Any experience with same tyres on different width rims?

[r1cey]

My CLK is fitted with 17" AMG alloys. The rear rims are wider than the fronts (8.5" compared to 7.5", I believe). The correct tyres should be 225/45 ZR17 and 245/40 ZR17 respectively, but can you fit the same tyre profile on all four rims? Has anyone done this, and were there any problems or disadvantages (handling, wear, etc.). I'm thinking that perhaps a 235/40 ZR17 tyre would be a good compromise.

Thanks,

 

[SG CL500]

225/45 17 can fit on rim widths between 7.5 and 9
245/40 17 can fit on rim widths between 8 and 9.5
235/40 17 can fit on rim widths between 7.5 and 9

So with a 7.5 width front tyre (&keeping the same front/back) you can go up to 235/40 profile tyres but 245's are too big.

235/40 17's are 1.27% smaller diameter than 245/40 17's so within acceptable parameters. (Note 235/40 17 are 2.29% smaller than 225/45 17 so pushing the 3% recommended limit)

So practically you can fit either the 235's or 225's on both wheels, but not 245's.

However, the manufacturer presumably staggered your wheels for a good reason and designed the suspension etc around this. Therefore I would expect (as a non techie) that changing the width of the tyres would affect the balance of the car - whether or not you'd feel it I couldn't say.

All info etc from here: http://www.carbibles.com/tyre_bible.html

 

[r1cey]

Thanks for the feedback SG.

Would you believe that my car is fitted with 245/40 ZR17's on each corner!!

I bought the car from a MB main dealer, and it was previously owned by a company in Glasgow. Since buying the car last year, I have had two tyres replaced under the used car tyre protection warranty (one was a front tyre), and when I queried the size of the tyres, the dealer said that the size was acceptable. An email to autoexpress also indicated that it was acceptable. I've still got about 5-6mm worth of tread on the fronts, but I must admit I don't feel comfortable with them, and am considering changing them regardless of the tread depth. I can only assume that the last owner of the car either (1) got a great deal on a set of four 245/40 ZR 17's or (2) the tyre fitter (would have to be an inexperienced one) looked at the rear tyre first, assumed they were all the same, and fitted the same tyre all round??

Thanks,

 

[Will]

You could fit a new pair of front tyres in the correct size, and keep the existing 245s that you remove as spares for the back

That's what I would do.

Will

 

[SG CL500]

No worries r1cey - hth

The recommended tyre sizes etc are only precisely that - recommended - and i would expect a healthy margin of error. Hence Merc/Autoepxress having a difference of opinion to the website.

Nevertheless, personally I would follow Will's suggestion and get the right size on the front, keeping the tyres that come of the 7.5' wheels for spare rears. Seems the sensible and cost effective approach to me

Is there a particular reason why you want the same size tyre all round?

 

[Chris Murray]

As SG indicates, there is a range of aceptable tyre sizes, but only one is published in the brochures etc. AMG have an info hotline in Affalterbach where you can request by fax the Teile Gutachten for your wheels (AMG 17" sizes are the same as non-AMG deisgns) and in this document, they have the German Transport Department approval for various different tyre and rim combinations. I think it helps speaking German though

 

[r1cey]

Thanks to both of you for your comments. I'd prefer to have the proper tyres fitted to my wheels, but thought I'd ask the question to see what other owners thought, and whether any had the same tyres on different width wheels.

Regards,

 

[bolide]

Wheels vs tyres

There's no problem per se with having a tyre on different-sized rims. There's always a range of rim widths a tyre will fit and, in general, a wider rim will support a given tyre better

More important in this instance, I'd have thought, would be ensuring that the ABS / ASR isn't fooled by having "wrong" tyre sizes on the car. Tyre size affects rolling radius and hence rotational speed of the wheel - and ABS / ASR monitor that to do their job

If it's working for you I wouldn't worry. But if you're getting error messages from the electronics maybe it's time to switch. Sometimes even replacing tyres on one end, and not the other, can throw these systems into a frenzy just because of the difference in rotational speeds caused by different tread depth

The tyre pressure monitoring systems on some cars work in the same way. They check the relative wheel rotation speeds via the ABS sensors and if one is high then the tyre may be low pressure


Nick Froome
www.w124.co.uk

 

[Satch]

Have two sets of wheels (7.5J Summer tyres and 8J Winter tyres) both fitted with 225/55 profile tyres. Both 16"

The 8J ones stick out about 1/2 an inch more but internal clearances are exactly the same because of differing offsets. So need to consider the offset and what that means in the context of your vehicle when fitting different rim widths.

Other thing is that because the rims are a bit wider the sidewalls on the 8J set are more "vertical" in terms of bulging out less. So that means the alloys are not quite so far recessed into the rubber and more vulnerable to kerb damage. (Actually I should have the Winters on the 7.5J rims because if you use snow chains they would be less likely to be damaged, but that was just getting too difficult)