They're important but often overlooked.
Motorcycles use a number of bearings you won’t see on a car, the most obvious of which are the steering head bearings. These bearings like any others can wear out, and when they do, they’ll create strange handling problems on your motorcycle. Nils Menten of Tuscon, Arizona’s RestoCycle gives us a great demonstration on how to check those bearings in this video.
The steering head is the piece of your frame that the steering stem sits in. The steering stem is a metal rod that connects the center of the upper and lower triple clamp, which in turn holds the forks. The bike’s steering head bearings sit between the bike’s frame and the steering stem so that you can move the handlebar, forks, and front wheel smoothly from side to side.
How do you tell when your bike’s steering head bearings need to be replaced? Sometimes you can tell from the way the bike handles on the road. A good feedback rider will notice the bike “hunting” instead of holding a good line through a gentle sweeper. The bike’s front end might feel wobbly or, in extreme cases, you may hear the bike clunking over bumps or falling too quickly into a turn. You may chalk the strange behavior up to a squared-off or under-inflated front tire, cheap suspension, or something else entirely, when, in fact, your steering head bearings are going.
Often it’s just age and miles that wear out the steering head bearings, but a crash can mess them up instantly. Any major impact to the front end–-and sorry, stunters, this includes wheelies–-can severely limit the life of your steering head bearings. It’s worth checking the bearings if a bike has been sitting still for a long time, too, to make sure they’re not rusty, grungy, out of grease, or otherwise frozen up.
The good news is, it’s very easy to check those bearings, especially if you have a center stand and a friend! If you have neither of those, a motorcycle jack will work. Even though the bike in the video has nothing attached to the triple tree, you don’t have to dismantle a thing to check those bearings. The only requirement is that you get the front wheel off the ground.
To check your bearings, use a lift, or put your bike on its center stand. Then, have a friend weight the rear of the bike (which will pick the front wheel up off the ground) and hold it there for a few minutes. Make sure you can swing the bars easily throughout their entire range of travel, stop to stop. When you do this, the wheel, forks, and handlebar should move perfectly smoothly side to side. You should not be able to grab the wheel and move it forward or backward (be careful, don’t knock the bike off the stand), and there should be no clunkiness in the travel. If you feel any kind of grabbiness, notchiness, or hesitation in the travel, replace those steering head bearings tout suite. Make this part of your routine whenever that bike’s front end is in the air: at least with every tire change. Often you’ll notice that the bearings have gone bad this way before you ever feel it on the road.
If you’ve never replaced steering head bearings before and want to DIY this project, make sure you have reliable information about the torque settings your particular bike’s steering head demands and the right tools to remove the old bearings and races and install the new ones. Watch at least three YouTube videos about this procedure. It’s not a particularly tough job, but there are quite a few “gotchas” and it is made monumentally easier with several specialized tools. Your best bet, if you are new to wrenching, is to have a knowledgeable friend who owns the right tools help you out.