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Old 01-15-2013, 06:12 PM   #36
Dave1027
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Join Date: Jan 2013
Location: California
Posts: 856
My Ride: '06 IR 330ci zhp
It's because if you go 40 all around and go wider in back then the back 40s will be taller than the fronts and would roll at a different rate making the DSC throw an error. It's because the 40 number is not the height measurement but the ratio. This is why the 225/40/18 is the same height as the 255/35/18.

Look at this converter http://www.discounttire.com/dtcs/infoTireMath.dos
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