best brakes for a 650B rando?

[Mark Ballogg]

Hey all,

I just ordered a custom 650B randonneur and I'm a bit overwhelmed by the brake choices.

Interested in having a weigh in on the best approach.

These are the facts-

Probable total weight of the bike/load/rider- 210-230 lbs

Fork Braze Ons with vertical dropouts

Wide Honjo Fenders

Want to keep a vintage French rando look

I am leaning toward a canti brake over center pulls because of stopping power and fender clearance although I think that a center pull would be a better match for the vintage look.

Don't care for the cheap look of V Brakes.

These are my initial thoughts but I am very open to suggestions since I have absolutely no real world experience owning/riding a randonneur.

Ride On,

Mark Ballogg

Chicago, IL

USA

[Peter Weigle]

Mark, 

This has all been rehashed here before, and imo you should be taking this up with your framebuilder.

But, because you asked,

 for your size, weight and the clearance that the big Honjo's require, Mafac Raids would do everything you need. You could go with canti's and if set up properly they would work fine,,,

 but many on this group will suggest the Raids, so it could be the end of the discussion,,,

but somehow I have a feeling this discussion is going to go on for quite a while;~)

Ducking,,

ptr

---

From: Mark Ballogg <ballog...@gmail.com>
To: 65...@googlegroups.com
Sent: Thursday, December 12, 2013 11:35 AM
Subject: [650B] best brakes for a 650B rando?

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

[Michael Mann]

Paul Centerpulls - the one's mounted to braze-on studs. My Ocean Air Rambler is designed for them and I couldn't be more happy with their performance. Similar to the Mafacs I hear, but available new instead of having to hunt fleabay. Keep in mind if you go this route, you're locked in or will need frame mods done if you change your mind - the studs are not placed in the same position as canti studs. But I'd go that route again in a heartbeat - good brakes, easy to set up and maintain, and all the power and modulation I desire.

Not cheap, but if you're ordering a custom, I assume you're not trying to go cheap.

I also like Paul cantilever brakes. But I like the centerpulls more.

Mike

--

You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

--
Michael Mann
http://baiku-velomann.blogspot.com/

[Alex Wetmore]

I'll add a question to Peter's excellent advice.

Has your framebuilder built a frame with centerpull brakes before?

They are harder to get right than cantilevers.  The boss spacing must be exact and boss alignment must be perfect to have the arm alignment work out.  If the bosses are splayed slightly apart you get a wierd gap between the arms, if they are too close then the arms hit.  If the spacing is too wide the arms don't overlap nicely and it looks terrible.

They aren't that hard, they are just different and you might not want the first bike that a builder does with them.

alex

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Peter Weigle <jpwe...@sbcglobal.net>
Sent: Thursday, December 12, 2013 10:26 AM
To: Mark Ballogg; 65...@googlegroups.com
Subject: Re: [650B] best brakes for a 650B rando?

 

[Steve Palincsar]

On 12/12/2013 01:26 PM, Peter Weigle wrote:

Mark, 

This has all been rehashed here before, and imo you should be taking this up with your framebuilder.

But, because you asked,

 for your size, weight and the clearance that the big Honjo's require, Mafac Raids would do everything you need. You could go with canti's and if set up properly they would work fine,,,

 but many on this group will suggest the Raids, so it could be the end of the discussion,,,

but somehow I have a feeling this discussion is going to go on for quite a while;~)

The Raids are a great choice.  There's only one problem with them: they've been out of production for a long time and there aren't many NOS examples left -- and those few fetch very high prices.   That wasn't true back in 2006: there was a guy on Cyprus selling one NOS pair a week on ebay for around $50-60 a set w/o boxes, but that's been over for quite a few years now.  Right now on ebay there's a pair for $129, used, one for $200 used and a couple for $155.50, all BIN.   So, if that's what you want -- and I agree, they'd be a fabulous choice -- I'd suggest you buy it now!

[Steve Chan]

   The Dia Compe 750's (the older Weinmann clone, not the new CNC model) are inexpensive, classic looking and functional. Easy to source, and currently in production.

   The are entirely free of cachet though.

   And, I realize this is blasphemy, but U Brakes are basically centerpulls and there seems to be wide compatibility and competition. The Eclat Unit in high polish actually looks better than Paul Racers (imo), and if you can get mounting hardware without the colorful finish, I think it would look okay. On the other hand, I have no idea how well they stop,

   If only Grand Bois would hurry up with their Dia Compe 450 clones...

   Steve

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

--
"Sow a thought, reap an action. Sow an action, reap a habit. Sow a habit, reap a character. Sow a character, reap a destiny." - Samuel Smiles

[Richard L.]

