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I would personally go the other way. A 245 / 265 R-comp on an 8" / 9" wide rim respectively is not going to be properly supported and will tend to roll under during cornering, especially on a heavy car like the C63.
You should go with the wider set up between your choices. You can run 275's on the rear as well.
I see you are actually running 245/275 on your OEM rims. Do you road track with those R888 sizes already?. What about the roll cornering effect Diabolis is mentioning?
Stay away from the R888's with the C63. The R888 is a good tire for a 3000 lb car, but looses it in the higher weight cars. Plus road noise is a bit more than I like.
I recently chewed up a set of R888R's on a road course (235/35/19 & 255/30/19). I choose to not put the widest possible tire that will fit on a wheel to reduce the sidewall roll as mentioned above. With that said, I just had a set of RE-71R's delivered the other day (same size) and they are noticeably wider than the Toyo's. Maybe you could get the same benefit on stock 18's. The picture shows a stack of 4 tires each, Toyo's and Bridgestone's.
The two key facts that you need to take into consideration here are that (1) R-comps provide a higher level of grip (adhesion) than street tires, and (2) the C63 is a heavy porker. Assuming a 4000 lb car, when you corner and you're able to pull, say, 0.8 lateral Gs with street tires, you essentially have 3200 lbs deflecting the sidewalls and causing the tires to roll under the car. With a racing tire that may be able to pull 1.2 lateral Gs, you have 4800 lbs deflecting the sidewalls and trying to roll the tires under, which is 50% more than you do in the first case with street tires. The rim width - which supports the tire and aside from the sidewall stiffness is the only other variable that affects how much the tire is going to flex - becomes that much more critical to support the 50% greater lateral loads. R-comps are already going to give a lot more grip that street tires; the extra 10mm of tread width is not going to matter much for the total amount of grip, but it will make a huge difference in how well the tire is supported on the rim. Evey tire has an approved rim width range, and for a heavy car like the C63, you pretty much need to be at the maximum in order to support the tire. You can go the other way on a stripped-out Miata, but not on a 4000 lb car.
I agree the R888s are far from ideal - but then again so is ANY tire on a 4000 lb porker. You can get a set of Trofeo Rs at twice the price, and while they grip a little more, as a result they also roll under the car more, by the same relative percentage as the increase in grip. The grippier the tires (and the heavier the car), the more they will roll under during cornering.
The two key facts that you need to take into consideration here are that (1) R-comps provide a higher level of grip (adhesion) than street tires, and (2) the C63 is a heavy porker. Assuming a 4000 lb car, when you corner and you're able to pull, say, 0.8 lateral Gs with street tires, you essentially have 3200 lbs deflecting the sidewalls and causing the tires to roll under the car. With a racing tire that may be able to pull 1.2 lateral Gs, you have 4800 lbs deflecting the sidewalls and trying to roll the tires under, which is 50% more than you do in the first case with street tires. The rim width - which supports the tire and aside from the sidewall stiffness is the only other variable that affects how much the tire is going to flex - becomes that much more critical to support the 50% greater lateral loads. R-comps are already going to give a lot more grip that street tires; the extra 10mm of tread width is not going to matter much for the total amount of grip, but it will make a huge difference in how well the tire is supported on the rim. Evey tire has an approved rim width range, and for a heavy car like the C63, you pretty much need to be at the maximum in order to support the tire. You can go the other way on a stripped-out Miata, but not on a 4000 lb car.
I agree the R888s are far from ideal - but then again so is ANY tire on a 4000 lb porker. You can get a set of Trofeo Rs at twice the price, and while they grip a little more, as a result they also roll under the car more, by the same relative percentage as the increase in grip. The grippier the tires (and the heavier the car), the more they will roll under during cornering.
Very true, and good points but the Trofeo R has better sidewall support for heavier cars than does the R888.
2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
Originally Posted by Clark Kent
I recently chewed up a set of R888R's on a road course (235/35/19 & 255/30/19). I choose to not put the widest possible tire that will fit on a wheel to reduce the sidewall roll as mentioned above. With that said, I just had a set of RE-71R's delivered the other day (same size) and they are noticeably wider than the Toyo's. Maybe you could get the same benefit on stock 18's. The picture shows a stack of 4 tires each, Toyo's and Bridgestone's.
CK, I've never seen tire wear like you have on the R888's - you must drive hard man. You didn't chew them up in one day like that did you? The MPSC2's don't look bad after one hard day, albeit on a high-speed track like WGI. 180TW helps. Last time I had the Dunlops out they folded the front sidewall and tore chunks out of the tread. They were finished after 3 days. Maybe the R888's like more pressure?
Originally Posted by Diabolis
The two key facts that you need to take into consideration here are that (1) R-comps provide a higher level of grip (adhesion) than street tires, and (2) the C63 is a heavy porker. Assuming a 4000 lb car, when you corner and you're able to pull, say, 0.8 lateral Gs with street tires, you essentially have 3200 lbs deflecting the sidewalls and causing the tires to roll under the car. With a racing tire that may be able to pull 1.2 lateral Gs, you have 4800 lbs deflecting the sidewalls and trying to roll the tires under, which is 50% more than you do in the first case with street tires. The rim width - which supports the tire and aside from the sidewall stiffness is the only other variable that affects how much the tire is going to flex - becomes that much more critical to support the 50% greater lateral loads. R-comps are already going to give a lot more grip that street tires; the extra 10mm of tread width is not going to matter much for the total amount of grip, but it will make a huge difference in how well the tire is supported on the rim. Evey tire has an approved rim width range, and for a heavy car like the C63, you pretty much need to be at the maximum in order to support the tire. You can go the other way on a stripped-out Miata, but not on a 4000 lb car.
