I sat behind Jim Hall and Smokey Yunick at Daytona in 1965 watching the test on a Chaparral 2A. You could walk in and watch at that time. No one was in the grandstands but us
I had another set of rotors so I changed them, but now that I look at them it looks like pad material. I had just changed brake pad material also. I would take the rotors off clean sand and see.