Headsets and associated standards

If you though bottom brackets were complicated, then you will love headsets!

Rather than use a third party naming system, I believe the simplest way to identify what headset you need it just to use the actual measurements. And the route to finding the correct headset can be reduced to a few simple questions.

1/ Is the bearing part of the headset internal or external to the head tube?

2/ Do you have to press cups in to the frame or do the bearings fit directly in to the headtube?

3/ Is the headtube straight or tapered?

4/ Is the fork steerer tube straight or tapered?

That’s basically it, you have narrowed down the type you need and if it doesn't give you the answer check the ID of the headtube and compare it to the poster. Sometimes there will be a new strange headset when a cycle manufacture decided to invent yet another new standard as the ones we already have are obviously not good enough...

Headtube standards measurements 

Conventional head tube: Straight traditional headtube with external bearings. 
ID = 30mm for 1” steerer tube
ID = 34mm for 1”1/8 steerer tube
ID = 49.57mm for 1.5” steerer tube

Conventional headset

Internal head tube: Often called Zero Stack or Semi-integrated, this head tube takes press in cups for 1”1/8 steerer tubes or external lower cup for 1”1/8-1.5” tapered steerer tube.
ID = 41.4mm, economy type for OEM manufacturers.
ID = 44mm, the most common MTB type. 

Internal, zero stack style

Differential head tubes: Tapered head tubes for press in cups (internal or external), mostly used on MTB’s.
ID = 44mm upper, 49.57mm lower
ID = 44mm upper, 55mm lower
ID = 44mm upper, 55.96mm lower

Internal for tapered head tube

Intellasett head tubes:  Press in cups with external cups the same diameter as the headtube for the integrated look.
ID = 34mm

Intellaset

Integrated head tubes: Direct bearing fit in to the frame, the two most popular types being Cane Creek (36 x 45) and Campagnolo (45 x 45).
ID = 41mm, 1”1/8 with 45 degree bearing seat (CC 36x45). *Upper seat can be 2.7mm or 3.2mm deep
ID = 41.7mm, 1”1/8 with 36 degree bearing seat (TH 36x36)
ID = 42mm, 1”1/8 with 45 degree bearing seat(Campy 45x45)
ID = 47mm, with 45 degree bearing seat 1”1/4 straight

Integrated headset

Differential Integrated head tubes: Direct bearing fit in to the frame for tapered head tubes.
ID = 42mm upper with 45 degree bearing seat, 52.10mm lower with 45 degree bearing seat. For 1”1/8-1.5” tapered steerer tube.
ID = 41.2mm upper with 45 degree bearing seat, 49.1mm lower with 45 degree bearing seat. For 1”1/8-1”3/8 tapered steerer tube
ID = 42mm upper with 45 degree bearing seat, 47mm lower with 45 degree bearing seat. For 1”1/8-1”1/4 tapered steerer tube
ID = 42mm upper x 6.5mm deep with 45 degree bearing seat, 47.1mm lower x 6.5mm deep with 45 degree bearing seat for 1"1/8 - 1" 1/4 steerer. NEW Overdrive system.

Integrated headset for tapered head tube

all you need to know!

1"1/8 to 1"3/8 tapered headtube