The quest for wider wheels and tires, 295, 305 and beyond...

[pdx_m3s]

Love this setup. It’s nice to see what’s possible in this thread.

 

[Lindenwood]

I've just trawled through this thread start to finish for the umpteenth time and added a bunch of different confirmed(ish) fitments into a disorganised notepad document. I was in a bit of a scattered state of mind trying to put different brake, wheel, spacer and subjective fit outcomes so please dispute my maths if something looks wrong. Any figures noted below are for non-Performance brake spacing (i.e. factory cast rotors or aftermarket rotors with aluminium hats) so adjust by ~4mm to apply to M3P factory rotors. All offsets are effective offset including spacers if used. Below are some key figures for your dissection, confirmation and/or disagreement:

For inboard fitment (i.e. from the wheel-to-hub mounting plane to the nominal inboard extent of the wheel):
The furthest confirmed inboard fitment for 19" is the @MountainPass MegaMesh 19"x10.5" ET+33: 166.5mm mount to inner. MPP have a vertical inner lip so a tapered lip at 19" would have a spare millimetre or two.

User @The Other Dan posts here showing 18"x11" ET+27*: 166.7mm mount to inner. This corroborates the above; 18" has less clearance to the upright, but this wheel has a tapered inner lip and some mild shaving of the upright resulting in acceptable clerance. (*ET+40 minus 13mm effective spacing: 17mm spacer but stock M3P brake rotors)

Coincidentally in Australia we can't make the track more than 25mm wider than the widest factory option. Allowing for rounding and variability in aluminium rotor hat thickness, my offset limit for an 11" wide wheel is ET+27. The universe is whispering to me.

For outboard fitment (i.e. from the wheel-to-hub mounting plane to a variable and somewhat subjective clearance to the guards):
Note: Outboard fitment is affected heavily by tyre size. I'm going to refer to the outboard extent of the wheel, not the tyre, because we can't even count on two different 295s to be the same width. Thanks for your Goodyear epiphany @MasterC17. I'm only looking at use cases with adjustable FUCAs, I consider it unwise to run this wide with factory camber.

Looking at the fitment from The Other Dan again we get 112.7mm from mount to outer. His post states it clears with approximately three degrees of negative camber, which I consider to be very reasonable for this width.

Next wildest is from @gearchruncher in this post showing an 18"x10.5" ET+25, giving 108.5mm from mount to outer, with confirmed clerance on 295/30R18 Hoosiers with 2.3 degrees negative camber. I consider this to corroborate The Other Dan's fitment in general terms.

Notes:
- 18"x11" ET+27 is the widest confirmed fit inboard and outboard
- 18"x10.5" wide is a sensible option if you want to avoid irreversible mods (i.e. upright shaving or hand-pulling the guards).
- 18"x11" with a wide 305 or any 315+ will cause you to have clearance issues both inboard and outboard
- 19"x11" can avoid the need to shave the upright but does not change the tyre clearance limitation at all
- 20"x11" looks badass but same limitation and restricted tyre choice/pricing
- We've found the limit of what the factory panels support without rolling or a wide-body kit

Oh! I do owe you some credit for compiling all of these data. Definitely made it easy for me to narrow down the target offset!

You can add to your pool: 19x11+28 did NOT require shaving the upright, but it’s comically close.

Of note, while 285 is not strictly the widest carcass width here, being stretched on an 11” wheel probably makes it closer to what might be considered a “290” on a 10.5” wheel. That said, at 26.9” this is likely the tallest “wide” setup since most are using smaller diameters. The extra height results in the same total tread surface area of roughly a 295 or even “300/30R19” tire, while maintaining best sidewall support.

 

[Collutio]

Is this actually monitored and enforced at millimeter level precision?

Not as a part of regular roadside inspections, but if you have an accident a savvy insurance assessor might measure it as a way to deny the claim.

 

[Lindenwood]

Not as a part of regular roadside inspections, but if you have an accident a savvy insurance assessor might measure it as a way to deny the claim.

Is there real precedent for this? Fears like this exist in the US but there are no actual examples. Just like if you get hammered and drive your car into a school, your insurance will still pay up to the covered limits. Yes, the company (or a victim) may use such details to further justify suing you after the fact, but in my experience those are usually only small parts in an otherwise easy win.

 

[shimmy]

@Lindenwood really appreciate the details and knowledge sharing! I was researching something similar and good to know a 19x11" wheel fits in that offset with 285/35 tires. Are you planning on sticking with that tire size when going to a track tire setup or would you consider a 295/30 or 305/30?

 

[MODEL+]

From experience with handling many different brands of wheels, I would like to point out that the rim flange thickness matters when we are talking this tight of tolerance in relation to the suspension upright. That specific wheel @Lindenwood used may not directly translate to clearance with another wheel from another manufacturer.


-Danny

 

[Lindenwood]

@Lindenwood really appreciate the details and knowledge sharing! I was researching something similar and good to know a 19x11" wheel fits in that offset with 285/35 tires. Are you planning on sticking with that tire size when going to a track tire setup or would you consider a 295/30 or 305/30?

The current plan is to race on 285/35R19 RE71RS. I might go down to a 275/35R19 RE71RS if I have any major fitment issues; a secondary benefit is the 275 is perhaps 1.5lb lighter than the 285 (I expect it’s like 29.4 vs 30.6lb, rather than the listed 29 vs 31 pounds, but it’s not insignificant.

However, I 1) do not plan to go any wider because I’ll only trade tire width for sidewall support, and 2) do not intend to choose any other tire model

 

[MountainPass]

Looks awesome @Lindenwood ! My suggestion would be to bring a pair of thin spacers to your next even just in case you need to quickly gain a little more clearance to the spindle. In my experience, it looks like it is going to rub under load, and you don't want that to ruin your weekend!

 

[Lindenwood]

Looks awesome @Lindenwood ! My suggestion would be to bring a pair of thin spacers to your next even just in case you need to quickly gain a little more clearance to the spindle. In my experience, it looks like it is going to rub under load, and you don't want that to ruin your weekend!

Yeah, and next time I have the wheels off I might also go ahead and shave a bit off the knuckles just to be sure!