depends if your chain was already stretched when you put it on. if it isnt, its going too and its going to go slack and come off all the time, then you will need a tensioner. if its stretched already and now you have removed your tensioner and its the correct tension, when you get a new chain then it will be far far too tight. you can usually remidy these problems with a half link, but i couldnt so good luck. oh and bucky. it stays on by being at the correct tension anyway. like on a bmx. althought with vertical dropouts its waaaay more hit and miss