Rambouillet/etc owners fat tire advice

[JL]

Hello all,

I might just be the kind of person that finds a happy mid zone in the 700x28c tire as I can't seem to enjoy riding my rambouillet with anything larger.  I do like supple, large volume, tires.  I ride big plush 650b tires or round 559 slicks on other bikes.  On the Ram a 32mm or larger tire feels too bouncy/springy.  I looked into information about tire pressure but it was confusing.  Jan Heine's chart about 15% deformation and load distribution claims that at my weight (175lbs with the bike) I should ride pressures in the 30s for 32mm tires - that seems very low.

Right now I ride various 28mm tires at about 80psi front and 90psi rear.

What setup (psi tires etc) are people enjoying on their 700c road bikes (in riv terms that is: RS, LL, Ram, Rom, Leg, AHH, Rodeo, Customs)?

Is personal size as much of an issue and I am expecting it to be?  I am 5'8" and 150lbs if I round up.  I expect that tire sizes would feel different for someone who is 6'3" and proportionally heavier. 

Why change my setup if it isn't broken?  Just to try new options and experiment with bike fit.

Thanks
JL

[Steve Palincsar]

On Thu, 2012-06-07 at 16:09 -0700, JL wrote:
> Jan Heine's chart about 15% deformation and load distribution claims
> that at my weight (175lbs with the bike) I should ride pressures in
> the 30s for 32mm tires - that seems very low.
>

I think you're reading that chart wrong. I'm guessing 60 rear, 50 front
would be about right, based on my reading of the chart. How'd you come
up with 30? That would be < 50 lb per wheel.
http://www.bikequarterly.com/images/TireDrop.pdf

[pb]

Hmmn, I'm baffled by your comments.  I'm 6'1", 200, and I have 33's on my Ram.  I drank deeply of the Kool Aid, and tried them at low pressure, hated it, the bike felt like a slug, and I promptly notched 'em up, five pounds at a time, until I got to 90, where the bike came back to life for me.  (I know, it's all in my mind, and they're actually running vastly slower than they would if I kept them at, say, 65.  That's OK -- I can use the handicap.)  

 

Even as high-pressure-oriented as I am, at your weight and pressures I don't know how a 32 could be feeling "bouncy".     

 

 ~Peter

[reynoldslugs]

I'm with Peter.

I weigh 205 lbs, my Rambouillet rides on Kojaks (which measure 32 mm)
pumped up to60 front, 80 to 85 rear. Comfy front, zippy rear, it's
groovy.

Max

[J L]

Thanks for pointing that out Steve.  I re-computed my math and I get similar numbers too you.  I was estimating the weight distribution different and rounding down my estimate in that space between 30 and 50 psi. 

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[J L]

A point of clarification on my original post.  I have tried riding 32mm tires on my ram at the same psi I use on 28mm tires (80/90 f/r) - too bouncy.  I lowered the psi to around 75 front and 80 rear - still too bouncy.  Then I read the chart but was having a difficult time imagining just how low to go on it.  My initial estimates put me around 38-40psi front and 50psi rear.  I thought that was odd and thought I should bring the issue to this pannel of experts :)  I have yet to try 32mm tires on psi lower than 75 and wonder where everyone rides.  Is there another thing that stops that bouncy feeling?  (not cushion-y, bouncy-y)

Thanks
JL

[David Faller]

I ride a Ram with Jack Brown (greens). Ram and I, with all our gear,
come in around 188, so that puts me in at 48 F and 60 R. I use 50 and
60. No bounce, no squish and I love these tires. I had Ruffy Tuffys
(28 mm for those aren't familiar) and ran them at the chart-recommended
pressures. They're great tires, too, but the Jacks are SO much more
comfy. No downside to the 33.3 mm tires. None. They are great in
every domain, with increased comfort over the RTs.

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[Jay in Tel Aviv]

I try to keep my 32-622 Supremes at 60 psi in front and 80 rear.
With my 170 lbs and ~ 10 lbs of gear the ride gets sluggish when I
start to lose pressure.
More that that feels harsh.

