Originally Posted by fixedpip
One thing to bear in mind here is that rim manufactures set pressure limits as well.
ie for a Mavic CXP-33
TIRE SIZE MAXIMUM PRESSURE
mm bars psi
19 10.00 146.00
23 9.50 138.00
25 9.00 131.00
28 8.00 117.00
Most clinchers are not spec'd for much more than 125 PSI. Some are rated lower than that (ie Corimas fancy carbon clinchers are spec'd at a max pressure of 115).
Thanks for publishing that chart. Many rim makers "hide" that information on their web sites. Rarely is that information provided on or with a rim. It is basic safety information, yet many guys who work in bike shops (as well as the writers at "Bicycling Magazine") are unaware of the importance of matching the width of a tire to the width of the rim, and the fact that the "best" PSI is related to both the width of the tire, and the weight of the rider.
One tire company marks some of its tires with maximum PSI levels of 150, 160, and 170. Those maximum PSI levels may exceed the design limits of the rims that the tires are mounted on. Owners need to make sure they match the tire to the correct rim, and stay within the design limits of both the tire and the rim.
The BEST PSI level for most riders is often far below the maximum. A typical 21mm tire can be safely ridden at 140 PSI. Yet, many Pros would ride that tire at around 110 PSI on smooth, dry roads, and at PSI levels as low as 90 PSI on wet, water covered roads. Some folks confuse the words "best" and "maximum". They are NOT the same thing.