rht69911s

Okay, next question. Is anyone running 19s all the way around so they can use Pirelli DH tires? I'm used to all of the alternatives but the DH is an actual pro series race tire and for my dollar gives the best bang for the buck and provides the best safety in the extreme track environment. What are your experiences with this? Thanks as always

dlefty

Short answer, absolutely the way to go when you are ready as a driver…. I suggest having a roll bar and harness to hold you in tight!


Generally I would urge start with Pilot Sport Cup 2 in order to learn the car…..
Next up would be a Pilot Sport Cup 2R (Black Series) tire, the hard compound for lapping OR the Nankang CR-Sv2…..
Once you have these mastered or figured, then the 19” all around with the Pirelli slicks is next step.

Keep in mind the full slick does not have a linear breakaway like a “street” tire, and will not give an audible warning to let you know it’s not happy.

Once it breaks away, it has broken away.

I am not sure what you refer to as the slick being safer, but my advice above would be for anyone asking the questions.

thebishman

One of the members here has extensive experience running 19”s at COTA; hopefully he will pipe in soon!

dlefty

Ill recap my experience/use, maybe was too long and rambling 😁
When OP is ready, yes, use, you’ll go faster.
Biggest needed upgrade along with them is staying more secure in your seat.

thebishman

It’s a travesty that AMG doesn’t see fit to allow the option of a seat such as akin to Porsche’s Light Weight Carbon Bucket to be specified with the car. Would transform the on-track experience tbh.

MBNRG

Agree. But at least they are available. (no longer available?) And make the perfect stocking stuffers

https://mercteil.com/amg-gt-recaro-c...retrofit-r8BqP

rht69911s

I'm sorry for not being more clear with my question. I have driven on the track for many years in cars from a 1969 911s up to club racing a 991 Cup. My question was more in reference to the car's ability to handle the slicks and 19s all the way around. Are different rolling radii a problem for ABS/traction control etc.? Do the slicks stress suspension components in unanticipated ways? Any heat issues? That sort of thing. I would certainly add proper restraints (can't imagine exploring this cars potential in three points) brake cooling and regular fluid changes to the routine. Also, for anyone running 19s, what wheels and offsets did you use. I'm a fan of Forgeline as they produce a safe, reliable product but no need to reinvent the wheel here. (Snort) BTW, the advice given has been very good and much like what I would tell a newer driver at the track. Thanks

thebishman

This is an old thread and it’ll take some time to go through, but it might be of use to you:

https://mbworld.org/forums/coupe-roa...-upgrades.html

dlefty

The rolling diameter is not an issue, the front overall diameter gets a little taller at 27.1” vs stock 26.6”, rear is almost identical at 27.75 vs stock of 27.7”…..specific to Pirelli slicks.

Not specific to tire choice, but you’ll heat up those rear rotors good if leaving any degree of traction control on.

Slicks add stress on any platform, no specific call outs on this platform other than make sure to give the car a good once over before and after each track day looking for tightness, leaks, etc….as should be done on street tires too.

Id still love to convince AP Racing to make their famous track brake kits for our cars, and have a Ferodo DS1-11 pad for us, but alas between them direct and Essex I haven’t got them there….yet 😁

Forgeline is fantastic, can’t go wrong there, a handful of Forgeline GS1R sets have already been made and are out in the wild for GTR and GTR PRO.

thebishman

Have you talked to Jeff Ritter at Essex? I asked him about one of their brake packages when I first bought my GTR and he said if I could get my car to him, (they’re in NC iirc) they could try various fitments to find the ones, F & R that worked. I asked the Collective at the time whether anyone was local to have this done, but got no response; however there were very few people tracking the GTR back then.

rht69911s

So I'll certainly start out with the car in stock form for the track to learn it. I tell students that they should only change things on their car when they become the limiting factor and I expect to follow my own advice. That said, I'm pretty sure the tires will become the limiting factor pretty quickly and since this is the winter of my discontent I'd prefer to get going on wheels and tires now instead of waiting for months for them during driving season. I'd also like to avoid doing and damage to the stock wheels on the track. Are we talking 295-680 front and 325 705 rears in the DH compound?

The brakes are another story. Obviously I can't experience them on the street like the track but so far they impress me much more than the Porsche CC brakes. However, I do still have my AP setup from my 991 street car and wouldn't have any issues with them on this car if the need arises. Really like the DS1-11.

dlefty

In two attempts with Essex, I couldn’t tell you who I spoke with, but heck if it GUARANTEED a front and rear kit and Ferodo pads, I’d absorb the expense myself and haul my car there for them. But I have zero confidence as I know the business side, and we simply are not a group buying enough, if they have to invest in engineering a new rotor hat for example, they have to sell some sets, my guess, 200+ sets need to sell quick to make it a worth while time for them.

dlefty

Agreed on leave it alone until it becomes the limiting factor!
I only have experience with Pirelli DH sizes of 275/675/19 fronts and 315/705/19 rears…..I “think” it can go plenty wider in front, and maybe even do the 325/705/19 rear, but I only did 10” wide front and 12” wide rear wheels….the 325 DH slick should really be on a 12.5-13.5 inch wide wheel, maybe I’ll try doing that at some point…..
But the 315 DH slick had a wider section width than the 325 Pilot Sport Cup 2, and the 275 front slick has a wider section width than the 275 street tire, so I went conservative so I didn’t have to find out there was a rub somewhere, but still get an effectively wider tire than stock….
I don’t remember the sizes, I’m sure I can find in a folder somewhere I wrote down but Michelin slicks on Forgeline wheels on another GTR car I was around at track rubbed in front at almost full turn. That owner switched to Pirelli by the next time we talked.

Forgeline likes to do a 11” front wheel for this car…..

