving? The wheels spinning
are doing more to keep the bike upright than the balance is doing to
make it fall.

> A sixteen ton cube of granite is very stable, but not much fun
> to ride :-)

If you can get it to the top of the ski hill it might be fun to ride it
down.

[Frank Krygowski]

On Tuesday, October 22, 2013 2:54:39 PM UTC-4, Duane wrote:
>
> My Bianchi (similar frame to a Roubaix) has a higher BB than my Tarmac
> and the Tarmac seems more stable in the turns (as long as the pedal is
> up <g>) Of course the Tarmac has a compact frame, better wheels, is
> much lighter and if CF instead of steel so it's not a very good test.

Agreed, it's not. If someone wanted to test this experimentally, this might be a way: Make up a heavy weight of a shape that wouldn't interfere with pedaling, and that could be clamped at various positions on the bike's frame tube - either high vs. low on the seat tube, or perhaps to the top tube vs. the down tube. (It would be best if this were done so a rider couldn't detect the weigh's position visually.) Then have riders rate the bike's handling.

It's a job for Fogel Labs. I miss Carl!

> couple things:
>
> Talking about balancing a pencil as opposed to a broom we're presumably
> not sitting on top of either.

It illustrates the effect of polar moment of inertia on the rate an object tips, and it explains why an antique "ordinary" or high-wheeler is so amazingly easy to balance.

> Talking about the height of the BB WRT the center of gravity, on a bike
> with a rider on it, the center of gravity is going to be near the seat.
> How does the smallish difference in BB heights affect this overall?

Very little, which was one of my points.

> And wouldn't the rider position make the most difference?

Well, the BB height does raise or lower the rider's position. That's the point. But yes, dropping into an aero crouch also lowers the C.G. of the bike+rider. In fact, I wonder if a typical bike racer (big thighs, upper body like a girl, to use Greg LeMond's analogy) has a lower center of gravity than, say, a triathlete who's got lots of swimming muscles as well.

> And my original question was why would the balance of the bike affect
> the stability that much when the bike was moving? The wheels spinning
> are doing more to keep the bike upright than the balance is doing to
> make it fall.

It's been pretty conclusively shown, I think, that the spinning wheels have little to do with balancing a bike. See p. 268 of _Bicycling Science_ by David Gordon Wilson. "It is widely believed that the angular (gyroscopic) momentum of a bicycle's spinning wheels somehow supports it in the manner of a spinning top. This belief is absolutely untrue." A spinning wheel may make a small contribution toward steering the fork and handlebars in the direction of a bike's tilt, but there are other factors doing this more strongly. And a bike fitted with extra, counter-rotating (but not ground-contacting) front wheel is reputedly just as easy to ride.

The issue of bicycle balancing and stability is extremely complicated. It's complicated enough that the chapter of _Bicycling Science_ containing the above quote was written not by D.G. Wilson, but by Jim Papadopoulos, who is (I think) unquestionably the world's top expert on the problem. Wilson felt unqualified to write the chapter, despite being an engineering professor at MIT, bike designer, HPV expert, etc. If anyone really wants to get into this, I'd recommend reading that chapter.

- Frank Krygowski

[Sir Ridesalot]

Take a touring bicycle or any bicycle and attach panniers half full of heavy stuff and half full of light stuff in each pannier to it with the weight in the panniers on top. Ride bike. Take the stuff out of the panniers and replace the stuff but this time with the weight at the bottom of the pannier. Ride bike. Notice the big difference in handling?

Cheers

[Duane]

I guess that's why it's important whether the swallow was laden or unladen.


Regarding Jim Papadopoulos and why a moving bike stays upright:
http://www.popularmechanics.com/_mobile/outdoors/sports/physics/physics-of-a-riderless-bike

Interesting. Definite proof that neither the gyro effect or caster effect
are essential to keep a moving bike upright.

http://news.sciencemag.org/physics/2011/04/how-keep-riderless-bike-crashing



--
duane

[John B.]

On Tue, 22 Oct 2013 11:32:33 -0700 (PDT), Dan O <danov...@gmail.com>

I'm not sure that is correct. I can imagine circumstances where it
might be a lot of fun to ride.... in early morning commuter traffic,
for example :-)

(I'll bet that they would give you plenty of room when they passed :-)
--
Cheers,

John B.

