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[avosough]

Has anybody ever put Michelin Pilot Super Sports on the rears and Continental DW on the fronts? When I bought my 135i it had brand new Continental DW on the front and a Bridgestone Potenza on the rears with much less tread remaining. I just replaced the rears with Michelin PSS and figured I'd keep the same fronts instead of throwing away all that tread. I'd eventually replace them with Michelin PSS as well.

Now that it's installed the car feels a little squirmy almost as if it's developed an alignment (toe in/out) problem that wasn't there before install. On the highway it feels like it wants to wander and is harder to keep straight. Around corners I detect more understeer, and it generally doesn't feel as confident. The ride is much harsher over bumps.

I acknowledge it's not ideal to mix two different types of tires front and rear, but would that explain these symptoms?

[Chunner]

Yes..... and somewhat dangerous..

[dtla1]

Install the MPSS now, keep the contis for emergency purposes only.

[John_01]

Your car may feel different if the Potenza tires previously fitted were runflats. Put your tire pressure up a bit (37 PSI front and rear) and see if you still have the weirdness. If the car hasn't has the alignment check in the last year, then it would be worth doing that. The ideal fix for rear end handling issues is to get upgraded rear subframe bushings, but that is a whole other matter.

The other posters have a point that you should get matching tires all round. Its a good idea to do that before going to far looking at other issues.

[avosough]

Thanks for the input.

The Potenzas were not runflats. I still can't decide if the squirminess is due to mismatched tires or finally having enough grip in the rear to notice the weakness of the stock RSFBs...

I wonder if a used tire shop would buy my Contis

[John_01]

Is it possible you may be driving the car differently since you got the new tires? There is no way for me to know how obvious the issues are, but I wonder if you have become more critical of these issues since you got the new tires.

Otherwise it could your tire pressures have been set differently from the shop, although I guess you would have double checked that already.

[Solo_M_Tech]

There is no major safety issue running different tire brands front and rear. It's not generally recommended though. Running different Tire types, yes. You don't want to mix A/S with Max performance, or winters and summers. As long as the load, and treadware ratings are the same, and the tires are the same type, they will not make a difference. The feeling you are percieving, is most likely the RSFB moving around under load. I noticed the same thing when I switched to PSS. Installing the M3 RSFB fixed all of these issues.

[lowbudgethero]

check alignment first

[dbronnik]

I was forced to run the exact same setup (225 DW up front with 245 MPSS in the rear) for a couple of weeks since there was a huge delay in shipping my 255 MPSS -- I didn't experience anything you're describing.

MPSS does seem to grip better, so it makes sense that your car in understeering more after you've upgraded the rear tires but not the front. As already mentioned above, check alignment and consider replacing your stock RSFB if the 'squirminess' feels like its coming from the rear axle.

[avosough]

Thanks!