Originally Posted by
Brian Ratliff
both incorrect.
In a clincher tire, the spoke tension does not change a whit with tire pressure. As the tire pressure is increased, the increased force on the rim is exactly opposed by the force on the bead holding the tire in place. Otherwise the tire would blow off the rim.
With a tubular tire, increasing the tire pressure decreases spoke tension because the tire casing is self supporting, so the pressure inside the tire is wholly born by the tire casing. As the pressure is increased, the casing stretches and the inside diameter of the tire wants to decrease but is opposed by the rim (thus compressing the wheel) while the outside diameter wants to increase but is kept in check by the membrane tension on the tire casing.
When I was building for Tim's Bikes in Everett, WA. I always had to jack the tires up from the minimal pressure the factory would put in them, usually around 20 psi. Most bikes being box bikes. When I took them to 60, the spokes would always do a little popping. 26" X 1.75/2.0" wheels/tires. When I moved out to GA. and started building for some of the big box stores in the Chattanooga area, the same thing happened. Always some spokes popping. I do think my statement was right. YMMV.