I've not had any experience with the Dia Compe 610 centerpull brakes Velo-Orange sells, but a guy I work with just installed those brakes on his vintage Centurion 700c bike, and he is very pleased with their performance and appearance.  I don't know if the reach for these brakes will be sufficient.  Here's the link to the Velo-Orange website.

 

http://store.velo-orange.com/index.php/components/brakes/calipers/dia-compe-610-centerpull-brake.html   

[Alex Wetmore]

"   If only Grand Bois would hurry up with their Dia Compe 450 clones..."

The Diacompe GC450 is a pretty small clearance brake.  They barely fit over 32mm tires with room for aluminum fenders and clearances to allow the wheel to be removed with the tire inflated.

I like them on my 700C Rando-style bike (designed for up to 32mm tires), but wouldn't put them on anything 650B.

This is not enough clearance between the brake and fender to allow the 32mm tire on 23mm wide rims to squeeze out through the brake:

http://alexandchristine.smugmug.com/Bicycles/Framebuilding/Ivy-T/P1050900/1172881004_MKDdZ-M.jpg

alex

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Steve Chan <sych...@gmail.com>
Sent: Thursday, December 12, 2013 2:07 PM
To: Steve Palincsar
Cc: 650b
Subject: Re: [650B] best brakes for a 650B rando?

 

[Ryan Watson]

Grand Bois is working on some Raid-sized ones as well! :-D

[Steve Palincsar]

On 12/12/2013 10:11 PM, Ryan Watson wrote:

Grand Bois is working on some Raid-sized ones as well! :-D

Yes, but you know this commercial works for Grand Bois as well as it did for Paul Masson
http://www.youtube.com/watch?v=oSs6DcA6dFI

[Nick Payne]

On 13/12/13 09:07, Steve Chan wrote:
>
> The Dia Compe 750's (the older Weinmann clone, not the new CNC
> model) are inexpensive, classic looking and functional. Easy to
> source, and currently in production.
> The are entirely free of cachet though.
>
> And, I realize this is blasphemy, but U Brakes are basically
> centerpulls and there seems to be wide compatibility and competition.
> The Eclat Unit in high polish actually looks better than Paul Racers
> (imo), and if you can get mounting hardware without the colorful
> finish, I think it would look okay. On the other hand, I have no idea
> how well they stop

We have a touring tandem using Deore XT U-brakes, and they stop fine,
even with two of us plus a full camping touring load - all up weight
around 400lbs. And the brakes easily have sufficient clearance for 2.1"
slicks plus full mudguards. But those brakes have been on that bike for
about 25 years - I have no idea what is available in U-brakes these days.

Nick

[Nick Bull]

And my experience with using Raid's _without_ mounting bosses is that the braking power just isn't up to snuff.  Mounted to a fork-crown bolt, they're too flexy for hard braking.  I'm thinking about having mounting bosses retrofitted onto my Waterford A.Homer Hilsen low-trail fork.

Nick

[Steve Palincsar]

On 12/13/2013 02:22 PM, Nick Bull wrote:
> And my experience with using Raid's _without_ mounting bosses is that
> the braking power just isn't up to snuff. Mounted to a fork-crown
> bolt, they're too flexy for hard braking. I'm thinking about having
> mounting bosses retrofitted onto my Waterford A.Homer Hilsen low-trail
> fork.

I have Raids without mounting bosses on my Kogswell P/R. I use Shimano
aero levers (the 1991 vintage battleship gray) and Koolstop Eagle Claw
II pads. I find braking just fine, and haven't detected the flex you
speak of. Perhaps some of the accessory hardware may be the source of
the problem? However, brazed on mounting bosses are just dandy.

[Ryan Watson]

I have both bolt-on and braze-on Raids, and can't tell a difference in stopping ability, but the braze on ones sure look cooler ;-)

[Rory]

I don't know how Mafac Raids got popular for 42mm wide tires. I don't think they offer any better function then cantis, and cantis offer better clearance.

I am wondering at what point did Rene Herse switch to just using cantis? I've noticed that a lot of the 650bx42mm tired herse's bikes have cantis, but I have no data to show it being the predominant method of construction. Does anyone on the list know how many of the bikes herse made were canti versus raids?

[Jan Heine]

At 2:19 PM -0800 12/17/13, Rory wrote:
>I don't know how Mafac Raids got popular for 42mm wide tires. I
>don't think they offer any better function then cantis, and cantis
>offer better clearance.
>
>I am wondering at what point did Rene Herse switch to just using
>cantis? I've noticed that a lot of the 650bx42mm tired herse's bikes
>have cantis, but I have no data to show it being the predominant
>method of construction. Does anyone on the list know how many of the
>bikes herse made were canti versus raids?

