Tire Pressure
 

For many years I have believed that the pressure ratings on tires are far too high. But I couldn't be sure just how much too high they are.

Tire manufacturers seem to be in competition with each other to make tires with the highest possible pressure ratings. We see 700x23 tires with ratings of 130psi and 26x40 tires rated at 85psi. "More is better" seems to be the guiding principle when it comes to perceived tire quality. If it will hold more pressure, it must be better, right? Well, no.

I frequently see rims with cracks running under the rim tape from spoke hole to spoke hole. This happens when the side load on the rim is too high. Let's say you use a 1", or 25mm wide tire and put 90 psi in it. That puts a certain load on the sidewalls of the rim. Now change to a 2" or 50mm tire on that same rim and put 90 PSI in it. Yes, I know nobody does this but, now you have twice the load on the sidewalls of the rim. The pressure in the tire is the same, the load on the rim is doubled. Maybe the tire will stay on the rim. I don't know. But not only is there a higher load on the rim but you'll have a much harsher ride on the 2" tire at 90 PSI than on the 1" tire at the same pressure.

And then there's the issue of rolling resistance. Higher pressure lowers rolling resistance, right? It sure seems like it does. But it ain't necessarily so.

The good folks at Silca have been doing research on the subject, and I'm inclined to think that they know what they're talking about. So from here on I'm done making guesses as to what pressure you should have in your tires. I recommend you just do what I do. Use the calculator on Silca's website. They have done the hard work. We get to benefit from their hard work. Thank you, Silca!

Click here to go to the pressure calculator on the Silca website.

And read the articles in their blog to understand what's really going on with your tires and the air inside them.

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This page updated: Monday, May 20, 2019

Peter White Cycles LLC
24 Hall Rd.
Hillsborough, NH 03244
USA
603 478 0900 Phone