[alohasurftoad]

235/35/20(26.5"), 275/30/20(26.5")

235/35/20, 265/35/20(26.3"), 0.8% difference

225/35/20(26.3"), 255/30/20(26.1"), 0.4%

[Ennoch]

Originally Posted by hurst01

I don’t find that to be true. I have had two different BMW X Drives, both 535 cars. I have run both staggered and square setup. I have never seen the rear tires wear faster than the fronts. You can’t rotate a staggered set because the rears won’t fit the front and would really look strange if you did.
If your rear tires wear faster than the front you have a problem. The rear tires will not spin independently from the front enough to wear tires unless the transfer case is out.
Ed

The original owner of mine definitely wore the fronts out before the rears but my experience of the PS4's and the winters is that if you drive country roads properly, as most of my driving is, then the rears take a significant portion of the torque and thus wear marginally faster than the fronts. If you are using weight transfer and getting on the power to slingshot out then it's the rears which are getting the biggest hammering from both the weight transfer (i.e the rear squatting down) and the rear tyres getting most of the torque (i.e if you've got a skew angle on the go). However, a lot of owners don't really drive their cars properly which means going into corners too quickly, understeering, turning the wheel too much and then only getting on the power once the car's straightened up and it's this which tends to kill front tyres faster than the rears.

[capt_slow]

Originally Posted by kzflags

its almost a given now that the rule of thumb to follow for xdrive vehicles is to keep the rolling diameters within 1% front and rear. However, from an online manual (which the link is expired lol) it states:

Sorry to revive this post from the dead, but I've been researching this too and figured to add context.

This quote is from the E83/53 xDrive training document. That chassis uses an older ATC 400/500 transfer case. The F3x transfer case is a newer ATC 35L unit. Aside from both being chain-driven TCs, I'm not sure where the similarities end.

[PeteyF36]

Again sorry to revive a old thread
im looking to replace my 225/45/18 square setup with a 245/40/18 and car is xdrive
so trying to match up a spare tire kit since ill be taking off the run flats and closest ive found is with 1.2%. only time i would be running that spare is if a tire goes out. so for a short time i would be on it would it ruin the system?

[visionaut]

Originally Posted by PeteyF36

Again sorry to revive a old thread
im looking to replace my 225/45/18 square setup with a 245/40/18 and car is xdrive
so trying to match up a spare tire kit since ill be taking off the run flats and closest ive found is with 1.2%. only time i would be running that spare is if a tire goes out. so for a short time i would be on it would it ruin the system?

You should be fine with that difference for short-term spare use.

[PeteyF36]

visionaut
thanks so much

[stevegwill600]

how would 245/35/20 and 275/30/20 fear on the x drive?

[visionaut]

Originally Posted by stevegwill600

how would 245/35/20 and 275/30/20 fear on the x drive?

As noted by Aloha in post #68 above — the correct staggered 20” combo is
235/35/20 Front (26.5"), 275/30/20 Rear (26.5") for X-drive.

Note 26.5” is 1/2” larger diameter than OE tires.

[stevegwill600]

Originally Posted by alohasurftoad

235/35/20(26.5"), 275/30/20(26.5")

235/35/20, 265/35/20(26.3"), 0.8% difference

225/35/20(26.3"), 255/30/20(26.1"), 0.4%

Would you be able to run 245/35/20 on the fronts with 275/30/20 on the rear?

[Musashi]

Originally Posted by stevegwill600

Would you be able to run 245/35/20 on the fronts with 275/30/20 on the rear?

NO- dont play- go at https://tiresize.com/comparison/ and lets compare. My 2104 came with stock 225/35/20. going to your 245/35/20 is a 2.3% increase in circumference AND a heavier, much heavier tire!

For years I ran 225/35/20 and 255/30/20. P Zeor. rears worse nearly x3 faster than rears. Brutal, they were cheaper then they shot to 700$ a rear.

2017 grew up and went 19, with Japanese rays. Tried:

235/40/19
275/35/19 PS4S.

35,000kms brilliant! Ceramic rotors helped make it even more fun by dropping 30 lbs unsprung mass.

2021 MICHELIN PS4S Set #2.

225/40/19
265/35/19

Bubble defect, warranty swap to same. 235 wore the Dinan spring on one side, presumably backing up in my driveway.

