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      05-20-2011, 08:39 AM   #11
First Lieutenant

Drives: 1(M)other f*^#er of a car
Join Date: Nov 2010
Location: Canada

iTrader: (0)

Originally Posted by Drillslinger View Post
I'm pretty sure the wheels are the exact same ones that are on the M3 Comp. so whatever those are...

Edit: Ok, according to

M Coupe
9x19 *vorne (Front) 245/35R19 ET 31, 11.90kg (26.23 lb)
10x19 *hinten (Rear) 265/35R19 ET 25, 11.20 kg (24.69 lb)

(I don't quite get how the rears weigh LESS than the fronts though )

The Calculations for offset that I have been able to make using is the following:

The object in these cases is to be able to use the same stock tire sizes of 245 front/ 265 rear with different aspect ratios to accomplish the same offset.

Using the stock set of
9.0 wide x 19" x 31mm offset (Front)
10.0 wide x 19" x 25mm offset (Rear)

Offset Calculation for 8.5 front and 10 rear in an 18" diameter:

Front - 8.5" wide x 18" x 25mm offset - this will keep the outside face of the wheel in its' current position and the inside face of the wheel (the part closer to the center of the car) will retract by 12mm

Front - 8.0" wide x 18" x 18mm - this will keep the outside face the same and the inside face will retract by 26mm

Rear - 9.5" wide x 18" x 19mm - this will keep the outside face the same and retract 12mm on the inside

Rear - 10" wide x 18" x 25mm - These dimensions will remain unchanged from the stock configuration as the wheel width is the same.

The Tires:

Stock Tires Read as follows:
245/35 R19 Front
265/35 R19 Rear

Using an 18" Winter tire to obtain the minimal loss of rotational speed using the following:
245/40/18 = 0.1% too FAST (Traveling at 60mph = 59.9mph in reality)
265/40/18 = 0.2% too SLOW (Traveling at 60mph = 60.1mph in reality)

235/40/18 = 1.4% too FAST (Traveling at 60mph = 59.2mph in reality)
245/45/18 = 1.4% too SLOW (Traveling at 60mph = 60.9mph in reality)

What a science...

Tire prices care of TireRack:

(Front) Bridgestone Blizzak LM-60 245/40/18 = $233.00 each
(Rear) Bridgestone Blizzak LM-60 245/45/18 = $229.00 each

(Front) Michelin Pilot Alpin PA3 245/40/18 = $243.00 each
(Rear) Michelin Pilot Alpin PA3 245/45/18 = $245.00 each

Last edited by rapter; 05-20-2011 at 08:54 AM.