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      01-27-2008, 07:00 PM   #1
kav
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Z4M offset quick help please.

I'm considering some new wheels and would really like to stick to the stock size rims.

Stock
Front wheel 18 X 8 Offset 42
Rear wheel 18x9 offset 30

New Rims
Front wheel 18x8 offset 34
Rear wheel 18x9 offset 40

Using a wheel offset calculator it says that:
Front - Inner clearance 8mm MORE & Outer position EXTEND an extra 8mm
Rear - Inner clearance 10mm LESS & Outer position RETRACT by 10mm

What are your thoughts on the clearance with these offsets as well as overall stance?

After some feedback on another forum, I'm considering running the above setup with either 10mm spacer, to bring the rear out to stock offset, or 20mm spacer to move the rear out about 10mm to match the front.

I any advice you could provide quickly would be a huge help.
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      01-27-2008, 07:32 PM   #2
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I have no idea how offset works, but if you go with what tirerack says you should be fine. I've never seen anyone complain about advise they got from tirerack.
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      01-27-2008, 07:41 PM   #3
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I'm trying to figure this out myself since the wheels aren't from tirerack... Any other advice.
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      01-27-2008, 08:39 PM   #4
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front should be fine.
rear might need spacers.. it might rub in the inside where the shock is..
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      01-27-2008, 08:42 PM   #5
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Quote:
Originally Posted by VoiD View Post
front should be fine.
rear might need spacers.. it might rub in the inside where the shock is..
What about with a 20mm spacer in the back. This would move the wheels out 10mm past the stock position.
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      01-27-2008, 08:53 PM   #6
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You might be okay but I think 20mm is too much..
10mm = ~2/5 inch.. See if it'll start rubbing on the outer side where the fender is..
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      01-27-2008, 09:02 PM   #7
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Quote:
Originally Posted by VoiD View Post
You might be okay but I think 20mm is too much..
10mm = ~2/5 inch.. See if it'll start rubbing on the outer side where the fender is..
You really think 10mm would be too far out on the rear? The fronts are 8mm extended outwards. I thought it would match nicely. But you are right, I'd hate to be dealing with fender rolling, etc.
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      01-27-2008, 09:34 PM   #8
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You really don't want to mess with spacers if you can avoid it. What you really need is lower offset rear wheels. When you add spacers you're adding another fail point, more unsprung weight, and putting additional stress on your hubs.
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      01-27-2008, 09:44 PM   #9
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Quote:
Originally Posted by Reach View Post
You really don't want to mess with spacers if you can avoid it. What you really need is lower offset rear wheels. When you add spacers you're adding another fail point, more unsprung weight, and putting additional stress on your hubs.
I have read this on some of the forums but I don't understand why this is the case. For all intensive purposes, if I added a 20mm spacer with longer bolts, wouldn't it be the same as if the wheels were -20 offset? Also the additional 2lbs literally on each hub, would be offset by 6 lbs of rotating weight loss.
Again, I am completely new to this and I am just trying to understand why spacers are seen in such a negative light.
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      01-27-2008, 11:43 PM   #10
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Quote:
Originally Posted by kav View Post
I have read this on some of the forums but I don't understand why this is the case. For all intensive purposes, if I added a 20mm spacer with longer bolts, wouldn't it be the same as if the wheels were -20 offset?
Spacers add stress points to the lug bolts. Imagine the shearing force between hub, rotor hat, and wheel, and add an additional piece of spacer in there...

I've seen sheared bolts at the track from running spacers. It's not pretty. For anything that sees moderate track use, if you're going to use spacers, convert everything to lug nuts instead of using bolts.
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      01-28-2008, 01:34 PM   #11
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...and the expression goes: "For all intents and purposes"
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      01-28-2008, 01:50 PM   #12
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Quote:
Originally Posted by The HACK View Post
Spacers add stress points to the lug bolts. Imagine the shearing force between hub, rotor hat, and wheel, and add an additional piece of spacer in there...

I've seen sheared bolts at the track from running spacers. It's not pretty. For anything that sees moderate track use, if you're going to use spacers, convert everything to lug nuts instead of using bolts.
I agree, and even if you don't track the car, the extra leverage acting on the bolts could cause you to exceed your maximum allowable sheer stress on the bolts if you hit a pothole going fast enough. Depends on a bunch of different variables, but unless you know the design conditions of the car I wouldn't mess with it either.
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      01-28-2008, 02:54 PM   #13
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Great advice guys. Thank you..
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      01-29-2008, 08:10 AM   #14
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I'm running
19 x 8.5 235/35/ Front
19 x 9.5 265/30 Rear
Offsets are 35/40 no rubbing on stock suspension, with room for a drop.

There are some photos posted in this thread on Bimmerforums
http://forums.bimmerforums.com/forum...d.php?t=890163

Quote:
Originally Posted by kav View Post
I'm considering some new wheels and would really like to stick to the stock size rims.

Stock
Front wheel 18 X 8 Offset 42
Rear wheel 18x9 offset 30

New Rims
Front wheel 18x8 offset 34
Rear wheel 18x9 offset 40

Using a wheel offset calculator it says that:
Front - Inner clearance 8mm MORE & Outer position EXTEND an extra 8mm
Rear - Inner clearance 10mm LESS & Outer position RETRACT by 10mm

What are your thoughts on the clearance with these offsets as well as overall stance?

After some feedback on another forum, I'm considering running the above setup with either 10mm spacer, to bring the rear out to stock offset, or 20mm spacer to move the rear out about 10mm to match the front.

I any advice you could provide quickly would be a huge help.
Appreciate 0
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