Quote:
Originally Posted by strangewierding
The benefits of increasing the pressure in your tires......
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I truncated this post just so everyone knows what I am responding to - but I don't want to repeat bad information - thereby reinforcing it.
Also: Strange Wierding - I hope you don't think I am picking on you. My intent is to get good information in your head and let you take it from there.
First, Tire Construction: Most passenger car tires are made of 1 or 2 polyester body plies. They go radially (straight across - 90° to the circumference) from bead to bead - and even wrap around both beads, so that in the lower sidewall area, there are even more layers.
Passenger car tires usually have steel belts and always in pairs. Belts are in the tread area only and each layer is at about a 15° angle (relative to the circumference), but in opposiyte directions. What this means is that as more pressure is added to the tire, the belts change angle (becoming more circumferential) and the tire not only grows in diameter, but the center of the tread expands more than the shoulder. Increasing pressure has a decreasing effect, but it is still there. The process is called "pantographing".
Some passenger car tires have nylon cap plies (1 or 2). These are circumferential, under the tread area only, and resist growth in the tread area. You'll definitely find nylon cap plies in H and higher speed rated tires.