[dradernh]

I bought Michelin PS4S 255/35-18 square and planned to use an Apex ARC-8 18X9½ ET58 with a 5mm spacer in the rear and an Apex ARC-8 18X9 ET42 with no spacer in front. This arrangement had worked for me at the track, differing only by running Toyo R888R 255/35-18 tires in the rear and R888Rs in 255/40-17 on 17X9 ARC-8 ET42s in front.

I assumed the PS4S in 255/35-18 would fit all around by changing the front ARC-8s to 18X9 ET42s. Partly, my assessment was arrived at by seeing on Tire Rack's site that the section widths of the Toyo 17" R888R tires and the Michelin 18" PS4S tires were the same 10.2". While the PS4S' did fit in the back, they weren't even close to fitting in front. This was due to the tires contacting the struts.

In addition to changing the front wheel diameter to 18" to accommodate the square 255/35-18s, I'd also installed an M Performance Brake Kit in the front. When it was discovered that the front wheel and tire combination wouldn't fit, I chose not to remove one of the M Performance Brake Kit's rotor assemblies to compare it to one of the originally-installed M Sport rotor assemblies. I suspect a difference in the depth (height?) between the two accounts for the Apex ARC-8 18X9 ET42s & Michelin PS4S 255/35-18 combination not fitting in front.

The issue was resolved by installing VAC Motorsports 8mm front spacers and Turner Motorsport hub extenders. The tires now clear the TC Kline Racing Koni-based struts by a fair amount, and the gaps from the front tires to the slightly-rolled fenders on the outside and the struts on the inside are pretty much even.

[spidy512]

heya!

Pics maybe?

josh

[dradernh]

Originally Posted by spidy512

heya!

Pics maybe?

josh

Sometime, yeah; right now I'm deep in the throes of a move to a new home scheduled for next week.

This is the car with the 255 R888R set on it; the 255 PS4S set will look much the same except for more rounded shoulders and the extra 8mm poking-out in front:
]

[jordan24c]

How much front camber are you running? And supplemental to that, how much poke? I'm thinking of switching to square whenever I decide to buy my next set of wheels but I've got 10/12mm spacers that may need to be changed to fit 255s - I really like the flush look up top (even though I'm still slightly tucked, maybe 12/15 would go flush on OEM setup) but could probably deal with a little poke.

[dradernh]

Originally Posted by jordan24c

How much front camber are you running? And supplemental to that, how much poke?

1) -2.6° I also have TC Kline Racing's Koni-based front single-adjustable coilovers. I've read that they offer somewhat more tire-to-strut clearance than some other coilovers, but I'm not very knowledgeable in that area. If you're interested in exploring that further, TCK Racing is just west of you in Hilliard. No affiliation.

2) No idea; my purpose was to have 255s on all four corners. FWIW, I'm not a fan of the poke look, but I do want wider tires than the 245/225 that came on my car.

[jordan24c]

Originally Posted by dradernh

1) -2.6° I also have TC Kline Racing's Koni-based front single-adjustable coilovers. I've read that they offer somewhat more tire-to-strut clearance than some other coilovers, but I'm not very knowledgeable in that area. If you're interested in exploring that further, TCK Racing is just west of you in Hilliard. No affiliation.

Might have to reach out to em. I've only read/heard good things from both you around the forums and a couple of local CCA guys during our meetings.

[230iZTR]

If you want a little less poke in the front, I've been running 17x9et42 Apex wheels with a 5mm spacer and 2.4deg camber. It'll save a few mm at least.

[dradernh]

Originally Posted by 230iZTR

I've been running 17x9et42 Apex wheels with a 5mm spacer and 2.4deg camber. It'll save a few mm at least.

Who knows, maybe -2.6° camber required 3mm more, at least on my car.

I suspect a 5mm spacer would have worked as well. However, I've learned to rely upon the shops I use to guide me in matters like this. I dig in as far as I think makes sense, but I'm not really a handy guy, and they've probably seen thousands of modified cars across the decades with many of the same issues cropping up over and over again.

I'm just satisfied that whatever issue caused me to be unable to run a front setup that should have worked has been made to go away. I agree with my shop that the depth of the M Performance Brake Kit's rotor assembly was the likely source of the fitment issue. Size-wise, the measured tire section widths and the 9" ET42 wheel offsets being equal led the shop to that assumption.

