chedarhead

I purchased a new floor pump today and it has an included pressure gauge. I was wondering if I should trust the gauge as at lower pressure it seems to co witness my calibrated car gauge and how close to max pressure do you ride? On one bike the max that the 23 x 700 tires is 120 lbs. but I filled them to 100 psi. My other bike has sew ups and I also filled them to 100 psi. Do you max out the pressure or run them under max? I lost my presta tire gauge awhile ago and according to the gauge the frame pump does not fill them up to more than 90 psi. so the floor pump will be my main source of inflation while the frame pump will be for the road.

Jeff Wills

Some food for thought: https://www.bikequarterly.com/images/TireDrop.pdf

aggiegrads

The best answer depends on your weight. No reason to ride on rocks if you are a lighter rider. If you are heavy or "ride heavy" and are prone to pinch flats, then higher pressures may be right for you.

bobbyl1966

I put on my tires the max pressure but i am not sure if is correct i do that.

Andrew R Stewart 

When I talk with customers about this I ask then if they drive a manual shift car. If so then I ask if the run the RPMs up to red line before they shift.

Tire side wall pressure labels (note I don't say levels) are the max that the manufacturer says the tire can handle when mounted on THEIR standardized rim at THEIR testing facilities. Not what the rider should run or what the rim manufacturer suggests.

I weigh 150+lbs and ride 700x25 tires (and when I used sew ups 23 or 24mm ones) and I run no more then 100 PSI. Sometimes on reinflation I find I have only 90 PSI in the tires and I had ridden the day before. I've suffered only one pinch cut in many years and have dented rims with no flatting of the tire. Only on the tandem do I run above 100 PSI. Andy.
run as little

bobbyl1966

You mean is safer put less pressure than the max? Example if in one tire the max pressure is 120 psi what pressure is the best to use.

canklecat

I used to run near maximum pressure with road bike Contis, but nowadays I adjust for comfort with my 700x40 Michelins on a 30 lb hybrid bike. No idea how accurate my floor pump's gauge is. Michelin suggests 76 psi for my weight, up to 85 psi maximum. Tried it, felt too jolty-jittery on the rough pavement and gravel I ride. I usually prefer around 60-65 psi, sometimes a bit lower, around 50-55 psi, if I plan to ride off road mostly on gravel or pastures.

StephenH

I'm on the heavy side, so I just run tires at the max pressure. If I don't air them up before a ride, that's okay. I use my floor pump and trust the gauge on it. Not that I think it's perfect, but it seems reasonable and consistent, so it's close enough.

bradtx

It depends on your weight, tire size, and to some extent the road surface. My 23 mm tires have a max. pressure of 120 PSI yet I run 100 PSI for most road conditions and my 180 lb. weight. I can't say whether it's safer, but with less air pressure in the tires there is less high frequency buzz on some less than perfect road surfaces. The 37 mm tires on one of my touring bikes have a max. pressure of 85 PSI, but when riding unloaded 70 PSI works fine.

Brad

Homebrew01

Lower pressure is probably more comfortable.
I am about 175 lbs, 100 rear, 90 front

acorn54

this is a interesting topic. i have read in mel allwood's book, who is a respected bike mechanic in england, (according to the jacket cover of her book), to keep the tires at "high pressure", to prevent flats.
at my lbs the mechanic, who primarily deals with high end racing bikes, inflated my hybrid 700cx32 tire at 65psi, saying "he didn't want my teeth to rattle". i don't know what this all means, but i thought it might add to the conversation we are having.

gsa103

Mel Allwood is just wrong. That was the classic wisdom that high pressure was fastest. More recent research has to that modest pressures are faster on real road surfaces. At high pressure the bike bounces off all the bumps, which requires considerable energy to vertically displace the bike and rider. The only time you want super high pressure is a velodrome.

Shimagnolo

+1
I tried that a few years ago as a cheap experiment, and it sold me.
I've used it for all of my road bikes ever since.

Online calculator based on same principle: Bicycle tire pressure calculator

Homebrew01

Yes, pinch flats are more likely at lower pressures within the range for each tire size. 65 psi for a 32mm tire sounds reasonable, but no reason you can't experiment and see if you have a preference.

