[jeegunkim]

I know there are threads on this but there seems to be a debate about what is proper tire size. I'm about to order a set of tires for my new wheels and am wondering what all you xDrive G8X's are running, I've ready some are 285/30 and 295/30 but it breaks the 1% threshold by 0.1%, there are others saying it should be 275/30 and 285/30 as it would be below the 1% threshold. I'm hoping the 285/295 setup will be fine to run. Any thoughts?

[JY01]

Running 285/30/20F 295/30/20R PS4S on my xDrive and it’s fine. The diameter only differs by 0.88% according to willtheyfit.com

[davidmct-M3]

Is it circumference or diameter that needs to be within 1%? I would have thought circumference as this causes the rotational distance difference though they are related of course. And is % calculated from smaller as increase?

[forcefed]

Originally Posted by davidmct-M3

Is it circumference or diameter that needs to be within 1%? I would have thought circumference as this causes the rotational distance difference though they are related of course. And is % calculated from smaller as increase?

Height.

[jeegunkim]

Originally Posted by JY01

Running 285/30/20F 295/30/20R PS4S on my xDrive and it’s fine. The diameter only differs by 0.88% according to willtheyfit.com

Thanks for the input, man. Funny enough, I'm installing the same wheels, ha! How long have you been running this tire setup?

[JY01]

Originally Posted by jeegunkim

Thanks for the input, man. Funny enough, I'm installing the same wheels, ha! How long have you been running this tire setup?

Only about a week. I do rub on the front fender liner fins, but plan on trimming those once I lower the car.

[jeegunkim]

Originally Posted by JY01

Only about a week. I do rub on the front fender liner fins, but plan on trimming those once I lower the car.

Gotcha, I'm already lowered and liners are trimmed so I should be good to go. Hopefully some other folks whos on xDrive with the same times can also chime in just to make sure. Last thing I want is transfer case issues because of the wrong tire sizes.

[JY01]

Originally Posted by jeegunkim

Gotcha, I'm already lowered and liners are trimmed so I should be good to go. Hopefully some other folks whos on xDrive with the same times can also chime in just to make sure. Last thing I want is transfer case issues because of the wrong tire sizes.

I put over 100 miles on my new setup and it’s been fine, no drivability issues or codes. To be specific here’s the tires I’m running:

F: Michelin PS4S Star BMW 285/30/20
R: Michelin PS4S N0 Porsche 295/30/20

I got this info from the TE37 thread, I think I saw a couple other xDrive owners on there running the same setup. Additionally, you can reference Apex fitment guides, they’ll tell you which setups are xDrive compatible: https://apexwheels.com/fitment-guide...-fitment-guide

[jeegunkim]

Originally Posted by JY01

I put over 100 miles on my new setup and it’s been fine, no drivability issues or codes. To be specific here’s the tires I’m running:

F: Michelin PS4S Star BMW 285/30/20
R: Michelin PS4S N0 Porsche 295/30/20

I got this info from the TE37 thread, I think I saw a couple other xDrive owners on there running the same setup. Additionally, you can reference Apex fitment guides, they’ll tell you which setups are xDrive compatible: https://apexwheels.com/fitment-guide...-fitment-guide

Thanks, appreciate it!

[to///m]

Have thousands of miles on my xdrive G80 with 285/30/20 front and 295/30/20 rear and 100% fine, you will be good

[rak299]

Originally Posted by davidmct-M3

Is it circumference or diameter that needs to be within 1%? I would have thought circumference as this causes the rotational distance difference though they are related of course. And is % calculated from smaller as increase?

Circumference is pi times diameter. If one is within 1%, so is the other one

[M3SQRD]

Originally Posted by rak299

Circumference is pi times diameter. If one is within 1%, so is the other one

Really?!?! How did you remember such a complex equation?

I ran into this problem on our g20 x-drive when buying winter tires. In my case, it was the front tire that was larger in diameter (front +0.8% wrt rear dia). Switched to a setup with the rear tire having a larger diameter (front -0.8% wrt rear dia) and it’s worked perfectly for the past 4 years.

I tried a few additional tire diameters and found for the g20 330ix with THP that front tires with diameters +0.5% to -1.00% wrt the rear diameter works perfectly. For some reason, the g20 330ix is slightly biased more towards a front tire that is smaller in diameter than the rear tire. I initially thought it was going to be +1.0% to -1.0% wrt rear tire. What is it for the g8x x-drive?

[fl1by]

I'll have 285/35/19 295/30/20 Supercar3 on at the end of the month. I'll update when I get them mounted on Apex wheels. already cleaned up the fins in the front fender liner. G80 xDrive

[MartinS]

Car comes 0,4% off from factory. So I think you’re good if you are +/- 1% from the 0,4%.

[G82 Jesse]

https://tiresize.com/calculator/

Thought I'd share the link to this calculator on this thread. You can enter the specs for your front and rear setup. IIRC, official xDrive recommendations are 1.1% or less variance between the front and rear.

As tires are circles, your diameter and circumference will be the same ratio when comparing front to rears. I've got 275/30/20 in the front and 285/30/20 in the rear, at a 0.8% rotational difference, which appears to be just fine; for example.

[mjponti]

Originally Posted by to///m

Have thousands of miles on my xdrive G80 with 285/30/20 front and 295/30/20 rear and 100% fine, you will be good

Looks great, are you also running spacers?

[to///m]

Originally Posted by mjponti

Looks great, are you also running spacers?

Thanks man! Just 5mm up front, didn't need to, just wanted the front to be a little more aggressive

[phillychoi]

Originally Posted by to///m

Thanks man! Just 5mm up front, didn't need to, just wanted the front to be a little more aggressive

Perfect stance! Great job.