[John B.]

On Tue, 22 Oct 2013 14:17:57 -0700 (PDT), Frank Krygowski
<frkr...@gmail.com> wrote:

>On Tuesday, October 22, 2013 2:54:39 PM UTC-4, Duane wrote:
>>
>> My Bianchi (similar frame to a Roubaix) has a higher BB than my Tarmac
>> and the Tarmac seems more stable in the turns (as long as the pedal is
>> up <g>) Of course the Tarmac has a compact frame, better wheels, is
>> much lighter and if CF instead of steel so it's not a very good test.
>
>Agreed, it's not. If someone wanted to test this experimentally, this might be a way: Make up a heavy weight of a shape that wouldn't interfere with pedaling, and that could be clamped at various positions on the bike's frame tube - either high vs. low on the seat tube, or perhaps to the top tube vs. the down tube. (It would be best if this were done so a rider couldn't detect the weigh's position visually.) Then have riders rate the bike's handling.
>

Easier then that. Simply stand up. Set the pedals level, stand
straight up, hands on bars, and try cornering.

>It's a job for Fogel Labs. I miss Carl!
>
>> couple things:
>>
>> Talking about balancing a pencil as opposed to a broom we're presumably
>> not sitting on top of either.
>
>It illustrates the effect of polar moment of inertia on the rate an object tips, and it explains why an antique "ordinary" or high-wheeler is so amazingly easy to balance.
>
>> Talking about the height of the BB WRT the center of gravity, on a bike
>> with a rider on it, the center of gravity is going to be near the seat.
>> How does the smallish difference in BB heights affect this overall?
>
>Very little, which was one of my points.
>
>> And wouldn't the rider position make the most difference?
>
>Well, the BB height does raise or lower the rider's position. That's the point. But yes, dropping into an aero crouch also lowers the C.G. of the bike+rider. In fact, I wonder if a typical bike racer (big thighs, upper body like a girl, to use Greg LeMond's analogy) has a lower center of gravity than, say, a triathlete who's got lots of swimming muscles as well.
>
>> And my original question was why would the balance of the bike affect
>> the stability that much when the bike was moving? The wheels spinning
>> are doing more to keep the bike upright than the balance is doing to
>> make it fall.
>
>It's been pretty conclusively shown, I think, that the spinning wheels have little to do with balancing a bike. See p. 268 of _Bicycling Science_ by David Gordon Wilson. "It is widely believed that the angular (gyroscopic) momentum of a bicycle's spinning wheels somehow supports it in the manner of a spinning top. This belief is absolutely untrue." A spinning wheel may make a small contribution toward steering the fork and handlebars in the direction of a bike's tilt, but there are other factors doing this more strongly. And a bike fitted with extra, counter-rotating (but not ground-contacting) front wheel is reputedly just as easy to ride.
>
>The issue of bicycle balancing and stability is extremely complicated. It's complicated enough that the chapter of _Bicycling Science_ containing the above quote was written not by D.G. Wilson, but by Jim Papadopoulos, who is (I think) unquestionably the world's top expert on the problem. Wilson felt unqualified to write the chapter, despite being an engineering professor at MIT, bike designer, HPV expert, etc. If anyone really wants to get into this, I'd recommend reading that chapter.
>
>- Frank Krygowski

--
Cheers,

John B.

[Frank Krygowski]

On Tuesday, October 22, 2013 7:19:36 PM UTC-4, Sir Ridesalot wrote:
>
> Take a touring bicycle or any bicycle and attach panniers half full of heavy stuff and half full of light stuff in each pannier to it with the weight in the panniers on top. Ride bike. Take the stuff out of the panniers and replace the stuff but this time with the weight at the bottom of the pannier. Ride bike. Notice the big difference in handling?

Well, I've not done that test. My first touring experiences (mid-1970s) were with a handlebar bag and loaded rear panniers on the Raleigh I now use as a utility bike. When I got the Cannondale touring bike, it came with front low rider racks and a rear rack, so I started using that scheme, which I still prefer. But the bikes themselves are quite different, and I've never done a direct comparison test.