When I bought the MPBK, I took quite a few measurements of its components and those of the blue M Sport brakes that came on the car but never thought to compare the depths of the rotor assemblies. I was mostly interested in weight and part number differences. Had I done the rotor assembly measurements, I might have saved myself a bit of confusion and a couple of weeks of time. Always learning...

[TrboMike]

If you still have the Toyos, would be interesting to see how wide their 255 tires are compared to the Mich's. I know "our tire is THIS size" can be way off not just between manufacturers but within tire lines of the same manufacturer.

[dradernh]

Originally Posted by TrboMike

If you still have the Toyos, would be interesting to see how wide their 255 tires are compared to the Mich's. I know "our tire is THIS size" can be way off not just between manufacturers but within tire lines of the same manufacturer.

The shop has the Toyos; they're unused but old now and going to recycling. The PS4S tires were unused, too.

We compared a mounted track tire to a mounted street tire to see if there was a difference. A 255/40 R888R mounted on an Apex 17X9 ET42 ARC-8 had a section width that measured exactly the same as a 255/35 PS4S mounted on 18X9 ET42 ARC-8.

[dradernh]

Originally Posted by spidy512

Pics maybe?

Here they are:

Front-to-Rear, from the Front and Further Away


Front-to-Rear, from the Front and Closer


Rear-to-Front, from the Rear


Front Tire, Head-On


Front Tire, from the Rear


Rear Tire, from the Rear


Rear Tire, from the Front

[AmuroRay]

MOAR!

Edit - Final wheel and tire specs, and how much clearance do you have?

[Mr. F22]

Originally Posted by dradernh

This is the car with the 255 R888R set on it; the 255 PS4S set will look much the same except for more rounded shoulders and the extra 8mm poking-out in front

so in summary, both a 255/35 R888R with an offset of +42, as well as a 255/35 PS4s with an effective offset of +34 are working up front for your specific application, correct? The latter potentially also would work without the 8mm spacer if you were running the stock m-sport brakes in front? I see you are also running 2.6 camber, are you running camber plates to achieve this? I'm really trying to make 9" fronts work on the set I plan on buying for next season so appreciate the insight!

[dradernh]

Originally Posted by AmuroRay

Final wheel and tire specs, and how much clearance do you have?

Sorry to be slow replying; for some reason, I just saw your post.

Front: M Performance Brake Kit / Michelin Pilot Sport 4S 255/35-18 / Apex ARC-8 18X9 ET42 / VAC Motorsports 8mm Spacer / -2.6° Camber / (slightly) Pulled Fenders

Rear: M Performance Brake Kit / Michelin Pilot Sport 4S 255/35-18 / Apex ARC-8 18X9½ ET58 / Turner Motorsport 5mm Spacer / -2.2° Camber / (slightly) Pulled Fenders

The clearances are unmeasured. I did rub the front fender liners slightly, but that was only after I began running the car hard on the track at Mid-Ohio. I think it would be very unusual to lean that hard on a car on the street, so I don't expect any more rubbing (I'm done with the track). There’s been no rubbing on the insides, nor on the rear fender liners.

Originally Posted by Mr. F22

so in summary, both a 255/35 R888R with an offset of +42, as well as a 255/35 PS4s with an effective offset of +34 are working up front for your specific application, correct? The latter potentially also would work without the 8mm spacer if you were running the stock m-sport brakes in front? I see you are also running 2.6 camber, are you running camber plates to achieve this? I'm really trying to make 9" fronts work on the set I plan on buying for next season so appreciate the insight!

For anyone just tuning-in and to be completely accurate: the front R888R was a 255/40-17 (with the same section width of 10.2” as the 255/35-18 R888R). The 17X9 wheel offset was +42.

The shop concluded the reason the PS4S 255/35-18 mounted on an 18X9 ET42 ARC-8 in front didn’t come close to fitting was that the other change I made – installing the BMW M Performance Brake Kit – introduced something that caused a tire that should have fit to not fit. Note that the section width of the PS4S is the same 10.2” as the R888R, so that didn’t change. That seemed to me to make sense.

