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      11-07-2019, 06:07 AM   #1
Ninefourteener
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How "close" do overall diameter tires need to be?

Currently researching a staggered wheel/tire setup.

Absolutely want to go with a 22x12 on the rear. I don't want to compromise on that.

For the front, I'm not as picky... I can go with anywhere from 9" to 10.5", so long as the offset is appropriate.... but I can determine that later.

The problem isn't finding tires.... the problem is finding MATCHING BRAND tires... and if not, exactly how much "difference" can there be between the overall height of the front tires for the front vs. the rear.

For example...

22x12 rear wheel, 335/25/22 tires, 28.6" overall height.

22x9.5 front wheel, 275/30/22, 28.5" overall height
22x9.5 front wheel, 265/30/22, 28.3" overall height
22x10 front wheel, 285/30/22, 28.7" overall height
22x10.5 front wheel, 295/30/22, 29.0 overall height

I think that ".1" height difference is likely ok... maybe even ".4" would be ok.... but exactly how much difference does the manufacturer allow for, without potentially damaging the drivetrain?

My "best guess" so far... is a 22x10/12, with 285/30/22 front and 335/25/22 rear. Front tires would be Toyo Proxes 4 (28.7"), Rear tires would be Toyo Proxes STIII (28.6"). That's about as "close" as I can get, and while they aren't the same "exact" tire, at least they are the same "brand"????

But... Definitely willing to hear recommendations, or successful similar setups from the past.
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Last edited by Ninefourteener; 11-07-2019 at 06:37 AM..
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      11-07-2019, 10:37 PM   #2
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Excellent question. I can add some real world insight. On my F15, my rear tires had worn down to 2/32”, while the fronts were down to 6/32”. This translates to 0.25” diameter difference. I experienced no issues as a result of this.
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      11-08-2019, 08:19 AM   #3
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Sooo... upon further research.... I've discovered the most commonly used "aggressive" wheel and tire combo is a:

22x10.5 Front, ET 35
22x12 Rear, ET 25

front: 295/30/22
rear: 335/25/22

Both sizes are available in Toyo Proxes STIII, which are a decent all-season, reasonably priced, and they match, and you don't have to buy cheap junk like "Lexani" or "Lionhart" tires from China. It's about a .4 difference in overall height, but I have to assume because that is what everyone is using, that it's ok.

That is EXACTLY the setup this guy is using.... and I specifically chose this one, because it's not an "X5M" that sits lower.

https://www.bcforged-na.com/project/...-x5-22-hcs21s/
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      11-08-2019, 01:32 PM   #4
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Except that is an F15, and rolling diameter increased by 0.4” up to 1” for G05. Your choice is 0.8” less rolling diameter than stock 22” setup.
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      11-12-2019, 07:04 AM   #5
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Quote:
Originally Posted by spike5150 View Post
Except that is an F15, and rolling diameter increased by 0.4” up to 1” for G05. Your choice is 0.8” less rolling diameter than stock 22” setup.
True... but I'm not terribly concerned with rolling diameter. The worst that would happen is that the speedometer may be off by 1 or 2 mph.... basically, negligible.

However, running a smaller or larger rolling diameter on the front vs. the rear, can cause problems with the transmission.... that is ultimately what this post was about.
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      11-12-2019, 09:30 AM   #6
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Quote:
Originally Posted by Ninefourteener View Post
True... but I'm not terribly concerned with rolling diameter. The worst that would happen is that the speedometer may be off by 1 or 2 mph.... basically, negligible.

However, running a smaller or larger rolling diameter on the front vs. the rear, can cause problems with the transmission.... that is ultimately what this post was about.
I'm not certain, but as long as the rims are the same size, I think you'll be OK. The X5 is not a space craft, I doubt the tolerances for proper function are that tight. I'm sure the engineers have factored in some sort of factor-of-safety to ensure you won't wreck your car if you mix match wheels. As with anything manufactured, there's manufacturing tolerances that BMW has to account for. Due to that, I'm sure everything is over designed.
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      11-12-2019, 12:53 PM   #7
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Quote:
Originally Posted by VTENGR View Post
I'm not certain, but as long as the rims are the same size, I think you'll be OK. The X5 is not a space craft, I doubt the tolerances for proper function are that tight. I'm sure the engineers have factored in some sort of factor-of-safety to ensure you won't wreck your car if you mix match wheels. As with anything manufactured, there's manufacturing tolerances that BMW has to account for. Due to that, I'm sure everything is over designed.
Way back in my Subaru STI days, I remember that running a staggered wheel setup was sacreligious, and would potentially cause catastrophic damage to the drivetrain. The manufacturer stated clearly in the owners manual that all 4 tires had to be within no more than .2 inches difference between them.

Which meant, if your tires were 50% worn, and one got destroyed..... you had to buy 4 new ones.

However.... that was a full time, 50/50 drive, manual transmission. I can understand why tolerances were so low.

My new X5 will have an automatic transmission (fluid driven, not gear driven)... plus the ability to xfer 100% of the power to the rear wheels... so I have to assume there has to be considerably more "flexibility" in the X5. But I'm certain there has to be a "limit". I seriously doubt you can run 30" drag radials in the back, with a 13" skinny up front Not that you'd want to, but you know what I mean

But... I'd like to read some sort of BMW documentation that specifically addresses this topic.
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      11-12-2019, 01:37 PM   #8
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Quote:
Originally Posted by Ninefourteener View Post
Quote:
Originally Posted by VTENGR View Post
I'm not certain, but as long as the rims are the same size, I think you'll be OK. The X5 is not a space craft, I doubt the tolerances for proper function are that tight. I'm sure the engineers have factored in some sort of factor-of-safety to ensure you won't wreck your car if you mix match wheels. As with anything manufactured, there's manufacturing tolerances that BMW has to account for. Due to that, I'm sure everything is over designed.
Way back in my Subaru STI days, I remember that running a staggered wheel setup was sacreligious, and would potentially cause catastrophic damage to the drivetrain. The manufacturer stated clearly in the owners manual that all 4 tires had to be within no more than .2 inches difference between them.

Which meant, if your tires were 50% worn, and one got destroyed..... you had to buy 4 new ones.

However.... that was a full time, 50/50 drive, manual transmission. I can understand why tolerances were so low.

My new X5 will have an automatic transmission (fluid driven, not gear driven)... plus the ability to xfer 100% of the power to the rear wheels... so I have to assume there has to be considerably more "flexibility" in the X5. But I'm certain there has to be a "limit". I seriously doubt you can run 30" drag radials in the back, with a 13" skinny up front Not that you'd want to, but you know what I mean

But... I'd like to read some sort of BMW documentation that specifically addresses this topic.
Yeah. Wouldn't venture to a staggered setup w/o documentation. But if you're just mix matching 22" wheels, I wouldn't fret over that as long as the tires on each axel are the same.
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