[redaljabri]

Hello everyone 👋
May car is m340 2021 xdrive
I want to run 225/45 r18 on front tires
And 265/35 r18 on the rear
Is that ok for the xdrive system or it could destroy the transfer case ?

[Matic94]

That difference is like a 2.7%, general rule
Of thumb is to be within 1%. Bump the front tires to 235/45 and rears to 265/40, and that would be almost perfect.

https://tiresize.com/calculator/

[Seba77W]

Originally Posted by Matic94

That difference is like a 2.7%, general rule
Of thumb is to be within 1%. Bump the front tires to 235/45 and rears to 265/40, and that would be almost perfect.

https://tiresize.com/calculator/

👆🏻yep this exactly same thing I would do.

[G30M]

Originally Posted by redaljabri

Hello everyone ��
May car is m340 2021 xdrive
I want to run 225/45 r18 on front tires
And 265/35 r18 on the rear
Is that ok for the xdrive system or it could destroy the transfer case ?

you will be at high risk of destroying transfer case

i have 2 cars with staggered and as i am wanting to keep them for a long time, i've bought square wheels for them and am in the process of changing to square for both of them

ANY difference = slippage = heat = excess wear

mind you with staggered, the difference could be exaggerated when rear tires wear more than front (depends if rear was smaller to start with, or front is smaller to start with), rear tire pressures higher/lower than front.

the saving grace is the car is most of the time RWD on perfect roads in perfect driving conditions, unless you're driving it hard

[Seba77W]

Originally Posted by g21

you will be at high risk of destroying transfer case

i have 2 cars with staggered and as i am wanting to keep them for a long time, i've bought square wheels for them and am in the process of changing to square for both of them

ANY difference = slippage = heat = excess wear

mind you with staggered, the difference could be exaggerated when rear tires wear more than front (depends if rear was smaller to start with, or front is smaller to start with), rear tire pressures higher/lower than front.

the saving grace is the car is most of the time RWD on perfect roads in perfect driving conditions, unless you're driving it hard

Within 1% he should be fine. I know you know this but obviously a lot of AWD cars come staggered from factory. My 2014 435ix came 225/255 and no issues in 7 years and over 110k miles. I’m sure 235/265 will be ok. I’m planning on doing the same on my M440. I currently have the 225 square and man the rear just doesn’t look right. 255 should’ve been a minimum but I’m thinking of doing 235/265 but need to by a set of wider rears or just new wheels all together.

[G30M]

Originally Posted by Seba77W

Within 1% he should be fine. I know you know this but obviously a lot of AWD cars come staggered from factory. .

it's called planned obsolescence

however the transfer case breaking is not the end of the car, not like if the engine implodes, but any difference in diameter is still not ideal, 1% is just the high risk point, it's not like 0.9% the transfer case won't break, 1.1% the transfer case explodes, it's a continuum

having said that, every time you turn the car the transfer case generates slippage/heat because all 4 wheels are now moving in 4 different speeds. which is why drifting an AWD car is the best way to get you a new transfer case.

[redaljabri]

I can’t do 235/40 18
On the front tire because my car speed limit locked on 200km/h GPS
So when I make the diameter shorter the speed limit on GPS will be less than that
It will effect the 1/4 mile that’s a thing
And If I make the rear 265/35/18
It will make the rear spin faster than the front and that should be ok because she already spin on launch control
I think if the different between the front and rear with the (-%) it should be ok
I don’t know 🤷

[G30M]

Originally Posted by redaljabri

I can’t do 235/40 18
On the front tire because my car speed limit locked on 200km/h GPS
So when I make the diameter shorter the speed limit on GPS will be less than that
It will effect the 1/4 mile that’s a thing
And If I make the rear 265/35/18
It will make the rear spin faster than the front and that should be ok because she already spin on launch control
I think if the different between the front and rear with the (-%) it should be ok
I don’t know 🤷

my car corrects the speedo to the GPS speed automatically

i tried different tire sizes and checked the GPS speed - the first time i drive the speedo is way off. after a while it's magically back to 3km/h difference. so i think the car knows what the actual speed is.

[Matic94]

Originally Posted by g21

it's called planned obsolescence

however the transfer case breaking is not the end of the car, not like if the engine implodes, but any difference in diameter is still not ideal, 1% is just the high risk point, it's not like 0.9% the transfer case won't break, 1.1% the transfer case explodes, it's a continuum

having said that, every time you turn the car the transfer case generates slippage/heat because all 4 wheels are now moving in 4 different speeds. which is why drifting an AWD car is the best way to get you a new transfer case.

My AWD literally came with 255/40/19 R 245/40/19 F, that's a 1.1% diameter difference. I highly doubt BMW threw those on knowing it was “high risk”.

[G30M]

Originally Posted by Matic94

My AWD literally came with 255/40/19 R 245/40/19 F, that's a 1.1% diameter difference. I highly doubt BMW threw those on knowing it was “high risk”.

your car is 99% of the time RWD if driven normally

just be prepared to toast the TC if you drive it hard and keep it beyond the warranty period. if you drive it normally, 99% of the time it's RWD.

TC is not expensive, so should be fine either way.