THALWIL, Switzerland (BRAIN) — Wheel brand Swiss Side has released an open letter to the international cycling union, UCI, objecting to recently announced rules that would ban rims taller than 65mm in UCI road races. The rule takes effect on Jan. 1, 2026.
The rule would ban Swiss Side's 68mm-tall Hadron Ultimate 680 wheel, which was launched on July 4.
In the letter, Swiss Side said its wind tunnel testing, on-road testing and rider feedback found that its Hadron wheels are more stable in cross winds that some wheels with rims that are 50mm or 60mm tall that are currently in use in UCI WorldTour events.
"Through the objective measurement of the steering moment, we can firmly state that rim depth has far less influence than tire width, tire tread pattern (and its effect on the aerodynamic characteristics), and the steering geometry of the bike frame (steering axis angle and trail). Furthermore, the rim shape and depth are the parameters which enable tuning the handling characteristics of the wheel. Deeper rims, apart from having more mechanical stability due to the increased rotating inertia, also allow for better tuning of the aerodynamic and handling characteristic of the wheel. A poorly engineered rim shape or the wrong combination of rim shape and tire, can lead to a very unstable, unpredictable and potentially unsafe aerodynamic characteristic, regardless of the rim depth," the letter reads.
"The purpose here is to show the importance of an objective, science-based approach, which needs to be a part of the decision-making process for implementing equipment regulations. The recently proposed limitation on the rim depth to 65mm for 2026, can be objectively shown with regards to the steering moment, and the front wheel handling characteristics, to be ineffective and even counterproductive in bringing any improvement in wheel stability and thereby rider safety," Swiss Side said.
In a press release announcing the letter to UCI, Swiss Side said, "With this letter, we aim to make the UCI more aware of all of these factors, and request an urgent reconsideration of the recent change to the equipment regulations implementation, as well as urge meaningful change and responsible governance from the UCI, by including the cycling industry, and in particular experts in the relevant fields, as part of the decision-making process."
The UCI announced the rim-depth rule in June, along with several other rules the UCI said were related to rider safety, including a restriction on narrow road handlebars. The bike fit brand MyVeloFit created a petition against the handlebar rule, which it said was "misguided" and would make it impossible to properly fit smaller riders and women.