The early Rene Herse bikes had cantis. Once centerpulls had proven
themselves, Herse switched to centerpulls. For wide tires, he first
used the Mafac Tigers (which required careful brazing of the posts,
since the pad height was not adjustable). Once the Raids became
available, Herse used them on bikes with wide tires.

Cantilever brakes are great, but they suffer from a few
disadvantages. The biggest one is that since the brake force tends to
twist the fork blade, which compromises the modulation of the brake.
Some are worse than others, but you never get the linear feel of a
good centerpull.

The reason a lot of the 650B bikes had cantis is that they were early
bikes. By 1960, when the Mafac Tiger was available, wide 650B tires
were pretty much out of fashion in France.

Jan Heine
Editor
Bicycle Quarterly
2116 Western Ave.
Seattle WA 98121
http://www.bikequarterly.com

Follow our blog at http://janheine.wordpress.com/
--

[Rory]

thanks for the clarification! I find it interesting that as the wider Raids caught on, the wider tire production slowed.

for what its worth, I currently use cantis on an imperial fork blade with my hetres, and I haven't noticed any lack of performance with their use. I weigh 220+, and generally ride with some form of front load. If Raids were available and had the spring and bad mount configuration of a diacompe center pull, I probably would have spec'ed those. as is, I'm happy with the canti's.

[Jan Heine]

At 2:51 PM -0800 12/17/13, Rory wrote:
>I find it interesting that as the wider Raids caught on, the wider
>tire production slowed.

Wide 650B tires went out of fashion when the Technical Trials stopped
being organized - 1949. At that point, there was nothing to make
cyclotouring bikes cool and cutting edge, and even randonneurs
started looking to racing bikes for technical inspiration. The result
were narrower tires, 700C wheels, but also bikes that became heavier
(racing components at the time were heavier than touring ones) and
didn't shift as well. The only progress after 1949 were the
centerpull brakes - one of the few places where racing pioneered a
technological advance.

Centerpull brakes - introduced in 1952 - were such a huge step
forward compared to the sidepull brakes racers had been using that
within a few years, almost the entire professional peloton was on
Mafac Racers. Whether Cinelli in Italy or Thanet in Britain,
top-of-the-line bikes used these brakes. The cyclotourists took a
little longer to catch on - the constructeurs may have figured if the
racers used it, it can't be that good. Within five years, the
constructeurs also followed suit.

The French think it's funny that we love the wide tires that are
pre-historic for them. In France, at least until recently, 650B
riders were old guys (and women) who grew up with 650B x 32 mm tires
on their cyclotouring bikes. So they try to hold on to the bikes of
their youth, just like the people in the U.S. who love 700C x 28 mm
tires because it was such a neat, versatile size.

>I'm happy with the canti's.

Cantis are great. I have them on my own bikes. I'd use them on all my
bikes if centerpulls didn't exist.

[Rory C]

On Tue, Dec 17, 2013 at 3:05 PM, Jan Heine <hei...@earthlink.net> wrote:

Centerpull brakes - introduced in 1952 - were such a huge step forward compared to the sidepull brakes racers had been using that within a few years, almost the entire professional peloton was on Mafac Racers.

 

...

Cantis are great. I have them on my own bikes. I'd use them on all my bikes if centerpulls didn't exist.

 

I whole heartedly agree with these statements. my only caveat is that the appropriate centerpull for hetres is difficult to come by. I wish someone would remake the raids, except better. but based on current selection, i'll stick with my brake rule of thumb: centerpulls for tires up to 35mm, cantis for tires past that.

 

[Harold Bielstein]

Sure would like to see a vector diagram of how canti brakes twist fork blades.

> --
> You received this message because you are subscribed to the Google Groups "650b" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
> To post to this group, send email to 65...@googlegroups.com.
> Visit this group at http://groups.google.com/group/650b.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>

Hal Bielstein
hkbie...@rap.midco.net

[Steve Chan]

   On the face of it, it seems that the longer reach of a centerpull brake arm like a raid would tend to cancel the advantage of being mount on the rigid fork crown compared to a cantilever brake with shortish "reach" on the fork blades.
   The fiddlyness of cantilever straddle cable tuning seems like a more significant issue, though one that can be educated away.

   Steve

[Jan Heine]

At 5:35 PM -0700 12/17/13, Harold Bielstein wrote:
>Sure would like to see a vector diagram of how canti brakes twist fork blades.

