Threadless Headset Overhaul

Until now I've only shown how to service threaded headsets. Most newer bikes have a different setup where the stem clamps onto the fork's steerer tube. Here's what a threadless headset looks like:

This is a stronger and lighter system than the old threaded setup, and slightly easier to service too. Shown here is a basic Dia Compe Aheadset on a Trek 930. The first step is to remove the top cap bolt:

Now you can loosen the side clamp bolts. If there's more than one then loosen each bolt in half turn increments or less:

The stem will slide right off at this point. Carefully lay it aside so you don't kink the cables:

Now remove any headset spacers:

Here you'll notice a plastic ring wedged inside the top bearing race. Sometime you can just shove the fork out of the head tube at this point. If there's too much resistance, then gently pry up on the bearing race to lift up both the race and the plastic ring. Afterwards if you push the race back down, you can slide the plastic ring off:

Now you can easily slide the fork out:

Time to clean out the bearings and add some fresh grease to the frame cups:

The fork goes in the same way that you removed it, so carefully slide it back into the head tube:

Wipe off any grease from the steerer tube, then replace the top bearing race:

And the plastic ring:

Now the dust cover:

Then the spacers:

Finally the stem:

 

Don't tighten the clamp bolts yet. Instead replace the top cap and tighten down the bolt:

This is the tricky part because this bolt sets the preload on the headset. I like to make it nice and tight at first in order to seat the headset parts together, then loosen the bolt until the fork turns freely without play. Only after this bolt has the correct tightness should you align the handlebars and tighten the clamp bolts:

 

These bolts will lock in the headset's adjustment, and basically secure the fork to the frame. Tighten them evenly in 1/4 turn increments so that the gap in the stem is the same by each bolt (if there's only one clamp bolt then just make it nice and tight). That's it, no big wrenches to fuss with or stuck quill stems to deal with. The only tools you need are allen keys.