Belt-Driven Gearbox Bike Wins Downhill World Cup — Les Gets

Les Gets isn't just another World Cup stop — it is a global showcase where manufacturers prove hardware under the most brutal racing conditions. Hattie Harnden's 4:11.966 run on the AON/Gamux equipped with a Gates belt and Gamux gearbox did what lab tests and demo laps could not: it won at the highest level. That win validates the entire system in the most visible arena for downhill mountain biking.

Beyond the trophy, the result has commercial and engineering implications. The Gates €100,000 Belted Purse specifically rewards a World Cup victory on a Gates-equipped bike, so Harnden's success puts a tangible prize behind the story. For brands like AON and Gamux, and for Gates as the supplier of belt technology, the headline equals credibility — and credibility sells frames and parts, accelerates dealer support, and encourages further R&D investment.

One of the principal selling points of a gearbox layout is mass centralization. Instead of a long drivetrain running to the rear triangle, a gearbox sits low and near the bike's centre. In practice that reduces polar moment of inertia, making direction changes feel quicker and improving traction when the rear wheel is loaded. Riders on technical, steep courses — the same terrain at Les Gets — report improved mid-corner balance and a planted rear end.

From an engineering standpoint, centralizing rotating mass also shortens unsprung distances compared with carrying derailleur components and long chain spans. For downhill bikes where split-second stability matters, those small gains can translate to measurable lap-time improvements. If you're evaluating bikes, look for how the gearbox integrates with frame stiffness and suspension kinematics: successful designs balance low mounting, service access, and protection from impacts.

Switching a derailleur/chain to a belt-driven gearbox bundle brings several real-world advantages. Gates Carbon Drive belts are widely praised for durability, cleanliness (no chain lube), and quiet operation. Removing the derailleur means one less vulnerable component to crush, snap or clog with mud — an obvious advantage in rough DH conditions. A belt also tolerates grit differently than a chain and can reduce drivetrain maintenance between race runs.

But belts and gearboxes also carry trade-offs. Belts require precise alignment and correct tension; frames must be designed with a split or removable section or accept a gearbox that routes the belt through the frame. Belt systems traditionally offer less range and more limited sprocket choices than modern 12-speed drivetrains. Cost, weight and serviceability remain concerns: gearboxes can add mass and need specialised service knowledge, and replacement parts are less common at local shops than derailleur components.

The headline system at Les Gets pairs a Gamux gearbox with a Gates Carbon Drive belt on an AON frame. Gamux is one of a handful of companies developing purpose-built gearboxes for mountain bikes; their units aim to deliver robust ratios and quick engagement suited to DH. Gates' Carbon Drive family (often referenced by CDX and CenterTrack variants) is the go-to belt technology — carbon-fiber reinforced belts with low stretch and high wear resistance used across e-bikes, commuters and now gravity rigs.

Alternatives and complementary systems to know: Pinion makes crank-mounted gearboxes used on some aggressive trail and enduro frames; Rohloff's Speedhub internal gear hub offers a proven 14-speed solution with a wide gear range and has long been paired with belts. Enviolo offers continuously variable transmission (CVT) hubs that suit low-maintenance urban and touring bikes but are less common in gravity racing. For riders considering conversions, check compatibility: belts need Gates-specific sprockets and frames with appropriate routing and split points, while gearboxes require frames designed for the loads and mounting points they impose.

If you want to try a belt-driven gearbox bike or spec one for aggressive riding, start with the right parts. For belts, stick to Gates Carbon Drive options and matching Gates sprockets/splines — they’re engineered to work as a system. For gearboxes, evaluate Gamux if you want a downhill-focused unit; Pinion and Rohloff remain excellent alternatives for broad-gear-range or endurance use. For cranks and power: heavy-duty options from Race Face (e.g., Atlas or Turbine) or Shimano Saint cranks are common on DH builds because they handle high torque and impacts.

Setup tips: 1) Follow the manufacturer’s belt tension and alignment specs — Gates tension gauges or app tools can help. 2) Ensure frame compatibility: if converting, verify split-frame or belt-path clearance. 3) Plan service: regular gearbox inspections, fluid changes (if required by the gearbox maker), and having a specialist tech for major service will keep you on track. If you ride in muddy, rock-strewn terrain, add bash protection and consider a full-coverage lower guard for the gearbox housing.

Despite a marquee win at Les Gets, several factors slow broad adoption of belt-driven gearbox bikes. Cost is a big one: bespoke gearboxes, Gates belts and frames engineered for belt routing push retail prices high. Weight is another — current gearbox+belt systems often weigh more than a high-end derailleur setup, though clever design is narrowing that gap.

Service infrastructure and parts availability also matter. Local mechanics are far more familiar with derailleur systems and 12-speed cassettes; gearboxes require specialised tools and training. Finally, gear range and efficiency in certain conditions remain sticking points: while gearboxes can offer smooth shifts under load and a compact package, they don’t yet match the ultra-wide range and fine-grained ratios offered by modern drivetrains in some setups. That said, race wins like Les Gets accelerate interest, dealer training, and investment — so these barriers could erode faster than expected.

Is a belt-driven gearbox legal for World Cup downhill racing?

Yes. The UCI has rules around drivetrains, but the AON/Gamux bike's win at Les Gets shows belts and gearboxes are permitted in elite downhill competition, provided the system meets safety and technical regulations. Manufacturers typically work with teams and homologation bodies to ensure compliance.

How much maintenance does a Gates belt require compared to a chain?

A Gates Carbon Drive belt requires far less maintenance than a chain: no lube, no derailleur adjustment, and less worry about stretching. You still need to check belt tension and alignment periodically, inspect for cuts or damage, and replace sprockets when worn. For gravity riders, the reduced day-to-day upkeep is a major advantage.

Can I convert my existing downhill bike to a belt-driven gearbox?

Conversions are non-trivial. Belts need specific routing or a split frame, and gearboxes require mounting points and space. Most riders choose a dedicated frame designed for a gearbox or an aftermarket conversion kit that matches their frame. Consult the gearbox and belt manufacturers and a specialist shop before attempting a conversion.

Do gearboxes weigh more than a traditional derailleur drivetrain?

Generally, gearbox systems can be heavier than a derailleur/12-speed setup, though differences vary by design. Modern gearbox manufacturers are optimizing materials and compactness, narrowing the gap. For downhill riders prioritising durability and handling benefits, the weight penalty can be acceptable.

How does gear range compare to drivetrain setups like 12-speed cassettes?

Internal gearboxes and hubs like Rohloff have respectable ranges (Rohloff's 14-speed hub is known for a ~526% range). Pinion and some gearbox systems offer wide ranges but may differ in step sizes. A modern 12-speed cassette can provide very fine ratio steps and extremely wide ranges in some setups; the choice depends on riding style and whether you prioritise range or simplicity/durability.

Are Gates belts durable in muddy, rocky DH conditions?

Yes — Gates belts are engineered for harsh conditions and resist stretching and corrosion. They do require protection from sharp debris and proper alignment to avoid premature wear. Teams running belt systems in DH typically pair them with robust sprockets and bash guards to resist rock strikes.

Will this Les Gets win make gearbox bikes mainstream?

It’s an important milestone, but mainstream adoption depends on manufacturers scaling production, lowering costs, and improving service networks. Harnden’s win proves the concept at the top level; wider adoption will follow if brands invest in rider-facing products, and if local shops receive training to support the systems.