Might be a stupid question but I don't know. Do prepped tires work the whole race to get better grip? In between races do you wash your tires and put prep on again or brush them off with a wire brush and wipe them with the prep. If I buy a used set of tires that the person has been using one type of prep can you change if you want. I am going to start racing again and I want to try and get on some type program. Would like to find one type prep and stay with that. I have done all the awitching back and forth. I will be racing on a smaller budget than most. Probably have a couple sets of tires to work with. Been out of it or 5 years but a track is being built about 10 miles from the house. I'm 73 now but I still feel like I can race. Gonna find out.