[Al Pinã]

Greetings 8-Series owners,

I'm an X-Drive G12 750 guy, but I figured staggered setups were much more common on this forum, so I'm looking for advice.

I've got my eye on a set of winter tires (255/35/19 front 285/30/19 rear) that effectively would give me about a 1.2% diameter difference front to rear. Revolutions per mile is about +9.

Anybody running a similar setup? I know these cars came from the factory with staggered wheels, but the difference is only about .8% diameter.

I've heard spooky stories about the differential getting stressed and possibly ABS issues... Any insights would be greatly appreciated. Thanks!

[Jenner]

Based on my research you can go within 3% of factory front to back (or back to front) but you need to be careful not to change the diameter of the tires much more than 1% compared to the factory diameter each axel on high hp X-drive models.

The biggest stagger for factory approved setups in the manual for the M5 and M8 would be the winter tire setup at 265/40/19 and 285/40/19 rear this is a 2.6% difference (still under 3%) and when we compare axels the front 275/35/20 is 1.1% larger the rear 285/35/20 is 0.4% smaller.

For example there is a tire size combo on the M8 that would achieve a 2.5% difference front to rear BUT in the process this tire size combo has a 1.1% bigger front tire (that's fine matches the snow tire front) and a 2.5% smaller rear tire. This setup would be out of bounds as it strayed too far from the factory diameter and ends up putting the X-drive torque balance out of tolerance which then causes too much power to be routed to the front wheels and things start breaking...

I am only speaking to the M5/M8 here based on my own research going to 21" wheels and speaking with another owner that had some issues. I'm not familiar enough with the G12 factory tires sizes to speak to your exact setup but the %s and rules should apply just the same.

[Al Pinã]

Originally Posted by Jenner

Based on my research you can go within 3% of factory front to back (or back to front) but you need to be careful not to change the diameter of the tires much more than 1% compared to the factory diameter each axel on high hp X-drive models.

The biggest stagger for factory approved setups in the manual for the M5 and M8 would be the winter tire setup at 265/40/19 and 285/40/19 rear this is a 2.6% difference (still under 3%) and when we compare axels the front 275/35/20 is 1.1% larger the rear 285/35/20 is 0.4% smaller.

For example there is a tire size combo on the M8 that would achieve a 2.5% difference front to rear BUT in the process this tire size combo has a 1.1% bigger front tire (that's fine matches the snow tire front) and a 2.5% smaller rear tire. This setup would be out of bounds as it strayed too far from the factory diameter and ends up putting the X-drive torque balance out of tolerance which then causes too much power to be routed to the front wheels and things start breaking...

I am only speaking to the M5/M8 here based on my own research going to 21" wheels and speaking with another owner that had some issues. I'm not familiar enough with the G12 factory tires sizes to speak to your exact setup but the %s and rules should apply just the same.

Thanks for the info! My car came from the factory with the 647M 245/45/19 square setup. Based on what I've read I should be within the boundaries of safe operation.

The car could be optioned with the 648M package which are 245/40R20 Front 275/35R20 Rear.

[FBMWWINS]

Originally Posted by ALPINA_DREAMS

Greetings 8-Series owners,

I'm an X-Drive G12 750 guy, but I figured staggered setups were much more common on this forum, so I'm looking for advice.

I've got my eye on a set of winter tires (255/35/19 front 285/30/19 rear) that effectively would give me about a 1.2% diameter difference front to rear. Revolutions per mile is about +9.

Anybody running a similar setup? I know these cars came from the factory with staggered wheels, but the difference is only about .8% diameter.

I've heard spooky stories about the differential getting stressed and possibly ABS issues... Any insights would be greatly appreciated. Thanks!

While many swear that a staggered setup cannot be driven, especially in winter and on XDrive models, I simply think that stance is very conservative. I have driven all my previous BMW cars on staggered setups in winter and never had any issues. As long as the wheel sizes and offsets are within "factory" specification or the variance is minimum and within tolerance levels then it's fine. Of course many opt for a square setup because BMW dictates so or simply because they want better grip under harsh conditions.

What I often heard and read is the variance in overall diameter should not exceed 1%. Also be sure (based on the wheels offset in case there is a difference compared to your original wheels) to check the scrub radius variance as that can also have "mean" consequences if there is a high deviation value from the standard wheels size (positive vs negative scrub radius). Actually scrub radius can have serious effects on the car's handling and driveability in general.