19,000 kms on set #3. Meanwhile, Dec 2023, nearly losing the car with new X Ice snow- brand new, hardened after 3,000 kms on our first snow- Michelin. tested them on compact slush-the blocks hard, do nto open roll and slush over, no longer bite.

What happened? Michelin is now garbage and ditched by connoisseurs I know- cracks, bubbles, hardened compound. What happened is Michelin introduced a new polymer for longevity- a plastic- on all its models without changing names. At 6/32, the 2022 PS4S skids at 15C, hot to night chill thud thud thud for 15-20 kms, plastic deformation. Dec 2023, after the X Ice snow incident, Michelin recalled and bought me a new Hakkappellitta R5 winter set, mor eexpensive, direct JP Morgan deposit, brilliant on the 3,600 lbs car.

Have the PS4S now, 6/32, atrociosu noise and hardened plastic compound! Last season three Michelin Power Cup cycling tires failed on me, got refunded, no accident, my mom's AS 3+ hardned up after 5,000 kms, DONE WITH MICHELIN. I do not care about 60,000 km treadwear if they lose grip or thud like Kumho Koreans!

T Case- replaced 2021- 7000$. The culprit was me having fun, two dozen launch controls, the part shot up from 800$ to 5000$.

Now, with Bilstein B6, new HRE sway bars (Thanks Farkle), the car is better than it ever was new.

As my PS4S are due in 2 months, going to Continental Extreme Sport 02.

Reminder, my base stock TC program is 225/35/20 and 255/30/20. So I will go for

225/40/19 Conti or
235/40/19 Conti S02

Rear:

265/40/19 Conti S02 (-0.4%) or
275/35/19 Conti S02 (+0.8%)

All are within the 2014 Stock 2%. Hope for even wear.

[marcthedark]

Originally Posted by PeteyF36

Again sorry to revive a old thread
im looking to replace my 225/45/18 square setup with a 245/40/18 and car is xdrive
so trying to match up a spare tire kit since ill be taking off the run flats and closest ive found is with 1.2%. only time i would be running that spare is if a tire goes out. so for a short time i would be on it would it ruin the system?

On my M240 the stock is 225/40-18 and 245/35-18 > a 1.35% difference
BMW must think that is OK for the long term so you are fine

[IsleOfMs]

Originally Posted by Billfitz

Rear drive biased, yes, but if you accelerate hard enough to burn the rear tires more power is directed to the front to prevent rear wheel slip. I do have xDrive.

xdrive doesn't prevent rear wheel slip. I know bc I drift mine with DSC on or off. I can't get huge smoky drifts but I can hold the car somewhat sideways under power for 5-10 seconds.

Regardless, there's always rear drive and sometimes front drive. The load from accelerative forces will be higher in the rear bc always > sometimes. The load from cornering forces probably depends on driving style but probably favors the front from turn-in to apex and favors the rear from apex to track-out.

[GixY2K]

So, it seems that there is no OFFICIAL guidance from BMW with respect to "Tire Circumference Allowable Percent Difference" (mouth full).

And from what I can gather reading information from AI, Google, and Bimmerpost, is that beyond 1% you are starting to push the comfortable limits. And based on MarcTheDark,2 post before mine, BMW is pushing that as far as 1.35% delta (calculator.net says 1.33%).

I'm personally here because I bought a X3M with 5k mi. on it, and it came with snow tires. Being that is so hard to get snow tires for the X3s, I bought it right away feeling confident that I shouldn't worry about tire sizing buying from a "reputable" BMW dealership. Well, I just had an oil change done and the dealer said I'm at 3/32". So that prompted me to look at new tires. Well, low and behold, the tires the X3M came with has a 1.22% delta. So now, I'm going to go with what Discount Tires is recommending, and is within .07% delta.

The only symptoms that I would attribute to the 1.22% delta would be that every time I come to a stop, I get a hiccup from the transmission. If this goes away, I will report back.

===============================
Quick note:
Look what this website recommends as far as sizes is concern:
https://apexwheels.com/fitment-guide...wMfEd7HmlaHOZu

It shows my size 255 45 20 265 45 20 which yields a 1.22% delta.