How To Install Your Bearings
First up, you’ll probably need to remove your previous bearings. Unscrew your axle nuts and take the wheels off of their axles. Next, hook the tip (about ¼ inch) of the axle inside of the inner ring of one of your old bearings. Whether or not you’d like to save your old bearings will dictate how gentle of a process this next step has to be. In one motion—no jerking around—pry the bearing out of the wheel. Older wheels will give you a little more guff, as they tend to dry out. Do the same for the rest of your wheels and you’re ready for your new bearings.
To install your bearings, the most common technique is to sit two bearings, shields facing down, on a truck axle. Situate your board so that your axles are pointing straight up and down. Set a wheel down on top of the bearings, and push straight down. This is where a lot of people damage their bearings—instead of pushing straight down, they see-saw the wheel down over the bearing. This does a number on the alignment of the inner ring, and is even worse when you go to install the wheel’s second bearing. The axle ends up jabbing at the first bearing from below. The trick here that’s going to save your bearings is to put your weight on top of the wheel and go straight down. Do this for the rest of your bearings and they’ll love you for it.
All that’s left now is to get your wheels back on their axles. One last trick is when tightening the axle nuts down, leave just a little bit of wiggle room for the wheel. You don’t want to crank that nut all the way down on your bearing—that would put stress on the tracks when you’re out skating on them. Give them just a little bit of breathing room, and check them every so often. They have a tendency to tighten up on you every so often. Now that you’re all set up-----Go skate!