Kumho Ecsta PA31 

Bought my first set of these last year primarily for autocross, with some minor amounts of road driving to and from events. These replaced my Dunlop Direzza ZII Star Specs (215/40-17), and in terms of outright grip they are light years beyond the Dunlops. Super sticky when hot, tolerant of high slip angles and tolerant of rapid/violent transitions. On a 60 second course I figure they have cut 2-3 seconds from my lap times from before. And while not the primary reason for using them, they are also nicer to drive on the street: quieter and more comfortable.

Only downsides specific to the tire (and not the size I run) is that they do struggle some to find traction on colder event days between 40-50 deg F (not surprising considering the type of tire), and they aren't quite as good in the wet as the ZIIs were, or how the RE71Rs are for other folks.

Definitely will still continue to run these unless something better comes around. Already have another new set ready to install for 2018 autocross season!

These are dedicated track and auto cross tires for me, they do not see street use. Love them for the SCCA Street eligibility, and they are consistently fast as long as they don't get too hot.

Great tire for SUMMER autocross. Be wary of running these tires on a light car in any type of cold weather - early spring or late fall autocross. Expect to use tire blankets to keep them warm between runs.. These tires, from what I've found with my light car, are only grippy when everything is HOT. This is normal of any tire, but you lose a lot of the grip before these tires get hot - as some other comments might have dictated by now. These are a tire that shines when fully heated - and if you can get them there, they will reward you.

If you want a high-grip tire with moderate road noise and decent tread, this would make a great summer autocross tire.
Do not drive these tires in any water. If you do, drive no faster than 30 mph - especially if there is any standing water.

Would I buy these tires again? Perhaps. Though I would be interested in trying other tires before coming back to these tires.
These are an excellent tire if you are on a bit of a budget, or are looking for a size that fits your wheel.

If you are on the fence, try them! My other tire order was gonna be out the entire summer last year before I got them, so I switched to these and am glad I did. If you don't like them, you can always sell them

I really like the BF Goodrich GForce Rival's. I drive my car to autocross events, not trailered, and I like the overall qualities of the tires. The steering response, traction and tread life are exceptional for this style tire. They warm up fast on the autocross course and provide the performance I'm looking for. I generally put 8000 to 15,000 miles on the car per year going to events and competing. I think it's hard to beat this tire.

The tire rack review system doesn't let you accurately describe these tires. They are phenomenal for a street/track tire, by far the best in class. I have them installed on my IS38 1.8T Golf which is fwd and has 350whp/350wtq. I've auto-x'd in torrential downpours, done two track days, driven 13000+ street miles, drag raced a few times and the tires still have over 50% life left. The off the line grip is this tires biggest weakness. Once your are rolling they will hook and go, but off the line launches, even on prepped surfaces, will result in some wheelspin. My 1/4 mile times were actually slower with these tires than with all seasons. They aren't loud or obxnoxious, but compared to a normal passenger car tire you will notice a little more road noise. The amount of grip these have is hard to explain, but you definitely want to watch your pressure. On track I typically run cold 30 PSI, warm 34 PSI, but after longer sessions(30+ min) the pressure would sometimes be 40+ PSI. I would recommend these to anyone who does a few track days a year, but also daily drives the car!

One anecdote: I got caught in a blizzard with these on my way home from an event. Unbelievable amounts of freezing rain and snow/ice/sleet with nothing I could do about it. There were spots with 2+ inches of precipitation on the highway. These tires actually did a great job despite not being rated for it. Next year I'll make user to throw my all seasons in the hatch just in case.

I use these for autocross with two drivers. These tires are really good at taking heat when you don't have much time to cool the tires down. Even on a sunny 86F day with 3 minutes between runs, the tires never got greasy.

I used one set as my daily + autoX tires on my 2nd gen Mini for over 10k miles about 17 autocrosses (avg. 8-9 (45) second runs). They still had enough tread for a few more events when I sold the car. I now have a dedicated autocross set on my 99' M3. I don't think they put the power down particularly well off the launch, but under hard breaking they are very manageable. Definitely forgiving in the corners if you steer too much, but still responsive enough for my car. I'm not sure if these will be my 3rd set of 200 tread wear tires when it comes time, but they are definitely in the running. I'm afraid the RE71R won't hold up to dual driver duty from a heat perspective and wear. Maybe try some Advan A052's?

These tires are soft so they stick like a leach until they don’t, I have never found the point on dry clean pavement that let go. In wet conditions on a lite car they will try to kill you. I love these tires on my track Miata makes want to a bigger engine in the find the limits of these tires.

Switching back and forth between the rival and the Bridgestone Re-71R over the last few season of autocross I can say that the Rivals are a very strong grippy tire. They are a tire you have to learn to trust as there is a little bit of slip before they get to their maximum corning potential. It is a little unsettling (especially in FWD cars) but they have tremendous lateral grip and speed when you figure them out. The weakness of this tire compared to the Re-71R is that they do not do well in the wet. If there is any standing water or just heavy rain at all they lose traction quickly. I have been caught in a rain storm driving to an event on a fresh set of rivals, and had to back down to about 45mph in a 70 just to have the car stop from floating in the lane. these are trade offs with a max performance summer tire, but even a well worn RE-71r will continue to preform better and be more predictable in the rain.

Good tire for autocross if you can figure out the tire pressure for your set up. High dry traction , very low in wet.