- Frank Krygowski

[Dan]

Frank Krygowski <frkr...@gmail.com> writes:

<snip>

[old beacj cruiser test ride]

>
> ... I was amazed at how stable it felt - that is, how much it insisted on maintaining a straight line instead of a turn...
>

I know the feeling, but don't think of sluggishness as stability.
My idea of a stable system is one that does not *self*-destabilize.
A bike can be both stable and responsive. You could characterize
extra tolerance for external inputs as more stability, and that's
valid if the application expects random inputs and resisting them
is desirable. I guess the application itself - which includes the
particular rider - becomes part of the system and "bumps" in the
system make it self-destabilizing. Hmmm...

Anyway, in handling terms this latter mode would be "forgiving".

"Graceful" handling is a good balance to strive for. (All these
terms really depend upon the rider.)

Have I got a start on the articulation needed to be a magazine
reviewer? Or do I need to bone up on marketing buzzwords? ;-)

As a sort of flip side ot your super stable beach cruiser story,
there's a kids ~BMX bike out in our driveway. It spit off each of
the first two riders that tried it. I rode it a short distance
and didn't like it at all. We were going to tie it to a tree with
a stout rope and a sign that read: "Killer Bike" (I know you'll
get the reference :-)

Maybe I'll take some measurements - the front end looks kind of
extreme in some dimension(s) - head tube angle, maybe - maybe it
has a wrong fork - I don't think anything's bent. Handling is
evil, though.

Going straight ahead without tipping over is exciting for the first
few minutes after you first learn to ride a bike, but after that,
turning and other "maneuvers" is where it's at.

[Graham]

"Frank Krygowski" <frkr...@gmail.com> wrote in message news:e287956a-84d8-4235...@googlegroups.com...

On Tuesday, October 22, 2013 2:54:39 PM UTC-4, Duane wrote:

[Snip]

Well, the BB height does raise or lower the rider's position. That's the point. But yes, dropping into an aero crouch also lowers the C.G. of the bike+rider. In fact, I wonder if a typical bike racer (big thighs, upper body like a girl, to use Greg LeMond's analogy) has a lower center of gravity than, say, a triathlete who's got lots of swimming muscles as well.

[Snip]

I have now measured up the two bikes I commented on in an earlier post and whilst they share the same top tube dimensions and basic cockpit geomentry there are a number of differences that could contribute to the Raleigh being a faster on a technical descent. The BMC has shorter chain stays with the lower part of the seat tube being concaved to give the necessary clearance for the back wheel. The seat tube angle and the bottom bracket height are the same to with my accuracy of measurement. The BMC also has a shorter top tube but more importantly it has a one degree slacker head tube angle and a longer trail. This compensates for the tight backend and gives an overall wheelbase just slighly less than the Raleigh. So it would appear that the key differences are the lateral positioning of the bottom bracket which will effect the fore and aft location of the CofG and the trail.

From the paper cited earlier the shorter trail should make the Raleigh more sensitive which does not appear to be the case. So how about the fore and aft positioning of the CofG. Is that more important for fast descending on real roads. I, like I guess many of you, ride high speed technical descents on the drops. Now this should both lower and move forward my CofG. I am an ex triathlete with broad shoulders so I guess this, taking Frank's point, should increase the effect in my case! From the discussion of CofG height so far the jury appears to be out but what about fore and aft. By moving the CofG forward this will change the weight balance increasing the load on the front wheel. Is it this effect that is in some way, via increased grip on the front wheel, giving that feel of greater stability or "cornering on rails" as some describe it. Whilst this might not be that noticeable on smooth roads on the roads we are having become accustomed to here in the UK many are now far from smooth. More weight on the front wheel, particularly with high pressure tyres, will increase the contact patch and should help the front tyre stay in contact with the road for longer. I have noticed over the last few seasons that riding with 10-15psi less in the front than the back has given me a better "feel" on descents.

Graham.

[Graham]

"Graham" <h2gt2g42-mi...@yahoo.co.uk> wrote in message news:7OCdnSPrBeTlDPrP...@bt.com...

P.S. There is typo in the first para. "The BMC also has a shorter TOP tube" should read "The BMC also has a shorter HEAD tube"

[John B.]

My thoughts are that there are a host of things that effect the
handling and feel of a bike. Wheel base, vertical C.G., trail, head
tube angle, weight distribution, saddle position vis-a-vis the pedals,
and probably more that I haven't thought about, and changing anything
will have some effect but that effect may be countered or added to by
something else.

