Quote:
Originally Posted by tetsuo111
Yes, but moving to an aftermarket wheel, like the ARC8 17 x 9 ET:30, drops real rotating mass. Stock BMW rims are around 25 lbs each, while ARC8's in the same size are 16.5 lbs. Remember a traditional tire is typically a pound or so lighter weight compared with its equivalently-sized RFT, and the total rotating mass drops somewhere between 35 - 40 lbs.
And the cost of 17" rubber is in a different universe compared with upsized 20" tires.
While this has a remarkable and noticeable gain in the suspension's ability to maintain contact between the tire and asphalt, I agree that nonetheless it's mostly relevant to regulars at the track.
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Dont disagree with you mate but as I stated the OP cannot go lower than 19s unless he swaps his brakes out (we are in the M2/C forum here, no F87 can fit smaller than 18" wheels on OEM brakes).
Also Ms dont come with RFT tries.
Also Also you need to compare 20" ARCs to 18" or 17" ARCs not really a fair comparison otherwise.
For OPs purposes a 2nd set of OEM 19s should fit the bill nicely as a balance between improved performance and cost if he is serious about Auto Xing repeatedly.
If OP is just starting out in Auto X/trackdays then 20s on any tire are fine for a session or two but will quickly get expensive as you correctly note.