How do you tell if Toyo RR is worn for qualifying vs practice in Miata?

[Stephen_L]

I’ve been running my spec Miata on the same set of Toyo RRs for the last three full race weekends, and I’m starting to notice the lap times are dropping off a bit even though the tread still looks okay. How do you guys decide when a tire is truly gone for qualifying pace versus just being a bit slower for a practice session?

[Grace69]

Yep, I treat it like data first. I pull the best lap on that set and compare it to a baseline from similar track temp and conditions (or to my own fastest laps earlier in the weekend). If the best lap is about 0.3 to 0.5 seconds slower and the pace keeps dipping as the stint goes on, that’s my cue the tires are past their prime for qualifying pace. If the times stay roughly steady but the rubber shows heat buildup or grip dropping later in the stint, I still think it’s near the end. I also keep an eye on temps; if temps stay in the target window and you still slow, it’s more likely the compound itself is aging.

[Harper.W]

Last weekend I felt the same; the rubber looked fine but the car wouldn’t commit in turn 3 and the times slid each lap. We swapped to a fresh set and instantly the pace came back; not a perfect proof but it helped me decide.

[EmmaET]

I’ve learned the hard way that a bad data point can come from wind or heat. One session I pushed on a worn set and the last laps were faster because the track cooled; another time the track got rough and the grip fell off even though the tread still looked decent. So I try to level conditions mentally and not over-interpret a single session.

[Donald.T]

Could it be setup or track conditions rather than the rubber? If aero balance or suspension shifts in the slow corners, you could see the same symptom without the compound being done.