Hardly any component on a mountain bike does its job as unobtrusively as the headset. As long as the handlebars turn smoothly and there is no noticeable play, most riders pay it little attention. However, when buying a frame, changing a fork or looking for spare parts, cryptic terms inevitably crop up – and this often causes a great deal of confusion.
Conclusion
Frame manufacturers should always be able to tell mountain bikers which headset standard they need. Fortunately, the difference in fork steerer tubes is easy to spot. Mechanics shouldn’t be put off by the combination of letters and numbers. The two-dimensional system makes choosing the right part much easier. - Jan Timmermann, BIKE editor
It’s not that bad
The basic principle of a headset is simple: it connects the fork to the frame and enables the steering to turn. The headset consists of the bearings situated between the steerer tube and the frame. It must absorb high forces, operate smoothly and, at the same time, withstand dirt, water and the stresses of tough trail riding.
As well as the actual bearing arrangement, the headset also has a slight influence on a bike’s geometry. Different stack heights can raise or lower the front of a bike slightly. Furthermore, modern angle headsets even allow the steering angle to be adjusted.
However, the way in which the bearings are housed in the head tube has changed several times over the years. This has resulted in various standards, some of which co-exist today. Early mountain bikes predominantly used straight fork steerer tubes with a diameter of 1 1/8 inches.
However, as suspension travel increased and loads became greater, the demands placed on the stiffness of the front end also rose. The industry responded with larger head tubes, tapered fork steerer tubes and new bearing designs. At the same time, manufacturers sought to reduce weight and improve the integration of components. This led to the standards in use today.
At first glance, the wide variety of different sizes and designations may seem complicated, but they follow a clear technical progression. For buyers and DIY cyclists, the rule is simple: the frame sets the standard. Anyone who understands the differences between EC, ZS and IS and checks the dimensions of their head tube will quickly find the right solution.
Which standard is the best choice today?
For most mountain bikers, the question of the ideal headset standard hardly ever arises in practice, as the frame dictates the required design. However, anyone buying a new frame will find that modern designs predominantly use ZS or IS systems.
Both solutions allow for a compact design, sufficiently large bearings and the use of the latest tapered forks, i.e. those with a tapered shaft.
So-called zero-stack (ZS) tax rates are regarded as a particularly well-balanced compromise. They combine good integration with high durability and are comparatively insensitive to manufacturing tolerances.
Integrated systems (IS) offer the cleanest look and the lowest weight, but require very precise frame manufacturing. The classic EC standard with an external bottom bracket shell now plays only a minor role in modern mountain bikes, but continues to impress with its robustness and ease of maintenance.
For most riders, it is ultimately not so much the design of the headset that matters as the quality of the bearings and regular maintenance. A high-quality headset will often last for many years, even under tough trail conditions.
So-called angle headsets are a special feature. Thanks to eccentrically positioned bearing cups, a bike’s steering angle can be adjusted by around 0.5 to 2 degrees. This allows a mountain bike to be tuned for a smoother ride or greater agility without having to change the frame. Such systems are becoming increasingly popular, particularly in the enduro and gravity sectors.
Which stem is suitable for which fork?
As well as the actual steerer tube standard, the steerer tube itself plays a crucial role. The classic straight 1 1/8-inch steerer tube has the same diameter along its entire length. Such systems are now found mainly on older mountain bikes and on affordable entry-level models.
The current industry standard is the tapered steerer tube, also known as a ‘tapered steerer’. It measures 1 1/8 inches at the top and 1.5 inches at the bottom. The advantages are greater stiffness, more precise steering, improved load-bearing capacity and larger bearing diameters.
Almost all modern trail, enduro and downhill bikes now feature tapered fork steerer tubes. Compatibility between the headset and the fork depends not only on the diameter of the fork steerer tube but also on the frame’s head tube.
The confusion usually arises from designations such as ZS44, ZS56 or EC44. The number always refers to the internal diameter of the steerer tube socket in millimetres. A typical modern trail bike, for example, has a ZS44 headset at the top and a ZS56 or IS52 headset at the bottom. This allows the use of a tapered steerer tube with a large lower bearing.
For example, a frame with a ZS44/ZS56 head tube can easily accommodate a modern tapered fork, provided the correct bearings are fitted. A frame with IS42/IS52 mounts, on the other hand, requires integrated bearings in the appropriate sizes.
Older frames with a straight 1 1/8-inch head tube require particular attention. In these cases, modern tapered forks are often only partially compatible, or not compatible at all. Although some manufacturers offer specialised conversion kits, these do not work with every frame.
Anyone looking to buy a new fork should therefore always check the head tube specifications first. The key factors are the frame’s mount, the type of headset and the diameter of the steerer tube. If these three factors match, almost any combination can be fitted without any problems.
An overview of MTB headset standards
EC – External Cup
The classic headset standard is known as EC (External Cup). In this system, the bearing cups are fitted onto the outside of the head tube and pressed into place. EC is still widely used on older mountain bikes today. Modern frames, on the other hand, rarely use this standard anymore.
Technical Specifications
- Bearing cups are fitted outside the head tube
- Large overall height
- Simple design
- The industry standard for many years
Advantages
- Sturdy and durable
- Large stocks possible
- High load-bearing capacity
- Easy bearing replacement
Disadvantages
- Greater weight
- Greater height
- Less elegant integration
ZS – Zero Stack
With the advent of larger head tubes, the industry developed what are known as zero-stack headsets. In this design, the bearing cups are partially pressed into the head tube and are largely concealed within the frame. Today, zero-stack systems are among the most common standards in the mountain bike sector.
Technical Specifications
- Some of the bearing cups sit inside the head tube
- Lower overall height than the EC
- Widely used in modern MTB frames
Advantages
- Good integration
- Low profile
- Wide range of components
- High stability
Disadvantages
- Changing bearings is a bit more involved
- Precision manufacturing required
IS – Integrated
Integrated headset systems go one step further. Here, the traditional bearing cups are completely eliminated. The bearings sit directly in specially shaped recesses in the frame. Modern carbon frames, in particular, often feature integrated solutions.
Technical Specifications
- No separate bearing shells
- The bearings are right within the tolerance limits
- Very compact design
Advantages
- Lightweight
- Very neat appearance
- Low profile
Disadvantages
- High demands on frame manufacturing
- Damaged bearing seats are difficult to repair
- Less tolerant of wear and tear
Have you ever had trouble finding the right headset for your mountain bike? Share your experiences in the comments!
Jan Timmermann
Editor