Rolling Radius

Z

ZedM

Member
 Derbyshire
Sorry guys, I'm sure there is an obvious answer to this question but can somebody explain (in simple terms) why the staggered 18" set up has 40 profiles on the front and 35s on the back? I looked at a couple of Z4s with 17" wheels and these were both shod with 225/45 R17 tyres ie the same profile on each end but all of the cars with 18" wheels/tyres seem to have the lower profile tyres at the rear. Surely this must change the rolling radius/gearing? My recently acquired 2.5 Z4 has got 225 40 R18s on the front and and 255 35 R18s on the back. Is this right?
Thanks
 
https://www.tyrebuyer.co.uk/page/tyre-sizes-explained

The middle number ie 30, 35,40 etc is a percentage of the width of the tyre to give the exact rolling radius.
 
Russ59 said:
https://www.tyrebuyer.co.uk/page/tyre-sizes-explained

The middle number ie 30, 35,40 etc is a percentage of the width of the tyre to give the exact rolling radius.
Click to expand...
Thanks Russ - I live and learn! :D
 
If you want to play around to see the impact of this on radius / diameter or revs per mile for example, there are several tyre calculators on the internet. Here's one:

http://tire-size-conversion.com/tyre-size-calculator/
 
A1GSS said:
If you want to play around to see the impact of this on radius / diameter or revs per mile for example, there are several tyre calculators on the internet. Here's one:

http://tire-size-conversion.com/tyre-size-calculator/
Click to expand...
Thanks Graham - I'll take a look.
 
You must log in or register to reply here.
Back
Top Bottom