Jim Michaels

If you've tried both for autocross, I'd like to hear what you think about the relative grip of those two across four or five AX runs; from the first run to the last.

I drive an '06 Cayman S in A Stock, so I'm stuck with OE-sized wheels and front camber is restricted to what I can get stock; about -1.0 degrees. I've gone through two sets of R888s, tracking and autocrossing, so I'm familiar with them at AX, but not the NT-01s. R888s heat-cycle out after a few track events; to the point where they seem not much quicker than my RE-11s for AX. I understand that NT-01s are good to the cords. I'll also drive to and from events on the tires, and realize that NT01s essentially become slicks with grooves way before cords show.

Thank you for your participation.

genikz

Here's my experience, as I'm running 225/50/15 NT01s now. I haven't used R888s, but came from RA1s.

1st run - 30 psi cold - decent grip, need to be warmed up
2nd run - ~34 psi hot - great grip, generally my fastest run
3rd run - ~36 psi hot - good grip, but difficult to match the 2nd run (slightly greasy feel)
4th run - ~36 psi hot - good grip, but nearly impossible to match the 2nd run (greasier than 3rd run)

This may be dependent on surface, pressures and driving style. I have a full cage and 6pt harnesses, so it's tough for me to adjust pressures in between runs.

I plan to run them until they start throwing sparks. In my past experience in doing so (with RA1s) they behave the same as described above, but that window of optimum grip is super small once you hit 30-40 or more runs. They fall off much faster and the grip level when they're at their best temp and pressure is probably only 70-80% of what it was when they are fresh.

Jim Michaels

Sounds like you could use a helper to check pressures and spritz off the tires between runs.

Actually, I'm somewhat surprised that they're falling off like that when tire pressures are still in the mid-30s.

Thanks for the run-by-run report.

genikz

Yeah, if I cared enough, but I don't have any competition in my class currently, so I just set it and forget it.

I should clarify that the drop off I describe is very small. Probably a tenth of two in run 3 and two to three tenths in run 4. It's likely this is just pressure related, as I doubt I'm over heating them.

Jim Michaels

I'd be happy to send my Corvette competition out to CA if you ran in A Stock. The average head-to-head delta in our best times across seven events this season was .3 seconds.

It's good to know that the NT-01s aren't over-heating.

cretinx

I have run NT01s on a Boxster at 37 psi all around, and in my Firebird (MURICA) at 32 front / 27 rear

I like them but they're not optimal for autocrossing - they have a long tread life and are great for DE events (have used both the Nittos and Toyos for DEs) because they don't fade off and love the heat. They never get warm enough to actually autocross.

best bet is a hoosier or kumho victoracer / v710 for autocross.

sjfehr

Yeah, I'll second what cretinx said; NT-01 and R888 are track tires that just simply require too much heat for autocross. You might be able to get good grip by your last run in the heat of summer, but in spring/fall in western VA, you'd honestly be better off autocrossing on good street tires than fighting to get grip with cold hard-compound r-comps! Hoosier A6 is really the only competitive autocross r-comp for our area. Even Kumho V710s require quite a bit of heat to work, but V710s get warm fast enough to give you good 3rd and 4th runs in most weather while lasting 3x longer than Hoosier A6. (I ran V710s last 2 seasons, but am going to run RT this year) A6 and V710 are both too soft a compound to use for DE; great for time trials/qualifying, but you're liable to cord a set in a single session.

Incidentally, were you at the VAC this year? I think I remember talking to you about tires.

Jim Michaels

I'm aware of their cold-natured limitations for AX, but I'm driving on my AX tires to and from events. Years ago, I used Michelin Sport Cups (even more cold-natured) for both track and AX (only in warm weather), so the initial switch to R888s for AX was actually a pleasant surprise.

You may be right about just driving on good street tires; at least until the mid-summer months. The R888s eventually heat-cycled to the point of being no quicker than my RE-11s.

Yes, I was at the VAC/Commonwealth Games/BRR-SCCA event at Virginia Tech this year, but I'd rather forget the Saturday part.

burglar

Perhaps the new Dunlop Z2 would be plenty good for a track day, while being the hot tire for RTR-AS.

How tough is the AS index? Could an AS car be competitive in RTR?

sjfehr

AS pax is virtually identical to BS pax, and should do pretty well regionally in RTR.

Jim Michaels

Our SCCA region has had an "open" PAX-based street tire class for all stock, street prepared, etc. cars for years. Since the class usually has from 6 to 10 cars in it, they haven't adopted separate FWD, RWD, and AWD street tire classes. When I drive on street tires, I always compare my PAX times to those in the TIRE class to see how I would have done. I would have won TIRE class a couple of times last season, but I would have also finished 3rd, 4th, or 5th other times. My car needs a better driver.