SCCA Club Racing Spec FF Radial Tire is crap to autocross on
Jim,
The issue with autocrossing on the spec radial has a bit to do with the R60 compound, but more to do with the radial tire dynamic response characteristics. The tires are heavy and numb, lacking any real feedback or feel. The only way you can detect the car understeering or oversteering is when the car is not pointed in the direction you want it to go. There is zero feedback coming thru the steering wheel, seat, or pedals. The tires do not respond to trail braking, preferring to understeer off the turn when turning in under braking. The tires are also prone to brake lock, particularly when not at full operating temperature, due to the combination of higher weight and inertia, very high static camber settings, and the inability for the tire to do more than one thing at a time. It will decelerate, accelerate, or turn, but not more than one thing at the same time. This is the same issue as in club racing, which is why most long time FF racers are migrating to various vintage series (SVRA/RCFFS/Crossflow Cup) where they do not have to run this tire. Most hate the feel and response of the radial tire and trying to get a mid-80's FF to work on it is a major challenge, assuming you can get there at all.
I tested both at Oscoda last year....I was testing my road racing set-up in an attempt to dial in the shocks for dynamics to get the car to respond better on turn-in and corner entry in club racing. It was pretty much a lost cause and the car was fairly unresponsive to most changes. We bolted on a 4 year old set of bias ply R25s (last run at Solo Nationals 2018), and, without changing anything other than the tires, the car was 0.5 sec faster, and much more of a joy to drive, on the second lap. That difference would have been much bigger if we had put the autocross set-up on the car with it.
It isn't so much the compound issue as it is the tire construction and poor response and feedback. I have had nothing but frustration trying to club race on them on my 88 Reynard. Besides destroying any established autocross indexes for the class, the tires are just not fun to drive on, and that would further weaken the class as people leave to find more enjoyable cars to drive.
My experience and opinion. YMMV.
May/22 Thread: "FC wheels on CM FF....Go!"...
I see the path forward being a rule change to allow FC/FF2000 wheels (ie 6" and 8"). That opens up additional tire brand/compound options. That said, at this point, I'm just not interested in the time and expense to figure out a new set up...
FYI- Ben's May/22 thread on the subject: FC wheels on CM FF....Go!