Originally Posted by
oledoc2u
I have 285/40/19 on the coupe. But I may change to a 275/40/19 from my roadster. The run flats just don't hook up at all. If I drive to the 1/2 mile event, I need road tires. Too far to drive on drag radials.
Interesting.....
So what you have achieved with those tyres and diff combo is a stock SLK32 setup.
No skite intended....
Your final 5th gear ratio is 0.83 x 3.46 =2.87
Stock SLK32 = 0.83 x 3.07 = 2.55
or 2.87/2.55 = 1.13 ratio
But your tyre setup is 2,232mm circumference for your 285/40/19's versus
the SLK32's 1,972mm
2232/1972 = 1.13 ratio.
So they cancel each other out.....
Very interesting.....
Unless I'm missing something not so obvious....
The 275/40/19's would give you 2207mm.
As always - comments/corrections welcomed.
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PS - circumference calc can be a little different between manufacturers, but basically....
Overall diameter = Rim Diameter + 2 x [track width x profile as a percentage].
so for a 285/40/19
19" Rim dia. = 482.6mm
Overall Diameter = 482.6mm + 2 x [285mm x 40%] = 710.6mm
Circumference = PI() x Diameter = 3.1416 x 710.6 = 2,232.4mm
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