Road Cycling - tire pressure and cornering

Latley I've really been pushing it fast going into corners and at rated tire pressure it just dosen't feel stable at the middle of the corner causing me to back off(I don't like to back off!). I have two road bikes; one has carbon comp elite rated at 125# and the other pro race @ 100#. I've noticed that if I keep them each at 90# that when going into very tight corners really fast that the tires have a more connected feel to the road. Am I doing something wrong here? The front tire is the one that seems to not feel "right" on each bike at the rated pressure. I only weigh 135#. Is this ok to set them at 90#? at 90# it seems like I can plow through any corner and lay her over as much as I want and I'm ok with the feel of things. Starting to think that tire pressure rating might be advertising hype.......?

I would think so- I asssume the high psi is for heavier riders to inflate and still keep the small contact patch. Lighter rider you can choose lower psi. Heavier you risk snakebite, large contact patch> increased resistance.
If YOU still feel in control, it's fine.
Also it's either between 2 psi values OR up to a certain psi.
Mtbers often alter psi to deal with different conditions.

Just as Jeff said, bicycle tires are duly dependant on rider weight, not what the max rated sidewall psi is; and to make things worst, no 2 tire models are the same! So you have to experiment with the air pressure to get the handling down. Sometimes, especially on rough surfaced roads, the next size up tire will actually be a faster tire. If your riding on city streets and commute you would be safer anyway going to the next size up tire; the wider tire will last longer, handle better, prevent (most of the time) the tire from dropping into grooves or ridges, and stop faster.

Yeah, tire pressure is highly dependent on rider weight, at 135 lbs you aren't deforming the bottom of the tire to meet the road surface nearly as much as I am at (shall we say) slightly more weight.

The listed pressure is more a matter of marketing/estimated maximum/reasonable guess. There's no reason to think that the best tire pressure would be the same for you at 135 lbs as it is for someone over 200 lbs. Play with it, see what works.

Just as Jeff said, bicycle tires are duly dependant on rider weight, not what the max rated sidewall psi is; and to make things worst, no 2 tire models are the same! So you have to experiment with the air pressure to get the handling down. Sometimes, especially on rough surfaced roads, the next size up tire will actually be a faster tire. If your riding on city streets and commute you would be safer anyway going to the next size up tire; the wider tire will last longer, handle better, prevent (most of the time) the tire from dropping into grooves or ridges, and stop faster.

As it has been said, your weight plays a large part of how your tire will handle, and because you put it on your front tire, less than 40% of your 135 pounds are on the front tire.

I think most people think that the narrower the tire, the faster it is. This may not always be true. A narrower tire might be faster on a straight line, it very likely will not handle as well. :rolleyes:

Most quality tires can handle a little overloading. In my roadracing days, we would routinely run our tires about 10 psi higher than the recommended rate. (I weigh 160 lbs)

If you're not comfortable with that I would suggest at least maxing them out to their recommended max psi.

I use Panaracer Stradius - rated to 150 psi - and I always fill them to 155.

Latley I've really been pushing it fast going into corners and at rated tire pressure it just dosen't feel stable at the middle of the corner causing me to back off(I don't like to back off!). I have two road bikes; one has carbon comp elite rated at 125# and the other pro race @ 100#. I've noticed that if I keep them each at 90# that when going into very tight corners really fast that the tires have a more connected feel to the road. Am I doing something wrong here? The front tire is the one that seems to not feel "right" on each bike at the rated pressure. I only weigh 135#. Is this ok to set them at 90#? at 90# it seems like I can plow through any corner and lay her over as much as I want and I'm ok with the feel of things. Starting to think that tire pressure rating might be advertising hype.......?

The pressure listed on most sidewalls is the maximum rated pressure, not a recommended pressure. Michelin is an exception....on their Pro Race, they show a range, 87-116 psi (6-8 bar). This sidewall advice makes a lot more sense to me than just the max rating.

IMO, unless you're over 250 lbs on 23 cm tires, running max pressure isn't a good idea as it results in a harsher ride, more cuts/puncture flats, and poor road grip. You even get more rolling resistance on most surfaces with max pressure, not less.

I'm 170 lbs, and like 95 front, 100 rear. At your weight, 90# sounds right.

'You even get more rolling resistance on most surfaces with max pressure, not less.'

Harry- can't get my brain started today- please elaborate, I'm not saying I disagree- can't figure how you arrive @ this conclusion.

'You even get more rolling resistance on most surfaces with max pressure, not less.'

Harry- can't get my brain started today- please elaborate, I not saying I disagree- can't figure how you arrive @ this conclusion.

A major advantage to rolling resistance is ability to absorb shock. If the tires are too inflated and too hard, the little bumps and knicks you hit on the road will hurt your rolling resistance.

Depends on the road surface and about fourteen million other factors.

