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      10-14-2008, 11:40 PM   #1
Geckorazer
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E90 Offset question

I bought some used AC Schnitzer alloys on eBay and thought they would fit my e90.

However, now I'm not too sure as the set up appears to be for an e46 - the offset is 43 front and rear and I think the e90 has something like 33 ?

The wheels and tyres are :

ACS Part Number 3611 60 300
8.5Jx19EH2 ET43
235/35 ZR 19

Any idea if these will fit or not ?
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      10-15-2008, 04:35 AM   #2
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my 20s are et40 and are fine
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      10-15-2008, 04:43 AM   #3
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my 20s are et40 and are fine
But what width are your 20"s ??!
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      10-15-2008, 04:54 AM   #4
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BMW OEM 19" wheels are a staggered fitment, in that the rears and wider than the fronts.

As standard...

Front wheels are 8J x 19" (or 8" wide by 19" in diameter), ET37 offset
with 225/35 tyres

Rear wheels are 9J x 19" (or 9" wide by 19" in diameter), ET39 offset
with 255/30 tyres


Your ACS wheels have an offset of ET43, and are 8.5" wide. Given that they have a 6mm greater offset than the standard 19" BMW front wheels (ie sit 6mm closer to the hub), but are 0.5" wider (12.7mm - or 6.35mm either side of the centreline), then the outside edge of the front wheel will be only 0.35mm further out than normal. The inside edge of the wheel will be 12.35mm closer to the hub. This shouldn't be a problem!!

However, you may find that the rear wheels (if you are using the same wheels as the front) are too narrow - offset difference is 4mm (so the wheel sits 4mm closer to the hub than normal), and to compound that the ACS wheel is narrower by 0.5" (12.7mm) than the OEM BMW wheel. Therefore, the outside edge of the ACS rear wheel (assuming it's a 8.5" ET43 size) will be 10.35mm further in than standard. Multiply the effect by two (both rear wheels) and your rear track is narrower by 20.7mmmm, or just under 1".

If you can, get yourself a 9J wheel for the rear, and use the 8.5J at the front.




See below for diagrams etc explaining offset measurement.

The offset, or ET measurement in millimetres, determines the position of the mounting point of the wheel in relation to the centreline of the wheel (see diagram below)

Name:  offset.gif
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Looking at the picture above, note that the left hand side is the brake side, and the right hand side is the outer edge of the wheel.

In the left image, you can clearly see that the mounting point is positively offset to the right of the centreline of the wheel - so for instance an ET37 wheel will have the mounting point 37mm to the right of the centreline.

The middle image shows no offset at all, so the mounting point is in the same position as the centreline of the wheel.

The right image shows negative offset.

The higher the positive offset value, the more the wheels sits IN towards the hubs. The lower the offset value the closer to the wheelarch. In both cases, the width of the wheel is constant, the only thing that changes is the mounting position relative to the centreline of the wheel.
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      10-15-2008, 02:17 PM   #5
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E92Fan - thanks for the detailed explanation - that is really helpful.

A couple of other (dumb) questions to follow which I hope you don't mind.

Does having 1" less track at the rear make much or any difference ?

ACS sell certain spacers for the wheels - does this sort out the offset/track width issue you've highlighted ?

Thanks
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      10-16-2008, 02:50 AM   #6
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Quote:
Originally Posted by Geckorazer View Post
E92Fan - thanks for the detailed explanation - that is really helpful.

A couple of other (dumb) questions to follow which I hope you don't mind.

Does having 1" less track at the rear make much or any difference ?

ACS sell certain spacers for the wheels - does this sort out the offset/track width issue you've highlighted ?

Thanks

To the normal person, 1" less track will have zero effect on the handling of the car. In theory, the rear of the car will be a teeny bit less stable, and you might get a smidgen more roll at the back. However, I defy any normal person to be able to tell the difference.

ACS do sell spacers, as do Eibach and other companies. If you get a 10mm or 15mm hub-centric spacer, as long as they are of high quality and the wheel bolts are long enough, then you can fit them without worry. I wouldn't go any more than a 15mm spacer however.
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      05-16-2009, 12:49 AM   #7
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Hi there, I'm hoping you (E92Fan) can help me out with a similar offset question. I have a 2008 E90 (323i). I am looking at some 5-zigen rims that are 18.75" with a 35mm offset. The tires are 225/40/18. Do you think that these would fit all right? Would it be best if I replaced the rear tires with larger ones?

Thanks,
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      12-11-2011, 06:40 AM   #8
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e92fan, you post was really helpful!

geckorazer, did you ran with your acs et43 without spacers? i just bought a set of acs type iv, 8.5jx19 et43 and 9.5jx19 et24 and was hoping i would not need spacers on the front.

is the pic in your profile the wheel you were asking about?
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