I agree the R888s are far from ideal - but then again so is ANY tire on a 4000 lb porker. You can get a set of Trofeo Rs at twice the price, and while they grip a little more, as a result they also roll under the car more, by the same relative percentage as the increase in grip. The grippier the tires (and the heavier the car), the more they will roll under during cornering.
Haven't yet had time to sort through all my data from WGI, but thought this data point was relevant here. The MPSC2's are amazing. Get the right size (as Doug knows, I probably have a little too much tire for my rim width but it seems fine actually) and load rating, and then get the pressures right. Last year I was lucky to corner at 1.1g on the Dunlop Sport Maxx Race r-comps, and before that barely 1g with the MPSS. Now with this setup I'm in the 1.3's consistently. (of course, take this with a grain of salt because my telemetry is all funky - mph and mapping/splitting laps is all over the place because of my terrible GPS signal acquisition, but the accelerometer seems to be recording accurate data)
The two key facts that you need to take into consideration here are that (1) R-comps provide a higher level of grip (adhesion) than street tires, and (2) the C63 is a heavy porker. Assuming a 4000 lb car, when you corner and you're able to pull, say, 0.8 lateral Gs with street tires, you essentially have 3200 lbs deflecting the sidewalls and causing the tires to roll under the car. With a racing tire that may be able to pull 1.2 lateral Gs, you have 4800 lbs deflecting the sidewalls and trying to roll the tires under, which is 50% more than you do in the first case with street tires. The rim width - which supports the tire and aside from the sidewall stiffness is the only other variable that affects how much the tire is going to flex - becomes that much more critical to support the 50% greater lateral loads. R-comps are already going to give a lot more grip that street tires; the extra 10mm of tread width is not going to matter much for the total amount of grip, but it will make a huge difference in how well the tire is supported on the rim. Evey tire has an approved rim width range, and for a heavy car like the C63, you pretty much need to be at the maximum in order to support the tire. You can go the other way on a stripped-out Miata, but not on a 4000 lb car.
I agree the R888s are far from ideal - but then again so is ANY tire on a 4000 lb porker. You can get a set of Trofeo Rs at twice the price, and while they grip a little more, as a result they also roll under the car more, by the same relative percentage as the increase in grip. The grippier the tires (and the heavier the car), the more they will roll under during cornering.
Thank you Diabolis, i will take this in consideration, I only have a final doubt about the Load Index for the R888R in 245/265 size are 93Y (1433 lbs) and the 235/255 are 91/90Y (1356 / 1323 lbs). This does not compensate in any way the roll under due the strong walls?
CK, I've never seen tire wear like you have on the R888's - you must drive hard man.
- lol, that's after 3 days. I was dialing in some lateral slide in T2, T4 and T5, and rotating at T1 & T13, grinding it out in the carousel of T16-17-18, and trying to cheat death at T19. Nothing unusual
2012 P31 C63 Coupe Trackrat, 2019 GLE63S Coupe Beast
Originally Posted by Clark Kent
- lol, that's after 3 days. I was dialing in some lateral slide in T2, T4 and T5, and rotating at T1 & T13, grinding it out in the carousel of T16-17-18, and trying to cheat death at T19. Nothing unusual
Awesome man, love it. I need to learn more about dialing in my suspension, it's new to me.
CK, I've never seen tire wear like you have on the R888's - you must drive hard man.
It's new to me as well so I can't share much experience yet. I've been to the track a number of times with the V3's in factory setting and they were fine. At least no glaring problems. Last time out I decided to crank down all 4 corners two clicks tighter - both rebound and compression. Can't say I felt an obvious difference but I did shave a consistent two seconds per lap. So the three variables in the equation were trying the Toyo's for the first time, tighter suspension, slight driver improvement. With that, I cannot pinpoint the main factor for lap time improvement.
Next time out I am going to tighten it up one more click all the way around. And maybe play with it some more until I feel the front pushing or the rear coming around.
AMG GTBS, AMG GTR Pro, AMG GT, C63 AMG, Porsche Panamera 4S, RX-7 FC Turbo II
Originally Posted by freddy-amg
I see you are actually running 245/275 on your OEM rims. Do you road track with those R888 sizes already?. What about the roll cornering effect Diabolis is mentioning?
Yes, I do road course lapping with the OEM rims (which are my track wheels now) and 275's and have had good success on horsepower tracks such as VIR and Summit Point main. I'm
not trying to run Mickey Mouse tracks or auto cross. R888s have stiff sidewalls for R compounds which helps because our cars are pigs and don't like to turn. Getting the power down is what the car does well and I feel like the wider tire helps with that. I've run 265's on the rear as well on track and I don't see very much difference in lap times.
According to all your data i'm doing not bad with my Yokohama AD-08R. It doesn't have R compond but still can reach 1.1g in turns with all car stock except Quaife LSD (i'm also using Harry's Laptimer). And price wise it's not an expensive tire.
But i'll definitely look for Michelin Cup2 for my next set.
Just got a 2012 c63 coupe , really interested in throwing R888R in the rear ..... have stock 18 on , any suggestions to size , was told to go up two sizes 275 , any imperssion or problems with having r888r ?
Just got a 2012 c63 coupe , really interested in throwing R888R in the rear ..... have stock 18 on , any suggestions to size , was told to go up two sizes 275 , any imperssion or problems with having r888r ?
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