Recently purchased a 2020 GT-C Roadster and she is in need of new shoes. I am a BIG fan of Michelin PS4S tires and have them on several cars.
The stock GTC 265 front 305 rear is very very limited and I do not even see a 305 PS4S rear rated for a 12" tire.
I would actually like to move up to the GTR 275 front 325 rear sizing. The only tires I see available in those sizes are the Cup2 and R888.
I live in Florida and sadly there is nowhere other than Sebring to enjoy the capabilities of this car. Our group of friends and the occasional Mustang, Challenger/Charger etc. do see a little stoplight action (I know thats not what this car is made for) so I would like something that hooked good from a dig. When I switched from Pilot Sport Super Sports on mt CTSV, my 60 dropped almost 9/10 and overall handling was GREATLY improved. Would love to find them for the AMG.
OPtions appreciated.

Additionally, I will probably have it aligned with a more neutral setting to extend the life of the inside tread. This car just wont see the kind of driving it was built for but I love it. Any suggestions on Camber, toe in, etc appreciated.

I got my car earlier this year. I just bought some Continental tires, but they are all season tires. Tire Rack has Michelin pilot sport 4s for our car.

First, congratulations—your car looks absolutely stunning.

Second, the dilemma you’re facing is understandable, and there are two viable paths forward. You can either:

Retain the OEM GTC wheels and mount one of the tire configurations listed below, or
Upgrade to a GTR wheel set, which features a different offset that achieves the wider, more aggressive stance you mentioned in your earlier post—without the need for spacers.

The table below outlines how each tire setup alters the outer positioning relative to the original 265 mm front and 305 mm rear sizes. I have personally tested all of these configurations on my 2020 AMG GTC, and all fit without any rubbing issues.

Hopefully, this helps you determine the best direction based on your desired appearance and driving goals.





This is how the GTR wheels looks on the GTC with 275 front and 345 rear





In addition, regarding your mention of camber reduction: the GTC’s factory camber settings are relatively mild, though wider rear tires can benefit from a slight reduction to optimize contact patch and wear.
On the GT platform, camber adjustment is achieved by replacing fixed shims. The stock configuration uses shim #6; switching to shim #7 on the rear will effectively reduce negative camber.
No adjustment is necessary for the front wheels.

Wow. Thanks GP for the info on tires and wheels.

GP, awesome info. Thank you very much. That chart should be a sticky.
The first option with the 345 PS4S show 20mm and looks flush. I like it. This is my car with a 15mm spacer and the 305 tire too far. You can see how "stretched" the tire is to fit. Your pic with the 345 on the GT-C rim looks very close to flush fit. Is that correct? Obviously moving the entire wheel out 15mm is different that a properly fitting tire.

Checking to see if my dealer can match Costco who generally has the best prices but of course I worry about how they will handle my rims. It also bothers me when they dont take the time to remove the sticky backing from the old balance weights and then mount silver weights out where they are easily visible. I may buy a pack of black weights just to hand to them.

Wait, maybe I am not understanding your comment correctly, but I want to make sure we are on the same page.

The photo I posted shows my GTC, is fitted with GTR RXA rims. The GTR rim has an offset of +52 mm, compared to the +46 mm offset of the GTC OEM rim. This means that mounting a 345 mm tire on the GTC rim would cause it to protrude about 20 mm further outward.

In the photo, the offset difference explains why it appears to extend only about 14 mm—the GTR rim sits 6 mm deeper within the wheel arch. As a result, when you account for the additional tire width measured from its centerline, the net difference compared with a 305 tire on the GTC rim is approximately 14 mm.
Mounting a 345 PS4S on your GTC rim will effectively push the tire outward by about 20 mm, producing the same stance change as running a 20 mm spacer with the 305 tire.

Just to clarify, you would need new rims to achieve the 14 mm effect.

My apologies in advance if that was already obvious.

List of GTC and GTR wheels offsets (ET)


See the attache PDF of MY2020 Sales booklet of the AMG GT. Pages 12-15 show the various wheel options.

Deleted because I had a cocktail.

Deleted because of bad math due to the cocktail/

Deleted because its LATE and I went down a rabbit hole.

Okay....
So this looks like the closest available PS4S combo that keeps me very close to OEM diameter and adds a little width that should be close to flush.

HaHa

It is unfortunate to report that these sizes will not mount safely on the GTC’s OEM wheels!!
The front wheel is 9 inches wide, while the tire you selected requires a minimum rim width of 9.5 inches for proper bead seating and sidewall support.
The rear wheel is 12 inches wide, yet the tire’s maximum approved rim width is 11.5 inches, which creates an unsafe stretch and compromises load capacity, carcass behavior, and lateral stability.

After running several compatibility combinations, the only configuration that fits within the physical limits of the OEM GTC wheels is the following:
Front: Michelin Pilot Sport 4S (Star BMW) France 275/35ZR19 (100Y)
Rear: Michelin Pilot Sport 4S (K1 Ferrari) France 315/35ZR20 (110Y) XL

This is not an ideal setup. The rear tire turns at 726 rev/mile versus the OEM 764, and the front turns at 783 rev/mile versus the OEM 790. The resulting delta is approximately +4.34 percent between front and rear rotational speeds. That remains just within the generally accepted 5 percent threshold for the GT platform.
Plus, I'm not sure what is the specialty mods for Ferrari and BMW and what effect it may or may not have on the GTC, specifically for track use.

