Full guide: Bicycle headsets explained


In order to have flawless steering, you’ll need a serious headset, that works smoothly. This part connects the fork with the frame and nowadays we have three big standards in this respect: external cups (EC), zero stack (ZS) and integrated standard (IS). You can find out more about them in the following.


Headset sizing and standards

The external cups are called this way for the simple reason that the bearings are situated outside the bike’s headtube, respectively at its ends. The other two types enable the housing of the bearings within the head tube, the two being different in the sense that the integrated standard doesn’t use cups at all, therefore requiring a specially designed frame for this purpose. The illustration below depicts the alignment of the various parts of the headsets.


Not only is the standard important, but the headset must be size-compatible to your head tube. Mondern bicycles employ 4 major dimensions: 1-1/4 inch, 1-1/8 inch, 1-1/8 – 1.5 inch (tapered head tube), 1.5 inch (oversized head tube). As the numbers reveal, only in the case of the tapered head tubes will the upper cup be smaller in diameter than the lower one. Also, if you plan on using a fork with a 1-1/8 inch steering tube on a tapered head tube, you’ll need a lower cup that will act as an adapter, having an outer diameter of 1.5 inches, and an inner one of 1-1/8 inches.


How do you pick the right headset? Although knowing the sizes mentioned above, there is a special headset denomination. In the case of semi-integrated, the adnotation for upper cups is ZS41/28.6, while the lower cups are reffered to as ZS56/40. ZS stands for “zero stack”, 41 represents the head tube’s diameter (in millimeters), while 28.6 is the steering tube’s diameter (again, in millimeters).


Recommandations concerning headsets

  • Cartridge bearing headsets outlast the classical ball-bearing ones in terms of durability, although you can still find this latter standard on 1 inch head tube bikes.
  • For mounting the headset, you’ll need a special tool. It’s highly recommended you use that special tool and not improvised mechanisms because you cand damage different headset parts or, even worse, the frame itself. Also, from time to time, show your headset mercy and grease it, and don’t wait for the steering to become difficult.
  • Do no tighten the stem cap more than it’s recommended. Not only will it become difficult to turn the handlebar, but you also risk destroying the bearings. As a guideline, apply just enough force as not to have a play in the front part, but if you can’t figure this limit out by yourself, visit your local bike mechanic.