Bike Forums - View Single Post - To the physicists here, ? re: tire pressure

07-24-14 | 06:48 PM

#30

MikeWMass

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Joined: May 2012

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From: western Massachusetts (greater Springfield area)

Bikes: Velosolex St. Tropez, LeMond Zurich (spine bike), Rotator swb recumbent

Quote:

Originally Posted by Shimagnolo

Because at the same pressure, the 38mm tire will be putting an outward pressure on the rim that is ~69% greater than the pressure imposed by the 23mm tire.

Source: Understanding the Influence of Pressure and Radial Loads on Stress and Displacement Response of a Rotating Body: The Automobile Wheel
Download the PDF, look at page 3, section 2.2, formula 5.
Reference Figure 4 to see what the variables mean.

This answers your question, although it is not spelled out. The pressure measured is exerted over the entire surface of the tire. A larger tire has more area, so less pressure x more area = the same force. This is why a bigger tire at the same pressure will exert more force on the rim as well.

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