I was referring to vinyl tape, it sticks to the car without leaving a residue behind. I usually buy it at the track so I don't know where to find it online so I could give you an example.

 

Stick the numbers on your rear quarter windows instead. I also suggest leaving your "dream car" at home in a comfortable garage and get a dedicated track car so you can go ***** out with any guilt. My .02

 

I've been running magnetic-backed vinyl for over 2 seasons now and never a problem. I used to tape the front with painters tape but stopped doing that last year. They have stayed on at 170+. As others have said, just clean both surfaces well each time you apply them.

 

Making sure both surfaces are perfectly clean is extremely important. Obviously put them on and remove them carefully.