PatrickGSR94

I replaced my old 26x2.1 knobbies with 26x1.5 smooth-tread tires for better road riding. The tires say max 65 PSI. Is it okay to go a little higher than that for a little less rolling resistance? Or should I just stick to the 60-65 PSI range?

Ira B

I run Tioga City Slickers in that size on my fenderbeast. They are also rated at 65 PSI but I run them at 75-80 PSI with no problems and they sure do roll a lot faster.
One interesting note is that the single flat I did get with these tires was when I was running them at 65 PSI.

Eric S.

I use Nashbar Streetwise 26x1.25 tires on my MTB commuter. They're rated for 90psi but I always pump them up to 100psi.

fietsbob

read what is on the sidewall of the tire?

well you ask safety .. over 65 psi, you are past the recommended safe
range, you are on your own..

ChrisM2097

kenda kwest - 26x1.5 (or 26x1.25) rated to 100psi. $17.

Well worth looking into these. I found them about a year ago, and love 'em. They even handle dirt/gravel just fine too.

rydabent

The people that make the tire, test the tire, and put their recommended max on the side. You cant go too far from wrong is you follow their numbers.

PatrickGSR94

Uh yes, as I stated in the OP 65 PSI is printed on the side of the tire. I just wondered if it was safer to go a little higher. That was the point of me making this thread.

lostarchitect 

Why put more than the max in? I'd go lower, if possible, for a comfier ride.

PatrickGSR94

higher for less rolling resistance.

As with most things I'm sure the max PSI probably has some amount of "safety" factor in there. A manufacturer would never put the absolute maximum failing pressure on a tire.

ChrisM2097

Which is probably somewhere around double the number printed on the side of the tire...for legal reasons.

dabac

And when was the last time you had your pump calibrated?

rumrunn6

stick to the MAX or get a road bike ...

SteamingAlong

OR

Post footage when that sidewall blows out at the worst possible time.

Shimagnolo

In my experience you are more likely to have the sides of the rims cracking, than have a problem with the tire.
The larger the tire size, the more pressure it puts against the rim bead AT THE SAME PSI.

fietsbob

guess you answered your own question..

when its so hot the tar melts and sticks to your tires that effects rolling resistance..

ursle

The perssure indicated on the side of the tire is 1/2 the bursting pressure of the tire.
I run my prii(2) at 42, easily another 10% increase in mpg, same-same, side wall indicated pressure is 1/2 the bursting strength.

ChrisM2097

Sure, you're saving a couple bucks at the pump, but you're going to be spending hundreds on buying new tires more often. It's not all about MPG.

But car tires and bike tires are completely different animals. Tread depth isn't all that important on a commuter/hybrid/road bike.

JTGraphics

My personal experience is that higher pressure doesn't always mean lower rolling resistance because the tire rather than roll over ripples and small cracks it starts to bounce rather than soak them up in a smooth fashion which can actually slow you down, While to soft can make for more resistance I have find that a harder tire isn't always better.
Tests have actually shown that some wider tires roll better that narrow tires.

PatrickGSR94

I don't use a manual pump. I set the regulator on my shop air compressor to what I want in the tire, and let the air pressure equalize.

Actually my regulator gauge is a touch off. I set it at 65, and then after filling I have two different tire gauges that both agree at 60 PSI which is what I have been running.

FBinNY 

There is a safety margin, so another 10psi probably won't be an issue, but safety margins are a tricly thing. For example tire companies have to allow for thermal expansion of tires inflated in air conditioned homes and ridden out doors in 100 degree weather, which raises pressure by about 10%, then there's an allowance for gauge accuracy so figure another 10%, meaning any decent tire maker needs to allow 20% minimum to be sure all will be OK in the real world. Then he has to allow for tire to tire variation in his manufacturing operation, and for tire/rim fit variation, etc. so he adds more, and eventually ends up rating his tires for far less than they actually hold (on average)

But if you use 10% knowing about the margin, and your tire gauge reads low, and you have thermal expansion, and maybe a not perfect fit on the rim, and happen to have one of the weaker tires... you can see that the margin will be gone and the tire could blow out.

As a professor told me in engineering school some 40+ years ago, safety margins only work if nobody knows what they are. Once people know, they factor them into their plans and if everybody assumes the other guy left a safety margin it's easy to run into a safety deficit.


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In any case, you're actually asking the wrong question. You should be asking "will there be a benefit in pushing the pressure above 65psi on my 1.5" tires?"

The answer to that is depends on your weight. Here's a link to a chart showing lowest net rolling resistance for tires based on load, width and pressure. This isn't rocket science, so there's a bit of allowance to be factored based on pavement, but it's a good place to start.

PatrickGSR94

That chart says I should run 40 psi in my front tire and 58 psi in my rear tire based on total weight of me and bike of about 100 KG and 40/60 weight distro. Interesting.

Thanks for the article. I'll probably verify my bike's weight distro with my bathroom scale sometime soon.

Myosmith

Running higher than recommended pressure is more than a safety issue (you are probably not in immediate danger but you are on your own) it also affect tire performance and longevity. I run my road tires at or just slightly over the max recommended pressure, but that's personal preference.

FBinNY 

Glad to help. When using the chart, don't forget that it's based on actual tire width which can be very different than the nominal width written on the side, So you might want to measure your inflated tires. Then you can adjust up or down a bit based on pavement.

davidad

The sidewall pressure is 1/2 the pressure necessary to blow the tire off of the rim. Proper pressure is a function of tire width and total vehichle weight.
https://www.adventurecycling.org/res...SIRX_Heine.pdf

FastJake

Exactly.

Seriously, how much do you guys weigh? I run my 700x28 tires at about 80psi/F 95psi/R. When figuring out inflation pressure I shoot for the highest possible pressure before comfort starts to suffer. On my mountain bikes, I shoot for the lowest possible pressure before I have to worry about getting pinch flats and damaging my rims. On 26x2.35 tires, that's about 20psi/F 25psi/R.