SBH-

I'm currently running 265/35 front and 285/35 rear. no issues so far, except for the grip you get when you floor it !

Matty779blue

Hi thanks for posting. Is that on the standard 19 x 9.5 wheels with the same geometry set up?


Interestingly I also asked this question of one of the tyre boffs at Mercedes Benz. His response was;


"You will be able to fit 275/35/19 with less than a 1mph variance at 80mph or go295/30/19 with the same result (though it will probably show slower than youare travelling)"


I simply want to go as wide as I can, with everything else remaining standard. If the 285/35 is working for you with no issues, I will give it a go.


Cheers Matt

shoe3k

I would go 275 rears and 255 for the fronts. Just because a person says that the size "seems" OK doesn't mean that the setup is ideal. You really need to account for the amount engineering that goes into the c63s because a lot of time was spent focusing on balancing everything between the electronic diff, traction control, suspension geometry, front/rear track, etc. that changing the profile of the wheels will have some sort of negative effect.

I'm not saying that going 285 in the rears is the end of the world but there should be some hesitation before making the jump. I personally would want everything done correctly and has 100% function, such as having the best contact between the tire and the road while not upsetting any of the other systems on the car.

Matty779blue

Wise words and the same sensible advice that msd3075 gave

SBH-

my main concern was moving away from the factory 20 mm difference between front and rear. I didn't want to change that, that's why I went for 285 and 265, rather than 255 up front.

msd3075

I wouldn't be as worried about keeping the 20mm width difference as I would keeping the aspect ratio/tire diameter from front to rear the same.

You want to maintain the percentage difference in tire diameter the same from front to rear as to not adversely affect any of the traction/skid control systems. Most of these systems work off of relative wheel speed (angular velocity) of each individual wheel, and programmed within the software will be a set difference between the front and rear tires. It knows with no tire slippage that the front tires will rotate at 'Y' angular velocity and the rear tires will rotate at '1.xx*Y' velocity. The ratio between those velocity numbers will stay constant no matter what speed the car is traveling. If that ratio changes, the systems know a wheel is slipping somewhere.

If you install tires that change this ratio, the traction/skid control systems will not operate as designed because they will not be able to accurately measure when/where this wheel slippage occurs. The system will either think a wheel is slipping when it's not, or it will not realize a wheel is slipping when it actually is losing traction.

Having the ratio be slightly different than stock should be fine, but it doesn't take much of a difference to cause issues. These systems nowadays as significantly more complex than they were just a few years ago, so keeping this ratio the same is as important as it has ever been.

SBH-

which means my current setup is fine or not recommended?

RDOCA

It may not rub but the 265 tires on the front are not recommended with the stock 8 1/2 in rims.
this means that if you want to go up the same front and rear the largest recommended is 255 f and 275 r.
This is what I will do.

msd3075

You are fine from a normal functionality standpoint, but the increased rubber width might not be giving you any performance advantage (and very well could be causing a performance disadvantage).

Just because a car with wider tires drives fine day to day does not mean those tires are optimal for better performance.

SBH-

i find what you say is true. in fact, when I first left the shop, I felt the car is heavier and the acceleration isn't like before ..

its a tradeoff really, cuz the rear view is absolutely worth the 285s