The paddock at Paris-Roubaix has always functioned as a high-stakes laboratory, where the desperation to survive the “Hell of the North” drives teams to the absolute edge of technical legality. This year, the conversation centered on the rubber. As riders prepared to tackle the most brutal cobbles in professional cycling, the visual trend was unmistakable: massive, meaty tires designed to absorb the bone-shaking impact of the French countryside.
While spectators and analysts focused on the sheer width of the tires—specifically the 35mm setups used by stars like Tadej Pogačar—the UCI tech police were operating on a different wavelength. During pre-race inspections, commissaires were seen deploying a mysterious, 3D-printed measuring tool, but they weren’t checking for tire width. Instead, the focus was on UCI tire checks at Paris-Roubaix regarding the vertical dimension of the equipment.
The UCI was measuring tire height to indirectly enforce wheel diameter compliance. Under current road rules, there is no specific limit on tire width, unlike the strict regulations found in cyclocross. However, the total diameter of the wheel, including the tire, is limited to 700mm. Because wider tires naturally necessitate higher sidewalls, the UCI feared that the trend toward “monster tires” would push the total wheel diameter beyond the legal threshold.
To streamline this process, officials used a custom-engineered piece of plastic designed to slip over the top of the tire. If the sidewall height appeared to be nearing the limit, commissaires could then trigger a more precise, comprehensive measurement of the entire wheel and tire assembly to ensure it didn’t exceed the 700mm cap.
The technical tug-of-war in the paddock
The deployment of the 3D-printed gizmo is the latest chapter in a perennial conflict between the sport’s governing body and the engineers of the world’s top teams. The UCI’s arsenal of enforcement tools has expanded rapidly in recent years, reflecting a constant cycle of innovation and regulation. On Sunday, the tire height checks were just one part of a rigorous screening process.
Commissaires conducted standard magnetic scans of frames and wheels to detect hidden motors—finding none—and measured handlebar widths and positioning. The same 3D-printed tool was also utilized to verify the inward angles of brake lever hoods, a regulation first introduced in 2024 to prevent riders from adopting overly aggressive, non-compliant aerodynamic positions.
This friction is often felt most acutely by the teams pushing the boundaries of efficiency. Visma-Lease a Bike, for example, received notification just weeks before the event that they could not utilize their tire pressure regulator during the race. Such devices allow teams to fine-tune pressure for different sectors of the course, a critical advantage when transitioning from smooth asphalt to jagged stones.
Compliance and the cost of victory
Despite the technical setback of losing the pressure regulator, the human element of the race remained the dominant story. Wout van Aert was forced to race without the device and suffered two punctures during the event, yet he still secured an emotional victory. His win served as a reminder that while the UCI’s technical focus remains on millimeters and angles, the race is ultimately won by the rider’s resilience.
The adoption of 35mm tires was widespread enough that at least three teams were spotted using the wider profile. In the case of Tadej Pogačar, the tires were so substantial that when fully inflated, they barely cleared the interior of his front fork. This proximity to the physical limits of the bike frame mirrors the proximity to the legal limits of the UCI rulebook.
| Check Component | Regulatory Focus | Method/Tool Used |
|---|---|---|
| Tires/Wheels | Total diameter (700mm limit) | 3D-printed height gauge |
| Frames/Wheels | Motor detection | Magnetic scanning |
| Brake Hoods | Inward angle compliance | 3D-printed measuring tool |
| Handlebars | Width and positioning | Standard measurement |
While the “tech police” remained vigilant, no official violations were reported following the pre-race checks. The teams had been briefed on the evolving rules since the start of the season, allowing them to calibrate their equipment to stay just inside the lines of legality.
As the season progresses, the UCI is expected to continue refining its enforcement tools, particularly as tire technology continues to migrate toward wider, more comfortable profiles for road racing. The next major technical checkpoint will be the upcoming summer classics, where the UCI is likely to maintain its scrutiny of wheel diameters and aerodynamic positioning.
We want to hear from you. Do you believe the UCI’s focus on tire height is a necessary safety measure or an over-regulation of equipment? Share your thoughts in the comments below.
