[RacerBowie]

So... I'm dumb and planning a One Lap of America entry for either 2024 or (more likely) 2025 and trying to figure out wheels/tires. The rest of the car setup is in progress as well, but looking like more or less a full "Stage 1" (intercooler/catted DP/intake/tune/etc) for power, probably a set of MCS one-way coilovers if we mess with the suspension. Car already has a limited slip.

As we're all aware at this point, BMW can't be bothered to put decent sized wheel openings on non-M cars, which is always fun. Stock diameter is 24.8" rear, 25.1" front on the staggered 18" setup.

Currently I'm running 17x9et42 square, 12mm spacer in front, no spacer rear, 245/40 tires - Diameter is 24.7". Lots of camber in the front.
A square setup is a must for me, for rotation purposes needed for this event, and for only carrying one spare.

For One Lap I'm looking at two options:

1. 18x9et42 with 235/40 RE-71 - Diameter is 25.4"
2. 18x9.5et35 or et43 with 255/35 RE-71 - Diameter is 25.0"

So current setup a tiny bit shorter than stock, 18x9 setup is a touch taller, 18x9.5 setup is right at stock diameter.

Long opening over: Can I fit the 9.5s in a square setup?

Rear: I know people fit 9.5et58 in the back, but that isn't going to work in the front. I'm unsure if the et35 will work in the rear with no spacer. It pokes about 13mm more than the 9.0et42, and those already seem pretty close. The et43s look closer for the rear, assuming there is space inboard.

Front: I haven't heard of anyone actually fitting 9.5s up front with stock fenders. Anyone done it? The current setup is an effective et30, and it fits no problem, but only has about 5mm to spare from rubbing the strut. A 9.5et35 with a 12mm spacer has the same inboard clearance but is 13mm farther out. Not sure there's space for that. A 43 would require a 20mm spacer to achieve that same thing... that's a LOT of spacer.

What are the thoughts of the group? Anyone been down this road? I've found a cracked 9.5et35 wheel to play with a little, but haven't gotten my hands on it yet.

[yaboibooch]

I've been running 18x9.5 square wrapped in 255/35R18 200tw for about a year now. You can find the steps I took in my post history. I think you're better off with either going widebody or sticking with 18x9. I'm happy with my wheel and tire selection but 18x9 allows for more alignment options and would probably go down that route if I were to again.

[230iZTR]

Originally Posted by yaboibooch

I've been running 18x9.5 square wrapped in 255/35R18 200tw for about a year now. You can find the steps I took in my post history.

Do you have a build thread or photos anywhere? I looked through a couple pages of results and had trouble following the details.

I think they're 18x9.5et45 square with a moderately sized spacer, but it was unclear what size. TC Kline coils but theyre modified for inner clearance? What camber, fender roll/pull, spacer size? Is it on stock msport 340mm/345mm brakes?

[yaboibooch]

No build thread but I should get some pics up. Ideally you want 18x9.5 with an offset in the +50 and over range. +45 is the limiting factoring for going wider. The fronts can handle a 265 but with my current offset a 265 would poke in the rear. I have considered shaving the backpad ~5mm, never got around to it. An extra 10mm section width won't make me faster and I enjoy the feedback through the thinner tire.

Spacer I'm using right now is a 15mm. You could use a 20mm or a 17-18mm depending on your fitment.

Stock MSport brakes, looking to move into Kern's F8x M4 rotor upgrade.

TCKlines were not modified at all. You will need to make sure whatever coilovers you're using have a shorter spring. I've seen people run 6" eibachs rated around 600#. Mine are longer and softer which I like since I daily the car, though not the wheel/tire setup.

Fenders were rolled (and pulled however not by much, just a sideeffect of rolling).

Alignment Settings were something like this:

F: -2.8 Camber, 1/16" toe out, I forget caster.

R: -2.2 Camber, 1/8" toe in.

Ride height is low but with enough clearance for the tire setup.


I would like to reiterate that I think 18x9 is a much easier setup. Less headache, more alignment options. You can get on track immediately instead of chasing after that extra bit of tire. I've seen people on here have a good time with 255/35R18x9.

UPDATE 12/21/2023: 12mm spacer, everything else is the same. Make sure your main spring is short enough.

[Dom147]

Sorry for being off-topic but i am very interested in seeing your 17x9ET42 setup. What suspension are you running? I ran a 18x9ET42 on my 228i with a 12mm spacer up front and it poked out maybe about 4mm at the tire on 255/35r18 at 2.5 degrees of negative camber. Does the rear poke at all either?

[230iZTR]

Originally Posted by Dom147

Sorry for being off-topic but i am very interested in seeing your 17x9ET42 setup. What suspension are you running? I ran a 18x9ET42 on my 228i with a 12mm spacer up front and it poked out maybe about 4mm at the tire on 255/35r18 at 2.5 degrees of negative camber. Does the rear poke at all either?

[Heres my build thread](https://www.2addicts.com/forums/show....php?t=1942610)

Its ever so slightly pokey. But thats the kind of meaty track fitment I like.

[dradernh]

Something to be aware of when going with wider tires and wheels is the effect upon scrub radius and what to do about it (if you choose to). This is explained by Steve Dinan in the youtube video below.

What has been important to me regarding this issue is the effect that variable rear toe can have on handling when you're really leaning on the car. My experience of the downside took place in a race car at Watkins Glen. The shop I used hadn't kept up with the status of the rear toe arms' bearing deflection, and I darn near crashed the car while accelerating hard out of T9 just like I always did. The car was determined to go straight into the Armco and I saved it only due to skills I'd learned at rally school.

On the street in my M240i, I've had no issues with wider wheels and tires, nor did I on the track at Mid-Ohio, where I never leaned on the car particularly hard. At the track in the F22, all the rubber bushings in the suspension made the car relatively loose anyway, so I just took what the car gave me.

If I'd kept going to the track and wanted to enjoy reliable performance out of the suspension, I would have had motorsport-level arms/bushings installed front and rear and lived with the added NVH and shortened maintenance intervals. Turner has a page with a good selection here: https://www.turnermotorsport.com/BMW...arms?N=1z141y6.

[AmuroRay]

I have a set of ARC8s 17X9 ET30. Would they fit on my M235i?

[RacerBowie]

Originally Posted by AmuroRay

I have a set of ARC8s 17X9 ET30. Would they fit on my M235i?

They're perfect for the front, as long as you have some camber, at least -2*.

They'd be pokey boys on the rear, and probably rub under load.