I don't have a vector diagram, but you don't need it to visualize the
forces involved:

- For a static load, the brake applies a force that is offset from
the centerline of the fork blade. (The brake is attached to the front
of the fork blade.) You apply the brake, and you push the front of
the fork blade outward. This twists the blade.

- For a dynamic load, you add the fact that the wheel is rotating. So
the rim pulls along the brake pad, which increases the twisting of
the fork blade. To compensate for this twisting, you need to toe in
the brake pad...

The effect is very real. You notice it when you brake hard - the
brake does not behave linearly.

It wasn't just the French who realized what was going on. Charlie
Cunningham identified the same problem, hence all his brakes -
Roller-Cam and others - were attached closer to the fork crown.

[Alex Wetmore]

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Jan Heine <hei...@earthlink.net>

> - For a static load, the brake applies a force that is offset from
> the centerline of the fork blade. (The brake is attached to the front
> of the fork blade.) You apply the brake, and you push the front of
> the fork blade outward. This twists the blade.

You can see this visually on an average steel cyclocross bike that has fairly small diameter seatstays. Not something extra beefy like a Surly Crosscheck, but for sure on a Bridgestone RB-T or most early 80s Trek touring bikes. When mountain bikes used cantilever brakes there were many companies making after market bridges that mounted to the front of the stud to counteract this twist. Magura hydraulic rim brakes (they also mount to canti studs) came with them as standard due to the very high forces that the brakes could exert compared to your average cantilever brake.

Double tapered chainstays are extremely nice for cantilever brakes because they are larger diameter (and thus more resistant to bending and torsion) right where the brakes mount. There isn't an equivalent of double tapered chainstays for fork blades (at least with fork crowns), so most builders who are building cantilever brake forks will choose a somewhat heavier fork blade to handle the braking loads. A classic example of where this wasn't done is the Bridgestone XO-1, a bike which is notorious for having unmanageable canti squeal issues. Unicrown forks typically use larger diameter blades that will also better handle canti stud twist.

Disk brakes make this even harder since they put the braking forces very far from the fork crown and on only one fork leg. The only disk brake fork that I've built is considerably heavier than my centerpull and canti forks due to using thicker wall and oversized fork blades to handle the braking forces. Likewise I used a a larger diameter (and a bit thicker) seatstay on that bike compared to other bikes that I've built. It isn't hard to make a bicycle that handles disk brake loads, it is just heavier.

A downside of putting the pivots above the rim is that as the pads wear the brakes are pulling the pads higher on the rim, until they can touch the tire. When the pivots are below the rim (cantilever brakes) pad wear puts the pad below the rim, a safer place to have (neither is very good). This is unlikely to be a concern for enthusiasts who are more likely to check out their brakes once in a while, but can be a good reason not to use centerpull brakes on utility bicycles used by less careful riders.

alex

[Fred Blasdel]

On Wed, Dec 18, 2013 at 7:35 AM, Alex Wetmore <al...@phred.org> wrote:

Disk brakes make this even harder since they put the braking forces very far from the fork crown and on only one fork leg.  The only disk brake fork that I've built is considerably heavier than my centerpull and canti forks due to using thicker wall and oversized fork blades to handle the braking forces.

The crown we've both used does use blades that are oversized by about a mm, but you don't need to use the tandem chainstay blades to hold up to disc use, their blade with light 0.9/0.6 butting has held up just fine for me with your Willits-style long disc tab, and I'm pretty sure they're only a few grams heavier than the very similar Columbus SL.

With a short disc tab it'd probably be better to add about 100g to the blades making them thicker and bigger in the lower legs, but it's less the torsional stiffness I worry about than fatigue failures where the disc tab acts like a can opener.

Likewise I used a a larger diameter (and a bit thicker) seatstay on that bike compared to other bikes that I've built.  It isn't hard to make a bicycle that handles disk brake loads, it is just heavier.

I used superlight S3 seatsays on mine, not quite the smallest diameter available but definitely the thinnest. The caliper is on the seatstay but there is a short brace made of 7/16" tubing inside the triangle supporting it.

There's no trouble with it in normal braking, but it does lack some lateral stiffness — I can sometimes make the inboard pad rub the disc by leaning the bike over to the left and stomping on the right pedal.

 

[Alex Wetmore]

From: Fred Blasdel <blas...@gmail.com>

> On Wed, Dec 18, 2013 at 7:35 AM, Alex Wetmore <al...@phred.org> wrote:
> > Disk brakes make this even harder since they put the braking forces very far from the fork crown and on only one fork leg.  
> > The only disk brake fork that I've built is considerably heavier than my centerpull and canti forks due to using thicker wall
> > and oversized fork blades to handle the braking forces.
>
> The crown we've both used does use blades that are oversized by about a mm, but you don't need to use
> the tandem chainstay blades to hold up to disc use, their blade with light 0.9/0.6 butting has held up just fine
> for me with your Willits-style long disc tab, and I'm pretty sure they're only a few grams heavier than the very
> similar Columbus SL.

