Our team, Team Slowtus, runs a 2005 Ford Focus, stock engine, with minor suspension modifications and a 215/45R-17 tire. We ran the A052 in Sonoma in December, and again in March until our wheel (not tire, wheel) got shredded. We had a backup set of wheels mounted with Falken RT660s that were slightly used, mainly for practice sessions and one autocross day. Given our back-to-back experience with the A052 and the RT660 on the same car during the same day, these are my subjective thoughts:
The A052 is super fast. We ran a best lap of 2:19 in traffic on the A052. The subjective feel of the tire is great, and inspires confidence. It sticks and grips, and when it starts to let go, it does so smoothly, which I really like. I don't think the car is heavy enough or we drove hard enough to get the tires greasy. They seem to wear very fast, especially the outside edge, which is because the compound is softer on the outside edge than on the inside edge. I suspect this is for cars that run a good bit of camber. I think these tires would last us a maximum of 4 races, but I think I would replace them after the 3rd race.
Our backup tire, which we've run mainly in the practice sessions, is the RT660. In a practice session, we've had a best lap of 2:17 on this tire. The subjective feel of the tire is that it feels greasy until it warms up, which in my experience, takes a bit longer than the A052. It's not as smooth on the limit as the A052, and has a tiny bit more abrupt "break", but it still inspires confidence. It seems to wear more evenly than the A052, I suspect it's because the compound is the same on both sides of the centerline of the tire. It also seems to take these tires a bit longer to come up to temperature. I think these tires might be able to do 4 races before needing replacement.
While I really love the A052s, I'm torn about purchasing them again. Tire Rack is currently selling them for ~$255 per tire, and the RT660s are about ~$165. I don't think the additional $400/set is really worth it for me, especially considering how close the RT660s are in performance. If the A052s were $60-70 cheaper I would buy them again in a heartbeat.
#22 Gas Relief Team Slowtus Ford Focus