Strange handling behavior, feels like traction control activating for no reason

[pablom2c]

Hi,

In December I replaced only my rear tires with Continental Contact Sport 5, the same tires that I had before and which are of course mounted on the front too. As soon as the new tires were mounted, I felt the car behaving strangely in corners like the traction control was activating without even pushing the car. I attributed this to the new tires since they need to break in.

Two months and 1000 km / 600 miles later the strange feeling has reduced, but I can still feel it. It seems like traction control or the ediff is applying brakes mid corner making the car feel unstable and twitchy which is very disconcerting. It feels like the car is trying to correct itself but there is no slip of the wheels, like if the traction control is in an extremely sensitive mode. The strangest part is that the traction control light doesn't light up on the dash. If I hold the traction control button down for 5 seconds ("YOYO" mode), the strange feeling disappears and the car drives normally even when pushing it.

What could be wrong? Could it be a bad ABS or other sensor? Which sensors does the traction control / ediff use? Could the shop have knocked some sensor and broken it when mounting the rear wheels? Shouldn't this show up when reading fault codes? When breaking hard I don't notice any strange behavior related to ABS.

I have BMW Carly app and have read codes and only saw a 005DEC fault, but even after clearing it the car still behaves strangely, and the fault doesn't come back. Please see image attached, maybe this is related.

Thanks for your help!

[iminhell1]

What size tires?


From what I and others have found, you can't deviate from stock diameters much or the traction stuff gets angry. It has target differential (difference between side to side and front to back) speeds that it wants to see.
What is probably happening is that it is using the brakes as you feel. Quick way to test is to turn traction off (long press) and go back over the same roads.


I know with my 205/45-17 front and 215/45-17 rear I had a hell of a time with what you're describing. Once I put the same sizes on, 215/45-17, I had no more problems.

[pablom2c]

I'm using the following wheels and tires:

OZ Ultraleggera F:18x8 ET 34 R:18x9 ET 40
Continental Contact Sport 5 F:225/40/18 R:255/35/18

But I have been using this same setup for over a year without problems.

I was reading another thread that the traction control system learns? Maybe it has adapted to the new tires having no traction and now it activates for no reason? How can I reset it?

[bagekko]

Hmmm... I sorta have the symptoms the OP described on my Nokian 205/45 snows all around. Always thought it was just because they are a little soft for my driving style. Has anyone ever harmed the traction control system putting it through this issue?

Originally Posted by iminhell1

What size tires?


From what I and others have found, you can't deviate from stock diameters much or the traction stuff gets angry. It has target differential (difference between side to side and front to back) speeds that it wants to see.
What is probably happening is that it is using the brakes as you feel. Quick way to test is to turn traction off (long press) and go back over the same roads.


I know with my 205/45-17 front and 215/45-17 rear I had a hell of a time with what you're describing. Once I put the same sizes on, 215/45-17, I had no more problems.

[pablom2c]

Quick way to test is to turn traction off (long press) and go back over the same roads.

When I turn traction control off (long press) the car behaves normally.

The strange thing is I have been using the same +size tires (225/40/18 & 255/35/18) on the OEM wheels for 3 years, and later also the wider OZ wheels (F:18x8 ET 34 R:18x9 ET 40) with the same size tires for over a year without problems, but now the traction control doesn't like it after I had the rear tires changed?

Also there is no traction control light on the dash when I feel the brakes in the corners is that normal? Or does it only activate when it cuts the throttle? I don't feel the car cutting throttle.

[02Pilot]

I get the same thing when on snows, but never on my summer tires. When it happens it's usually under power, especially uphill or exiting a corner. Based on this my operating theory is that it is a combination of tread squirm and sidewall deformation. Going into DTC mode usually solves it.

I haven't tried it, but if my theory is correct adding air pressure might mitigate it (it will reduce sidewall deformation, but not tread squirm). As the tires wear you should experience it less often (shorter tread blocks = less squirm).

[pablom2c]

Any other ideas?