If you’re anything like me, working on your bike is half the fun of owning it. Sure, you can have a bike shop do maintenance for you, and if it’s a big job requiring specialty tools, this might be a good idea. For me, I want to know every part of my bike inside and out, know what makes it go, and know how to take it apart and put it back together. I’m working on overhauling my commuter bike, a Montague Boston, and making it truly custom with all new components. Last time, I stripped most of the old parts that had been beat up from 2 years of all weather commuting. I pulled the crankset, removed the bottom bracket and old brakes, and gave the frame a thorough cleaning.
Now it’s time to take a look at the headset, the set of bearings that allow the front fork to rotate freely in the frame. There are essentially two types of bicycle headsets; threaded, and threadless. A threaded headset, surprisingly, uses a fork with a threaded steerer tube. The top of the headset is a large lock nut which threads onto the fork, and when tightened, sets the compression on the bearings. The headset on my Boston is threadless. The stem clamps directly around the steerer tube and is simply pushed down against the headset bearings to provide compression. This is a more recent design and has become very popular on modern road and mountain bikes. It’s simpler, easier to install and maintain, and doesn’t require anything more than an allen key to take apart.
Start by removing the top cap. This bolt threads into a star nut which is wedged inside the steerer tube. When tightened, it pushes the stem down against the headset to compress the bearings:
In order to get at the headset bearings, you’ll need to remove the stem completely. Simply loosen the two bolts that clamp it to the fork, and slide it up and off:
At this point, the fork will be free to slide down and out of the frame. Part of the headset is a circular wedge, or compression ring, that fits snugly around the top of the steerer tube. Sometimes it does it’s job a bit too well and the fork gets stuck in the frame. If this is the case, just give the top of the steerer tube a tap with a rubber mallet:
As you remove the fork, you’ll see there are several parts to the headset, both above and below the frame’s head tube. As you take them off, try to keep them in order to make re-installation easier. The headset also includes the cups that are press fit into the frame, and the crown race which is pressed onto the base of the fork’s steerer tube. We’ll leave those in place and give everything a thorough cleaning:
My headset bearings were pretty dirty and gummed up with debris, so it’s no wonder they weren’t turning smoothly. This headset uses caged ball bearings. They’re easy to clean, and difficult to lose. As you can see above, they came out looking pretty good. Some headsets have sealed cartridge bearings, some have loose ball bearings, but with any of these designs, grease if your friend:
Make sure you’ve cleaned the inside of the cups that are still in the frame, and the crown race which is at the base of the steerer tube. Apply grease generously and put each part back around the steerer tube in the same order:
Slide your (in this case new) stem on to the steerer tube, and push it down so it’s snug against the headset. The top of the stem should actually stick up above the top of the steerer tube by about 3-4mm. If it’s too short, add another spacer under the stem. Put the top cap back on, and thread the cap bolt back into the star nut. Make it snug, to compress the headset bearings, but don’t overtighten. If you do, it will be hard to turn the fork, and you’ll be putting extra wear on the bearings and cups.
Lastly, you need to secure the stem in place by clamping it to the steerer tube. These bolts are responsible for holding all of this together, so properly tightening them is extremely important. Check with your stem manufacturer for the recommended torque (it will probably be around 8 – 9N/m), and if possible, use a torque wrench to ensure they’re safely tightened.
With freshly cleaned and greased bearings, this fork turned effortlessly, a great improvement from it’s former state. My headset now feels nice and buttery 🙂