The biggest names in the cycling industry are always competing to achieve the best ergonomics, handling properties and, of course, the lowest weight. It comes as no surprise that carbon with its captivatingly good properties is the most sought-after material for lightweight builds. Early attempts to use the material for frames and forks during the late 1980s and early 1990s were often unsatisfying, making aluminium the most popular lightweight material for a number of years. In 2003 Scott pioneered the first large-scale production frame weighing less than 1,000 grams with its CR 1, and since then the carbon wave has been unstoppable.
Tremendous progress has been made with carbon as a bicycle material. Nowadays, no user of any well-established brand needs to be afraid of the once dreaded ‘sudden death’, i.e. abrupt and total failure of their frame. The rims of disc brake wheels, cranks, handlebars and seat posts have also become very reliable. Only steerer tubes keep causing problems.
What exacerbates the situation is that impending steerer tube failure often occurs on the inside, i.e. under the stem, spacers and headsets, invisible from the outside. We know from the many related recalls we were involved in over the years that riders do not notice the impending failure. The deterioration becomes apparent only once the handlebar including the stem comes off in the rider’s hands – a picture known from many a spectacular race-day photo. Unfortunately, with the handlebar detached from the fork, crashing is unavoidable.
Hidden defects with many potential causes
There are many reasons why this high-performance material is difficult to master when used for steerer tubes. The influencing factors include:
- 1. The quality of the steerer tube
- 2. The quality of the expander or compression plug
- 3. The quality of the stem
- 4. The installation conditions
- 5. The quality of installation and maintenance
All this means that manufacturers have a hard time getting to grips with the problem. In cases where all components are left as they were in series production, the manufacturer is able to optimize points 1 to 4, leaving only installation and maintenance. This is where the trouble starts. Many tinker with bikes without the right tools (e.g. a good torque wrench) and useful aids, which in this case is a carbon-specific assembly paste to increase friction between the components.
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Foto: Zedler-Institut
