Max Thrust

There are about twice as many tires available if you use the 225/40/18 + 255/35/18 tire combo that the BMW 330i Performance Package uses...

Tires are pretty similar in overall diameter.

Thoughts?

PJmak

What does a stock c55 normally run?

ez53436

I think the C32 has the same fitment, and my car fits 255/35/18s no problem at all. Really depends on offset. I've got Brabus Monoblock VI 18x9.5s in the rear with +35 offset and I was able to fit 10mm spacers in the rear with 255/35/18 Dunlop Direzza DZ101s. Different tires fit differently though, like shoes. I'm now on 245/35/18s with Bridgestone Potenza S-04 Pole Positions and the fitment is exactly the same as it was with the 255 DZ101s.

Hope that helps.

EDgineered

225/40/18 + 255/35/18 Michelin Pilot Super Sports is my set up on stock rims. No issues at all.

busta55

+1

I have two sets of wheels, stock C55 AMG R18 and CLK AMG ones (R18 also). Both with 255/35/18 on rear. I also think 255/35 looks better than stock 245/35. No rubbing issues or something with 255/35.

Max Thrust

Ok thank you.

Viper98912

Absolutely. The tire patch is slightly wider, it fits the rim width better, the sidewall more closely matches the front, and the front/rear diameter becomes equal. It truly is the CORRECT tire to run in the rear.

The CLK55 uses this size tire stock. I'm not sure why they did the smaller 245 on the C55.

Max Thrust

I would not exactly call it the "correct" size to run. Clearly the design engineers at Mercedes/AMG made the decision to set up the car on these front and rear tire sizes. As you increase grip at the rear, you reduce a car's tendency to rotate, so maybe they chose the 245 vs a 255 or bigger because they preferred the car's manueverability with the 245. Or, maybe they got a deal on 245's from the OE tire supplier at the time. We will never know.

But what we do know is that the car's speedometer is calibrated to a 245/35/18. If you go to a taller tire, the speedometer will read slower than the car is actually going, and the car will accumulate mileage on the odometer slower than it should...

Of course, 255/35/18 is not that much taller. But it's not accurate to say it is the "correct" size to run.

Forums should aim to provide accurate information, not spread disinformation.

Viper98912

Sigh I knew this would come up. Yes, I agree with you 100%. But there's lots of reasons that we will never know, both economical, comfort, and performance based for this vehicle.

So for me? I'm fine with this size. "Correct"? Sure, it's not.

Max Thrust

Yep. I think we understand each other.

I ordered a set of 225/245's for my "new" C55 today. Definitely thought long and hard on it, and went with the 245's because I'm a factory original kinda guy, sometimes more than I even want to be

Cheers!

13TSCC

changing the the rim diameter means you need to change the aspect ratio to something equally smaller or larger within 2%
Changing the aspect ratio smaller is incorrect practice and makes no sense for performance, keeping the same ratio and plus sizing will be incorrect aswell!


Stock mercedes C32 AMG has

225/45r17 =
Diameter: 24.97 in, Sidewall: 3.99 in Width: 8.86 in
245/40r17 =
Diameter: 24.72 in, Sidewall: 3.86 in Width: 9.65 in

A correct plus size to an 18 inch rim would be as following:

225/40r18 =
Diameter: 25.09 in, Sidewall: 3.54 in Width: 8.86 in
255/35r18 =
Diameter: 25.03 in, Sidewall: 3.51 in Width: 10.04 in

To show you the difference here is the same aspect ratio in 17"
Front and rears are now 4.00% larger with the same ratio

225/45r18 =
Diameter: 25.97 in, Sidewall: 3.99 in Width: 8.86 in
245/40r18 =
Diameter: 25.72 in, Sidewall: 3.86 in Width: 9.65 in

Trying to get away with more surface area creates more friction which in turn provides more grip, Hope this post helps you confirm your decision if your uneducated about tires