Looking at the guys that make a lot of frames they usually recommend a
sort of standard frame. Head tube angle, seat tube angle, wheelbase,
bottom bracket, etc. then the offer variations for racing - say a half
degree different head angle, 1 cm higher BB, a centimeter, or so,
shorter chain stays. Cruiser? Well a half degree slacker head tube a
might lower BB, a bit longer stays, etc.

It seems to me that people have hit of a combination of sizes and
angles that produce a well behaved bike, although those dimensions may
be different then another builder's. The bottom bracket drop and trail
combinations in the Chris Kvale study for example.

I think that the Tri bikes went through quite a cycle of design.
Fairly heavy guy for his size, sitting so far forward that his elbows
are on the handle bars, riding essentially a time trial..... a bit
different then the usual Tour bike.
--
Cheers,

John B.

[Duane]

On 10/23/2013 7:46 AM, John B. wrote:
> On Wed, 23 Oct 2013 10:11:16 +0100, "Graham"
> <h2gt2g42-mi...@yahoo.co.uk> wrote:
>
>>
>> "Graham" <h2gt2g42-mi...@yahoo.co.uk> wrote in message news:7OCdnSPrBeTlDPrP...@bt.com...
>>
>> "Frank Krygowski" <frkr...@gmail.com> wrote in message news:e287956a-84d8-4235...@googlegroups.com...
>> On Tuesday, October 22, 2013 2:54:39 PM UTC-4, Duane wrote:
>>
>> [Snip]
>>
>> Well, the BB height does raise or lower the rider's position. That's the point. But yes, dropping into an aero crouch also lowers the C.G. of the bike+rider. In fact, I wonder if a typical bike racer (big thighs, upper body like a girl, to use Greg LeMond's analogy) has a lower center of gravity than, say, a triathlete who's got lots of swimming muscles as well.
>>
>> [Snip]
>>
>> I have now measured up the two bikes I commented on in an earlier post and whilst they share the same top tube dimensions and basic cockpit geomentry there are a number of differences that could contribute to the Raleigh being a faster on a technical descent. The BMC has shorter chain stays with the lower part of the seat tube being concaved to give the necessary clearance for the back wheel. The seat tube angle and the bottom bracket height are the same to with my accuracy of measurement. The BMC also has a shorter top tube but more importantly it has a one degree slacker head tube angle and a longer trail. This compensates for the tight backend and gives an overall wheelbase just slighly less than the Raleigh. So it would appear that the key differences are the lateral positioning of the bottom bracket which will effect the fore and aft location of the CofG and the trail.
>>
>>From the paper cited earlier the shorter trail should make the Raleigh more sensitive which does not appear to be the case. So how about the fore and aft positioning of the CofG. Is that more important for fast descending on real roads. I, like I guess many of you, ride high speed technical descents on the drops. Now this should both lower and move forward my CofG. I am an ex triathlete with broad shoulders so I guess this, taking Frank's point, should increase the effect in my case! From the discussion of CofG height so far the jury appears to be out but what about fore and aft. By moving the CofG forward this will change the weight balance increasing the load on the front wheel. Is it this effect that is in some way, via increased grip on the front wheel, giving that feel of greater stability or "cornering on rails" as some describe it. Whilst this might not be that noticeable on smooth roads on the roads we are having become accustomed to here in the UK many are now far from
>> smooth. More weight on the front wheel, particularly with high pressure tyres, will increase the contact patch and should help the front tyre stay in contact with the road for longer. I have noticed over the last few seasons that riding with 10-15psi less in the front than the back has given me a better "feel" on descents.
>>
>> Graham.
>>
>> P.S. There is typo in the first para. "The BMC also has a shorter TOP tube" should read "The BMC also has a shorter HEAD tube"
>
>
> My thoughts are that there are a host of things that effect the
> handling and feel of a bike. Wheel base, vertical C.G., trail, head
> tube angle, weight distribution, saddle position vis-a-vis the pedals,
> and probably more that I haven't thought about, and changing anything
> will have some effect but that effect may be countered or added to by
> something else.
>

Don't forget the wheels themselves or the tires. Even handling and feel
are relative to both the rider and the way that he rides. Probably the
most noticeable change I've made was going to wheels with a wider rim
and lower PSI.

