Tire pressure (Page 2)

Maybe 100-105?

To the OP, you said you use HED wheels?  Do you use one with a wider brake track (aka the C2 rim design)?  If so they're meant to be run at lower pressure to begin with.  I use Jet C2's with 23mm tires on my race wheels, and Velocity A23's with 23mm's for training (same basic concept) and at 202lbs I'm running 85psi in mine.  I'll try to find the Continental data that showed lower pressure offering better rolling resistance. 

As for tubulars, the big benefit is being able to run even lower pressure without risking a pinch flat.  I can't remember the exact number that Tom Boonen was using at Roubaix, but I believe it was under 60psi. 

Very, very few people should be running MAX psi.

low pressure by a lighter rider in the Paris-Rubaix is understandable.  85psi for a 200 pounder is not a wise choice (I assume you aren't riding cobblestones).

Are you calling Tom Boonen a lightweight rider?

85psi on 23mm rims is a fine choice, call HED and ask for their recommendation if you don't believe me.

ETA: In your view what is the downside of running lower pressures?

I just did this. I'm 165 lbs and had a 50/50 distribution with 96 lbs on each 23mm tire. By the chart, I should have about 100 psi in each tire. I test drove several hard tail and soft tail mountain bikes earlier this year and saw much better power transfer in the hard tail because there was way less shock (energy) absorption.

1) Would the same hard tail power transfer also apply to tri and road bikes? With a 50/50 split in weight distribution, should I run the back tire a little harder?

2) Is anyone's efficiency perfect enough that the back wheel does not experience surges most of the time, especially in races?

3) Should I go by the chart and work to achieve pedaling perfection in all situations?

Mountain bike had parasitic loss of pedal power to the shock, especially if it didn't have a lock out. 

A tire doesn't have the same issue - your weight compresses it and your pedal power rotates it (unless you're bouncing like a lunatic).

The idea of being softer is to allow the tire to deform and roll over the million small imperfections in the surface rather than bouncing backwards against it (and thus slowing you down).

As mentioned, if your surface was glass smooth you would go with as high a psi as possible. In the real world you go low but not so low than you risk pinch flats.

DanielG - 2012-07-12 7:48 AM This is used as a general rule for pressure no matter what's printed on the side of the tire.

Woah, woah, woah, woah, woah......so, at 150 lbs I should be running about 75 PSI on my 700x23?

LSUfan4444 - 2012-07-13 11:11 AM

DanielG - 2012-07-12 7:48 AM This is used as a general rule for pressure no matter what's printed on the side of the tire.

 

 

Woah, woah, woah, woah, woah......so, at 150 lbs I should be running about 75 PSI on my 700x23?

  

I think you are reading the wrong line.  More like 105 or so.

I was...but I just looked and see he is 180lbs, so I take that back.

85 is a fine choice for comfort, you are right.  I was discussing pressure from the standpoint of optimized rolling resistance.  The only downside, is rolling slightly slower in a race situation.

FWIW, rolling resistance is hurt more by exceeding the optimal pressure than it is by inflating less than optimum.  (which you may know).

Damn - dislexia strikes again....much better when I read the right line

GatorDeb - 2012-07-13 2:40 PM I won't be riding before the race   So I guess 120 it is for the race?  That's ALL I've ever ridden.

Go down to at least 110.  And 100 would not be very 'risky' as something new on race day.   There is no reason for you to be riding at 120, so don't do it.

Deb, going with a lower tire pressure within the reasonable range is NOT something I'd classify as a risk on race day at all.  In fact, if it were raining on race day I'd say you are at a risk running 120psi.

You've seen the chart on tire pressure based on tire size and rider weight. 

There are a couple of other well known pressure adjustments:

- If it's raining 5psi less in each tire for better traction

- If you have an aero position on a TT bike, even pressure in both tires, but if you have a road bike or an upright position on your tri bike then 5psi more in the rear tire than the front.

You never mentioned which model of gatorskins you have?  Are they 23 or 25mm wide?  I'm going to assume 700x23mm.  I will also assume you have a tri bike with aerobars and fairly optimized aero position (so weight on the front tire is close to the weight on the rear).

So I recommend 95psi for both tires if dry and 90psi if wet.

If roads are very rough, something like chip seal pavement then only go to 90psi even if dry out.

If the roads are extremely fresh, nearly glass smooth asphalt and dry then go 100psi.