tyre size for rims

[alzieboy]

Can 235/40/R18 winter tyres be fitted to a 8.5 rim , I thought it was okay but the dealer said not advisable . I found a rim chart calculator that said 235 was the ideal size for a 8.5 Rim

 

[whitenemesis]

It might well be the ideal size for the rim but if the tyre change results in a greater than 1% difference in rolling radius the speedo error will be significant and possibly also trip out the CC/ESP

What is the original tyre size fitted to the rim?

 

[Chris Murray]

HI

Are you looking to run the 8.5 rims all round? as the normal winter set-up for C207 on an 18" rim would be staggered or just the 8"width all round? Normally you would put 18x8 ET45 all round with a 235/40R18 and if staggered the rears would be 18x8.5 and a 255/35R18 running these sizes will also keep the rolling circumference the same as what is specified by Mercedes.

Thanks Simon

 

[alzieboy]

Hi

The original tyre size is 255/35/R18 rears 8.5 rim
235/40/R18 fronts 7.5 rim

 

[whitenemesis]

Hi

The original tyre size is 255/35/R18 rears
235/40/R18 fronts

That would be a 1.5% change, possibly why the dealer recommended against it

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[alzieboy]

Thanks for the Help