I am on my 3rd set of RR's.
I am currently running -3.5 Front and -2.5 rear which worked fine with RA1's.
First set of RR's all corded on the outside edge. One showed some of the tread separation, even though it was mounted in the proper direction. Tracks were Steets of Willow and two times at Chuckwalla (CW) (It is very smooth asphalt Jim). Tires had 12 or 13 heat cycles. Dates were weeks 31 and 32. Adhesion had fallen off somewhat, but if not corded could have been used a few more cycles.
Second set of RR's - Three corded on outside edge. BOTH rears showed severe tread separation and have been sent back to Toyo for eval. These had around 11-12 heat cycles from Chuckwalla and California Speedway (Auto Club). These were "flipped" after Chuckwalla due to outside edge wear. All mounted properly. Dates were week 31. They had lost some adhesion, but were still usable.
Third set is newer. Some wear on the outside. A little loss of stick after 8 heat cycles. No separation.
Love the Stick! Hate the shorter life! Hate the inability to rotate as needed and need to mount in specific direction!