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      01-09-2013, 02:15 PM   #3
Porschefile's Avatar

Drives: E92 M3
Join Date: Jul 2008
Location: Tennessee

iTrader: (7)

Originally Posted by M3SQRD View Post
Track width is measured from wheel centerline to wheel centerline.

I would calculate the new and old wheel front spacing, subtract the old front spacing from the new front spacing, and then add two times the delta front spacing to the orig track width (TW):

New TW = Old TW + 2*Delta Front Spacing
= Old TW + 2*[(new wheel width-old wheel width)/2 -
(new offset - old offset)/25.4]

This assumes TW is in inches, wheel width is in inches, and offset is in mm (offset is usually listed in mm).
Thanks. Old wheels were the stock 19", 8.5" front 9.5" rear. I'm not sure what the offset is though.

New are Forgestar 19x11 et33 and 19x9 et 25 I think. I need to double check the offsets.