Jay

[Cyclofiend]

Late to the party with a couple of thoughts -

First, when the Rambouillet was designed, 28's were pretty much the
upper end of the scale. I remember putting a pair of (Speedblend!)
Rolly Polly's on a bicycle which had never seen anything large than
23's and thinking - "Whoa! Those are some beefy tires!" My point
being - arguably, and probably much more subtly than I can feel - that
the design of the Rambouillet optimizes performance with tires that
size (28). Now - there are waaaay too many variables to make that
point anything other than a sidebar. How you ride, where you ride,
the pressures you run and alla that there stuff is going to make it
perform in a way you like or dislike. That's what you have to trust.
Dropping to BQ guidelines just because it says so is the other end of
the scale to what we used to do - each tire to max pressure plus a bit
for every ride.

Secondly, since my past habits were just that (max pressure +5-10) I
probably have a tendency to run higher pressures for my weight. Plus,
where I ride, the topography tends to have a fair number of sharp-
edged rocks embedded in the trail (and I dislike pinch flats). So,
the Hilsen with JB's tends to be reset to the 85# range. But, I'll
also let it settle down as low as 50/60 if I'm doing more road miles.
I've run them as low as 25, which is (IMO) dangerous, but was
instructive.

http://ramblings.cyclofiend.com/?p=208

- Jim / cyclofiend.com

[charlie]

Back when I weight 168 pounds I could ride 23mm tires at 70 psi on
smooth asphalt..... these days ( 92 pounds heavier) I ride a 35mm at
80 psi and a 38mm at 70psi. 32's require 90+psi and are annoyingly
buzzy (for me) on local chip seal roads.....so I went to the 35's at
80 psi which is my personal lower limit. I think lighter riders can
get away with more and also less pressure. Lets face it, high pressure
narrow tires are faster on smooth surfaces and light riders can ride
them more comfortably and safely than the rest of us. At your weight a
28mm tire is fine at whatever pressure the tire performs best at on
the surfaces you ride on.

[Michael Hechmer]

I'm pretty much  in complete agreement with Jim about the Ram and tire size.  When I bought mine (2005?) the Riv fliers boasted about using 35mm tires for trail riding. But if you add fenders the bike won't handle a true 35.  It is really designed around 28mm tires and road riding.  My two favorites on this bike have been the Ruffy Tuffy and now the Grand Bois Cerf, Green.  With those tires the bike is an absolute joy on decent pavement or good dirt roads.  I'm 200 lbs and ride mine at 80 & 90.  When I know I will be doing lots of gravel roads or urban debris I ride my Ebisu, which is very similar to an AHH with Jack Browns, at 70/80.  Yup, there's a trade off in performance but they feel really nice going over rough ground and offer excellent flat protection.  

BTW, in the course of my cycling life, 35+ years I've had almost as many pinch flats as puncture flats.  Riding two low a pressure over broken pavement or rough gravel, may add to comfort but doesn't feel good when your standing around in the middle of a dark rain storm changing a tube.

I love BQ, and have great respect for Jan Heine, but I'm not riding long brevets and don't need to obsess over a few pounds of tire pressure any more than a few grams crank weight.

On the tandem, we head out with a bike and rider weight of 400+ lbs on Marathon racers 26x1.6 at 70/80.  Mostly on dirt roads and a very sweet ride.

Michael

[Bill M.]

My Road Standard currently wears nominal 32 mm Vittoria Randonneur Hypers.  On Velocity A23 rims they measure a good 34 mm wide.  They shouldn't fit under short reach brakes, but they do.  I weigh about 180, and don't carry significant loads on that bike.  I can run as low as 60 front, 70 rear which is  what I used yesterday and today.  Lower than that starts to feel too squishy and vague.  Optimum for me might be 65/75.

The bike does handle a bit better with 28's, and after the next bike shuffle it will wind up going back to 28 mm Rubino's.

Bill

On Thursday, June 7, 2012 4:09:18 PM UTC-7, JL wrote: