[big gear head]

I don't believe that's enough air pressure in the tires. Radials need more air pressure than bias ply tires. I had radials on the back of my car and tried running 15 pounds. I had a terrible tail wag at just over 100 mph. I increased air pressure to 30 pounds according to Hoosier and it helped a lot. I changed to bias ply slicks and it went away completely.