Hey Guys.. I usually post on the A8 site, but since more of you read this, I'll ask the same question. I bought a set of SL55 Wheels and Tires for my A8 and they look great! However... they are different sizes. The fronts are: 235/40/18 and the rears are: 284/35/18 This means the rears are just slightly larger in diameter than the front (About 10mm) and the rears are about 2" wider.
After Installing them, I read the User Manual (good timing huh?) and it warns against going with a staggered setup saying that the wheels must have the same 'rolling Radius'. I think I know what this means, but I have two questions for you guys:
1.) What do they mean by Rolling Radius?
2.) Do you think this wheel/tire combination will ruin the transmission?

I'll be posting pics of the wheels shortly.
Thanks in Advance!

 

http://images.google.co.uk/imgres?im...lr%3D%26sa%3DG

 

Thanks for the Physics lesson.. its been a couple of years since engineering school, however I was looking for the definition of Rolling Radius.. not rolling friction.

Anyone?

 

Its the outside of the tire measurment the totaly circumfrence and yes it will F $hit up if you dont make sure there the same, id take it to a tire shop and make sure there the same

 

haha i went to look up drag cars cause i wanted to show u guys the "rolling radius" of drag cars but i found this instead hahahaha





here:

 

Having a staggered wheel fitment on an all wheel drive car is very bad for the entire running gear (trans, t. case drive shafts ect...). It is because with the larger tires in the back, it will effectively change the rear gear ratios. When you have different gear ratios from the front and rear of the car, you will have the car trying to go two different speeds simultaneously. Therefore putting wear on all components mentioned above. Your options are to go with 1. same tire size all around. or 2. Do the staggered wheel set up, but make sure the circumference of both front and rear tires is the same. ie a taller front tire should pick up those ten millimeters of difference you are looking for.
hope this helps
-Jamis