APEX ARC-8 18" Wheel Fitment Guide for Z4 M

[rawlinstr]

Hi all,

Been doing a lot of forum surfing looking at pictures of Z4M's with 18" Apex ARC-8's to try and work out what sizes I would choose if I was to buy a set. Thought I'd post a summary of everything I've found here so it's all in one place on this forum and it might help others in the future!

Feel free to post pictures of your car / other cars you know if it has a different fitment to the ones I've included.


Fitment Guide from APEX

18x8.5" et38 wheels fit up front with great ease and either 235/40/18's or 245/40/18's.

18x9.0" et42 wheels also fit up front without the need for a spacer with 245/40/18 tires summer tires.
255/35/18 tires can be run on this size wheel, but a spacer may be needed.
Negative camber and spacers may be required depending on the 255 tire run as r-compounds and extreme summer tires can run wide.

18x9.5" et35 & et22 two offsets available, both work well, but the et22 offset is the best fit. APEX suggest a 12mm spacer for flush fitment
They can be run with either 265/35/18 or 275/35/18 street tires or r-compounds.
The 9.5" et35 wheel can also be used up front with 245/35/18's or 255/35/18's with added negative camber.

18x10" et25 fit the rear with 275/35/18's with ease on stock and lowered cars.
R-compounds may have slight rubbing on the inner rear fender liner material.
This is a foam sound deadening material that can easily be trimmed or ignored.


Example Photos

So far I've found the following examples with known specs for both wheel and tyre sizes:

Example 1:
Front: 18 x 9.5 ET22 with 245/40/18 tyres
Rear: 18 x 10 ET25 with 285/35/18 tyres


Example 2:
Front: 18 x 8.5 ET38 with 235/40/18 tyres
Rear: 18 x 9.5 ET22 with 255/40/18 tyres


Example 3:
Front: 18 x 8.5 ET38 with 235/40/18 tyres (and a 10mm spacer)
Rear: 18 x 9.5 ET22 with 265/35/18 tyres


Example 4:
Front: 18 x 9 ET42 with 245/40/18 tyres
Rear: 18 x 10 ET25 with 275/35/18 tyres


Example 5:
Front: 18 x 9.5 ET35 with 265/35/18 tyres
Rear: 18 x 9.5 ET35 with 265/35/18 tyres


Example 6:
18 x 8.5 ET38 with 235/40/18
18 x 10 ET25 with 265/35/18


Example 7:
Front: 18 x 9.5 ET35 with 255/35/18 tyres
Rear: 18 x 10 ET25 with 275/35/18 tyres


Example 8
Front: 18 x 10 ET25 with 275/35/18 tyres
Rear: 18 x 10 ET25 with 275/35/18 tyres


Example 9
Front: 18 x 9.5 ET35 with 255/35/18 tyres
Rear: 18 x 10 ET25 with 275/35/18 tyres

 

[3002 tii]

Re 9.5 et35, the spacer isn’t just for flushness but depending on suspension setup you may need the spacer just to clear the strut. I run a wide 255 on a 9.5 et35 and need 5-10mm (depending on how square the shoulders are for given tire).

 

[rawlinstr]

Re 9.5 et35, the spacer isn’t just for flushness but depending on suspension setup you may need the spacer just to clear the strut. I run a wide 255 on a 9.5 et35 and need 5-10mm (depending on how square the shoulders are for given tire).

Thanks for the info, just to check are you talking about on the front or the rear?

 

[3002 tii]

Thanks for the info, just to check are you talking about on the front or the rear?

Fronts only. Rear 9.5et 22 fits fine for 255/265.

 

[TomK]

I'd take that fitment guide with a pinch of salt if you are going to drive the car hard on a track.
18x8.5 ET38 Front 235/35 -3ve - rubs archliners
18x9.5 ET22 Rear 265/30 -1ve - rubs archliners

 

[rawlinstr]

I'd take that fitment guide with a pinch of salt if you are going to drive the car hard on a track.
18x8.5 Front 235/35 -3ve - rubs archliners
18x9.5 Rear 265/30 -1ve - rubs archliners

Thanks Tom that's good to know. Could you add your offsets to your post as well please?

 

[Ed Doe]

I know not quite Arc-8s, but EC-7s so similar, albeit I think with slightly more brake clearance???

Fronts: 8.5J ET35, tyres are 245/40/18 Yoko AD09 (semi-slicks)
Rears: 10j ET25, tyres are 265/40/18 (same YokoAD09)

Mine has had the rear arches rolled slightly to accommodate the tyres (previous owner did also run 275 for a bit..!

Fronts do catch the arch liners - they have been eaten a fair bit from tracking it.

 

[rawlinstr]

18 x 9 ET30 test fitted with a worn 245/40 tyre - rubs on the arch liners at full lock in both directions but I’m not too fussed about that, however I need to drive it to see whether it rubs on the arch lip under compression!

Currently running less than 2 degrees of negative camber (closer to 1) so I have that as an option if needed. Will report back

 

[RMB]

Crikey that looks really close to your lovely performance calipers no?

 

[rawlinstr]

It’s close yeah, but there’s clearance!

 

[rawlinstr]

Finally got them fitted today (still waiting for centre caps). Final spec:

Front: 18 x 9 ET30 with Continental Sport Contact 7s in 235/40

Rear: 18 x 10 ET25 with Continental Sport Contact 7s in 265/35

The tyres on the front are a bit stretched for my liking but I wanted to minimise rubbing as much as possible.

 

[AndyBeech]

Looking good, suit the car well, nice colour. Why'd you go for 9 and 10" widths on those tyres out of interest rather than 8.5 and 9.5?

 

[Ed Doe]

Looking good, suit the car well, nice colour. Why'd you go for 9 and 10" widths on those tyres out of interest rather than 8.5 and 9.5?

I'd have gone 9 and 10 if I'd been buying mine fresh! 8.5 doesn't have quite the same concavity as the 9s irritatingy!

 

[rawlinstr]

Exactly as Ed says - the 8.5” wheel has a flatter face profile than the 9”

Also as the car evolves I’ll probably start adding some suspension geometry mods that will allow me to run a 245 and and a 275 more comfortably in the future!

 

[TheZ4M]

Here is mine SM-10's
18x8.5 ET35 Front 235/40 Conti Sport 02
18x9.5 ET22 Rear 265/35 Conti Sport 02

No issues

 

[Mr Tidy]

Presumably it's all about aesthetics, but you're never going to get proper concave on a Z4M given the limitations of the axle width and space in the wings, unlike the rear of a Z3M.



And a 265 tyre won't offer any more grip however wide the rim is, surely you're just adding unsprung weight with wider rims and a stretched look?

Maybe I'm just my age.

 

[v10m]

Concave FTW like my old ZM...