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Old 10-15-10, 10:32 PM
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Sixty Fiver
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Originally Posted by brianogilvie
This is a little off the main topic, but since it came up:



Jan Heine and Mark Vande Kamp measured the real-world performance of various tires, and they determined that a wider tire (28-30mm on 700C rims) with a supple casing, run at moderate pressure, was more efficient than narrower tires run at high pressure. The higher rolling resistance of the wider tires was more than balanced out by the lower suspension losses from road irregularities. See Jan Heine and Mark Vande Kamp, "The Performance of Tires," Bicycle Quarterly vol. 5, no. 1 (2006), p. 1. (Not available online, unfortunately.)

They also found enormous variation in the performance of different brands of tires, depending on how supple their casings are.

Finally, Frank Berto has calculated that the ideal pressure is that which results in the tire dropping 15% of its width under load. This article from Bicycle Quarterly explains the principle and provides a handy chart for calculating optimal pressure.
I agree with this completely... this tire "dropping width under load" is called deflection and if a tyre is pressured up to a point where it does not deflect under load it will have a negative effect on performance and handling.
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