Tyre Sizes ???

[ralphypat]

Hi Guy's,
I've a Mercedes C Class, C220 CDI Sport (2010 my), and I was wondering what would be the consequence of fitting the same size tyres to the front wheels that are fitted on the rear wheels?
All of the wheels are 17" with 225/45/17 tyres on the front and 245/40/17 tyres on the rear.

 

[paulshep69]

I'm not too sure what size your wheels are, as in J size, I know mine are 8J on the front and 9J on the rear, effectively 8" bead to bead & 9" bead to bead for the rears, therefore if you're trying to fit 20mm wider tyres to an inch narrower wheel it would have a couple of effects.

One would be that the tyre side walls would be bulged to take into account of the wider tyre size, this may make contact with your front struts and possibly your wheel arches.


There is also the possibility of the treaded area of the tyre being deformed whilst it's trying to fit the narrower wheel.


My advice would be to stick with the manufacturers recommended sizes, then you don't need to worry about insurance implications, the possibility of the tyres ruining your handling, tyres rubbing on wheel arches etc.

 

[hotrodder]

As above. You almost certainly have staggered wheel widths as well as tyre sizes, given the latter it's fairly likely your front wheels are 7.5J and the rears 8.5J. There are various calculators around for this sort of thing that'll spit out min, ideal & max tyre widths for a given wheel or (better IMO as it takes aspect ratio into account) spit out wheel widths for a given tyre size. There's one of the latter on Car Bibles : The Wheel and Tyre Bible Page 4 of 4 towards the bottom of the page which'll tell you that a 245/40r17 is too wide for a 7.5J wheel but a 225/45r17 is acceptable on a 8.5J.
Doing things that way round definatly won't result in clearance problems but will look just as weird i.e. the rear tyres will look stretched compared to the front