MTB headsets

How to choose your MTB headset

It is the component you only pay attention to once it starts feeling notchy. You do not choose its spec: it is determined by the frame, and secondarily by the fork steerer.

Reading the frame code

• IS (Integrated System): the bearing sits directly inside the head tube, without a cup. Example: IS42.
• ZS (Zero Stack), known as semi-integrated: a cup is pressed into the head tube and houses the bearing. Example: ZS44 or ZS56.
• EC (External Cup): external cup, the bearing sits outside the head tube. Example: EC34.
• The number indicates the bore diameter in millimetres : most commonly 42, 44, 49 or 56.
• The top and bottom can be different types. A common tapered frame uses ZS44 at the top and ZS56 at the bottom.

Straight or tapered steerer

A straight steerer measures 1"1/8 along its entire length. A tapered steerer goes from 1"1/8 at the top to 1.5" at the bottom. The headset must match the fork steerer and to the frame: this is the dual requirement that is systematically forgotten when swapping forks.

The crown race

• This is the ring pressed onto the base of the steerer tube, which supports the lower bearing.
• It is specific to the steerer tube diameter (1", 1"1/8, 1.5") and to thecontact angle (36° or 45° depending on the brand).
• Steel for durability, aluminium for low weight.
• Some models add +3 or +6 mm of height, allowing the front end to be raised slightly without changing handlebars.

Parts that can be replaced individually

Top caps, compression rings, seals and replacement bearings can be ordered separately. A headset that feels notchy usually only needs its two bearings replaced: there is no need to buy a complete set, especially on a quality model whose cups are still in perfect condition.

When to take action

• A tight spot in a straight line, felt riding hands-free at low speed.
• A knocking under front braking.
• A noticeable play by holding the front brake and rocking the bike back and forth with one hand on the headset.
• As a rule of thumb, after a full winter on a bike washed with a hose.

To find out more: How to choose your MTB headset

See also: MTB Stems · MTB Headset Spacers · 29-inch MTB Forks