F30 Wheels on E89

[bimmerboi]

Hey guys! Had a quick question. Would it be possible to fit F30 400m rims on the E89?

Info for the F30 rims:
18x8" ET34 225/45-18 front
18x8.5" ET47 255/40-18 rear

Info for the E89 18 set-up:
18x8 ET29 225/40 ZR18 88W 5x120 in front
18x8.5 ET40 255/35 ZR18 90W 5x120 in rear.

Thank you in advance!

[bimmerboi]

Sorry if this is a silly question, but I wanted to make sure before purchasing the 400m wheels for the Z4. I understand the tires are different, but will I need spacers, etc? I see they are both a staggered set-up...

[enuff_zed]

Welcome aboard.
Looks to me as though the fronts will sit further in by 5mm and the rears by 7mm.
Given that I've stuck 15mm spacers on my standard E89 rear wheels to fill the arches better I think you'd be looking at possibly adding 20mm spacers to the rear and maybe 5 or 10 to the front?
There are other more expert wheel people on here who will no doubt advise better than I.

[B21]

I'd go 5mm front and 10mm back spacers (and of course longer bolts)..you could go 15mm rear with those sizes

[Burakkiliboz]

Hi, I understand that we need spacer and longer bolts. What about tires? Can we use 225/40/18 in front and 255/35/18 in rear with F30 wheels???

[B21]

Hi, I understand that we need spacer and longer bolts. What about tires? Can we use 225/40/18 in front and 255/35/18 in rear with F30 wheels???

Yes

[Pondrew]

Hi, I understand that we need spacer and longer bolts. What about tires? Can we use 225/40/18 in front and 255/35/18 in rear with F30 wheels???

To expand on the answer above, which is correct of course, the important number is the rolling circumference or radius.

Tyre sizes are quoted in width (say 225), profile (say 40) and diameter of wheel (say 18"). Why the sizes are both metric and imperial is anyone's guess. The width is in millimetres. The profile is a percentage of the width, in this case 40% (90mm). This will give a rolling circumference of (90mm + 90mm + 457mm x pi) = 2,000mm.
So a different wheel with the same diameter (18" in this case) will need the same tyre dimensions to give the same rolling circumference.
Tyre profiles go up in 5% increments, 30, 35, 40 etc. If you were to increase your diameter of wheel to 19" and put a 40 profile tyre on, it would give a rolling circumference of (90mm + 90mm + 483mm x pi ) = 2,082mm. So 82mm larger. So you reduce your profile by one increment to 35 in this case: 78.75mm + 78.75mm + 483mm x pi = 2,011mm. Only 11mm larger circumference, or 0.5% which is acceptable. I think the 'rule of thumb' is around 1.5% as being OK without problems.

Rolling circumference staying within 'limits' is important to ensure speed is shown correctly and, with modern cars, sensors in and around the wheels operate correctly.

Wheel spacers is a completely different subject....but I'm tired now. HTH

[Burakkiliboz]

Perfectly understood and will follow the advise many thanks Pondrew