What are a-head headsets?

Headsets are bearings located in the head tube of the frame. The fork sits on them, allowing you to move the handlebars and change direction. This shouldn't require force—the movement should be smooth. At the same time, there shouldn't be any play, which would result in unstable handling and bearing damage. The key is to properly tighten the entire assembly to achieve the happy medium. How is this achieved? For decades, the solution was traditional, screw-in headsets. They functioned exactly like traditional hubs. The fork's steerer tube and the upper bearing cup were threaded. This allowed for the elimination of play and the headset to be locked in place using a nut above the cup. The disadvantages? The need for two specific, large, flat wrenches, extremely unwieldy to take with you on the road. Furthermore, the threads wore out, causing the headset to loosen more quickly. When, in the late 1980s, cartridge bearings began to be used instead of ring bearings, requiring greater precision in adjustment, it became clear that a new solution was needed. The answer was a-head headsets. Their design is simpler. The thread is moved to the center of the steerer tube. It's inserted using a hammered star nut (aluminum tubes) or an expandable expander (carbon fiber). A through-the-hole stem and spacers are placed on the smooth steerer tube, allowing them to protrude slightly above the tube. A cap is screwed on from the top. This tightens the assembly and eliminates any play. Simply tighten the stem to secure everything. Simple? Just remember a few things. Learn more about the types of rudders

A-head headset adjustment

Above all, don't overdo it with the height. The washer (or the bridge, if it's placed at the top) should protrude 2-4 mm above the pipe level. If there's not enough height, the cap may touch the bridge when tightened, making it impossible to remove any play. If the bridge is too high (above the level of the top screw), it or the pipe may be damaged. Everything in place?

Clearing the backlash

Make sure the stem is loose and rotates freely on the steerer tube. Now tighten the top cap screw until you feel slight resistance. Now you need to check two things: play and resistance to fork movement. First, tighten the stem slightly, just enough to prevent it from rotating. It's best to control play by gripping the head tube, headset, and spacers/stem. Now simply apply the front brake and rock the bike back and forth. If you feel the components moving vertically relative to each other, loosen the stem and tighten the top cap. Repeat this process until the entire assembly is stiff and no vertical movement is felt.

Smooth movement

Next, check the bearings. They should move easily and, above all, smoothly. Just turn the handlebar. If you can clearly feel the balls moving, grinding, or have to use force, you've overdone it. Loosen the stem, loosen the screw in the cap, and check everything again. Repeat this until you succeed. Also, remember that the bearings themselves have their own rolling resistance. However, it's small—just enough so that you don't feel like you're spinning "in the air." Finally, tighten the stem according to the manufacturer's recommendations; this information is almost always located next to the bolts. If you don't have a torque wrench, proceed with caution. The bolts can easily break, so I don't recommend overtightening them. Next, lock the wheel between your knees and try (but don't overtighten) to turn the handlebars. This shouldn't be possible without considerable force. It's worth noting that from this point on, the top cap has no role in transferring force or holding the stem in place.

Is it possible to replace classic headsets with a-head headsets?

Technically, yes, but practically, it's too much work. It's worth noting that most classic headsets are available in 1-inch sizes, and most a-head headsets in 1 1/8 inches. With a little effort, however, you can find both in non-standard sizes. The steerer tube is a more problematic issue. In a classic headset, it doesn't extend above the headset, while in a a-head headset, a stem is placed over it. The only solution is to have the steerer tube replaced by a specialist, but this is a rather expensive operation. In short, it's usually a triumph of style over substance.