[matowi]

Makes me wonder how BMW in different markets approaches the tire size matter. First thing that’d happen if I showed up at a dealer for service with non-OEM tire size: voided warranty. They’d immediately hop on me saying the tires will create too much tension, or whatever forces which will lead to increased wear and tear on the x-drive components, and so on

I heard this warning so many times with my prior 3 BMWs that I’d never consider putting on any tires in sizes varying from the OEM specifications

Some dealers would go as far as saying that you lose warranty when you put on tires without the BMW star marking, even if the said tires meet OEM size requirements

My head swells in amazement every time I see a thread discussing how well your cars perform on whatever tires you dream up

[mojoJJ]

Well, if you look at the specs of the OEM 22” tires, they have the same 0.7% (3 revs/mile) difference in diameter between the front and rear tires as the 21” Michelin tires being discussed here. Although, in the 22” OEM setup the front tire is larger whereas in Michelin 21” the rear is larger. But that shouldn’t make a difference to the xDrive system or the drivetrain. So technically even if BMW denies warranty on drivetrain because of this, you could always argue that 22” OEM setup has same size difference.

[slicky]

The screen shot above misses an important point that star tires are not going to be the same diameter as non star tires of the same size. They could be either larger or smaller to provide a perfect match front to back. Designed as a matching set. This is why BMW wants you to use star tires. You are not going to have a 0.7% missmatch with them.

[mojoJJ]

Originally Posted by slicky

The screen shot above misses an important point that star tires are not going to be the same diameter as non star tires of the same size. They could be either larger or smaller to provide a perfect match front to back. Designed as a matching set. This is why BMW wants you to use star tires. You are not going to have a 0.7% missmatch with them.

The tire size (including diameter) is defined by the three numbers above, the “star” has nothing to do with that. What might vary (and missing from the discussion here) is the load index and the speed rating, which has nothing to do with xDrive system.

[matowi]

Well, what I see in this picture is that the taller 21” wheels are over 1 inch bigger in diameter than the OEM specified 22” wheels

In my post above this was the factor I was referring to — the wheels don’t meet the diameter limit set by OEM. Consequently, showing up to a BMW dealer/authorized service shop with such wheels would void my warranty on the spot. Greater wheel size translates to greater weight, and that adds whatever forces which may impact whatever components of x-drive or other parts of the drivetrain. At least that’s the spiel I heard so many times

On the star marked tires: they are manufactured in such a way that the difference between rear and front are (close to) eliminated, as stated in another post above

[slicky]

Originally Posted by mojoJJ

The tire size (including diameter) is defined by the three numbers above, the “star” has nothing to do with that. What might vary (and missing from the discussion here) is the load index and the speed rating, which has nothing to do with xDrive system.

This is incorrect. Star rated tires are not going to be the same size as non star tires. BMW specifies the compounds as well as the size, which may and does deviate from the theoretical diameter defined by the width/aspect ratio/wheel diameter for 21" X5 wheel application. Star rated 275/35/21 and 315/35/21 tires are exactly the same diameter. Non star rated 275/35/21 and 315/35/21 tires are not the same diamter. Non star rated tires will absolutely result in additional slippage and wear in the transfer case. How much more? No idea.
This is just the kind of bs we have to deal with with an xdrive staggered setup. If I knew it when buying our X5, would have excluded with the 21" staggered tires or the xdrive 40i and bought the sdrive 40i. Its a fn nightmare.

[mojoJJ]

Originally Posted by slicky

This is incorrect. Star rated tires are not going to be the same size as non star tires. BMW specifies the compounds as well as the size, which may and does deviate from the theoretical diameter defined by the width/aspect ratio/wheel diameter for 21" X5 wheel application. Star rated 275/35/21 and 315/35/21 tires are exactly the same diameter. Non star rated 275/35/21 and 315/35/21 tires are not the same diamter. Non star rated tires will absolutely result in additional slippage and wear in the transfer case. How much more? No idea.

Is there a conclusive evidence to this? I understand that star rated tires might have much tighter tolerances which might lead to “closer” matching in diameter vs non-star rated tires on extreme ends of respective tolerances. But saying that star rated tires have different diameters vs standard tires? Why have the tire size stamped at all? Wouldn’t this goes against the tire sizing convention?

[TexasBimmer89]

Just had a set installed on my wife’s X5. It will be nice to not have to look at daily temps during the winter before driving.

[crazyDriver_bimmer]

Taller tires are good. But what about the space saver tire. I don't think a taller space saver would fit in the wheel well in boot. How to go about it during a puncture.

[mojoJJ]

Originally Posted by crazyDriver_bimmer

Taller tires are good. But what about the space saver tire. I don't think a taller space saver would fit in the wheel well in boot. How to go about it during a puncture.

My car didn’t come with a space saver tire. I will probably buy a after market kit (they have them in various sizes and come with a carry bag) but for now I just carry 2 flat tire repair kits and pumps with slime.
I guess spre tire vs run flats is a whole another debate, you can find that searching the forum. It has been discussed at length.

[BmwJoel]

Have you posted any full side view pics with these tires?

