On 1 January 2026, the maximum rim height for wheels will be 65 mm. This was announced by the International Cycling Union UCI in its new regulations has been laid down. There are also new rules for handlebar width and gear ratios. The planned changes have been widely criticised by manufacturers, team managers and riders alike. The UCI claims that the changes will make the races safer. Many observers doubt that this is true. In its open letter (on 16 July 2025), the aero expert Swiss Side explicitly opposes the UCI's planned limitation of the rim height to 65 mm for the 2026 season and instead calls for an evidence-based, industry-wide dialogue. The central arguments can be summarised as follows:
Swiss Side contradicts UCI arguments
For over ten years, the company has been carrying out structured wind tunnel tests and on-road measurements in which the so-called "steering moment" has been established as an objective measure of stability and predictability in crosswind conditions.
According to Swiss Side, measurement data shows that the rim depth has significantly less influence on the steering moment than
- Tyre width,
- Profile design,
- Frame steering geometry (steering axle angle and caster).
A higher rim also offers mechanical advantages (higher inertia) and enables finer tuning of aerodynamic and handling properties. A poor design, on the other hand, can lead to unstable behaviour despite the low height.
Wind tunnel example: 50 mm vs. 60 mm vs. 68 mm
With identical tyres (28 mm, 45 km/h), the following weighted steering forces were obtained according to Swiss Side:
- 0.45 Nm for the 68 mm "HADRON3 Ultimate" from Swiss Side
- 0.60 Nm for a 60 mm model ("Wheel C")
- 0.51 Nm for a 50 mm model ("Wheel D")
Despite the greatest height, the 68 mm model shows the lowest steering forces and therefore the best stability.
Scientific basis vs. UCI decision
Swiss Side demands that rule changes be based on solid, objective measurements. The UCI specification of a maximum rim height of 65 mm is "ineffective" and could even worsen safety, as it does not address the relevant parameters.
Economic and time aspects
Last but not least, Swiss Side criticises the fact that the UCI is causing economic damage with its decision. The development of a high-end cycling wheel takes around 2.5 years and, according to Swiss Side, costs six-figure sums in euros and only amortises over a four-year product life cycle. A lead time of just six months until it comes into force (from 1 January 2026) is insufficient, especially as Swiss Side had already presented its new 68 mm model two weeks after the announcement. Unexpected, short-term regulations damage manufacturers, retailers, teams and consumers alike. Products lose value, investments can no longer be utilised and confidence in transparent, long-term planning suffers.
Demands on the UCI
Swiss Side is calling for the 65 mm limit to be postponed until 2027 at the earliest or for the rule to be reorganised. In addition, the involvement of all relevant industry players and experts in the rule-making process in order to achieve real safety improvements. Swiss Side therefore appeals to the UCI to base its decision on a solid, data-driven basis and to take greater account of the interests of the entire cycling industry and end consumers.
Kristian Bauer
Editor