Remember that in the human mind, more is better. :D

Pump those suckers up to 400lbs and blow by Lance. :eek:

That rating is the MAXIMUM rated pressure. Not the optimum workng pressure. The optimum pressure will be somewhere below the max rating, not above it. This takes into account rolling resistance and cornering.

Remember that in the human mind, more is better. :D

Pump those suckers up to 400lbs and blow by Lance. :eek:

That rating is the MAXIMUM rated pressure. Not the optimum workng pressure. The optimum pressure will be somewhere below the max rating, not above it. This takes into account rolling resistance and cornering.

your loosing me here, on these tires it says (Rec Pressure 125 ) and below that it says ..... (Max Pressure 125) does not "Rec" mean recommended? so I just assumed that the recommended pressure was the max pressure? eh?? or what? either way 90 lbs seems to be my number.

Cleveland,

Have you TRIED running them at max pressure to see how they feel?

harry & brillig, Don't agree with your comments.

"A major advantage to rolling resistance is ability to absorb shock. If the tires are too inflated and too hard, the little bumps and knicks you hit on the road will hurt your rolling resistance."

With a lower-inflated tire, you still hit the bumps and nicks on a rough surface. A bike will be slowed as the tire deflects and deforms in an attempt to absorb the shock. A lower psi will result in a softer tire, which will deflect and deform more easily. A more consistent contact area will contribute to reduced rolling resistance.

Sure harder tires make for a harsher ride, but ClevelandGuy wants to go fast, and a little harsher ride comes with the territory. And depending on the frame material and geometry, there may not be a noticable differerence in ride.

And tread compounds are another variable that should be considered. Many tires have a variety of hard/soft compounds on different areas of the tire. The tires I mentioned are shown here http://www.panaracer.com/05lineup/road/eroad_cl.html#pro
The Hutch carbon comp elite's also use a silica blend on the tread. They kick a$$ in corners.

Cleveland, in addition to trying various tire pressures, maybe you could experiment with your cornering technique to see if some small adjustments can also make a difference for you?

as always, MHO

"A major advantage to rolling resistance is ability to absorb shock. If the tires are too inflated and too hard, the little bumps and knicks you hit on the road will hurt your rolling resistance."

With a lower-inflated tire, you still hit the bumps and nicks on a rough surface. A bike will be slowed as the tire deflects and deforms in an attempt to absorb the shock. A lower psi will result in a softer tire, which will deflect and deform more easily. A more consistent contact area will contribute to reduced rolling resistance.


The two forces don't even out.

Tests have shown that the fastest descending bike on on perfect [edit: sorry, that's supposed to say imperfect] surfaces is one with suspension.

Lennard Zinn in a recent Velonews column:

Dear Langley,
It entirely depends on the road surface. If it is chip sealed and you ride with a 19mm tire at 140psi, there is no question that you will have higher rolling resistance than with a 23mm pumped to 90psi (assuming that both are high quality high-thread-count tires). Every time you deflect the bike and rider up and back, it costs you energy, as opposed to absorbing the gravel hunks into your tire. This is the same reason that suspension makes a mountain bike, car or motorcycle faster on rough terrain. If you are riding on a smooth track, by all means use a 19mm tire and pump it up to super-high pressure.
Lennard

There's plent more if you'd like. Not saying I'm definitely right, just that I'm basing it on a lot of sources not just my own conclusions.

http://www.fitwerx.com/NewFiles/BicycleRollingResistance.html

"Conclusion: More vertically compliant frames (especially suspended frames), wheels and components have lower rolling resistance than less vertically compliant frames, wheels and components."

I read something similar. The suspension allows the bike to deflect under less load, which reduces the energy (speed) loss. But I'm not sure that shifting the deflection into a softly inflated tire (vs the suspension) would yield the same results.

I still go by what my years of road biking experience has been, which is, harder is faster. But I'll admit that my bias toward choosing smooth roads (like most roadies I know) may have a lot to do with my experience.

all that stuff is fine and dandy.
wanna go fast in the corners and feel like you are
on a rail? buy tubulars.
Don't want to buy new rims?
buy Tufo Tubular clinchers.
review at PEZcycling news (http://www.pezcyclingnews.com/?pg=fullstory&id=1294)

Marty

It's also true that what is fastest for going in a straight line may be different for what works in a turn. The original poster was talking about not feeling stable in turns and having to back off.

Maximum straight-line speed may come with maximum pressure, but maximum control is going to be at less pressure.

It's also true that what is fastest for going in a straight line may be different for what works in a turn.

Ahhh. The truth has been spoken. OR typed.

Y'know, after reading CG's original post, I'm wondering - what was I thinking - he's already tried maxing them out - duh. Whatever - it was interesting to do some research on rolling resistance.

But I *do* love the feel of an overpumped tire =-)