Nuts and Bolts: Wrapping your head around headsets

Controlling your steering is an essential part of riding a bike, transferring the actions of your arms down to the front wheel.

By Adam Newman and Eric McKeegan, illustrations by Andrew Roberts

 Threaded headsets

By far the most popular headset style through the years has been the “threaded” headset. It derives its name from the threads cut into the fork steerer that are secured by a nut at the top of the headset. They are still found on many less-expensive or transportation bikes. They are easily identified by the type of “gooseneck” or quill stem that makes a bend and disappears into the head tube.

The simplest way to explain how it works is to imagine the fork steerer as a large bolt and the top of the headset is a nut. A threaded bearing race ensures the proper tightness on the bearings and the top lock nut holds it in place. Adjusting these headsets was one of the primary uses for the thin, flat wrenches that adorn nearly every bike shop service area in the universe.

Advantages: Easy to adjust handlebar height by loosening expander wedge in stem.

Disadvantages: Fork steerer needs to be just the right length for the frame with threads cut into it, making fork changes more difficult. Headset adjustments require specialized tools.

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 Threadless headsets

Most modern performance bikes used threadless headsets. You’re never going to believe this, but they are called this because they don’t have threads. Crazy, I know. Instead of the fork steerer terminating flush with the top of the headset, it extends above it to provide a space for the stem to clamp to. Because the stem can be clamped anywhere along this extended portion (within reason, not too high!) it can be adjusted up and down with the use of spacers. Some threadless headsets use external cups that you can see, while others use cups that press into the frame directly and are hidden from view. Some frames have built in cups, with bearings that drop directly into the frame.

Instead of a threaded race and nut providing the proper tension on the bearings, a bolt through the tpp cap pulls up on the star-nut or expander plug installed in the steerer tube to adjust bearing preload.. The stem holds this adjustment by clamping around the steerer tube.. In theory the top cap could then be removed, but we don’t recommend it. The fork steerer still needs to be cut to length, especially on smaller frames, but it doesn’t need to be exact as long as it is still long enough. The spacers allow for some flexibility.

Advantages: Usually lighter, allows for greater flexibility in fork design, including the use of carbon fiber or aluminum steerers. Bearing adjustment can be done with one or two hex wrenches.

Disadvantages: Very little height adjustment possible without swapping stems. More expensive? Aesthetics? Honestly we’re having trouble thinking of more than one.

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 Troubleshooting headset issues

Issue: My handlebars, stem and fork seem clunky or loose
The easiest way to test if a headset is loose is to hold the front brake, turn the handlebars to the side and rock the bike back and forth, holding the junction between the fork and the frame at the bottom of the head tube. If you can feel some play here, the headset is likely loose. With a threadless headset, you can adjust it easily with a multi-tool.

1. Loose the stem clamp bolts.
2. Tighten the top cap bolt until it’s snug, then back it out ⅛ of a turn.
3. Make sure the stem is pointed straight, and re-tighten the stem clamp bolts. Check the torque specs to avoid over-tightening.
4. Recheck adjustment.

Issue: I tightened my top cap all the way but the headset is still loose
Check to make sure the stem clamp bolts are loose so the stem can slide up and down the steerer to put tension on the bearings. Also make sure you have a few millimeters of space between the top of the steerer tube and the top of the stem.. If the top cap is bottoming out before it can push down on the stem and spacers, it won’t achieve the proper tension.

Issue: I’m trying to remove a quill stem but it’s stuck in the frame
Metal parts can corrode and stick together if not coated properly with a layer of grease, especially anything made from aluminum. Turn the bike upside down and try squirting some penetrating fluid into the underside of the steerer tube. Let it sit for a few hours and try again. It’s also a lot easier to get some leverage on the stem with handlebars installed. You can also remove the stem bolt and strike the stem with a rubber mallet.

Issue: My steering seems to have a notch in it.
This might seem like a nice feature to have, but it actually means your bearings and bearing race are worn out. It’s probably a good idea to have them replaced.

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