Fred and I talked about this off of the list and it reminded me that I have a lot of fork blades to weigh, including these ones.

The Nova OS fork blades are about 360 grams per pair.

Some "oddball" (not sure if you can buy them anymore) True Temper 9/6 blades that are 4cm longer are 320 grams. Fred reported that he found Columbus SL blades weigh about 310 grams. So there is a roughly 50 gram penalty for the oversized blades.

The disk tab dropout used with these blades is also heavier. I don't have one handy to weigh.

Anyway, it isn't a huge difference, but I do think a durable disk brake fork is going to be about 100 grams heavier than a centerpull brake fork, and will have a stiffer ride as well.

> With a short disc tab it'd probably be better to add about 100g to the blades making them thicker and bigger in the lower legs,
> but it's less the torsional stiffness I worry about than fatigue failures where the disc tab acts like a can opener.

I agree.

alex

[Nick Bull]

Hi, Jan,

Why don't brazed-on centerpulls that are mounted to brazed-on studs on the fork blades have the same problem of twisting the blades? 

With cantilevers, it seems like the pad pressing against the rim is like the middle of a teeter-totter where the far end is fixed to the stud.  So the cable pulling the arm at one end of the teeter-totter is like pushing down on the teeter totter and thereby trying to "lift" the other end of the arm away form the rim but it can't move because of the stud, so it thereby puts twisting force into the stud and fork blade.

With centerpulls, it seems like the pad pressing against the rim is like the far end of a teeter-totter that is on the ground.  And the stud attached to the fork blade is like the pivot on which the teeter totter rotates.  The cables pulling on the arm is like someone pushing up on the end of the teeter totter to try to force the far end further into the ground.  So the force generated on the teeter-totter pivot is putting twisting force into the stud and fork blade.

Nick

[Jan Heine]

At 7:48 AM -0800 12/19/13, Nick Bull wrote:
>Hi, Jan,
>
>Why don't brazed-on centerpulls that are mounted to brazed-on studs
>on the fork blades have the same problem of twisting the blades?

The brazed-on studs on centerpulls are much closer to the fork crown
or the seatstay bridge, rather than in an unsupported portion of the
stays/blades.

[Ken Freeman]

Exactly!

On Thu, Dec 19, 2013 at 11:54 AM, Jan Heine <hei...@earthlink.net> wrote:

At 7:48 AM -0800 12/19/13, Nick Bull wrote:

Hi, Jan,

Why don't brazed-on centerpulls that are mounted to brazed-on studs on the fork blades have the same problem of twisting the blades?

The brazed-on studs on centerpulls are much closer to the fork crown or the seatstay bridge, rather than in an unsupported portion of the stays/blades.

Jan Heine
Editor
Bicycle Quarterly
2116 Western Ave.
Seattle WA 98121
http://www.bikequarterly.com

Follow our blog at http://janheine.wordpress.com/
--

--
You received this message because you are subscribed to the Google Groups "650b" group.

To unsubscribe from this group and stop receiving emails from it, send an email to 650b+unsubscribe@googlegroups.com.

To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

--
Ken Freeman
Ann Arbor, MI USA

[Mike Schiller]

It would seem that a front fork blade mounted rack, either attached to the cantilever studs like the Nitto M12 or M13 or the Mini Campee attached to the fork blades via braze-ons would add some stiffness.   

I was also wondering of the Imperial blades are more or less susceptible to this twisting? 

~mike

Carlsbad Ca.

[Alex Wetmore]

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Mike Schiller <mikey...@rocketmail.com>

> It would seem that a front fork blade mounted rack, either attached to the cantilever studs like the Nitto M12 or 

> M13 or the Mini Campee attached to the fork blades via braze-ons would 

> add some stiffness.   

Any benefit from the rack will be quite minor.  The 8mm tubing used by most of these racks (which is heavy compared to most custom racks) can be bent quite easily and doesn't add a lot of stiffness.  The load path from one canti stud to the other through a rack is very long, which makes it worse.

A device that worked well is this Salsa brake stiffener:

http://fcdn.mtbr.com/attachments/salsa/541630d1359601749-favorite-salsa-product-past-present-salsa-bb.jpg

> I was also wondering of the Imperial blades are more or less susceptible to this twisting? 

They have a narrower cross section and are more susceptible to it.  This might be another reason why the 1993 Bridgestone XO-1 fork was so susceptible to brake chatter.  It used light fork blades with an imperial cross section and canti brakes.