[Sir Ridesalot]

I own a vintage 1985 Cinelli frame Columbus SLX racing bike and have two sets of wheels that fit it. Whenever I use the tubular wheels I'm amazed at the difference in the feel of acceleration nd responsiveness when starting and/or climbing.

Cheers

[Duane]

Good wheels are nice. What I like about mine is the way they corner and
grip on descents. Like I said that's how I judge stability. There's this
one ride I do with a nice climb then a fast descent along an S curve that
ends with another climb. One of my favorite places to test new equipment.

--
duane

[Jay Beattie]

Tubulars still offer exceptionally light weight (tires and rims) and a very "lively" feel, for lack of a better word. They're great climbing, but a long descent on a hot day . . . not so much. I think high quality clinchers are pretty close to sew-ups these days, particularly on 23mm rims -- and way better than the sew-ups I rode on a day to day basis back when they were the only game in town and spec'd on any decent bike, e.g. my 1969 PX10.

The geometry of my current Cannondale SuperSix is virtually identical to its aluminum predecessor (a CAAD 9). The bikes descend differently, though -- and I think it has to do with the stiffness of the front end on the SuperSix, which makes the bike feel more stable. The bikes also transmit vibration differently, which give the CF bike a more inert feel. It feels more like "riding on a rail," at least when I set in to a well engineered turn. There is also less slop when riding tight, twisting turns, e.g. http://tinyurl.com/p44u22y The hardest part of that descent is down the hill from where the photo was snapped -- a steep, tight and blind right/left turn, and if you fade over the center-line, you can get smacked by uphill traffic. Making that turn has more to do with traction limits than frame geometry.

-- Jay Beattie.

[John B.]

On Wed, 23 Oct 2013 08:52:13 -0400, Duane <duane....@group-upc.com>
wrote:

>On 10/23/2013 7:46 AM, John B. wrote:
>> On Wed, 23 Oct 2013 10:11:16 +0100, "Graham"
>> <h2gt2g42-mi...@yahoo.co.uk> wrote:
>>
>>>
>>> "Graham" <h2gt2g42-mi...@yahoo.co.uk> wrote in message news:7OCdnSPrBeTlDPrP...@bt.com...
>>>
>>> "Frank Krygowski" <frkr...@gmail.com> wrote in message news:e287956a-84d8-4235...@googlegroups.com...
>>> On Tuesday, October 22, 2013 2:54:39 PM UTC-4, Duane wrote:
>>>
>>> [Snip]
>>>
>>> Well, the BB height does raise or lower the rider's position. That's the point. But yes, dropping into an aero crouch also lowers the C.G. of the bike+rider. In fact, I wonder if a typical bike racer (big thighs, upper body like a girl, to use Greg LeMond's analogy) has a lower center of gravity than, say, a triathlete who's got lots of swimming muscles as well.
>>>
>>> [Snip]
>>>
>>> I have now measured up the two bikes I commented on in an earlier post and whilst they share the same top tube dimensions and basic cockpit geomentry there are a number of differences that could contribute to the Raleigh being a faster on a technical descent. The BMC has shorter chain stays with the lower part of the seat tube being concaved to give the necessary clearance for the back wheel. The seat tube angle and the bottom bracket height are the same to with my accuracy of measurement. The BMC also has a shorter top tube but more importantly it has a one degree slacker head tube angle and a longer trail. This compensates for the tight backend and gives an overall wheelbase just slighly less than the Raleigh. So it would appear that the key differences are the lateral positioning of the bottom bracket which will effect the fore and aft location of the CofG and the trail.
>>>
>>>From the paper cited earlier the shorter trail should make the Raleigh more sensitive which does not appear to be the case. So how about the fore and aft positioning of the CofG. Is that more important for fast descending on real roads. I, like I guess many of you, ride high speed technical descents on the drops. Now this should both lower and move forward my CofG. I am an ex triathlete with broad shoulders so I guess this, taking Frank's point, should increase the effect in my case! From the discussion of CofG height so far the jury appears to be out but what about fore and aft. By moving the CofG forward this will change the weight balance increasing the load on the front wheel. Is it this effect that is in some way, via increased grip on the front wheel, giving that feel of greater stability or "cornering on rails" as some describe it. Whilst this might not be that noticeable on smooth roads on the roads we are having become accustomed to here in the UK many are now far from
>>> smooth. More weight on the front wheel, particularly with high pressure tyres, will increase the contact patch and should help the front tyre stay in contact with the road for longer. I have noticed over the last few seasons that riding with 10-15psi less in the front than the back has given me a better "feel" on descents.
>>>
>>> Graham.
>>>
>>> P.S. There is typo in the first para. "The BMC also has a shorter TOP tube" should read "The BMC also has a shorter HEAD tube"
>>
>>
>> My thoughts are that there are a host of things that effect the
>> handling and feel of a bike. Wheel base, vertical C.G., trail, head
>> tube angle, weight distribution, saddle position vis-a-vis the pedals,
>> and probably more that I haven't thought about, and changing anything
>> will have some effect but that effect may be countered or added to by
>> something else.
>>
>
>Don't forget the wheels themselves or the tires. Even handling and feel
>are relative to both the rider and the way that he rides. Probably the
>most noticeable change I've made was going to wheels with a wider rim
>and lower PSI.
>