The shop suggested that the rotor hat height differed and that was the cause of the inside rubbing issue. We didn’t measure the two to know for sure. However, I just now went to Brembo’s site to look up the specs for both rotor assemblies, and Brembo shows the MPBK at 73.1mm in height and the M-Sport at 73.2mm. So, we still don’t know what caused the need for an 8mm front spacer to fit a mounted tire that we think should have fit.

As I’ve pointed out in many posts before, I’m not at all expert in these matters, and that’s why I use qualified shops to help me choose upgrades for my cars. I’ve no doubt that if I gave the car and the front M-Sport brakes back to the shop and asked them to figure out why the MPBK required an 8mm spacer, they’d figure it out fairly quickly after removing the front MPBK components.

Anyway, on to your questions:

1) Yes, an R888R with an effective 255/35-18 on an 18X9 ET42 and a PS4S 255/35-18 on an 18X9 ET42 with an 8mm spacer for an effective offset of +34 both fit in front

2) Yes, it’s my distinct impression that an 8mm spacer wouldn’t be required with the M-Sport brakes

3) Yes, I’m running camber plates that came with the TC Kline Racing coilover kit I bought and had TCK install for me. TCK also pulled my front fenders slightly (not enough to be visible as far as I’ve ever been able to tell).

Some other things:

One of the vendors here (HP Autosport, I think) mentioned that some coilover kits leave more inside room for a wider wheel/tire combo than do other kits. TCK’s coilover kit was one they listed as leaving more room. TCK’s kit is Koni-based (valved to TCK’s specs), so maybe that has something to do with it(?). That bit of information is an example of why I generally go to qualified shops to help me (keep from making more mistakes than I already do! ).

Again, I’m no expert, but I think you should plan on choosing components that leave you the most space possible to fit the wider front tires you want to run. Whether that’s narrower coilovers (if you end up getting them), camber plates that give you a minimum of -2.5° (my estimate), pulled fenders, or, and this obviously will generally make life easier, going with 245s in front instead of 255s, assuming you’re not aiming for square wheels and tires.

TCK’s recommendation to me for tires was 265 in the rear and 245 in front. When I asked him about understeer, he just waved it off as not being enough to be an issue. The context was driving on the track, as that was why I had him modify the car. With his experience, I didn’t doubt that his assessment was accurate. I was stuck on square tire widths, though, so I didn’t take his advice.

I go to experts with decades of racing and high-performance BMW street car performance-build experience for their advice, service, and products, but I don’t always follow the advice. I’ll be the first to admit that hasn’t always worked out.

If I could get the money back from all my purchases of wheels and tires over the years that turned out not to fit or that I never got around to using for one reason or another, I’d be able to take a nice vacation. The cheapest way to test the limits is to either find someone who knows the limits of what will fit with your setup, or, for many of us, to buy a single wheel and a single tire and do a test fit. When it turns out to fit, the latter is somewhat more expensive than buying pairs (or quads, when the setup is square), but it's cheaper when it turns out the combo doesn’t fit.

Good luck with it – please let us know what you end up running.

[Mr. F22]

Thanks for the detailed response. I am with you – by no means am I an expert but trying to do my homework at this point to find some relevant examples of what’s worked for others before I consult with my local experts. Ultimately I’m trying to run a 9” square setup (255 ideally but willing to size down to 245s) on KW DDCs on a xDrive. I guess where I’m at right now is trying to understand if 9” fronts, even with the right offsets, can be done without camber plates. Unfortunately, I think camber plates and their added NVH is likely out of the question with the wife . There are K-Mac adjustable camber bushings but those seem to have mixed reviews...

[dradernh]

Originally Posted by Mr. F22

I guess where I’m at right now is trying to understand if 9” fronts, even with the right offsets, can be done without camber plates.

Unfortunately, I think camber plates and their added NVH is likely out of the question with the wife

I'd guess not.

Well, all else being equal, I'd say you've got a choice to make there, don't you!

[yaboibooch]

Man I wish I saw this earlier so I could have offered some help. I'm fitting 18x9.5 +45 square -2.7* F, -2.2* R. Also, I have the TCK kit in 300# F 600# R thanks to your recommendation.