A good but ugly fork blade for cantis would be ovalized at the fork crown (for tire clearance), round at the brake studs (for lateral stiffness) and start tapering below that point.  I haven't seen anything like this used in practice.

alex

[Ken Freeman]

Wow, Alex, that's a lot of section changes!

--

You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

[Mike Schiller]

Alex, yes, I didn't think it added much stiffness.  I  think the Mini Campee is a a little stiffer when it is attached directly to the blades lower down when mid fork braze-ons are there. 

I've never heard of any issues using the Kaisei Graqnd Bois blades so far. I know a few well known builders are using them with cantilevers so they must be stiff enough in the upper section to mitigate any serious issues.  I'm planning on using those on a new custom I'm having built with cantilevers because of compatibility with off-the-shelf racks.

~mike

Carlsbad Ca.

 

[John Clay]

Has anyone actually measured the deflection of the components involved; blade rotation, arms and post deflection? Given the relatively high section modulus of the steel blades compared to the much smaller section modulus of the long, aluminum brake arms, and the difference in the Young's Moduli between the two materials, the arms would be my prime deflection suspect. The relatively skinny brake posts would also merit a glance.

If blade deflection IS relevant then the anti-torque advantage goes to the continental blades as opposed to imperial, since the former has a larger section modulus (or polar moment, whichever piece of the equation you want to use).

I have a pair of RAIDS that I'm saving for a future project, and I like their compact form as compared to cantis, but if the Racers I've been using for a few years are any indication I don't see them as providing extraordinary braking performance; the no-name cantis on my beater bike provide noticeably more power.

Just my perspective on things.

[Ken Freeman]

I can appreciate your approach to analysis of this set of deformable bodies.  But after I felt give in my rear brake lever, I checked things, and checked my seat stays with a straightedge.  It laid true on my seat stay when the brake was not activated, and showed a definite bow with a hard lever squeeze.  Brakes are Paul cantis, so caliper flex was hard to see.  There was certainly some cable compression.  So in my hand I felt pad compression, cable flex and seat stay flex.  But with the straightedge, I saw seat stay flex.

I think it would be different if I had a much bigger brake with longer arms that are inherently  more flexible.  I'd probably see less seat stay flex, but the principle is the same.  Lateral force is applied to the frame member and there is a tendency for it to flex.  Whether the deflection is visible or easily detected is another matter.

--
You received this message because you are subscribed to the Google Groups "650b" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 650b+uns...@googlegroups.com.
To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

[Hal Bielstein]

What dia were the seat stays? 

Sent from Hal's iPad

[Ken Freeman]

13.5 mm including powder coat.

[Ken Freeman]

But one doesn't usually ask a rear wheel to develop a lot of brake torque.  I nearly always depend on the front brake for stopping power.

[John Clay]

Seat stays will definitely deform to a noticable degree. They're long, slender and kind of noodle like.

[John Clay]

Cantis, at least the ones I have or can remember, are shorter and have a larger section modulus than side or centerpulls and would provide more resistance to flexion. While I'd rather not have a squishy rear brake I don't ask much of them. The cantis on my beater are perhaps 2x the optimum distance from the forks (refitted with 559s but fork originally made to fit 622s). They arent squishey so fork deflection would appear to be a very minor term. Seat stay deflection would be far greater.

As to the brakes rhemselves, the most powerful rim brakes I've ever used (my perception, not at all quantified and quite a few years ago) were V-brakes, their advantage being drastically reduced losses to cable friction but the aesthetics (poor) are too much for me.

[Matthew J]

My 650B had braze on Raids.  They stopped the hell out of the bike.

[Matthew J]

> As to the brakes rhemselves, the most powerful rim brakes I've ever used (my perception, not at all quantified and quite a few years ago) were V-brakes, their 

> advantage being drastically reduced losses to cable friction but the aesthetics (poor) are too much for me.

Have had good luck with Vs as well.  Aesthetics are subjective, but I find the new Paul Min-Vs very good looking.

[Jan Heine]

At 6:03 PM -0800 12/21/13, John Clay wrote:
>Has anyone actually measured the deflection of the components
>involved; blade rotation, arms and post deflection? Given the
>relatively high section modulus of the steel blades compared to the
>much smaller section modulus of the long, aluminum brake arms, and
>the difference in the Young's Moduli between the two materials, the
>arms would be my prime deflection suspect. The relatively skinny
>brake posts would also merit a glance.

On a centerpull brake, the brake arms below the pivots are very
short. They also are solid aluminum. I doubt they deflect much. The
posts also are very massive and short.

