Headsets

There are two different styles of headsets: threaded and threadless. In the threaded configuration, the top of the fork column is threaded, and headset adjustment is performed by turning an adjustable cup and securing it with a locknut. The stem is attached with a wedge inserted into the fork steerer. Threaded forks and headsets are no longer in use on modern mountain bikes.

In the threadless configuration, the fork column is unthreaded (Fig. 1). The headset is adjusted by means of a top cap, and the adjustment is secured by the stem, which clamps firmly onto the exterior of the fork. In our illustration, the dashed blue line represents the fork's steerer tube - note that the steerer passes completely through the headtube, bearing cups, and stem; and is secured on the bike by the clamping action of the stem.

All modern mountain bikes and many road bikes use the threadless system.

Fig. 1 - Typcial threadless headset setup

What size?

Almost all threadless headsets, stems, and forks are of the 1 1/8" size. Remember, ALL of these components must match in size - it is not possible to mix and match 1 1/8" components with 1" or 1 1/4". The size you need is determined by the internal diameter of your frame's head tube.

Integrated headsets

In some new bicycles, a special type of headset is used where the bearings rest directly in the head tube. If you intend to purchase such a frame, your sales rep can assist you in determining the proper headset size.

IMPORTANT NOTE: In a threadless system, the top cap does NOT secure the stem to the fork! Although the top cap bolt looks similar to the wedge bolt used in a threaded system, it is used only to adjust the preload on the headset and does not hold the stem to the bike. Always tighten the stem's bolts securely after adjusting the headset preload with the top cap.

Some info sourced from our affiliate partner: Jensonusa