mercster4life

Why is the rear tire diameter 0.3 inches smaller than the front on the c43? The rear is a 245/40Z-R18 which is 25.7 inches in diameter. The front tire is a 225/45Z-R18, which is 26" in diameter. Why would they not install a 255/40Z-R18 in the rear which is also 26" in diameter?

I've asked my dealer but seemed to have baffled them.

Star4life

this is actually a great question. probably because mercedes wanted a special sized tire for the rear that is almost always a special order from tire dealers thus forcing you to go to the dealer if you are in need of a change quick.

synergize

Perhaps it to make the car handle better, that little bit extra width in the front probably does make a difference!

Antoun

Question guys, will changing the width of my wheels and tyres from 245 at the back to perhaps 255, have any impact to my speedo reading?? I didnt think it had any impact, but being told it actually does??

guhvies

The radius/diameter has a bearing on speed and therefore speedo. The width of the tire would affect grip as the contact patch would theoretically be greater.

Star4life

255 is not a noticable change. 265 /35 is not noticable. as long as you are within .5" diameter of 26" you are fine. depending what side you are on you would be faster or slower than speedo by 1.5 mph around 80 mph. above that does it really matter how fast you are actually going? you are going to get flicked either way... lol.

Antoun

thats also my argument till i was told the width can also impact your Speedo. Wanted it to run it by you guys to see if i was missing something...