[mrluxiao]

The original tire size of my G05 X5 is:

Front: 275/45 R20 with 9J hub
Rear: 305/40 R20 with 10.5J hub

The tires needed to be replaced after 50,000 km. My friend happened to buy a new Porsche Cayenne at the time, with a tire size of:

Front: 255/55 R20 with 9J hub
Rear: 295/45 R20 with 10.5J hub

He changed R22 hubs and gave the brand new ex-factory tires to me, then I installed them on my X5 because they have same hub size.

Now after calculation, I found the Cayenne tires have a 1.9% diameter difference between the front/rear. However, I already used them for 5,000 km with no errors yet.

Will this 1.9% difference harm the xDrive system? If so, how can Porsche design such big difference of the Cayenne tires?

Thanks!

[mrluxiao]

To minish the diameter difference, I adjusted the tire pressure to 2.2bar front and 2.5bar rear. Will this work?

[915M]

Can you post some pictures?

[slicky]

The Cayenne may have a different type of a transfer case that is more forgiving to size deviation. I would absolutely not put on tires that are 1.9% off onto an X5.

[Alan l.]

Considering some people have the transfercase fail bone stock I would NOT risk it. The dealer would not cover it the moment they look at your tire size.

[nZtiZia]

I echo others’ statements. 1.9% difference between front/rear is too large for the BMW xDrive transfer case. your setup will very likely void any warranty claim related to the system

[eelnoraa]

I agree as well. Not worth the risk. I think the largest front vs rear difference in X5 family is X5m 21/22 setup

295/35R21
315/30R22

The difference is only 1%. So maybe this is a good reference

[MADBMWX5MC]

Originally Posted by nZtiZia

I echo others’ statements. 1.9% difference between front/rear is too large for the BMW xDrive transfer case. your setup will very likely void any warranty claim related to the system

...and that's what freaks me out about altering the OEM set up. Bravo to those who do, but with these expensive machines, last thing I need is for the dealer to find me at fault for the transfer case going t!ts up on me bc of my non-OEM set up.

PS: At least for as long as this thing is under warranty

[5wany]

A little bit of a thread hijack but can you increase the side wall height by 5mm (so 10mm overall on diameter).

I'm on stock UK model with 22"
Front: 275/35 R22
Rear: 315/30 R22

Is it reasonable to go to
Front: 275/40 R22
Rear: 315/35 R22

In the UK there just seems to be more tyre choice when you search on tyres with the deeper side profile.

[slicky]

Originally Posted by 5wany

A little bit of a thread hijack but can you increase the side wall height by 5mm (so 10mm overall on diameter).

I'm on stock UK model with 22"
Front: 275/35 R22
Rear: 315/30 R22

Is it reasonable to go to
Front: 275/40 R22
Rear: 315/35 R22

In the UK there just seems to be more tyre choice when you search on tyres with the deeper side profile.

People have done this and I haven't heard of any issues. BMW may give you a hard time if there is a transfer case issue.

[mojoJJ]

Originally Posted by slicky

People have done this and I haven't heard of any issues. BMW may give you a hard time if there is a transfer case issue.

IF there is a transfer case issue, buy used OEM tries and slap them on before taking to the dealer.

[slicky]

Originally Posted by mojoJJ

IF there is a transfer case issue, buy used OEM tries and slap them on before taking to the dealer.

Yup. Precisely why I kept my mostly worn OEM tires when I switched to non star tires.

[Edmund1812]

Even 1% is pushing it. Factory does that. So
But if I was replacing things less than 1% diff is better.

[Appalachian]

Originally Posted by eelnoraa

I agree as well. Not worth the risk. I think the largest front vs rear difference in X5 family is X5m 21/22 setup

295/35R21
315/30R22

The difference is only 1%. So maybe this is a good reference

I have an X5M with 808M wheels from the factory with 295/35/21 front and 315/35/21 rear. Per my calculations that’s a 14mm difference, close to 1.9%. Is this ruining my transfer case?

[nZtiZia]

Originally Posted by Appalachian

I have an X5M with 808M wheels from the factory with 295/35/21 front and 315/35/21 rear. Per my calculations that’s a 14mm difference, close to 1.9%. Is this ruining my transfer case?

I believe that is not an issue for the X5M transfer case. IIRC, even the 22” front: rear diameter difference is around 2%. again, this refers only to the X5M.

you may want to seek clarification in the F95/F96 sub forum