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Hello All,
Thank you to everybody who's contributed to this discussion.
I think I too may have this driving behaviour on my Z4 (e89 23i).
The behaviour was noticed immediately driving home with the new rear tyres, my wife has mentioned the driving behaviour too, so it's not just me! It's noticeable on uneven road surfaces and particularly exiting bends. The Z4 will feel like the rear-end is being pushed or pulled from one side to another.
Both rear tyres have been replaced from
Bridgestone Potenza 255/35 R18 90W RE 050A (OEM)
to
Continental SportContact 5 SSR 255/35 R18 90Y (non-OEM)
As it happens the Z4 was in at the BMW Dealership shortly after having the tyres replace, as part of a health-check the Dealership took the following tyre measurements (in brackets I've calculated the average):
NSF 5.0/4.2/4.6 (4.6mm)
OSF 4.6/3.9/4.3 (4.3mm)
OSR 6.5/6.8/7.1 (6.8mm)
NSR 6.4/6.5/7.1 (6.7mm)
The greatest difference in measurements is 7.1-3.8 = 3.3mm
The greatest average difference is 6.8-4.3 = 2.5mm
Does anybody think these measurements could point the driving behaviour cause being due to the difference in rotational speed differential from front to rear?
OR
Having traveled just 400m / 644km should I wait for the new rear tyres to "bed-in" i.e give the mold release a chance to wear off?
I've checked tyre pressures, wheel nut torque, tyres have been fitted correct with outside on the outside, additionally, balancing seems fine giving a smooth ride. The old tyres wore evenly so I don't suspect tracking.
THANKS, all comments appreciated.
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