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Headset Fit Finder

HEADSETS

HOW DO THEY FIT

The headset is often overlooked and neglected, but it is an essential component to your bike. Your bike’s headset is the bearing assembly that keeps your fork attached to your bicycle, and it’s what allows you to turn your fork and handlebars to steer your bicycle.  All bicycle headsets work in a similar way – there are two bearings, one for the top and one for the bottom of the headtube, and your fork’s steerer tube passes through the headtube with lower and upper bearings. The steerer tube protrudes out past the upper head tube and is clamped down and held in place by the handlebar stem. Before you clamp the handlebar stem to the steerer tube, the system must be preloaded / compressed together in order for the headset to work and withstand loads and abuse. 

What headset will fit my bike?

There are three things you must determine in order to identify the correct headset you need for your bike:

1. HEAD TUBE TYPE – There are two types of head tubes: press-fit, and integrated.  Press-fit head tubes require headset cups that are pressed into the bicycle headtube, and the headset bearings sit inside those headset cups.

You can have ZS (Zero Stack) headset cups or EC (External Cup) headset cups. Both of these are for press-fit head tubes, but they are different types of headset cups- the external cup has a much taller stack height because it houses the bearing on the exterior of the headtube, where the Zero Stack headset cups house the bearings inside the headtube.

 

Integrated (IS) headtubes have molded integrated races inside the headtube that are a part of your bicycle’s frame, and you simply rest the headset bearings onto these integrated races

2. HEAD TUBE DIMENSIONS – A press-fit headtube should be measured with a good set of calipers, the inside diameter in millimeters, of the bare headtube top and bottom.

You’ll likely find numbers like these: 30mm, 34mm, 44mm, 49mm, 56mm, and more recently 62mm.

With an integrated headtube, be sure you are measuring the very edge of the top and bottom bare headtube because the integrated headtube races are angular- if you measure with your calipers in too deep, you could get incorrect measurements. If you have the stock or original headset bearings, you can measure the outside diameter of those bearings to be sure. You’ll likely find numbers like: 41mm, 41.8mm (we round up and label this 42mm), 47mm, and 52mm.  

Measuring Bare headtube

3. FORK STEERER TUBE DIMENSIONS – Almost every single modern bicycle fork has an upper steerer tube outer diameter of 28.6mm, or also referred to by 1 ⅛ in.

Some forks have straight steerer tubes, and some have tapered. Straight 1 ⅛ in steerer tubes have a crown race seat of 30mm, so they require a 30mm crown race.  Tapered steerer tubes can taper out to 1 ¼ in (33mm crown race seat) and sometimes have integrated crown races (like the 2nd image), so no press-fit crown race is needed.

More commonly, tapered steerer tubes will taper out to 1.5 inches, which has a 40mm crown race seat so a 40mm crown race is needed. Most modern single crown mountain bike forks have a 1.5 in tapered steerer tube (40mm crown race)

WHAT DO ALL THOSE NUMBERS MEAN

We developed the most commonly used headset identification system – SHIS which stands for Standardized Headset Identification System.  We use the measurements you get from the headtube and fork to influence the naming of different headset specifications. 

The identifier starts off with two letters which signify the type of headset it is. “EC” stands for External Cup, and “ZS” stands for Zero Stack, “IS” Stands for Integrated System.   The numbers following the two letters signify the headtube and fork dimensions.

Headset configurations

Take this headset for example: ZS44/28.6 EC44/40.  This headset would work for a press-fit headtube with an inside diameter of 44mm top and bottom (ZS44 upper cup and EC44 lower cup) , and the fork has a 1 ⅛ in (28.6mm upper steerer tube) to a 1.5 in tapered steerer (40mm crown race). 

headset ID Diagram

A ZS44/28.6 EC44/30 would work for the same 44mm press-fit headtube, but it has a 30mm crown race which would work for a straight 1 ⅛ in steerer tube.  A ZS44/28.6 ZS44/30 would also work on the same 44mm press-fit headtube, and also work on a straight 1 ⅛ in steerer tube, but the lower headset assembly would not have as much stack height as the EC44/30 bottom assembly.

ZS44/28.6 EC49/40 will work on a press-fit headtube that has an upper inside diameter of 44mm and a lower headtube inside diameter of 49mm, and a fork that has a 1 ⅛ inch to 1.5 inch tapered steerer tube.

IS42/28.6 IS52/40 would work on an integrated headtube (IS) that has an upper headtube with a 41.8mm inside diameter (which we round up to 42mm) and a lower headtube inside diameter of 52mm, and the fork would have a 1 ⅛ in to a 1.5 in tapered steerer tube.  IS41/28.6 IS41/30 would work on an integrated headtube that has an upper and lower headtube I.D. of 41mm and a fork with a straight 1 ⅛ in steerer tube.

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