Hi my pump only goes to 100psi. I was wondering if there are disadvantages of riding 10-20 psi lower than max psi. Or is this perfectly ok. Thanks

Yes, it's perfectly okay. That's the maximum, not the optimal, pressure. And it's not necessarily the maximum, just the maximum their legal department is comfortable with.

(And are you sure that your pump only goes to 100, or that the gauge only goes to 100? )

Go here and read this: https://www.bikeforums.net/showthread...=tire+pressure

Decide on your optimum pressure according to your weight, surface and tyre size. Maximum suggested pressure is nearly irrelevant. There's a chart linked here along with other tips and video flat fix instructions.

Not to hijack or divert us from the roadie theme in the 41, but is there a formula for 26" tire pressure?

Hmm I know the gauge goes to 100, but the box advertised 100psi. I'm not quite sure if it goes over that, well according to psmimet's equation 100 psi should be more than enough for me. Thanks for the help everyone

Your correct tire pressure depends on your weight and the tire size: https://www.michelinbicycletire.com/m...rpressure.view
Do not use the max pressure printed on bicycle tires; just like you should not use the maximum pressure that is printed on car tires.

For mountain bike tires, you also need to factor in your terrain and tire style. I've been using 40-50 psi for smoother trails; 35-40 psi for more technical trails. Here are Michelin's recommendations: https://www.michelinbicycletire.com/m...essuremtb.view

Hmmm. I have been running my Forte Versa-Tracs at max pressure (26x2.0, 65 psi) for a few years now with no ill effects. I am also 185-190 lbs and ride mainly on the road and soft trails. I guess my question should have been am I asking for trouble by running at max psi for my weight?

I always run my tires somewhere between 90 and 100 psi, and I see from psimet's calculations I should have my tires at about 95 psi.

Continuing with the hijack..

Would it matter whether the bike has suspension or not? That is, is it still an improvement to run lower pressure if a full-suspenion rig absorbs the big hits that would otherwise cause pinch flats (or burp tubeless tires)? Or is it more about finding better traction?

According to the chart, I should only be running 100psi in my 23s, but that feels a bit soft to me; it seems like a minimum.

What possible disadvantage do I face by running 120psi other than a harsher ride? Surely the lower rolling resistance is worth it...?

Depends on your road conditions. On a rough road, a higher pressure can cause your bike to bounce around a lot; worsening your rolling resistance and reducing grip in the corners.

i run all my tires at 120 psi, even if it says 110 is max, but im a heavier guy...

So is there any scientific basis for this bogus formula, or is it just like those "fit" calculations.

and make you slower...

I was helping an Italian tour guide (and amateur racer) fix a flat in Italy ( I provided the pump, first time he saw a Road Morph)
and he started talking about goofy Americans and their love of high pressure. You want just enough, any more and you start making new problems for yourself.

MAX PSI for me.. I rode 15923 miles on Max PSI.

Who else rode 15923 miles last year period?

I ride 100 psi on 700X23 clinchers and have not had a pinch flat. I check tire pressure before each ride and do not try to jump anything.

Not even in my car.... I do use max on my rear tire, but since I have a bad wrist, I use 95 in the front. Seems to help.

My last two rides has been a sorta revelation to me. I am 215Ibs, ride a carbon Lemond, 23mm tires that are always inflated to 120psi front and back. My typical ride is about 60miles. I am currently "experimenting" with tire pressures. My last two rides had my front tire at 100psi and my rear at 110psi, and I could not believe how much better I felt after the rides.

I am sorta worried about pinch-flatting(especially at my weight), but the lower pressure and resulting comfort is making a believer out of me.

I pump up my tires till the pressure equalizes with the air in my head...that said, the chart is interesting as it shows why I can't stand 100psi pressures in anything that rolls (lightweight)

Actually, yes, there's a basis for it (and since I don't remember it exactly, I'll be paraphrasing) --

Using a higher pressure in back is a no-brainer since the rear tire carries more weight, but I don't think that's what you're talking about. How he arrived at determining pressures by size and rider weight was to ensure that the tire deforms a certain amount. Like I said, I can't remember for sure, but it's something to do with getting a good shape to the contact patch, maximizing the contact of the center of the tire on the ground, while neither overinflating and losing grip nor underinflating and allowing pinch flats.

I've been experimenting with pressures on my road bike, and that formula works out just right for me. If I inflate to a higher pressure, the ride gets harsh and the handling gets more skittish. At lower pressures, the ride is more compliant, but sharp bumps seem to hit harder (just not enough air support to prevent bottoming out the tire), handling is a bit squidgy, and I feel like I have to work harder to maintain my usual speed. Using pressures as recommended in that chart gets me a good balance of ride quality, handling, and efficiency.

I've ridden over 125,000 km in the past several years ... all with my tires below max psi.

All this proves, if true, is that you rode 15923 miles last year. Plenty of people -- especially randonneurs -- ride that kind of distance and more.

It doesn't mean you know anything about optimum tire pressure ... if you did, you'd understand that the pressure you prefer has no relevance for other riders. Also, if you ride a single tire pressure, I guess that means you ride on the same roads at all times.

I'm glad this thread popped up with the link to Psimet's recommended calculations. I complained earlier on here about my cheapo tire (came with the bike) that says "inflate to 100 psi" feeling like it was about to flat. People assured me that no tire should feel like that at 100 psi. Little did they know that I'm huge. ~210 pounds says I need at least 120 in the rear.