[rob_f22]

I have a 2015 M235i xDrive with 57k miles / 92k kms. I recently performed a fluid change on the ZF8 transmission with a new pan along with a fluid change on the transfer case about 1,000km ago. Everything seemed to run smoothly without issues.

Previously, I had been running all-seasons 245/35 R19 square setup but the fitment was off and was causing rubbing at the front. I also failed the inspections in Germany due to incorrect sizes being used. The official recommended sizes from the rim manufacturer for 8.5J x 19” rims all around was front: 225/35 R19 and rear: 245/30 R19. This was probably for the non-xDrive variant.

I decided to get some Michelin PS4S summer tires with the above sizes in a staggered setup. Once mounted, I noticed within the first 30 minutes that there were some issues with acceleration where the car was shuddering a bit and the gear shifts were not smooth at all. I’ve checked and the % difference between the front and rear tires is 1.67%. This is above the “recommended 1% difference”.

What I’m wondering is whether or not the extra circumference % difference would cause such sudden issues in the acceleration and power delivery smoothness? Or is it perhaps a bad transfer case that was on its way out and just happened to be failing at the same time as the tire change?

No fault codes and no errors in iDrive.

I’ve tested with xDelete also and the issues went away. I’ve recalibrated the clutch on the transfer case also with no help in AWD Mode.