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Why rear tires are smaller than the fronts?

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Old 11-10-2014, 08:00 AM
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E-class Coupe C207
Why rear tires are smaller than the fronts?

Hi guys!
I am a new owner of E-Coupe C207 2014.
There is one thing i can not understand.
AMG package wheels/tires are as below for E-Coupe;
8x18 ET45 - 235/40/R18
8,5x18 ET49 - 255/35/R18
With this setup overal diameter of front wheels is 645mm (25,4") and rear wheels is 635mm (25").
I guess MB engineers are doing everything good but to me it is not logical)))
I always think that rear wheels must be bigger or at least same size with the fronts)))
Ok, rears are larger (255>235) but why are their diameter is smaller???
Old 11-10-2014, 08:24 AM
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2012 E550 Coupe
Probably because you would need a 255/37/18 to get a perfect match in diameter...and such a tire isn't made. You could go 255/40, but the rear would then be 26" in diameter. Perhaps they tried that and it didn't look right.


235 and 255 refer to the tread width in mm. The diameter is specified in the second number (35, 40, etc) which is the ratio of sidewall height to width.
Old 11-10-2014, 08:29 AM
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I think 245/40 would be ok for 8,5" wheels
and so, rear wheels overall diameter could be not that big and not smaller either.
front 25,4" and rear 25,7"
Old 11-10-2014, 10:32 AM
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'12 E550C, Sierra Denali
Originally Posted by keremorhan
I think 245/40 would be ok for 8,5" wheels
We went to 245/40 front with no issues and it diminished under steer. It's taller, but most don't notice the difference.
Old 11-10-2014, 06:46 PM
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2010 E350 Coupe
Lighter weight, quicker spool up. Lower apparent final drive ratio yields quicker acceleration for the low HP and heavy MB coupes.

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