Certainly. and another guy has posted that when he went to sew-ups and
light "glue on" wheels it made a great difference.

--
Cheers,

John B.

[John B.]

And another guy says that when he went to larger, lower pressure
tires....

I think that, to some extent, the old saying that "beauty is in the
eye of the beholder" is the deciding factor. We like it and it's
wonderful sort of determination of what is good (for us).

The Great Bike Light Controversy comes to mind :-)
--
Cheers,

John B.

[Duane]

Not larger tires. Wider rims. Still 23s for the tires. You might be right
about eye of the beholder but better grip in a tight turn is pretty easy to
detect.

--
duane

[Dan]

John B. <sloc...@gmail.com> writes:

<snip>

>>Cheers

(left that part :-)

>
> And another guy says that when he went to larger, lower pressure
> tires....
>
> I think that, to some extent, the old saying that "beauty is in the
> eye of the beholder" is the deciding factor. We like it and it's
> wonderful sort of determination of what is good (for us).
>

It's not about the bike (except to the extent that it is).

<snip>

[Sir Ridesalot]

So is the ease of acceleration the and effort to climb.

Cheers

[Frank Krygowski]

On Wednesday, October 23, 2013 8:48:49 PM UTC-4, Phil W Lee wrote:

> Sir Ridesalot <i_am_cyc...@yahoo.ca> wrote:
>
> >Take a touring bicycle or any bicycle and attach panniers half full of heavy stuff and half full of light stuff in each pannier to it with the weight in the panniers on top. Ride bike. Take the stuff out of the panniers and replace the stuff but this time with the weight at the bottom of the pannier. Ride bike. Notice the big difference in handling?
>
> >
>

> That would only work if the panniers (and the load they contained)
> were mounted absolutely rigidly to the frame, and the frame itself was
> sufficiently stiff that the additional weight wouldn't cause flex.
>
> Probably not insurmountable problems, but not trivial enough that you
> could just load up a touring bike and go play.

That brings to mind the final note in the stability & steering chapter in the book _Bicycling Science_. That note was written by the main author, David Gordon Wilson, designer of the Avatar 2000 recumbent. Since I don't have the book at hand now, I'll have to work by memory; but he described some very troublesome instability (sounds like a shimmy) with that bike. IIRC, it was somehow connected with the pack he carried on the rear of the bike, but again IIRC, the instability occurred only when the pack and its load of tools, lock, etc. was _absent_. At the time of writing, he still hadn't succeeded in diagnosing the problem.

I've mentioned before having only one hint of shimmy with my Cannondale touring bike. It was on a long, fully loaded tour. Turns out the ancient handlebar bag, which had several heavy objects in it, was flexing and shaking side to side at a certain speed. Attaching it more firmly and removing a little weight made the bike perfectly stable (as in, descending mountain passes at 45+ mph).

So yes, luggage can make a difference.

- Frank Krygowski

[Duane]

Sir Ridesalot <i_am_cyc...@yahoo.ca> wrote:
> On Wednesday, October 23, 2013 8:12:00 PM UTC-4, Duane wrote:

<snip>

>> Not larger tires. Wider rims. Still 23s for the tires. You might be right
>>
>> about eye of the beholder but better grip in a tight turn is pretty easy to
>>
>> detect.
>>
>>
>>
>> --
>>
>> duane
>
> So is the ease of acceleration the and effort to climb.
>
> Cheers

Yep.
--
duane

[John B.]

