Instead of masking the tire-
my friends and I go to dollar tree and buy some packs of playing cards, flash cards or 3x5 note cards (whatever you get the most of for $1) and slip them between rim and tire in an overlapping fashion.

 

I know super old post but use playing cards. You slide cars one by one between wheel and tire. Dont need to use any masking tape for the cards will protect everything. Put the cards one by one over lapping 1/3 of the card. I am talking about poker playing I do this all the time and works like a charm r regions.