dudes... bent rims, if bent side ways more than 5mm or more would demand either loosening the nipples where the bent is and tightening it on the other side. but doing this will probably round up the edges of your spokes specially when the spokes are tight. i suggest before doing such, inflate your tire to 50 psi., and look where the most bent part is and smash it on a wooden chair or table with control not to overdo it. check from time to time if the bent becomes less either by placing it back on the truing stand or by putting your wheel on the bike. if the bent is less enough true your wheels to finish the job. with all this you lessen the chances of having your nipples replaced due to inability to true your wheels due to rounded up nipples.