rx8_250f

I have been researching this Dunlop SP Super Sport Race tire on tirerack and it has pretty good reviews. I am thinking of buying these tires for autocross. The price is very cheap $128 in size 255/35/18, so i figure its worth a try. Does anyone have any experience with this tire or heard anything about it, and will this size fit the stock 8inch wide rims, or will i have to go with the 245/35/18's. it says its rim range is 8.5-10.5 but i think people have put wider tires than this on their stock rims.

Dark8

If you are not after a nationals trophy then they will probably work for you. There was some discussion about these in the past:

https://www.rx8club.com/showthread.p...ghlight=dunlop

mlx8

I purchased a set early last summer ~ 255/35x18 mounted on SSR Comp 18x8.5" wheels. I've put probably 8 track days on them. The tires have held up fairly well except for a tendency for the front tires (some what track dependant to wear a deep grove @ 1.5" to 2" in from the outside edge of the tire. I also installed a set of these, but in 245/40x17's on an older Audi S4. Can't say as I noticed as big a difference in handling changes on the Rx8, but on the much heavier Audi S4 (previously running Michelin Pilot Sports, and a set of Sumitomo HTRZ II's in the same size) they, the Dunlop make a night and day difference. On the Rx8, a lot of stick, but the stick +chassis set up was already pretty good IMO on the original stock tires. FWIW, I liked, and still like them. I'll be picking up at least another pair to cover the two front "groved" tires on the Rx8. I don't know why, but didn't have the same kind of groving show up on the Audi.

HTH
mike

Imp

Grooving usually happens because of rubbing under full load in a turn. Isit hitting the lip of the fenter in hard turns? Is there a bolt/attachment there that sticks out just a tad? I'd look around to see if any rubbing is going on.

-kC

Dark8

mlx8: Possibly a stupid question but did you shave them? They recomend shaving them for dry track use to avoid abnormal wear and heat build up. The Kumho V700s had the same problem.

mlx8

The groving was not caused by hitting or rubbing. At the old "Continental" divide track (just off I-25 near the Mead, Colorado exit), while running clockwise, the grove mostly manifested itseld in the left front tire. Tires weren't shaved. Some speculation has been that the stock suspension could be partly to blame. And unsure of what pressure to run with the 255's for track purposes (I was trying @ 32-33psi cold, on all 4 corners) perhaps under inflation coupled with heavy tire/cornering loads on the outside left front. Between two different events at Pikes Peak Raceway south of Colorado Springs, and one 3 day event at Heartland Park in Topeka, I seemed to have evened out the front tire right side/left side grove, and by rotating the tires front to back, I've been able to even out tire wear more or less equally now all the way around the set, such that I should be able to get several more track days out of them.

I've since installed a set of Racing Beats front and rear stabilizer bars, and both the MazdaSpeed front & rear strut tower braces to see if that might not stiffen the chassis up a bit. In the finaly rounds at Heartland, I also tried bumping up the tire pressure 3+ psi in the rear, between run sessions (tires were hot.) Adding the extra 2-3 psi in the rear seemed to noticeably help at Heartland. I've yet to get back to the track with the stabilizer and upper strut bar changes to see if that might help with the front wear.

I don't know (perhaps someone else in the forum does) what, if any differences there might be in the Dunlop tread construction between the outer edge, and inner center tire rubber. I believe, for example in the Michelin Pilot Sports, Michelin uses a different tire compound around the out edge, and the center to inside edge of its tire. I've wondered if the grove development in the Dunlop Race could be related in part to something like that.

Regards
mike

mlx8

Oh, re shaving. FWIW, I believe Dunlop's Super Sport UTOG 60 tire already comes, as is, from Dunlop with a reduced tread depth with track use in mind. I'm not sure additional "shaving" as one might do with a "normal" street use tire is necessary, or even desireable.

mike

PedalFaster

The Tire Rack site specifically mentions shaving as an option for the tire, although not a necessity. As a rule of thumb, shaving will always help dry performance, and may help tread life as well, due to reduced heat buildup from reduced tread flexion.

Not necessarily -- several tires (most notably the old BFG Comp T/A R1s and the Kumho Ecsta V700) tend to develop Grooves of Doom if underinflated. Perhaps the Dunlop is susceptible to a similar problem.

Steve