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[Vulcan50]

I'm (going to be) running square 18"x9" and my math says I need a 3.35mm spacer. (what are the odds, right?)

Based on the specs of style 189 (my stockers) and assuming that the faces on the front and rear are even from the factory, here's what I came up with.

Rear: 18x8.5J ET37 (18x215.9)
Center line: 107.95 (215.9/2)
Hub face to wheel lip: 70.95mm (107.95-37)


Front: 18x8J ET34 (18x203.2)
Center line: 101.6 (203.2/2)
Hub face to wheel lip: 67.6mm (101.6-34)

70.95mm-67.6mm=3.35mm

So the rear hub should sit 3.35mm further inboard. And is the setup is square the rear wheel lip/edge should sit 3.355mm inboard.

So to push it out I need a 3-4mm spacer.

[Vulcan50]

Somebody out there has to be able to tell me if I'm right

[squaredphoto]

Math looks ok but are the track widths front and rear equal on your car?

[Emilime75]

Why would you assume the track width(hub faces) are the same front and rear? Not saying they aren't, but I at least know that LCI E90 is wider in the rear than pre LCI E90, while the front stayed the same. E92/93 didn't get wider with LCI. Don't know about E91

Why do all this silly conversion and math instead of just comparing your stock width and offset, to your new width and offset, front and rear. There are tons of online calculators designed just for that. Not even going to try and tempt a headache to decipher your math.

I'm going to assume your new 18x9s have a +30 offset. If your offsets are different than +30, add/subtract the difference from the info below.

Front:
Compared to your existing wheel, this new wheel will have an inner rim which is 8.7mm closer to the suspension strut. The outer rim will poke out 16.7mm more than before.

Rear:
Compared to your existing wheel, this new wheel will have an inner rim which is 0.6mm further away from the suspension strut. The outer rim will poke out 13.4mm more than before.

16.7mm - 13.4mm = OMG...3.3mm. (what are the odds, right?)

[Vulcan50]

Your long explanation seems like exactly what I did, and explained 🤷*♂️

[Emilime75]

Negative. It took me less than 30 seconds and my way revealed that you don't need spacers to achieve your result.

[Vulcan50]

Originally Posted by Emilime75

Why do all this silly conversion and math instead of just comparing your stock width and offset, to your new width and offset, front and rear. There are tons of online calculators designed just for that. Not even going to try and tempt a headache to decipher your math.

"Based on the specs of style 189 (my stockers) and assuming that the faces on the front and rear are even from the factory, here's what I came up with."

Originally Posted by Emilime75

I'm going to assume your new 18x9s have a +30 offset. If your offsets are different than +30, add/subtract the difference from the info below.

While not important, they are 33et

Originally Posted by Emilime75

Front:
~will poke out 16.7mm more than before.

Rear:
~will poke out 13.4mm more than before.

16.7mm - 13.4mm = OMG...3.3mm. (what are the odds, right?)

"Rear:
~Hub face to wheel lip: 70.95mm (107.95-37)


Front:
~Hub face to wheel lip: 67.6mm (101.6-34)"

Originally Posted by Emilime75

Negative. It took me less than 30 seconds and my way revealed that you don't need spacers to achieve your result.

So again you just restated, in almost the exact same fashion, what I said.

Additionally, both your math and mine (which is somehow way different) show I need a 3mm spacer in the rear. Though you say I don't.

[Emilime75]

Maybe I misunderstood your end goal, but I think I now understand your thought process. This was even easier and faster to determine with an online calculator.

Simply type your stock widths and offsets in, and you get this...
Compared to your front wheel, the rear wheel will have an inner rim which is 9.3mm closer to the suspension strut. The outer rim will poke out 3.3mm more than the front.

So, yes, if you're simply trying to match what you had, then you'd need a 3.3mm spacer in the rear.

[BM3Rrrr]

All of this over 3mm....

[Vulcan50]

It started off simple enough