For street use, this delta is likely manageable. For track work, the increased rotational discrepancy risks provoking ABS and ESP intervention during threshold braking and high-load transitions. There are no verified community reports confirming stable behavior beyond a 5 percent F/R rotation delta, so it enters uncharted territory.
It could be that reseting the ASB/ESP can be done to compensate for it, but I don't have the information about it. See my posting at https://mbworld.org/forums/coupe-roa...ml#post9227106

Looks like it is Cup2's or R888 then.

This is what tire rack recommends when I put my cars info in.. The front is fine but I don't understand why they are recommending that 305 rear which has an 11.5" width max

Funny, but I have alerted them over a year ago about it and they still recommend it.

IMO, you’re better off staying with the PSS in the 275/335 setup mentioned above. It’s the best overall fit and performs very similarly to the PS4S. The only real advantage the 4S might offer— and only marginally— is improved grip in colder temperatures (around 50°F and below).



Compared with the OEM 265/305 configuration, this setup will give you an effect equivalent to running a 5 mm spacer up front and a 14 mm spacer in the rear. If you want to reach your 10 mm target in the front, you can always add a 5 mm non-hubcentric spacer.

Called Michelin and they recommended the stock size Cup2 OEM. When I pointed out that the 305/30ZR20 wasn't rated for a 12" wide wheel they said thats what Mercedes put on it OEM. They are rated to 11.5".

OEM Cup 2
Front:
265/35ZR16
Dia, 26.3"
Rim width range 9"-10.5"

Rear:
305/30ZR20
Dia. 27.2"
Rim width range 10.5"-11.5"

Closest comparable PS4S
Front:
275-35ZR19
Dia. 26.6"
Rim width range 9"-10"

Rear:
315/30ZR20
Dia. 27.5"
Rim width range 10.5"-11.5"

Those are probably my only choices on these wheels which I actually like quite well. The above PS4S will be almost exactly the same diameter and fill out the wheel wells a little better.

Based on your other post ( https://mbworld.org/forums/amg-gt-gt...ml#post9228594 ), the focus there was to identify a tire configuration that achieves the outward stance you are targeting for both the front and rear wheels. If this is not the target anymore, please ignore most of my posting above, Therefore, the PS4S in 275/315 is a reasonable option if a 5 mm outward shift at each axle relative to the OEM 265/305 specification is acceptable to you.

Stretching a tire designed for a maximum 11.5-inch rim onto a 12-inch rim introduces advantages and disadvantages, together with a mild safety consideration. The primary drawback on a rear-wheel-drive platform is a reduction in rear grip caused by the stretched sidewall profile. It is simply something to consider when evaluating overall handling behavior.

For clarity regarding the Michelin comment referenced abover:

The only OEM tire specification ever supplied by AMG on any model year of the GTC was the Michelin Pilot Super Sport in 265/35ZR19 (98Y) for the front and 305/30ZR20 (103Y) for the rear. Both carry the MO designation, which indicates Mercedes-specific construction. This does not prevent you from choosing alternative tires. The intent here is only to state the factual OEM configuration. There are NO OEM CUP2 for tne GTC

It is common for tire representatives across manufacturers, dealers, and shops to overlook the differences among GT variants, which may lead to recommendations that are technically correct for a GT or GTS but not accurate for a GTC.
The GT and GTS use 11-inch rear rims, making the PS4S a proper fit, which is not the case for the wider rear rims on the GTC or GTR.
In addition, Michelin Pilot Sport Cup 2 tires were never supplied as standard equipment or as a factory option on any GT, GTS, or GTC model.

Both MB and Michelin said the car was delivered new with Cup2 tires. I think I am probably going with the 275/315 option. My friend just put wheel and tires on his GT-R and really has my thinking LoL.

Nice GT-R and custom wheels. I assume this is your friend’s car, since you have a GT-C.

Regarding the tires originally delivered with the vehicle, check the window sticker or the build sheet for confirmation. If you do not have access to the build sheet and cannot locate it online, send me your VIN via private message, and I will retrieve it for you from the AMG/MB WIS system.

Yes it is.

Just to clarify for everyone that is new to these cars, regarding the AMG GT-C’s OEM tire specification:

After reviewing the OP’s build sheet, it is confirmed that the factory-equipped tires are designated R01 “Summer Tires”, which correspond to the Michelin Pilot Super Sport.
This differs from the R03 “Sport Tires”, which refer to the Michelin Pilot Sport Cup 2 and are reserved exclusively for the GT-R and GT-R Pro models.


PO's Build Sheet tire/wheel data



This does not mean that Cup 2s cannot be installed on the GT-C—many owners do so successfully—but it is important to distinguish between factory specification and aftermarket fitment.

The claim by Mercedes-Benz or Michelin that the GT-C originally came with Cup 2s is incorrect. This type of error is not uncommon, as tire codes are often misinterpreted across different model variants or advisors.

While educating myself on tires I came across this video that explains what they difference between on OE spec and aftermarket tire of the same make and model can be. Apparently the BMW spec PS$S is quite good.

Great info, thanks.