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      05-29-2015, 04:14 PM   #1
Zeta Macchina
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Stock 18x8.5" ET50 on all four corners

I have the opportunity to pick up 4 stock wheels in great shape. But all four are the standard 18"x8.5" ET50 that are found on the rear of the Z4 3.0 with sport suspension. Will the wider wheels be an issue if used on the front? As I understand wheel fitment, these are 12 mm wider and the offset is 3 mm more than the standard front wheel. So the outside edge will be closer to the fender by only 3 mm, but the inside edge will be closer to the liner and/or strut by 9 mm.

Anyway I will have to decide on the purchase before I can get home (away on travel for a little bit). Otherwise I would put the existing rear wheels up front and see if there is an issue.

The follow on question will be whether I can go to a square 255/35/18 tire set up (i.e. the rear tire size) on all four corners as well. From what I have been able to gather from other threads the offset will be too large, and a tire that size may just not fit up front. At least I'll be able to run experiments using the rear tires before I have to decide on tire size.

Definitely have to commit on the wheel size before that however.
Thanks in advance for your help.
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      05-29-2015, 04:54 PM   #2
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Quote:
Originally Posted by Zeta Macchina View Post
Will the wider wheels be an issue if used on the front?
No. Your biggest issue will be tire clearance, not wheel clearance.
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      05-29-2015, 05:34 PM   #3
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Thanks, that is what I thought. Appreciate the response.
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      05-29-2015, 09:13 PM   #4
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Quote:
Originally Posted by Zeta Macchina View Post
I have the opportunity to pick up 4 stock wheels in great shape. But all four are the standard 18"x8.5" ET50 that are found on the rear of the Z4 3.0 with sport suspension. Will the wider wheels be an issue if used on the front? As I understand wheel fitment, these are 12 mm wider and the offset is 3 mm more than the standard front wheel. So the outside edge will be closer to the fender by only 3 mm, but the inside edge will be closer to the liner and/or strut by 9 mm.

Anyway I will have to decide on the purchase before I can get home (away on travel for a little bit). Otherwise I would put the existing rear wheels up front and see if there is an issue.

The follow on question will be whether I can go to a square 255/35/18 tire set up (i.e. the rear tire size) on all four corners as well. From what I have been able to gather from other threads the offset will be too large, and a tire that size may just not fit up front. At least I'll be able to run experiments using the rear tires before I have to decide on tire size.

Definitely have to commit on the wheel size before that however.
Thanks in advance for your help.
Before I upsized the tires I was running I swapped the front and rear wheels (rears are 18 x 8.5 ET50) and drove around a bit. No issues noted running that in the front so now I'm running 255/35 x18 tires in the front on 18 x 8 ET47 and 275/35 x 18 in the rear on 18 x 8.5 ET50. No issues at all and still enough space in the front I think I could run 265/35 x 18 in the front and possibly the 275/35 x 18 would fit.
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      05-29-2015, 11:17 PM   #5
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I wouldn't do 275 wide on 8.5" rims.
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      05-30-2015, 12:06 AM   #6
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Quote:
Originally Posted by The HACK View Post
I wouldn't do 275 wide on 8.5" rims.
The minimum suggested rim width for 275/35 x 18 Hankook RS3's is 9" so it's only 1/2" pinch putting them on the 8.5" rim. You don't quite get the full benefit of the 275 tire width because there's a bit more radius at the shoulder than there'd be on a wider rim, but it's certainly a significant improvement over the stock 255/35 x 18" size.
I'd happily run wider rims, but the SCCA doesn't see eye to eye with that for Street class. You can change wheel diameter +/- 1" but you can't change wheel width.
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      05-30-2015, 09:22 AM   #7
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For off-road use its fine, but the tire width recommendations are there for a reason. I wouldn't do it for a street driven setup.
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      05-30-2015, 10:23 AM   #8
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For a stretch or pinch fit the concern is the interface between the bead and the rim. The 1/2" total pinch I'm running is only 1/4" per side and the RS3s have enough flex at the bead point of the side wall that the angle hasn't changed. Also 35 series tires are low profile enough that they're difficult to mount in the first place so the bead popping off is pretty low risk. If it's holding with no issues at the 31 psi I run for autocross it's going to hold at 36 psi for normal driving.
The main effect of the pinch fit is you don't get the full tread width increase of changing from the 255 to the 275.
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      06-05-2015, 12:00 PM   #9
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Thanks for the replies.

Well, I was checking prices on the internet because I always doubt whether I have gotten a good deal or not. So, at the risk of hijacking my own thread; does anyone know why the OEM 18x8.5" Style 101 two piece rims are selling so cheaply right now? ECS has them (Genuine BMW) for $145 and Morristown BMW (my absolute favorite place to buy OEM online) has them for $130.00 a piece! The 18x8" are still over $530 a piece, about the price of all four 8.5" inch ones. All I can think of is a large overstock but that seems kind of drastic. I'm not complaining though, I've ordered a set of four from Morristown last Sunday. I'll let you know when they arrive.
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