I try to communicate with GiroDisc often, the only good iron disc conversion for the GTR / GTR PRO out there now…..still charge a bit much for disc replacement in my opinion since Essex/AP replacements for platforms they support are half the cost and at least on par with……but alas, we don’t do enough volume as a community….

thebishman

You really need to speak to Jeff, and only Jeff at Essex re: an AP Racing Radi-Cal solution for the GTR tbh. He thoughts were: get my car to him and let them try existing solutions to see if say a Porsche; Corvette, etc existing kit fits and is suitable for the GTR platform. Alas I live in the middle of the country and couldn’t get my car to him; I should have tried harder.

Agreed that AP Racing are not going to create a one-off solution for the few numbers of GTR/GTR Pro owners who track the car.

It would be a perfect solution for someone like yourself who does multiple tracks days/year, as you know from your Corvette ownership.

thebishman

You are obviously far from a track day neophyte, so I’d strongly suggest this before heading out:

1: upgrade to Castrol SRF; Endless 650, etc. or which ever is your favourite high performance brake fluid;

2: Get a track alignment on the car. I had a square -2.5 camber F and R, which also worked perfectly on the street. Just remember you will need two boxes of OEM shims and it’s expensive but the beauty of the GTR is that once it’s set, it won’t deviate;

3: invest in Tikt brake ducts F and R and have them on the car before you head out for your first session. Brake cooling is extremely important on the car and it will mitigate wear on the brakes which is especially important on the CCMs;

4: install Pagid RSC1’s on the car. These are awesome rotor friendly track pads that are better than the OEM pads for the CCMs and can be used on the street perfectly well;

5: I’m not sure on your preference for PPF but I’d highly recommend it at least for the front clip and other areas prone to damage from debris kicked up at a road course

6: make sure to fully disengage Active Brake Assist as it’s very intrusive and frankly dangerous imho.


Lastly, I always felt the car was under tyred at the front as it was prone to understeer on the OEM SC2s, especially with the stock alignment. So I was using the optional, (at least in the ROW) Michelin SC2 ZPs as found for the C7 Corvette Z06 with the Z07 option on a dedicated set of Signature wheels in the OEM sizing. You may well have this sorted since you’re investing in a dedicated set of 19” track wheels, but hopefully as wide as possible without risk of rubbing at the front.

rht69911s

1: upgrade to Castrol SRF; Endless 650, etc. or which ever is your favourite high performance brake fluid;

2: Get a track alignment on the car. I had a square -2.5 camber F and R, which also worked perfectly on the street. Just remember you will need two boxes of OEM shims and it’s expensive but the beauty of the GTR is that once it’s set, it won’t deviate;

3: invest in Tikt brake ducts F and R and have them on the car before you head out for your first session. Brake cooling is extremely important on the car and it will mitigate wear on the brakes which is especially important on the CCMs;

4: install Pagid RSC1’s on the car. These are awesome rotor friendly track pads that are better than the OEM pads for the CCMs and can be used on the street perfectly well;

5: I’m not sure on your preference for PPF but I’d highly recommend it at least for the front clip and other areas prone to damage from debris kicked up at a road course

6: make sure to fully disengage Active Brake Assist as it’s very intrusive and frankly dangerous imho.


Lastly, I always felt the car was under tyred at the front as it was prone to understeer on the OEM SC2s, especially with the stock alignment. So I was using the optional, (at least in the ROW) Michelin SC2 ZPs as found for the C7 Corvette Z06 with the Z07 option on a dedicated set of Signature wheels in the OEM sizing. You may well have this sorted since you’re investing in a dedicated set of 19” track wheels, but hopefully as wide as possible without risk of rubbing at the front.

Bish,

Thanks again for your helpful replies. The thread (all 500+ posts) was also very helpful. This is what I really appreciate about communities like this; so much good information shared willingly and saving folks from unnecessary pioneering.

Don't have any interest in a Coke versus Pepsi discussion but I'm really surprised that the many debates on brake fluid don't include PFC. Having multiple track cars and a son who also drives I've changed gallons of fluid including lots of SRF. I loved the SRF but I have never experienced brakes like the ones on the Cup car. Caught lots of folks under braking with that car.

Alignment and brake cooling are also on the immediate to do list along with a complete wet maintenance.

Thanks for the tip on the pads. How about rotors? Has anyone had any luck with an alternative CCM rotor to the stock ones? Surface transforms?

Already on to my PPF guy. He's very good and he knows track cars.

Definitely going to address the ABA possibly with the Renntech solution.

Yes, back to the original point, I'm thinking Forgelines with Pirelli DH tires are the most stable, safest high performance solution as they have been on my other cars.

One final question for the moment. I'm in the DC area. There are plenty of track oriented shops but none Mercedes specific. This is obviously a fairly rare car, especially in the track world unfortunately and I think I need to find someone who has that on point knowledge of the product. I'm pretty sure the dealer won't have it. Do folks travel for track specific issues or what? I'm not really interested in having a general service shop learn on my car.

thebishman

You’re correct; there’s nothing like having pro’s working on the car that can relate. Have you thought about checking with the local Porsche; BMW CCA club guys to see who they use? Good luck with the search!

MBNRG

Does Renntech offer a 'code-out' solution for the Active Brake Assist?

rht69911s

RENNtech Pre-Safe Module and Data Logger (renntechmercedes.com)

Here you go.

MG1422

Yes you can fit 19s all around. I had a custom made Finspeed set 19x10.25F (even though i think it is slightly wider than 10.25) 19x12.5 rear.

I've ran Pirelli DH slicks, Michelin slicks and hankook slicks

As for the pirelli slicks I've ran the 295F and 325R as well as a ferrari challenge 305F tire that my shop got on accident and there was no rubbing at all.