canucklehead

I was running the CUP 2 ZPs at that time.
Cold pressures are about 26 psi starting, and try and keep hot pressures around 32-35 psi. You will probably have to run 1-2 psi lower in the front left tire.
It will take at least 2 good full laps of Area 27 to get tires up to temp at that cold pressure.
Once tire temps hit 90C I usually shut it down at that point as that is the limit of max grip and tires get pretty greasy.
I do have wing set to max.

user33

The following pictures show the EOL wear situation for the first set of Cup 2 front tires on my GTR Pro after the high-camber alignment. This is after 6 track days (3x VIMC, 2x Mission Raceways and 1x Area 27) about 10 hr on-track running and about 20 hr highway driving ... I'm fairly aggressive at VIMC and Mission. VIMC has 19 corners in 2.3 km (1.43 mi). I target hot-running pressures of 36-38 PSI and try to keep tires below 100 deg C (though sometimes have hit 110 deg C).

The outside edges (both front/rear) have had much less wear, with the high-camber alignment ... as was the goal/expectation. The inside edges (both front/rear) have had increased wear. The increased inside-edge wear was expected during highway driving, but the majority of that wear is occurring on the track, which I did not expect. In fact the wear is mostly on the inside edge of the tire that's on the inside of the curve -- i.e., the one that's not taking the cornering load.

QUESTION: Is it possible that a toe-in change is needed? If so, any educated recommendations?
[alignment data is posted elsewhere in this thread]

supertanch

That does look like toe wear rather than camber. What's the front total toe you are running? I'd keep it close to zero for the front if you are comfortable with the turn in.
But in general, the inner will be wearing out much faster than the outer if the camber is right, especially when the tires are at temperature. Our cars are relatively heavy unfortunately...

user33

The alignment info is at https://mbworld.org/forums/coupe-roa...ml#post8796944.

It was the fact that the most severe inside-edge wear was on the unloaded (when cornering) side that (maybe erroneously?) led me to think it might be able to be reduced. I have only a rudimentary understanding of alignment vs tire-wear, but I'd guess it has a little too much toe outwards ... but the alignment info shows an almost perfectly neutral toe. The alignment was done with new tires but I'm assuming it doesn't change a lot with tire wear ... especially since Cup 2 tires have a minimal diameter/height change due to their relative lack of tread depth.

It's also interesting that, although I run relatively high pressures to help prevent outside-edge wear, the center portions of the tread get little wear. Still, when I check the tread temperature with an temp gun (not as good as a pyrometer) after returning to the pits, the temps across the tire are what I'd expect ... pretty even except for a few degrees C elevation on the inside edge of the "mostly inside/unloaded cornering" tires and the outside edge of the "mostly outside/loaded cornering" tires.

It could be that I'm expecting too much ... I mean, 6 track days with 5 of them on short twisty tracks (and VIMC with it's 19 corners is 8x 15 min sessions) probably means the tires are completely "heat-cycled out" long before the inside edge is gone. #;-))

supertanch

I know we are nit picky here - that's an awesome tire life that you were able to get out of those tires. I'm still on 2 days a set if really pushing for it...

user33

Yeah, I have some Scottish blood in me and I do work a bit at trying to maximize tire life ... within the tradeoffs that still allow serious fun. The 15 min vs 20 min sessions at VIMC help, as does the fact that I tend to avoid track days (unless evening "days") during July and August, when it's likely to be quite a bit hotter. Cup 2 tires _are_ expensive.

Say, I just measured the tread depth on the new fronts I installed ... has anyone else noticed that they advertise 7.2 32nds of tread (which I did measure some years ago) but that they're now significantly less than that? The max depth I could find was across the rib-lines and that was, at best, 6.8 32nds?! $:-((

Seems to be the common trend, these days ... pay more for less (yes, I know, it's a first-world "life is tough, then you die" issue).

boosted20v

I went into the dealer on Friday inquiring about shims. They told me $950 for 12 shims!!!

G. P

Assuming that GTR Pro and GTR shims are the same part number, a complete set of shims P/N 197-357-06-00 cost $133 at https://www.mercedesofannarbor.com/o...D197-357-06-00
Each Shim Set has 4 x shim numbers 1-9 (total of 36 shims). If you do both Camber and Caster adjustment, you will need one set per corner (total of 4 sets). Camber use 2 shims and caster 2 shims, see illustrations below.
If you plan to do camber only, 2 sets will be enough for all 4 corners. Even if you plan to do both camber and caster on each corner (although rear caster is very unusual), chances are that you will use different shim numbers for caster than camber, so it will make sense to get 2 sets and see.

VintageFD

Jumpstarting this thread.
I recently had my alignment done on my Pro. -2.5 camber on the front. I will need to double check the toe but I believe it was 0.3mm out? One track, many spirited canyon drives ~2k miles left me with this wear pattern both sides. I do not think my camber can account for this much accelerated inside wear but my toe should have been too far off either. I would have noticed when I reviewed my alignment specs. Should we be looking at possible bushing issues?

s

supertanch

I'd definitely check the toe, toe out is wears the inside edge more. -2.5 is not really that much of camber. But again, depends on how hard you ran at the track day, 1 track day + 2k miles of spirit driving is a lot on the cup 2s, those don't last long.

thebishman

That’s a Toe issue unless proven otherwise