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      08-30-2013, 12:44 PM   #1
dhirm5
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Offsets - experts please chime in

Stock offsets for the 20" wheel are:

9Jx20 ET34
10Jx20 ET34

Most people use 12mm spacers in back for perfect/flush fitment, so the ideal offset for a custom 20" wheel of the same 10" width would be 22 (fixed). I think this part is solid (but correct me if I'm wrong).

Now - let's say I move up to an 11" width in back. Since 1" = 25.4mm, an 11" wide wheel would stick out past the stock 10" out the gate by half of it's width, or 12.7mm. So a 20" wheel with 11" width using an offset of 34 would actually stick out FURTHER in back than the OEM 20+12mm spacer by 0.7mm.

Therefore the ideal offset, being slightly conservative to avoid rubbing, for a 20x11 wheel, would actually be 35, which would tuck under by 0.3mm vs an OEM 20+12mm spacer.

Does all this sound right?

Once this is confirmed (or corrected), I can figure the front and finally consider myself as having fully understood offsets.

Thanks

Last edited by dhirm5; 08-31-2013 at 05:30 PM..
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      08-31-2013, 03:53 PM   #2
Charlie Brown
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Quote:
Originally Posted by dhirm5
Stock offsets for the 20" wheel are:

9Jx20 ET34
10Jx20 ET34

Most people use 12mm spacers in back for perfect/flush fitment, so the ideal offset for a custom 20" wheel of the same 10" width would be 12. I think this part is solid (but correct me if I'm wrong).
I think you meant to type 22 not 12?

Yes; a 11Jx20 ET35 will have the same look as a 10Jx20 ET22 (ET34 with a 12mm spacer)

Check out www.willtheyfit.com to help visualize the look as well as diff tire sizes.
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      08-31-2013, 05:31 PM   #3
dhirm5
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Quote:
Originally Posted by Charlie Brown View Post
I think you meant to type 22 not 12?
Yes indeed - fixed in the original post. Basic math skills deserted me.
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      09-01-2013, 09:26 AM   #4
dhirm5
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So optimal flush offsets for our cars for custom 20" wheels with 9.5"/11" widths front/rear is:

Front: 9.5Jx20 ET29 (equiv to an 11.4mm spacer on OEM)
Rear: 11Jx20 ET35 (equiv to an 11.7mm spacer on OEM)

** Some might want to use a bigger offset in back to stay closer to the somewhat more common 10mm spacer in the rear - add 2mm to the offset to bring that poke down to a more conservative 9.7.

Hope this helps someone.
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      04-16-2014, 10:32 PM   #5
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Sorry to revive an old thread but need expert opinion. I want to go with some custom wheels and would like to do 20x10 front and 20x11 rear. Has anyone went with a 10 inch wide wheel upfront. I was planning to go with 20x10 et 34 front and 20x11 et 35 rear. Do you guys think this would work.
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      04-16-2014, 10:48 PM   #6
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Yeah that should work... Japanese wheel makers (Advan, Rays, and Volk) make F10 M5 specific specs with 20x10 fronts at mid 30's offsets.
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      04-17-2014, 05:20 AM   #7
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You should send a pm to pertplus. He's our resident wheel king
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