An MTB (Mountain Bike) gearbox is a self-contained, multi-speed shifting system housed within the frame of the bike, typically near the bottom bracket, designed to replace the traditional derailleur-based drivetrain. It offers a different approach to gear changing on mountain bikes.
Understanding MTB Gearboxes
Instead of using external derailleurs to move the chain between different cogs, an MTB gearbox uses internal gears similar to those found in automatic car transmissions. This provides several advantages, as well as some potential disadvantages.
Advantages of MTB Gearboxes
- Durability: Gearboxes are significantly more durable than derailleur systems because all the shifting mechanism is sealed inside the gearbox, protecting it from mud, water, impacts, and other environmental factors.
- Low Maintenance: With the internal components sealed, gearboxes require less frequent maintenance and cleaning compared to derailleurs.
- Instant Shifting: Gearboxes can typically shift instantaneously, even under heavy load or while stationary.
- Centralized Mass: Placing the gear mechanism near the bottom bracket centralizes the bike's mass, which can improve handling and suspension performance.
- Chainline Optimization: Gearboxes allow for a more consistent and straighter chainline, which can improve efficiency and reduce chain wear.
- Ground Clearance: Eliminating the rear derailleur increases ground clearance and reduces the risk of damage from rocks and obstacles.
Disadvantages of MTB Gearboxes
- Weight: Gearboxes can be heavier than traditional derailleur systems, although advancements are reducing this difference.
- Cost: Gearbox systems are generally more expensive than derailleur systems.
- Complexity: Servicing and repairing a gearbox can be more complex and may require specialized tools and knowledge.
- Efficiency: Early gearbox designs were sometimes less efficient than derailleur systems, but modern designs are greatly improving.
How MTB Gearboxes Work
An MTB gearbox uses a series of planetary gears or other internal mechanisms to provide a range of gear ratios. Shifting is typically controlled by a cable-actuated shifter on the handlebars. The internal mechanism then selects the appropriate gear ratio. The power is transmitted through a chain or, in some designs, a belt drive to the rear wheel.
Examples of MTB Gearbox Brands
Several companies produce MTB gearboxes, including:
- Pinion: Known for their durable and wide-range gearboxes.
- Rohloff: Offers internal gear hubs suitable for both mountain biking and touring, though typically integrated into the rear hub rather than a frame-mounted gearbox.
Conclusion
MTB gearboxes offer a robust, low-maintenance alternative to traditional derailleur systems on mountain bikes. While they come with a higher initial cost and potential weight penalty, their durability, shifting performance, and other advantages make them an appealing option for riders seeking a more reliable and consistent drivetrain.
