i was spinning the back wheel of the bike, this kid in my neiborhood is selling it, and i would go over atleast 3 times a week to check it out, and ive ridden it aroudn and everything, its very nice, one day i was watching him put it into first gear on the stand its on, and i have seen him do this a bunch and never even noticed it its so slight, but the back wheel seems to beraly whiggle, you know wut i meen, like not rattling but kinda wobble, but its so slight that it odnt know if it would make a difference, can neone tell me if this is a big deal or not, should i not buy the bike cuz of it?