For what it's worth, here is my opinion on both sets of tires. The AOs were 225/50/16, all four on 8inch wheels. Tire pressure was 36psi hot. RT-615 were 225/45/17 on 8s ft and 255/40/17 on 9s rear. Tire pressure was 38 hot. Tires were tested/used at differant tracks so a time can not be given. Car was a FC, same suspension, camber and ridehieght. Lap 1-5, the RT-615 were better. The AOs took two to three laps to heat up. Lap 6-10, I would have to rate the tires even. Lap 11-16, the RTs seem better, not by much but better. One thing I noticed was the tire build up afterwards. The AOs showed build up on both front and rear, very even. The RTs showed build up on the front only, the rears really did'nt have any tire build up. If I was just to look at the tires after each race, the AOs looked like they were pushed to there limits. The RTs did not show much fethering at all, especially in the rear. Maybe the 255s had something to with that. The AOs had a softer ride. ( 50 sidewall )
Both set of tires were new. Both tracks took an average of 45-47 seconds to complete.
chuck

 

Not sure if you read it but GRM just tested these two tires, same size, track (tirerack's track), day and the yok's were two seconds faster than the 615's.

 

Like I said this is just my opinion. The only "real" differance in the two tires were in the first few laps. It was scary in the AOs the first few laps until the tires had some heat in them. Other then that, both tires felt good. At my next race I will try both sets, then I will get times to see if my seat of the pants opinion is correct.

There was another forum member that strongly suggested the 615s over the AO32s.

I'll have to read that write up. thanks
chuck

 

GRM used a miata to test the R compound tires and a Sentra SER Spec V tuned by Nismo to test the street class tires. Miatas are much quicker autocross cars than SERs.

 

I think the RT-615's are a better value (last longer & CHEAPer).