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Discussion Starter · #1 ·

I'm a newbie so please be patient as this is my first post.

Car: E46 Sport 2003, M Sport wheels, 6 speed box etc.

My current tires, as supplied from new by BMW are:
224-40-18 and 255-35-18 Michelins.

I have read the forums and understand that the M3 has:
225-45-18 and 255-40-18 tires.

Can I fit the M3 size tires, since I understand they are cheaper, and if so what effect will this have?

One of my rear tires needs replacing whilst the other one has 3mm of tread. I realise that if I changed the size I would have to fit a pair on the rear. Can I just change the rears since the fronts are in good condition, assuming that I can fit the different M3 size?

Finally, irrespective of the above, could I just change one of the rears, assuming I kept the standard tires?

I normally change tires in pairs but had a bill of £1.200.00 yesterday for new disks, pads and service etc. so money is tight at the moment.

Many thanks in advance.



Legendary BFuk Member
12,959 Posts
Hi John,

If you changed the sizes to M3 then the difference in rolling circumference would show on your speedo as follows. (showing fronts just to display size/speed differences)

225/40 18 - 225/45 18 would mean that your speedo would be displaying 70mph but actually travelling at 72.47mph

255/35 18 - 255/40 18 @ 70mph you would actually be travelling at 72.81mph

Tyre sizing is supposed to be kept within +/- 2.5% of the original tyre size.

Fronts = 3.53%

Rears = 4.01%
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