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      07-21-2017, 05:58 PM   #1
kiwi_chris
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21" rim offset dimensions for the i8

Hi all - am about to put 21" rims on my ride (21x9 and 21x10.5), along with H&R lowering springs.

If anybody else has done the same, could you please tell me what rim offsets you used to obtain that perfect fitment?

Were spacers also required? If so, what width?

Thanks.
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      07-27-2017, 11:54 AM   #2
Amgeater2
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Quote:
Originally Posted by kiwi_chris View Post
Hi all - am about to put 21" rims on my ride (21x9 and 21x10.5), along with H&R lowering springs.

If anybody else has done the same, could you please tell me what rim offsets you used to obtain that perfect fitment?

Were spacers also required? If so, what width?

Thanks.
+35 front and +47-50 rear
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rominun169.50
      07-28-2017, 04:22 PM   #3
13pauls
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What size tires are you going with?
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      07-29-2017, 09:42 AM   #4
Amgeater2
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Quote:
Originally Posted by 13pauls
What size tires are you going with?
I am running 245/35/21 and 285/30/21.
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      08-17-2017, 01:40 PM   #5
Rostman
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Does anybody know the fitment parametrs of the AC Shnitzer wheels? I really like how it sits on the car, but don't like the design of the wheels.
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      08-17-2017, 03:03 PM   #6
Amgeater2
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Quote:
Originally Posted by Rostman View Post
Does anybody know the fitment parametrs of the AC Shnitzer wheels? I really like how it sits on the car, but don't like the design of the wheels.
21x8.5 fornt and 21x9.5 offsets are not avaliable but pretty sure they between +35-38 front and +45-50 rear.
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      08-21-2017, 04:49 AM   #7
Rostman
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Quote:
Originally Posted by Amgeater2 View Post
21x8.5 fornt and 21x9.5 offsets are not avaliable but pretty sure they between +35-38 front and +45-50 rear.
Thanks
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      08-21-2017, 09:49 AM   #8
phoenixcsl
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Schnitzer wheels are:

21" x 8.5" ET42 (Front), 21" x 9.5" ET52 (Rear)

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      08-23-2017, 06:52 AM   #9
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Quote:
Originally Posted by phoenixcsl View Post
Schnitzer wheels are:

21" x 8.5" ET42 (Front), 21" x 9.5" ET52 (Rear)

They have charged me almoust EUR10000 for the set of their rims (without tyres and sensors). I found it too pricy. Looking for some other options.
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      02-02-2019, 01:42 PM   #10
416tt
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hi

would the following offsets work?

20x9 ET31 in the front
20x10.5 ET55 in the rear

thanks
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      02-05-2019, 10:00 AM   #11
evanevery
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Here is a link with the offsets for the various factory wheels on the i8:

https://bimmercat.com/bmw/EN/search/...i8/USA/36_2467

The size of the wheels (21") is not really the defining dimension here. What mostly matters is the WIDTH of the wheels.

Looks like they are using 36mm for 7" wide, 40mm for 7.5" wide, and 50mm for 8" wide wheels.

Generally, if you are trying to keep the wheels centered in the wheel well, you would simply add 12.7mm offset (25.4mm/inch / 2) for every 1 inch width increase of wheel. At some point, you are going to hit something (suspension inside or fender outside) and then you'll have to move the wheel one way or the other to maintain clearance.
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      02-05-2019, 10:36 AM   #12
416tt
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Quote:
Originally Posted by evanevery View Post
Here is a link with the offsets for the various factory wheels on the i8:

https://bimmercat.com/bmw/EN/search/...i8/USA/36_2467

The size of the wheels (21") is not really the defining dimension here. What mostly matters is the WIDTH of the wheels.

Looks like they are using 36mm for 7" wide, 40mm for 7.5" wide, and 50mm for 8" wide wheels.

Generally, if you are trying to keep the wheels centered in the wheel well, you would simply add 12.7mm offset (25.4mm/inch / 2) for every 1 inch width increase of wheel. At some point, you are going to hit something (suspension inside or fender outside) and then you'll have to move the wheel one way or the other to maintain clearance.
Thank you very much for the reply! makes sense.

I see @phoenixcsl reply above, his rear which is 21x9.5 (+52 offset), I wonder how close that is to the suspension on the inside because adding 1 inch with similar offset (+55) might be an issue :/
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      02-05-2019, 04:01 PM   #13
evanevery
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Just to make things blurrier... ;-)

Its usually not the wheels which provide interference issues. Its the tires.

A particular size of wheel might fit just fine without rubbing a tire, but change tires and you might have problems.

For example: I have been running Hoosier 265/35ZR-19 R7 slicks on my M4 track car. I just mounted a set of Toyo Proxes 265/35ZR-19 R888R slicks on an identical set of wheels (Apex Arc-8 19x10 ET 25). (Same exact wheels, same tire size). I know the 19x10 ET25 wheels will fit my M4 just fine. I also know the 265/35-19 Hoosiers will fit just fine when mounted on those wheels. However, I can't be sure the Toyo Proxes, of the exact same size, will fit until I get the car up on the lift and mount them! (Even though both tires are EXACTLY the same size, the Proxes have a 1/2 inch wider section width than the R7's)

IOW: Even though the wheels are exactly the same (mfr, model, size, dimension), you still need to take into account the actual dimensions of your intended tires (not just the "size")...
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