Tyre Equivalents

[Corpulent Tosser]

I guess tyres are part of thre drive train so I have put the question here.

Is there a table of equivalent sizes, for example if I want to change from 225/40 x18" to a 15" wheel what tyre would give the equivalent or similar rolling radius, I am sure I have seen such a table but cannot think where.

Thanks
CT

[grahambell]

All you could ever want to know here: www.carbibles.com/tyre_bible.html