Playing around with 15mm, 17.5/18mm, and 20mm spacer up front and nothing in the rear. Main problems with fitment have been:

1. +45 offset on a 18x9.5 wheel is enough to tuck the wheels when the fenders are rolled/pulled and with enough camber (1.8* is the minimum). The relatively aggressive offset means I'm not sure if I could fit a 265/35R18 on the rear.

2. The front effective offset is anywhere from +30 to +27.5 to +25. This works but if I'm going to the track I run the bigger spacer to make sure the tire doesn't get caught on the spring perch when the tire expands.

3. Wider spacer means I rub somewhat on heavy load or occasionally when I fuck up getting in and out of driveways or over parking lot speed bumps. Note: The driveway/parking lot bump issue has only occurred with the track alignment and 20mm spacers.


Potential Fixes:

1. Since my wheels are good quality and forged, I have considered shaving the back pad of the rear wheels by 5-ish mils to get more clearance for a wider tire. If that worked out I would potentially shave all 4 wheels so I could rotate them as I see fit.

2. There's another poster here, @Anthony235 who also ran 255/35R18x9.5 +45 and he used a 5.51" 600# Eibach spring in the front to clear the tires on the inside near the spring perch. Personally I would choose a 6" (but hopefully 7") hypercoil/swift spring rated around 450#. Car is dual duty right now so I want more compliancy than a 600# spring without risk of bottoming out the shocks. Also not sure if I want to then run a stiffer spring in the rear to keep the balance where I like it.

3. Hoping the #2 fix provides me with a #3 fix. I don't *want* to run a 20mm spacer up front since the 15mm or 17.5mm would definitely suffice even with the wider tire if I had shorter spring.

Anthony's fitment thread is here (Go to page 2): https://www.2addicts.com/forums/show....php?t=1321230

There's another guy here who has 255/35 on 18x9 but I can't find the thread.

Looks like you have this pretty figured out but I just wanted to share my experience in case it helped you or anyone else. Good luck.

[AmuroRay]

I curious about the 265s and 18x9.5 - let us know if and you get it fitted

[yaboibooch]

Originally Posted by AmuroRay

I curious about the 265s and 18x9.5 - let us know if and you get it fitted

https://www.2addicts.com/forums/show...1142121&page=3

This guy fit 18x9.5 +45 on the rear with 265/35.

https://www.2addicts.com/forums/show...1487864&page=2

This guy fit 18x9.5 with an effective offset of +30 in the front, +50 in the rear.

For my wheels the first guy's fitment in the rear is obviously more applicable to me. The second's is relevant to my front fitment. Seems like the latter had issues with the tire expanding during hot laps and rubbing against the wheel well aft of the tires. Though the dudes at EAS did this...

https://europeanautosource.com/blog/m2-or-m235i

And it seems they were able to work in a 265/35 RE71R on 18x9.5 square. I haven't heard anything about the car so I can't confirm if it worked when Capt_and's had issues.


If I can fit 265's in the front without issues I'll post the modifications needed in its own forum post. 265's for the rears is definitely common on 18x9.5, for my offset of +45 it should work but I might need to shave ~5mm off the backpad of the wheels if it comes down to it.

[AmuroRay]

Originally Posted by yaboibooch

https://www.2addicts.com/forums/show...1142121&page=3

This guy fit 18x9.5 +45 on the rear with 265/35.

https://www.2addicts.com/forums/show...1487864&page=2

This guy fit 18x9.5 with an effective offset of +30 in the front, +50 in the rear.

For my wheels the first guy's fitment in the rear is obviously more applicable to me. The second's is relevant to my front fitment. Seems like the latter had issues with the tire expanding during hot laps and rubbing against the wheel well aft of the tires. Though the dudes at EAS did this...

https://europeanautosource.com/blog/m2-or-m235i

And it seems they were able to work in a 265/35 RE71R on 18x9.5 square. I haven't heard anything about the car so I can't confirm if it worked when Capt_and's had issues.


If I can fit 265's in the front without issues I'll post the modifications needed in its own forum post. 265's for the rears is definitely common on 18x9.5, for my offset of +45 it should work but I might need to shave ~5mm off the backpad of the wheels if it comes down to it.

Please please please keep us posted on this. Wider wheels/tires is one of the weakest links on this chassis - being able to fit 255-265 tires would be awesome.