On Thu, 24 Oct 2013 00:12:00 +0000 (UTC), Duane <sp...@flarn.com>
wrote:

I shan't argue but the only time I felt I might not have enough grip
was the time I hit the partially rotten leaves on a corner. Up till
then I always thought I had plenty of grip :-)
--
Cheers,

John B.

[John B.]

On Thu, 24 Oct 2013 02:17:59 +0100, Phil W Lee <ph...@lee-family.me.uk>
wrote:

>John B. <sloc...@gmail.com> considered Wed, 23 Oct 2013 08:46:47

>Having hauled loads like that (and larger), I can only say that I wish
>it was the case :)
>
>That's partly why abnormal loads are given escorts, and in places
>where clearance is limited, road closures and/or police assistance.

Err... In America a 16 ton load isn't a particularly large load :-)
--
Cheers,

John B.

[Duane]

Like I said there is this one section of a ride that has a descent on an
S curve right before another climb. It's where I test my wheels and
tires. I've taken this at a speed where I start to lose the grip and
have to brake. I changed the wheels and could get more speed. The idea
here is to get as much speed on the descent as possible to help with the
subsequent 18% grade climb. Also, it's lots of fun.

If I ever hit rotten leaves on this descent I would be in trouble. <g>

[davethedave]

On Thu, 24 Oct 2013 08:50:39 -0400, Duane wrote:

<epic snip>

>> I shan't argue but the only time I felt I might not have enough grip
>> was the time I hit the partially rotten leaves on a corner. Up till
>> then I always thought I had plenty of grip :-)
>>
>>
> Like I said there is this one section of a ride that has a descent on an
> S curve right before another climb. It's where I test my wheels and
> tires. I've taken this at a speed where I start to lose the grip and
> have to brake. I changed the wheels and could get more speed. The idea
> here is to get as much speed on the descent as possible to help with the
> subsequent 18% grade climb. Also, it's lots of fun.

Surely if you have enough available grip, excepting leaves, for a braking
operation mid corner you have enough grip to get round it.
--
davethedave

[Duane]

Maybe he didn't have enough light to see the leaves.

[davethedave]

Mr. Slocomb wasn't the one talking about braking mid corner due to lack
of grip / bottle, Mr Hebert.

<considers smiley...>

<rejects as superfluous.>

<adds one anyway>

;)

Anyway purple shorts of power trump low light leaf mulch interaction.

Seriously though. There does come a point where braking will introduce
more woe to the situation you find yourself in due to excessive speed
than it will cure.
--
davethedave

[Duane]

On 10/24/2013 3:28 PM, davethedave wrote:
> On Thu, 24 Oct 2013 14:44:10 -0400, Duane wrote:
>
>>> <epic snip>
>>>
>>>>> I shan't argue but the only time I felt I might not have enough grip
>>>>> was the time I hit the partially rotten leaves on a corner. Up till
>>>>> then I always thought I had plenty of grip :-)
>>>>>
>>>>>
>>>> Like I said there is this one section of a ride that has a descent on
>>>> an S curve right before another climb. It's where I test my wheels
>>>> and tires. I've taken this at a speed where I start to lose the grip
>>>> and have to brake. I changed the wheels and could get more speed.
>>>> The idea here is to get as much speed on the descent as possible to
>>>> help with the subsequent 18% grade climb. Also, it's lots of fun.
>>>
>>> Surely if you have enough available grip, excepting leaves, for a
>>> braking operation mid corner you have enough grip to get round it.
>
>> Maybe he didn't have enough light to see the leaves.
>
> Mr. Slocomb wasn't the one talking about braking mid corner due to lack
> of grip / bottle, Mr Hebert.
>
> <considers smiley...>
>
> <rejects as superfluous.>
>
> <adds one anyway>
>
> ;)
>
> Anyway purple shorts of power trump low light leaf mulch interaction.
>

lol.