[915M]

Originally Posted by BmwJoel

Have you posted any full side view pics with these tires?

https://g05.bimmerpost.com/forums/sh...0&postcount=45

[AngelitoPstar27]

quite interesting what Im reading here.. soo important info for the guy arguing about the star on the tires...
bmw specifies how a tires compund is made to meet their requirements in handling... fuel economy and comfort... thats all...
tire sizee.. diameter and width... are based on the numbers the tires have... a 275/35R22 tire has a 751mm in diamter... a non star 275/35R22 tire has a 751mm diameter.... what the star stands for.. is that bmw engineirs. worked with that tire brand modell.. and adjusted the compund for that bmw... soo
its not requiered to use star rated tires for bmw...
sadly dealers look for the finest detail to void your warranty... thats all
what matters is that the difference between the front axle and the rear axle tire diameter is less than 1%... it doesnt matter if the running diamter is over and inch bigger... but that the 1 inch is the same in the front as the rear... thats why running a 275/45R21 and 315/40R21 rear matches even better for bmw transfercase

[AngelitoPstar27]

watch this video from tyre reviews... he explaisn the diference between oem wheels the famous bmw star and a non star tire

[AlexGT]

Originally Posted by mojoJJ

tl;dr : happy with Michelin primacy tour AS 275/45/21 315/40/21 tires. No rubbing, no CEL or other problems. Great ride compared to stock performance RF tires.

Heya Fellas!

So after about 2000 miles, I got tired of horrible stock runflats on my LCI X6 40i (no air suspension) and decided to look for something with better ride and all season-ness. Searched the forums and found this thread discussing non-standard sizes and a few forum members running those without any problems and decided to give that a shot.

I ordered Michelin Primacy Tour AS - 275/45/21 and 315/40/21 at America’s Tire. I had talked to dealer service shop foreman and he said (unofficially, off the record) there should be no issues with rubbing or the xDrive system since the front and rear diameters are within 1%.

No rubbing at full lock, no CEL lights or any other problems after driving 300 miles.

The ride quality is so much better, all I hear now is the faint drone of the I6 engine and wind noise. There is of course some noise from rough roads but it’s still all very dampned.

The car obviously doesn’t automatically recognize the size now but I have set it to “winter/all-year” and “other authorized” tire settings in iDrive. As for tire pressure, the system no longer shows recommended tire pressure, it just shows the current tire pressure.

The only question I have is how do I calculate tire pressure for the new set? I used the tire size calculator and it give me suggestions but not sure if that’s accurate? Can someone please confirm? (Attached images)

Apologies for reviving your 2 y/o thread, but I wanted to ask you if you can share your experience with those new sizes after these years of usage? Handling, steering feel, etc.

I'm seriously considering doing this change on my G05 M Sport.

Thanks so much if it'd be possible for you to share.

[mojoJJ]

Originally Posted by AlexGT

Apologies for reviving your 2 y/o thread, but I wanted to ask you if you can share your experience with those new sizes after these years of usage? Handling, steering feel, etc.

I'm seriously considering doing this change on my G05 M Sport.

Thanks so much if it'd be possible for you to share.

Hey! So I have close to 18K miles on these tires and no issues whatsoever. Been to tahoe in light snow for two ski seasons and handling was as expected.

I suggest you still do your own research before switching.

[AlexGT]

Originally Posted by mojoJJ

Hey! So I have close to 18K miles on these tires and no issues whatsoever. Been to tahoe in light snow for two ski seasons and handling was as expected.

I suggest you still do your own research before switching.

Thanks so much for the reply. I've just installed the same size setup as you today, the change in comfort is a whole new level, those Pirelli runflats I had were definitely like the Flintstone's rock tires lol.

They look a little bit "chubbier" but not that much and, I feel that my wheels are more protected in case of any rubbing against a curb or a sidewalk.

Thank you again mojoJJ

[baadsha88]

Originally Posted by AngelitoPstar27

sadly dealers look for the finest detail to void your warranty... thats all
what matters is that the difference between the front axle and the rear axle tire diameter is less than 1%... it doesnt matter if the running diamter is over and inch bigger... but that the 1 inch is the same in the front as the rear... thats why running a 275/45R21 and 315/40R21 rear matches even better for bmw transfercase

so you’re saying as long as the difference is less than 1% the warranty won’t be voided?

[AngelitoPstar27]

Originally Posted by baadsha88

so you’re saying as long as the difference is less than 1% the warranty won’t be voided?

I never said.... the warranty wont be voided. Once the OEM tire size spec.... is changed.... bmw will void the warrantyy.... so upsizing... will cause advance wear on the components... which is true...
Everyone in this forum says that bigger tires don't cause anything.... but they do.
Thing is... bmw transfercase is really delicate... usually it fails in the first years... luckily it happens while in warranty...
If they find... something outside their specs... you will have problems

[elJames]

Originally Posted by AngelitoPstar27

I never said.... the warranty wont be voided. Once the OEM tire size spec.... is changed.... bmw will void the warrantyy.... so upsizing... will cause advance wear on the components... which is true...
Everyone in this forum says that bigger tires don't cause anything.... but they do.
Thing is... bmw transfercase is really delicate... usually it fails in the first years... luckily it happens while in warranty...
If they find... something outside their specs... you will have problems

Care to prove any of this?