The problem
Let's be honest: Who uses a torque spanner to tighten stems, handlebars and the like? You have a feel for the correct torque. Or maybe not? We put it to the test in the BIKE workshop. Five colleagues were asked to clamp a handlebar to the stem with 5 Newton metres. The result: even our professional tighteners were off by at least 1 Newton metre. That's 20 per cent. Inexpensive attachments made of robust, heavy materials are less of a problem. It usually doesn't matter whether five or eight Newton metres are applied. However, aluminium has an enormous memory for damage. Once the structure is damaged, the part in question can become a safety risk. It becomes really dangerous with carbon fibre parts: Carbon fibre reacts particularly sensitively to constrictions caused by jamming. One bold twist and the brand-new carbon handlebars are gone - or worse: they only come apart on the next downhill. Too little tightening torque can also be dangerous, for example if the stem is clamped too weakly to the steerer tube - and the bike goes straight ahead in the next bend. The maximum torque must also never be exceeded when clamping the fittings.
By the way: Above a certain tightening torque, the clamping effect no longer really increases. However, the load on the material increases many times over. Even if the material does not fail directly during assembly, the life expectancy is reduced enormously. The correct torque therefore not only protects the material, but is also a protective measure for the rider.
The fact is that most screwdrivers are more wrong than they think. A torque spanner provides professional safety!
THE RIGHT TURN
You can find this article in BIKE 11/2018. You can read the entire digital edition in the BIKE app (iTunes and Google Play) or the print edition in the DK shop reorder - while stocks last:
Stefan Frey
Editor