> Seriously though. There does come a point where braking will introduce
> more woe to the situation you find yourself in due to excessive speed
> than it will cure.
>

Well, I wasn't talking about a corner, but a curve. Actually 2
curves. And braking is what I am usually trying to avoid, Mr. TheDave.
<g> The last thing you want to do when on a descent coming to an 18%
climb is slow down. Aside from that, I agree totally. Especially about
the shorts/low light thing.

[John B.]

On Thu, 24 Oct 2013 08:50:39 -0400, Duane <duane....@group-upc.com>
wrote:

??? if you are losing grip how do you brake? I would think that if the
tires were losing grip that braking (which depends on the tire to
ground contact) would be reduced dramatically?
--
Cheers,

John B.

[John B.]

I thought that the purple pants only helped on the up-hill portions of
the ride?
--
Cheers,

John B.

[John B.]

On Thu, 24 Oct 2013 15:43:36 -0400, Duane <duane....@group-upc.com>
wrote:

A corner is not a curve? Or a curve is not a corner?

(amazing the knowledge one can pick up on the Internet :-)
--
Cheers,

John B.

[Duane]

You've never had to brake in a twisting descent because you were losing it?

--
duane

[Duane]

Well no.

> (amazing the knowledge one can pick up on the Internet :-)


--

duane

[James]

Would a corner be a curve of zero radius?

--
JS

[James]

On 25/10/13 12:25, Phil W Lee wrote:
> John B. <sloc...@gmail.com> considered Thu, 24 Oct 2013 18:38:36

You ride 16 ton loads?

> Nor here - that part was about the (and larger).
> We could go about 25 tonnes load on a normal run when I was still
> driving heavies, but it's gone up a bit since then.

Um, the comment was about a 16 ton cube of granite being stable, but not
much fun to _*ride*_.

--
JS

[John B.]

On Fri, 25 Oct 2013 11:34:14 +1100, James <james.e...@gmail.com>
wrote:

Be an interesting looking six lane highway :-)
--
Cheers,

John B.

[John B.]

On Thu, 24 Oct 2013 23:59:22 +0000 (UTC), Duane <sp...@flarn.com>

No. God is good and I've always been able to brake before I reached
the "losing it" stage :-)
--
Cheers,

John B.

[John B.]

On Fri, 25 Oct 2013 02:25:29 +0100, Phil W Lee <ph...@lee-family.me.uk>
wrote:

>John B. <sloc...@gmail.com> considered Thu, 24 Oct 2013 18:38:36

>Nor here - that part was about the (and larger).
>We could go about 25 tonnes load on a normal run when I was still
>driving heavies, but it's gone up a bit since then.

>Max gross is up from 38 to 44, but some of that is the extra axle you
>have to have, so maybe 30 tonnes on a normal trip.
>On STGO, if you can figure out a way to do it (and there's no other
>way - it's only allowed for indivisible loads) I don't think there is
>an absolute limit, although above certain limits you'll have teams of
>engineers in advance and following, so that obstacles can be cleared
>and damage noted to be billed to the haulage company. That's the sort
>of stuff that has the rig specially built or assembled for it though.
>I never did anything quite that huge though - the most I ever had was
>a single advance warning vehicle with police escort on pinchpoints.
>
>I do remember asking before taking one such load through the Dartford
>Tunnel, where I had to be central in the 2-lane round-bore tunnel for
>safe clearance: "What do I do if someone gets past you and tries
>coming up alongside, do I try to block them, or squeeze over as far as
>possible to let them through?"
>The police escort driver said not to worry about that, as "We'd put
>them in the wall before they got that far" :)
>
>For more normal loads, you just have to watch out for idiots taking
>liberties/risks, and if in doubt, stop. The worst that will cause is
>a traffic jam.

Interesting. While I haven't actually looked at the license, more and
more the trucks I see here are what appears to be about a 40 ton flat,
or stake body truck towing what appears to be approximately the same
capacity trailer. I'm looking at the tires and rear springs and
guessing the load based on the Kenworth oil field trucks I once worked
with that I know were rated 40 tons.

No police escorts on these "regular" trucks :-)
--
Cheers,

John B.

[John B.]

On Fri, 25 Oct 2013 13:23:47 +1100, James <james.e...@gmail.com>
wrote:

Hard to get a saddle on, but not too many SUV's are going to impede
your travels :-)
--
Cheers,

John B.