Quote:
Originally Posted by Pat68
Hi ard,
Thanks for the warning
Do you mean rolling circumference?
The static diameter of the new rear tyres is <1 cm greater than the fronts, which considering the fronts are part worn I think is quite close. That said, this gives a difference of 18mm (3/4") in the static circumference front to rear.
Do you know if there is an allowable difference/tolerance and if so what it Is?
Thanks Pat
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Technically it is 'rolling diameter' or 'rolling radius' (since the tire deflects when rolling it really isnt a perfect circle so there isnt a circumference per se, or the circumference just gets distorted and doesnt change.)
0.75 is WAY TOO MUCH.
The stock BMW tires allows up to a 1% variance. We actually dont know the actual specification, but certain BMW wheels from the factory come with (I think) 712 rev/mile on one axle and 720 on another 8/720=1%. Hence one might infer that if BMW ships cars with that mismatch, that the engineering allows at least 1% tolerance
Stock size is roughly 29.0"... 29.0 versus 29.75 is way more than 1% You are probably running 3 times the tolerance.
You are likely stressing, perhaps wearing and maybe overheating the diff.