Problem solved with these Quick Slicks tires. This is the Extra Firm (XF) compound, with rounded edges on both inside and outside of the tire, nice flat contact patch. See pics below:



Testing on my Carrera track, this car runs about same lap times as a Slot.IT Group C car, an excellent drive. Smooth accelleration, no chattering around the turns, tires are true, when pushed to limits the car slides a bit to give you a chance to recover instead of tipping over, or flying off the track. I have radius 2 and 3 banks, and the tires are the right size so the car doesn't wash out on the bank or transition straights coming in and out the turn.
Several racers wanted this tire made in silicone, but requests were declined from another manufacturer, until now with Quick Slicks. to Quick Slicks for listening to racers, by making a silicone tire for this series of cars that nobody else does. Getting ready to run a series of races at the big Carrera track at Pinion Twisters in Riverside, NJ, looking forward to it.
Hoping BRM plastic track racers will buy these tires to help support a company comprised of guys that actually race the cars they make.