The long brake arms above the pivot are stressed only in one
direction, and their section is quite large in that direction, so
they don't flex significantly, either. That is the reason why
centerpull brakes are so much lighter than sidepulls - sidepulls have
the entire arms stressed in torsion, and thus need to be a lot
beefier.

[Ken Freeman]

I agree with your expectation for the upper arms of CP brakes, but only if the yoke and cable are in the plane of the the brake caliper arm rotation - i.e, perpendicular to the pivot axes.  If that condition is not met, there will be a lateral component to the tension on the caliper upper arm, and it could flex out of the plane of the intended rotation.

That's the principle, but will it be a noticeable effect?  In my experience with Mafac Racers, it's minuscule compared to the pad compression, even with Kool-Stops.  Raids have longer arms, however, and I have not owned a set.  It might be a lot more noticable with a long-arm brake.

On Sun, Dec 22, 2013 at 9:36 AM, Jan Heine <hei...@earthlink.net> wrote:

At 6:03 PM -0800 12/21/13, John Clay wrote:

Has anyone actually measured the deflection of the components involved; blade rotation, arms and post deflection? Given the relatively high section modulus of the steel blades compared to the much smaller section modulus of the long, aluminum brake arms, and the difference in the Young's Moduli between the two materials, the arms would be my prime deflection suspect. The relatively skinny brake posts would also merit a glance.

On a centerpull brake, the brake arms below the pivots are very short. They also are solid aluminum. I doubt they deflect much. The posts also are very massive and short.

The long brake arms above the pivot are stressed only in one direction, and their section is quite large in that direction, so they don't flex significantly, either. That is the reason why centerpull brakes are so much lighter than sidepulls - sidepulls have the entire arms stressed in torsion, and thus need to be a lot beefier.

Jan Heine
Editor
Bicycle Quarterly
2116 Western Ave.
Seattle WA 98121
http://www.bikequarterly.com

Follow our blog at http://janheine.wordpress.com/

--

You received this message because you are subscribed to the Google Groups "650b" group.

To unsubscribe from this group and stop receiving emails from it, send an email to 650b+unsubscribe@googlegroups.com.

To post to this group, send email to 65...@googlegroups.com.
Visit this group at http://groups.google.com/group/650b.
For more options, visit https://groups.google.com/groups/opt_out.

[John Clay]

I like to correct some comments I made wrt this thread and general subject:

I indicated my not being all that impressed with the performance of my Mafac Racer brakes. I was wrong. Trying to isolate and judge the stopping performance of a brake on a fixed gear bicycle is a poor approach. That occurred to me after my comment. I installed a freewheel for a little while and made a few test stops. With nothing special pads ( afaik) and no particular attention to straddle cable geometry they stop very strongly with excellent modulation. I couldn't evaluate that well while my legs were locked to the drivetrain. Duh. My beater (at sis-in-law-in-SF) has front cantis that are quite strong too but i dont recall the modulation being as nice, lightly grabby actually.

I remembered, incorrectly, that the Racer brake arch was very small in diameter where it flows into the pad mounting area; that struck me as a structurally sub-optimal design detail, hence my comment wrt arch flex; which is likely the reason the smart folks at Mafac didn't do it. Some weeks after my "brilliant" observation I took another look and went away wondering only what the heck I was thinking, or drinking.

Canti induced blade flex. It was clear to me that the SS could flex noticeably due to the large post distance but the fork blades? Well, lets just say that I was skeptical of meaningful flex; but I'm guessing there is more to it than I previously thought. And to whatever degree the blades flex with cantis, the power to do that comes from your hands and must contribute to fatigue. It may be a high order term, and a lot of bicycles stop well with cantis, but I'd imagine there is more merit to the idea than I first thought....oh, and short, fat posts aren't going to flex much themselves.

Summary: The Racers are great, I'm sure the RAIDS are too and why build a frame/choose components that make unnecessary compromises if you don't have too?

John Clay,
Tallahassee, FL

[Brad]

I would like to see a vector diagram of how any brake twists.  My thought is that most of the twisting happens in the bushings, not in the arms or the mounts. 

My experience, Mafac Racers work and can be adjusted to pretty much any rim in the general area of their reach.
Weinmann/Diacompe 610 and 750 work, but, for me, not as well as Mafacs.
Mafac Raids work where Racers are not long enough.

[Alex Wetmore]

Cantilever brakes cause the fork blades and seatstays to twist.  It is very noticeable on a bicycle with small diameter seatstays and you can see it happening with a hard application of brakes.  When cantilever brakes were commonly used on mountain bikes there were a lot of aftermarket bridges for sale (Salsa had a popular one) that resisted that twisting and added a lot of braking power at the expense of weight.

