What tyre size?..

[jon.bleeze.3]

Hi there.. Ive got a C219 CLS 350 Grand Edition.. I know these cars are a pain when it comes to getting tyres for them.. especially for the rears.. Now, the rears run at a 35 profile compared to the 40 profile on the fronts.. Question it.. can i run 275 40 18's on the rear.. Couple of reasons.. one being they seen to be easier to obtain and second being, the current 35 Profile makes the rear wheels look smaller the than fronts.. so want to balance the look by fitting 40 profile rears.. I've read that the width can be increased by a certain amount.. but wasn't sure about the profile?.. I mean, was there a reason why the rears run around 35 compared to the fronts at 40?..

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[Blobcat]

Wider rears need a smaller profile to match the overall diameter of the front tyres.
They need to match so that there isn’t a speed imbalance which would upset the stability system

 

[onefortheroad]

Sizes are on the fuel flap.

 

[JBell]

Tyres are easy to find

275/35 R18

https://www.camskill.co.uk/m61b0s33...yres_-_18_inch_R18_inch_-_275_35_18_275_35R18

 

[Naraic]

Tyres are easy to find

275/35 R18

https://www.camskill.co.uk/m61b0s33...yres_-_18_inch_R18_inch_-_275_35_18_275_35R18

Only if you have Google...

 

[Naraic]

Hi there.. Ive got a C219 CLS 350 Grand Edition.. I know these cars are a pain when it comes to getting tyres for them.. especially for the rears.. Now, the rears run at a 35 profile compared to the 40 profile on the fronts.. Question it.. can i run 275 40 18's on the rear.. Couple of reasons.. one being they seen to be easier to obtain and second being, the current 35 Profile makes the rear wheels look smaller the than fronts.. so want to balance the look by fitting 40 profile rears.. I've read that the width can be increased by a certain amount.. but wasn't sure about the profile?.. I mean, was there a reason why the rears run around 35 compared to the fronts at 40?..

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The profile number is a ratio, not an absolute.

So a 245/45 will have a sidewall depth of 45% of 245 = 110.25mm. A 315/35 will have a sidewall depth of 35% of 315 = 110.25mm...the same as the narrower tyre.

If you put a greater profile number on the back for the given width you may find that cruise control and other things will not operate.

Your front tyres are narrower than the rears, so, to maintain the same rolling radius (or very close to), you have different aspect ratios. Your car is not meant to look like a Grand Prix car, the tyres should look the same front and back when viewed from the side. In your case a 275/40 will have a 27.5mm greater diameter than the 275/35. So...too great a difference.

What is the size of your front and rear tyres?

 

[John Laidlaw]

^ this is the question. You may be able to switch to a square set up which might suit you better, maybe with all weather tyres....but do check the manual to see what’s ‘allowed’ else your insurance could be adversely affected....