Make sure to drive the races in to the lip that is the stop for them. Also tighten the nut till the bearing pre-load just starts to slow the wheel, then back off a till the wheels spins freely and put the castle washer and cotter key in. Be generous with the grease. Most first timers don't get the grease packed into the rollers good. Make sure that it is packed completely through the roller and squeezing out the other end and between the rollers and cage.