BMW Forums : BimmerForums banner
1 - 2 of 2 Posts

32 Posts
Discussion Starter · #1 ·

I've looked at a few, however this is simply the best by a mile :thumbsup

  • Calculators for calculating rolling radius
  • Comparison calculator for comparing different rim/tyre sizes
  • Lots of well written information on tyre physics (in simple English, mostly) even manages to explain something that my mechanical engineering lecturer never could:

if pressure = weight/area

then in simple terms: a fat tyre has no more grip than a thin tyre..

The experiment my old lecturer used to demonstrate this works very well to prove the point - get two square slices of rubber, one around twice the size of the first. Place a solid square slice of wood (or something else hard/stiff) on top of the small rubber square slices. Place a weight on the wood. Attach a spring measure (i.e. the sort used to weigh fish) to the rubber mat and pull the spring - record the force/weight required to get the assembly to begin moving and maitain a constant speed. Repeat the test with the larger rubber slice and you will see that the values you see with be "exactly" the same. Magic! I immediately asked him why sports cars have bigger tyres - he couldn't explain it. If you want to know but can't be bothered to read the article on the excellent website, it is primarily due to heat build up (for various reasons) being less the bigger the tyre is; allowing you to have softer compounds and maintain tyre longevity.
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.