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Headset
From WikiPedalia
The bearing assembly that connects the front fork to the frame, and permits the fork to turn for steering and balancing.
A headset consists of four races plus associated parts:
- The crown race, which is pressed on to the bottom of the steerer, just above the crown.
- The lower head race is pressed into the bottom of the head tube.
- The upper head race is pressed into the top of the head tube.
- The adjustable race attaches to the steerer. The adjustable race is secured by either a:
- Keyed washer and lock nut, for threaded headsets or a:
- Star fangled nut and cap, or compression rings in the case of some threadless headsets.
Threaded vs Threadless
The images below show how to identify whether a headset is threaded or threadless.
| Threaded Headset Note wrench flats on locknut and top threaded race. 
|
Threadless Headset Note pinch bolts on stem. and no wrench flats. 
|
|---|
- Traditional threaded headsets fit forks with threaded steerers. The adjustable race screws on to the steerer, and a locknut screws on after the adjustable race to secure it. There is normally a keyed washer between the adjustable race and the locknut for extra security.
- Threadless headsets have an adjustable race that slips over an un-threaded steerer.
If you want to replace one headset with another, you must take into account the stack height of the new headset. There are other variations, in dimensions and in how parts are sccured. .
