using different tread type tires on the same axle, bad?

[omodos]

Hi all, did a search for this and couldn’t find anything, although I am sure there are related posts comments somewhere, read elsewhere on the web its not a good idea to do this mixing? On tirerack etc have read that it can mess up the drivetrain etc as the different treads have different traction with the road surface and awd system tries to compensate for this by working ‘overtime’ thus causingmore wear, be great to know the truth from some seasoned bmw techie who has seen evidence of this…..or anyone else who knows more than us humble diyers..thanks

[JCL]

Different tires can have different handling responses, but also different actual sizes even though they have the same size label on the sidewall.

First difference can be with rolling diameters. They need to be very close side to side. If not, you are wearing the differential, and risking intervention by the traction control system which sees a different speed left and right.

Second difference is with handling characteristics. This is entirely mechanical, not electrical. Different tires respond differently, and you can get unpredictable (and thus unsafe) responses from having different tires left and right.

Third difference is with the electronic systems that monitor vehicle dynamics. This is the electrical intervention side of the second point. The vehicle sensors measure yaw, steering angle, etc, and respond by applying a single brake or reducing power. If the responses are 'out of range' ie not what the computer expects, which is more possible with different tire handling characteristics, you can get electronic interventions that you don't want.

Short answer is you should have the same tires on a single axle, with similar wear %. That extends to all four tires, but not to the same extent. The rolling diameter is important for all four, but the tread pattern not so critical front/rear. I would still strive to have all the same tires on the vehicle, with similar wear %.

[4.6toddy]

DON'T DO IT!

/end thread

[omodos]

Originally Posted by 4.6toddy

DON'T DO IT!

/end thread

haven't done it, and@jcl Thanks for the input, really appreciated, I downgraded my 19”staggered (front were 9j rear 10j) to 18” 8.5 J all round (LA star spoke 74 style) in the hope I would have a slightly softer ride due to higher sidewalls and be able to rotate tires all way round now, and threw on Avon ranger sports tires all round bit noisy but ok tires, alloys where used looked fine but the previous owner in his wisdom coated the inside with primer paint! This paint flaked so my tires were not sitting 100% flush with alloy so I had big air leaks by the time I got home…anyway garage cleared flaked off paint added a coating of bead sealer to lip of rim and fitted my tire and all seems ok now, was worried alloys may have been crooked etc but doesn’t seem the case, paid about 73 dollars per alloy…..BUT spending all day on my wheels as opposed to my wife didn’t go down too well….not one little but!