Tires, ETRTO standard, and sustainability in the cycling industry.

A tyre looks simple from the outside but behind the round rubber ring hides both an international standard and a choice between several construction principles — and in recent years also growing focus on what happens to the parts you replace.

§Clincher versus tubeless

The classic 'clincher' or wire tire has an open edge that grips the rim hooks and requires an inner tube to hold the air. A tubeless tire is constructed like a clincher tire but sits tighter on the rim and doesn't need a tube — instead a liquid sealant is often used inside that seals small punctures itself while you ride on. On motorcycles there are similarly both 'tube-type' tires with built-in tube and tubeless tires where the air is held directly between tire and rim.

• 01Tubeless: lower tyre pressure possible for better comfort and traction, and typically lower rolling resistance without the tube's friction
• 02Clincher: cheaper to buy and easier to repair by the roadside
• 03Sealant in a tubeless tyre can seal small holes continuously but does not replace proper repair work for major damage

§ETRTO—the common standard

For a tyre and rim to fit together, regardless of what country or brand they come from, the industry uses the ETRTO standard (European Tyre and Rim Technical Organisation). An ETRTO measurement is given as the tyre width and rim bead seat diameter in millimetres, for example '37-622'. It is far more precise than the older imperial-based measurements, which historically have caused confusion because two tyres with the same imperial specification do not necessarily fit the same rim. Learn to read the ETRTO number and you avoid ordering a tyre that does not fit.

§Repair instead of replacement

A circular principle in the trade is to utilise a part's full technical life before replacing it — a patched hose a trued wheel or a cleaned and lubricated chain often works as well as a new part if the work is done properly. Several Danish initiatives work directly with that principle; among other things volunteer projects collect and repair used bicycles that would otherwise have ended up as scrap and hand them on to new owners.

§Batteries and producer responsibility

Spent lithium batteries from e-bikes and e-scooters—so-called LMT batteries (Light Means of Transport)—are covered by the Danish battery regulation which is based on the EU's battery regulation. The regulations require producers and importers to establish and finance collection schemes so that batteries do not end up in ordinary waste. The purpose is that valuable and partly environmentally harmful materials such as lithium cobalt and nickel can be extracted and reused instead of being lost.

§Sustainability as part of the trade

The education's competency goals explicitly state that you must be able to act with environmental awareness and in accordance with the principles of sustainable development in all work tasks. In practice this means that the choice between repairing and replacing, and the correct handling of oil, tires, and batteries, is not a side consideration alongside the professional craft—it is a part of it.