Centerpull brakes have the mounting bosses very close to the fork crown and seatstay bridge, and that makes for a much shorter span of tubing that can twist.

alex​

---

From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Brad <riendeau...@gmail.com>
Sent: Saturday, June 21, 2014 12:51 PM
To: 65...@googlegroups.com
Cc: hei...@earthlink.net; ror...@gmail.com
Subject: Re: [650B] best brakes for a 650B rando?

 

For more options, visit https://groups.google.com/d/optout.

[Ken Freeman]

Apologies, I just cross-posted to iBob by mistake.

---------- Forwarded message ----------
From: Ken Freeman <kenfre...@gmail.com>
Date: Sat, Jun 21, 2014 at 10:59 PM
Subject: Re: [650B] best brakes for a 650B rando?

To: Brad <riendeau...@gmail.com>, internet-bob <intern...@googlegroups.com>

Bradford, I won't draw it but consider:  A canti brake is on a pivot, and is located about 3 cm away from the seat stay or fork blade.  This distance is a moment arm.  When the brake shoe is pressed against the rim, that shoe force appears at the canti pivot, and it acts to move the pivot away from the rim.  Due to the moment arm this outward force tends to twist the seat stay or fork blade.  Fork blades likely flex a lot more than seat stays, so I'd expect to see twist effects more on rear brakes than on front brakes.

Another thing that can happen is that the seat stays move sideways at the points where the pivots are brazed to the seat tube, especially if the pivots are a few cm away from the brake bridge.  This widening of the seat stays can be measured on my OX-Plat frame with canti brakes.

For more options, visit https://groups.google.com/d/optout.

--
Ken Freeman
Ann Arbor, MI USA

[Ken Freeman]

Another source of twist is that as the caliper squeezes the moving rim, the rim exerts drag force on the shoes, trying to pull them along with it.  This also tends to pull on the caliper, post, and ultimately the seat stay or fork blade.  Since the post is closer to the axle than the brake track, it tends to twist the end of the canti post so it wants to move toward the axle.    

On Sat, Jun 21, 2014 at 3:51 PM, Brad <riendeau...@gmail.com> wrote:

For more options, visit https://groups.google.com/d/optout.

[Harold Bielstein]

But if your brakes are adjusted correctly and they both apply equal pressure on the rim, wouldn’t you only notice fork movement in a for and aft direction as compared to a “twist” of the fork blade? Or is that what you’re trying to say?

Hal Bielstein
hkbie...@rap.midco.net

[Ken Freeman]

For what I'm talking about, each front brake shoe tends to make its fork blade twist relative to the fork crown, and in opposite directions.  It would not cause a bias to the steering.  Similarly each rear fork blade tends to create a twist of its seat stay.

[Ken Freeman]

"Fork blades likely flex a lot more than seat stays, so I'd expect to see twist effects more on rear brakes than on front brakes."

I said this wrong, it should have said that fork blades are likely stiffer than seat stays, due to their much greater outer  diameter.  

Sorry!

On Sat, Jun 21, 2014 at 10:59 PM, Ken Freeman <kenfre...@gmail.com> wrote:

Bradford, I won't draw it but consider:  A canti brake is on a pivot, and is located about 3 cm away from the seat stay or fork blade.  This distance is a moment arm.  When the brake shoe is pressed against the rim, that shoe force appears at the canti pivot, and it acts to move the pivot away from the rim.  Due to the moment arm this outward force tends to twist the seat stay or fork blade.  Fork blades likely flex a lot more than seat stays, so I'd expect to see twist effects more on rear brakes than on front brakes.

Another thing that can happen is that the seat stays move sideways at the points where the pivots are brazed to the seat tube, especially if the pivots are a few cm away from the brake bridge.  This widening of the seat stays can be measured on my OX-Plat frame with canti brakes.

On Sat, Jun 21, 2014 at 3:51 PM, Brad <riendeau...@gmail.com> wrote:

For more options, visit https://groups.google.com/d/optout.

--
Ken Freeman
Ann Arbor, MI USA

[Steve Chan]

   I don't have it any more, but my old trek 720 had slim, flexible seat stays and if I applied the brakes with lots of force, it was obvious that the stays were bowing outwards due to leverage from the cantis.

   Steve

[Brad]

Has anyone experienced stay or fork blade deflection with center mounted center pull brakes?
This may be one of those things where evolution was for a reason and we are re doing the evolutionary process.

[Ken Freeman]

Exactly what my Terraferma does.  I haven't observed much twist, though physics says the forces line up to create twist.