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Which Headset Do I Need?

March 15, 2016

Here at Mountain Bikes Direct, we're commonly asked, “What headset do I need to fit my…..”

Well, here it is, the ultimate headset guide!

Rather than confuse you a heap of standards that are now obsolete, we're going to stick to the ones that are current and common.

You can see our range of complete headsets here.

Or our range of headset parts and bearings here.

Anatomy Of A Headset

Top Cap & Cap Bolt – These are the two parts you can see on the top of your stem. You can tighten your headset by loosening your stem bolts (and your top crown bolts on a DH bike) and tightening down on this bolt till firm. Don't forget to tighten your stem/crown bolts back up!

Star Nut - This is the part that is driven into your forks steerer tube. They are designed so they can be hit in and not come back out. tThe Cap Bolt screws into this nut.

Dust Cover – The name kind of says it all. This is the cover that sits over your headset bearings to ensure that no dust/dirt can get into your bearings.

Compression Ring – This is a tapered or conical shaped ring that is the most important part in keeping your tight.

Cartridge Bearings – Most headsets will have sealed cartridge bearings in them. This is the part that allows the steerer to turn in the frame.

Upper & Lower Head Tube Cup – This is the cup that is pressed into the frame using these tools.
Note - If you have an "internal" headset, you won't have this part. (more on that later).

Crown Race – This is performs a similar job to the Compression ring in that the bearing is tightened down so the tapered part sits snugly into the tapered part of the cartridge bearing.


Different Styles Of Headsets

EC - External Cup. The Headset bearing sits outside or external to the frame.

IS – Integrated or Drop Fit.  There is no cups in this headset, the bearings drop straight into the frame. Effectively the cup is built in to the frame

ZS – Zero Stack / Semi Integrated / Internal


Types Of Steerer Tubes

There is 2 major and 2 much less common types of fork steerer tubes.

The two more common ones are:

  • Tapered 1 ⅛th to 1.5”. (1.125” to 1.5”) - This is by far the most common type. It tapers from 28.6mm where your stem clamps out to 39.8mm where the crown race sits. This set up is basically the same weight as a straight steerer while also boosting stiffness and strength. This is by far the most common on high quality bikes.
  • 1 ⅛th (1.125”) – This is becoming outdated now, but is essentially a straight steerer tube that measures 28.6mm except for the where the crown race is installed that is 30.0mm This is considered as being an older standard with almost everything now running Tapered.

The two less common are:

  • 1.5 Inch (onepointfive) – This is discontinued now, but is a straight steerer that is 38.1mm where the stem bolts on and 39.8 at the crown race.
  • Overdrive 2 or OD2 – This is a Giant specific size that tapers from 1 ¼ to 1.5 Inch. Giant used this on some of their mountain bikes for between 2012 and 2014. It is still used on Giant road bikes.


Which Headset Will Fit?

If you can't find the exact details of your frames head tube online, then you're going to have to do some measuring!

  1. You're going to need a Vernier Caliper – like this one.
  2. If there is already a headset in your bike, you're going to have to remove the cups (if it is a ZS or EC headset)
  3. Now measure the internal diameter of the upper head tube and write this down.
  4. Now measure the internal diameter of the lower head tube and write this down.
  5. Measure the external diameter of your steerer tube where the stem clamps on to it and write this down.
  6. Measure the external diameter of your steerer tube where the crown race sits and write this down.




The wonderful people at Cane Creek came up with S.H.I.S. (Standard Headset Identification System). This system offers a standard way of describing a headset. After taking a few measurements of your frame and fork, you can look at the string of letters and numbers and know for sure if the headset will fit you frame

An example of a S.H.I.S Headset description is:

ZS44/28.6 | EC49/40

Let's break this down. The first half of the description refers to the upper half of the headset. ( ZS44/28.6)

  • ZS – Zero Stack
  • 44 – 44mm Internal Diameter of the top of the headtube on the frame.
  • 28.6 – 28.6mm is the size of the steerer tube where the stem will clamp on

The second half of the description refers to the lower half of the headset. (EC49/40)

  • EC – External Cup
  • 49 – 49mm is the internal diameter of the headtube at the bottom.
  • 40 – 40mm is the diameter of the fork steerer tube where the crown race will sit.

So, this headset has got a zero stack top cup, with an external bottom cup and it is to suit a tapered steerer.


Common Headset Sizes

Upper Headset (Based On A 28.6mm Steerer Diameter At Stem Clamp)

Head Tube Internal DiameterEC - External CupZS - Zero StackIS - Integrated

Lower Headset

Head Tube Internal DiameterEC - External CupZS - Zero StackIS - Integrated
34mmEC34/30 ONLY--
41mm--IS41/30 ONLY
42mm--IS42/30 ONLY
44mmEC44/30 or EC44/40*ZS44/30 ONLY-
49mmEC49/30 or EC49/40*ZS49/30 ONLY-
52mm--IS52/30 or IS52/40*
56mm-ZS56/30 or ZS56/40*-

* The headset cups and bearings are the same for 1 ⅛th forks and 1.5" forks. It's just the crown race that changes.

Meet Tim!

After a brief hiatus living in Canada, Tim is back on our sunny shores and loving it! Tim loves anything on two wheels but favours steep, gravity fed technical trails. He has spent almost his entire working life in the industry, as former owner of an iconic MTB store in Brisbane and now stock manager for Mountain Bikes Direct.