Case1906

For those of us running or interested in 275/35/18 R888s there is a problem. They've been on "back-order" for a while as I found out a few weeks ago I needed some rears for a track event. I just called Tire Rack today to get details and was told not only that they are not available, but that there are none currently under production. Not good.

Anybody have a secret source or stockpile? (I've check the usual suspects.)

Does anybody run 275/40/18's (which by the way are alot more expensive)?

Diabolis

I run the OEM sizes on the OEM rims for track duty. 255s seem to be readily available. Seeing as it's an R-comp and all, I figured the sidewall shifting/flexing because of the narrow rim size would negate any benefit due to the wider tire so I opted to stay with OEM size. No issues with rear grip - if I had to choose, I'd go with wider rubber in the front.

Properstyle

switch to the RA1 in the mean time. it is the NASA track tire, it has better wet traction ablity over the R888, same tread ware rating and I run them on my Z32 with no issue in the rain and I make 602 at the rear wheels.

Case1906

Thanks, what size are you running on the front these days?

Diabolis

235 - OEM size. With a wider tire on the 8" OEM rim I figured I'd be rolling on the sidewall and have to increase the pressures, which would likely negate the marginally wider contact patch. Would like to see if I can fit a set of R-comp 255s on the front, but I would need two 9" rims and I don't want to shell out for 2 custom wheels just to experiment (I dont think that a set of OEM rears would have the right offset on the front even if it clears the calipers). Front brake caliper clearance on the C63 is a problem with any non-MB 18" rim I have ever tried to fit (including three different aftermarket sets I had from my B6/B7 Audis - same bolt pattern and hub bore), so I'll probably stay with the 235 if I decide to still track the C once these wear out. I have an old P-car that is much more suited to the task so that is my primary track rat.


How do you find the 245s? What pressures are you running and do they roll over if you're not overdriving the car? The sidewalls are pretty stiff on the 888s, but on the stock 8" rims and a nose-heavy car I though I'd better play it safe when I got them.


P.S. If you really want an awesome set of R tires, get a set of Hoosier R6s... they come in the right sizes.

Diabolis

Can't do. Need at least an 18" rim to clear the front AMG calipers, and the only 18" size for the RA1s is 275/35. I used the RA1s almost exclusively on my old E30 M3, but it had 15" rims. Or are you suggesting running the RA1s on the back but the R888s on the front?

ab0bab0i

Have you tried Nitto Nt01 tires?

Case1906

No issues with the 245s on the OEM wheels in the front.I don't feel any roll over but this is probably due to the very stiff Toyo sidewalls. I'm thinking I"m getting a bit more grip, but have not tried 235 R888s. I usually start cold round 33-34 psi and the tires seem to like 41-42 the most on my car.

How many track days can you get out of the Hoosiers with a C63? I see they have a faster burn rate than the R888s.

Properstyle

I'm not sure what you mean as My z as 18x10.5 et 35 NTO3 allround and I am running 275/35 18 RA1s The are made in 18s SMH.

http://www.tiresdirect.net/TOYO-Prox...R18-P2269.aspx

Again they are a R888 counter part.

roadtalontsi

nt05's suck *** just an fyi

Diabolis

What I meant was that 275/35-18 is the only 18" size the RA1s come in - he can't get 245s for the fronts for example. I've never driven a car (on track) with different compound tires front and rear, so I have no clue how it would behave.

Diabolis

Due to the weight of the C63, I suspect you could cord the fronts in a single weekend if you're really pushing - but if you're the only person running them, you will almost certainly be the fastest car around by quite a margin.

I've never had R6s on the C63, but had them twice on my ~3000 lbs, ~300 rwhp P-car. Both times I got 2 DE weekends (~16 heat cycles) before they were corded, compared to 4 DE weekends on the Toyos. IIRC with the R6s I was lapping Mosport 2-3 seconds faster than with R-comp Toyos. They don't last long, but they do grip.

Properstyle

I see what you are saying now. But the Ra1 and the R888 are the same compound different thread design, the r888 is set up for a constant contact patch while the ra1 is not. being that at least in my experience the c63 will understeer before powering out having the full contact of the r888 might actually help. It's not gong to make the car handle crazy running two different thread patterens.

Diabolis

Interesting observation about the contact patch and compound - I guess the differences are the thread pattern and possibly carcass construction / sidewall stiffness. You are right that the C63 will understeer first, so having the R888s at the front and the RA1s on the rear just might balance out nicely.

My only "issue" with the RA1s was thread squirm when new and/or unshaved (and if they're worn or shaved they get pretty scary in the wet - I thought the R888s were better), but they always gave me consistent grip pretty much until corded while the R888s seem to lose some grip after several heat cycles. If someone is willing to buy me a set of R888 fronts and RA1 rears, I will happily experiment and let you know how it turns out.

Case1906

I just can't run mismatched tires on my cars anyway. I ended up ordering 265/35/18s R888s for the rears and will run them until I kill the fronts. I'll see if I notice any significant differences. (Maybe not based on your thoughts on wheel size.) At that point I may look to the Hoosiers or something else.

Diabolis

Well, 265s on the rears are probably a better match both in relation to the 9" rim width and the 245s you're running at the front. As I mentioned earlier (and I think Properstyle was also saying the same thing), if anything you'd want wider rubber at the front - the rear seems to be fine even with the narrower rubber. Let us know how you make out.