Andrew R Stewart 

The higher the air pressure the less the amount of tire contacting the road, since contact patch is approximately equal to weight of rider (on that wheel) divided by the tire's PSI. Less PSI equals more contact patch surface area. More contact patch area is generally considered to have greater traction. Try skidding a 120 PSI tire and then when it's at 80 PSI.

The 'working" side wall height greatly indicates how large a square edged bump (like a curb) the tire will absorb without collapsing against the rim, and getting a pinch flat. Of course this is greater when the tire has higher pressure.

The more a tire has deformed when loaded the greater it's contact patch will be a long and narrow shape. this means there is more casing deformation and the resulting internal to the casing friction. This is but one reason that wider tires are faster then narrower ones AT THE SAME PSI. It's this last bit that gets lost in many people's discussions.

One major reason that narrower tires have been is such fashion is that racers use them. Racers use them because they have less rotational inertia, they get to speed faster. When you race all that maters is that you've gone faster at one point of the race then all the other riders, at the finish line. So the ability to out accelerate the other riders is of prime importance. And that narrower tires "feel" faster due to their acceleration and shorter side wall flexing less when cornering.

But even the racing world is beginning to understand the mechanics and physics of tires better. More and more riders are using tires a notch or two wider then was the fashion just a few years ago. This allows a rider to minimize pinch flats, increase traction, reduce rolling friction and decrease fatigue. Andy.

acorn54

well gsa and andy, i am learning alot lately about the workings of a bicycle. i'll have to reconsider the size/psi, i keep my tyres at. presently i have a fuji hybrid with 700x28 tires, at 80-90 psi on both front and back.

RubeRad

+1000, this is the canonical answer. Start with whatever this chart recommends for your tires' widths and loads (load is always heavier in the back, if you want to have the same tire pressure, you can run wider tires in the back), adjust for comfort/speed preferences and I bet you land within 5psi of the chart.

I am 250lbs, I have 700x50 (aka 29x2") tires, and I air them up to 60 rear/40 front, approximately monthly. They run down to like 30 each. So I experience a whole range of fast-rolling and super-cushy.

T Stew

That is a great starting point. Just realize this is making a lot of generalizations. For one, on my 'normal' bike path, I can run very high pressures with no detriment. I've had my 700x23 Masters up to about 140 psi and I am no heavyweight either, about 155 lbs. The performance increase is very noticeable and the bike path surface very smooth.

On the open road, out on the rough roads in the country around here, I'll take my bike with larger tires (naturally need less air pressure) and run them lower than I usually would on the bike path.

So I don't believe there is an exact right answer, but the chart on that link will get you in the ballpark and then you can adjust from there if you are on smoother or rougher than usual surfaces, or simply prefer a softer or firmer ride.

Viich

I run 700x25 on the rear, 700x23 on the front, 100psi in both. The bike quarterly gives me 85psi front, 90 psi rear. Hmmmmm..... I guess I sometimes have some more weight on the bike for commuting when I'm running the 100psi, and I'm fit fairly far forward on the bike.

fietsbob

20" x 1.75 (Bike Friday, Schwalbe Marathon Plus Tires) I dont even measure other than squeeze it an feel the resistance with my hand..

DrIsotope

Woo, tubeless, yeah! Running 700x32 Maxxis Re-Fuse @ 60F / 70R for a combined bike +rider weight of 216lbs. Fastest rolling tire I've ever used.

ltxi

200 pounds. Nominal 90 psi for 700x25 works well for me. Fill to 95 and refill every week or two unless pinch test tells me earlier different

JanMM

I've been airing up based more or less on 15% tire drop for at least a couple of years. I'm no slower with less pressure.
Front 1.25" tire on one of my bikes = 50 psi. Front 1.6" tire on our tandem = 80psi.

Jseis 

I'm 200 & 26 X 4.7 Big Fat Larrys roll great at 3 psi on the beach. H-Billies in the pic.

CafeVelo

100 rear, 90 front, 700x26, 185lb. I have no reason to believe this is the correct pressure other than my experience that lower pressure is notably slower. I don't recall actually having any gains by dropping from my previous 110/100 setup, but did so when I was aware I had lost weight.