[JuiceDude]

Hi there,

I have a UK BMW 430D X drive 2017 with aftermarket 20" wheels.

The fronts are ET35 offset (8.5J) and rears are ET45 (10J)

The rear wheels currently have 275/30/20 tyres and I would like to fit 245/35/20 tyres to the front.

Will these front tyres fit and have no impact on the X-Drive system?

Thanks
JD

[alohasurftoad]

oem=26" diameter.
245/35/20=26.8", 275/30/20=25 5", 1.2% difference. Ok for xdrive.

F32 have smaller fenderwells(than f30) and theres a slim chance the outer tire shoulder of a 245/35/20 may graze the fenderwell liner while turning full lock, unless you're lowered. Here is how tight things are on an F31...
https://f30.bimmerpost.com/forums/sh...54&postcount=1

235/35/20(26.5") would be better since it is same diameter as 275/30/20. Sidewalls are same height(not reverse rake) with no contact issues.

If 245/35/20 doesnt rub, 285/30/20 would be a better rear tire size to pair it up with for closer match diameter(and sidewall height)

[JuiceDude]

Hi there,

Thanks for your message. The 275/30/20 rears are already fitted to the car. The fronts currently have 225/35/20 fitted which is exposing the edge of the rim and something i want to cover up/reduce.

235/35/20 would be the ideal size but the manufacturer, Blacklion, does not make them. So instead of buying four new tyres I want to go for the 245s

As the fronts are ET35 8.5J i am getting mixed messages from people. Some are saying that 245/35/20 will be perfectly fine whereas others are saying it will impact the Xdrive system so I am really confused now.

Originally Posted by alohasurftoad

oem=26" diameter.
245/35/20=26.8", 275/30/20=25 5", 1.2% difference. Ok for xdrive.

F32 have smaller fenderwells(than f30) and theres a slim chance the outer tire shoulder of a 245/35/20 may graze the fenderwell liner while turning full lock, unless you're lowered. Here is how tight things are on an F31...
https://f30.bimmerpost.com/forums/sh...54&postcount=1

235/35/20(26.5") would be better since it is same diameter as 275/30/20. Sidewalls are same height(not reverse rake) with no contact issues.

If 245/35/20 doesnt rub, 285/30/20 would be a better rear tire size to pair it up with for closer match diameter(and sidewall height)

[thejeremyman9]

Originally Posted by JuiceDude

Hi there,

Thanks for your message. The 275/30/20 rears are already fitted to the car. The fronts currently have 225/35/20 fitted which is exposing the edge of the rim and something i want to cover up/reduce.

235/35/20 would be the ideal size but the manufacturer, Blacklion, does not make them. So instead of buying four new tyres I want to go for the 245s

As the fronts are ET35 8.5J i am getting mixed messages from people. Some are saying that 245/35/20 will be perfectly fine whereas others are saying it will impact the Xdrive system so I am really confused now.

For X-drive concerns, you are just supposed to be about ~1% different or less between overall tire diameter front and rear. Basically just go to tire rack, look up the overall diameter of your specific tires (or the ones you want) and compare front/rear to see the % difference. If its alot more than 1%, you probably dont want to run on xdrive. You can also estimate it based on width and aspect ratio, but best thing to do is look up the actual specs for the tire.

[JuiceDude]

Hi again,

Done some calculations using

https://www.tirerack.com/tires/tiret...e.jsp?techid=7

and just want to confirm the xDrive will be fine:

Fronts: 26.751969" (245/35/20)
Rears: 26.496062 (275/30/20)

%difference = 0.961196%

I have not rounded up the numbers, but the % difference is under 1.

Thanks
JD

[thejeremyman9]

Originally Posted by JuiceDude

Hi again,

Done some calculations using

https://www.tirerack.com/tires/tiret...e.jsp?techid=7

and just want to confirm the xDrive will be fine:

Fronts: 26.751969" (245/35/20)
Rears: 26.496062 (275/30/20)

%difference = 0.961196%

I have not rounded up the numbers, but the % difference is under 1.

Thanks
JD

It looks like you calcualted those sizes using the section width and aspect ratio values? You should look up actual tire height on tirerack for your specific tire rather than calculating just incase it is a little different. But yeah as long as you are within about 1% should be fine. Can't comment on fitment through.

[JuiceDude]

Originally Posted by thejeremyman9

It looks like you calcualted those sizes using the section width and aspect ratio values? You should look up actual tire height on tirerack for your specific tire rather than calculating just incase it is a little different. But yeah as long as you are within about 1% should be fine. Can't comment on fitment through.

It looks like you calcualted those sizes using the section width and aspect ratio values? = Yes, that is correct.

You should look up actual tire height on tirerack for your specific tire = Tirerack dont seem to stock Blacklion BU66 Champoint

[thejeremyman9]

Originally Posted by JuiceDude

It looks like you calcualted those sizes using the section width and aspect ratio values? = Yes, that is correct.

You should look up actual tire height on tirerack for your specific tire = Tirerack dont seem to stock Blacklion BU66 Champoint

Ah, well maybe manufacturer gives it? If not, your calcs should be fine as backup.

[kuradile]

Originally Posted by alohasurftoad

... 1.2% difference. Ok for xdrive.

Really? Isn't 1% already pushing it?

Originally Posted by alohasurftoad

F32 have smaller fenderwells(than f30) ...

What exactly do you mean by "smaller"?

[alohasurftoad]

Originally Posted by kuradile

Really? Isn't 1% already pushing it? What exactly do you mean by "smaller"?

here, codestar busts the 1% myth with 2.3% on his xdrive.
https://f30.bimmerpost.com/forums/sh...5&postcount=61

this is what bmw writes about x-drives. basically it says it should be as close to even as possible.
https://f30.bimmerpost.com/forums/sh...5&postcount=37

BMW uses OEM staggered setups on F22 x-drives which are 1.67% on 19" and 1.2% on 18", so go figure?

personally, i'd try to stay close as possible. but there is much evidence that it can be way over 1%. do what you want at your own risk.

although 4 series are wider than 3 series, the fenderwell tubs seems to have slightly less overall room on the insides of 4 series, especially F36.

[JuiceDude]

Originally Posted by thejeremyman9

It looks like you calcualted those sizes using the section width and aspect ratio values? You should look up actual tire height on tirerack for your specific tire rather than calculating just incase it is a little different. But yeah as long as you are within about 1% should be fine. Can't comment on fitment through.

Hi again,

You mentioned - You should look up actual tire height on tirerack for your specific tire rather than calculating just incase it is a little different.

Where do i find the actual tyre height? I am just seeing the 245/35/20 as the measurements for the tyres sizes?

[thejeremyman9]

Originally Posted by JuiceDude

Hi again,

You mentioned - You should look up actual tire height on tirerack for your specific tire rather than calculating just incase it is a little different.

Where do i find the actual tyre height? I am just seeing the 245/35/20 as the measurements for the tyres sizes?

Yeah just scroll down to specs. You can also look at rev/mile, as this is really what matters for xdrive considerations (and it is a function of tire size) - you really want the revs/mile to be as close as possible due to the transfer case on xdrive.

Example below.