Summit Point Main Tire Shootout: Toyo RA-1, Toyo RR, Maxxis RC-1
Test car: 1990 Miata prepared to WDCR SSM rules.
Toyo RA-1 setup: 205/50-15 on 7" wheels, dry, 40°F ambient temperature, started with 1-2/32" tread and corded all 4 tires by the end of the day.
Toyo RR setup: 225/45-15 on 9" wheels, dry, 40°F ambient temperature, 5th DE day on the tires, started with 3/32" tread.
Maxxis RC-1 "cold" setup: 205/50-15 on 7" wheels, dry with puddles/rivers at turn 1 exit, turn 3 entry and turn 10 entry, 50°F ambient temperature, first day, second session on the tires.
Maxxis RC-1 "warm" setup: 205/50-15 on 7" wheels, dry with a puddle at turn 3 entry, 65°F ambient temperature, first day, fifth session on the tires.
Unlike all other tires which have 205 section with, the RRs have 225 section width. This is because I use RRs as DE tires and I like having more lateral grip in the corners.
The wider tires are supposed to be slower on the straights but RRs come out on top in terms of overall lap time at 1:30.3.
RRs did very well in the cold conditions. The tires required minimal warm-up (less than a lap before I could start pushing them, maybe two laps to attain full grip in all sessions other than the very first morning one). Overall grip level was very pleasing, I would say I ran them at 9/10ths of their ultimate pace. The tires inspired confidence, especially under braking given the cold conditions. The car was very balanced on the RRs, in fact I would say I enjoyed driving the car more on the RRs even in 40 degree ambient temperature than I did on RA-1s in the summer.
As far as pace goes, RRs went a full second under RA-1s. Which brings us to:
This is the required WDCR SCCA tire. I raced on this particular set in 2016 and they had just about a single track day in them left.
My best lap on the RA-1s was 1:31.5. I ran RA-1s on Saturday, switching to the RRs covered above on Sunday. Conditions were very similar both days, with Sunday being slightly colder.
I was pleasantly surprised by the grip level of RA-1s in the cold conditions. The tires felt solidly planted, though RA-1s offer less lateral grip than RRs and therefore the car sometimes went into drifts exiting turn 6 and had to be muscled somewhat into turn 1. Warm-up of RA-1s was very similar to that of RRs - a single lap was sufficient to get the tires to get some stick going and after another lap the tires were in their temperature envelope.
RA-1s were just over a second slower than RRs over the course of the lap, with the losses being primarily suffered in turns 3 and 10. RA-1s also had less grip in turn 4 than RRs, resulting in me lifting through the turn.
Consistent with my previous experience with RA-1s, they continued to be easy to lock up under braking. When I took the wheels off the car at the end of the day, both front tires had multiple flat spots on them.
I bought this set of RC-1s to be as a cheaper proxy for RA-1s on the SSM race car. I knew that RC-1s were not as sticky as RRs, and after going a second quicker on RRs compared to RA-1s I figured I should get a slower tire to practice the SSM setup better. I ordered RC-1s in 205/50-15 figuring this size would be closer to a 205/50-15 RA-1 in terms of grip than a 225/45-15 RC-1.
I used the first session to scuff the tires in. In the second session the ambient temperature was somewhat higher than what RRs and RA-1s experienced the previous weekend, but there were several places with water puddles and rivers at turn in points and corner exits and RC-1 struggled to develop grip in these conditions. RC-1s were prone to locking up under braking, and I think they tend to do so silently which creates a very real possibility of ruining tires and not even knowing it. RC-1s abruptly lost all of their grip when driving over wet pavement, which typically manifested in immediate and large yaw angles in the car. In completely dry corners RC-1s squealed for their life when I tried running them the same way I ran RA-1s and RRs the previous weekend.
The best lap time of this early morning session on RC-1s was 1:35.8 - five seconds slower than the best lap of RRs and four seconds slower than the best lap of RA-1s. Needless to say, this level of performance from RC-1s is underwhelming.
With the weather warming up another 15 degrees, RC-1s finally started gripping like an R compound and not a treadless street tire. With the track mostly dry except for turn 3 entry I went two seconds quicker for a 1:33.9 lap time. This is still two seconds off my pace on RA-1s and three seconds off my pace on RRs, in significantly colder conditions.
Unlike RA-1s and RRs on which the car was well balanced, on RC-1s the car was prone to losing grip on both ends. Strong understeer was the name of the game for turn 1 entry and to a lesser extent turn 6 entry. I lost most of the throttle steering characteristics of RA-1s and RRs - RC-1s under throttle typically produced understeer. That said, the car was quite tail-happy in turn 10 on RC-1s even in warm weather, whereas it was mostly planted and balanced on RA-1s and RRs. I think the key is track smoothness - on relatively flat surface RC-1s ended up understeering under throttle, whereas on relatively bumpy surface the car would often oversteer under throttle. Neither was great, with sudden mid-corner oversteer arguably being worse than a persistent push which could be driven around.
Due to the deficient pace of RC-1s compared to RA-1s, RC-1s are a poor RA-1 substitute if the goal is to run competitive lap times. However, given that RC-1s are less sticky than RA-1s, being able to run a good lap on RC-1s should translate into being able to run a good lap on RA-1s. Unfortunately the car behaves differently on RC-1s and RA-1s, and driving on RC-1s misses the opportunity to learn how to drive the car at the limit of RA-1s as that limit is substantially above RC-1s' limit. Hence, at the end of the day I will practice on RA-1s once this set of RC-1s is worn out (and I will try to move these RC-1s to my DE car).