Run-flats vs Ordinary Tyres

[MustangGT]

I have just acquired a 2019 Mercedes C300d with different size tyres front/rear. The tyres on the front are marked up as run-flat, the rears not. IIRC it is possible to put 'ordinary' tyres on a 'run-flat' rim, but not the other way round?

I cannot find any 245/40/18s in run-flat (rears), but can find 225/45/18s (front). I want to change them for 4-season, want to avoid making an error in purchase, and want them all the same.

Many thanks.

[stevieturbo]

Are the rims even different ?

The only 100% stipulation, is you must have TPMS with runflat. Although really all, cars should have this anyway

https://www.youtube.com/watch?v=sTRn1E1uF6c

https://www.youtube.com/watch?v=Ro_IOrrnP-E

[Pica-Pica]

Run-flats require a JJ rim profile to keep the tyre on the wheel rim. You can use non-run flats on JJ rims. You should not fit run-flats on ‘ordinary’ rims.

[MustangGT]

Pica-Pica said:

Run-flats require a JJ rim profile to keep the tyre on the wheel rim. You can use non-run flats on JJ rims. You should not fit run-flats on ‘ordinary’ rims.

That is what I thought, many thanks Pic-Pica.

Interestingly, the car was bought from a mainstream MB dealer, they are looking to assist with the tyres, saying it should not have been sold with 'mis-matched' tyres, so my swap to 4-season may be relatively cheap.