SAND PAPER!!!! YOU NEED SAND PAPER!!!! If you don't rough up the rim surface your tape will roll off (just barely) when you change tires 6 months from now, and then air will leak into your rim, but it will only leak out of your valve, and you'll think your valve is the problem, and you'll spend hours trying to fix the seal on your valve, but it's not your valve, it's a huge gaping section of your tape that rolled out of the way and is letting air in through the spoke holes, and then when you finally figure...