Kappstein Doppio 2-Speed Gearbox | Bottom Bracket Transmission System
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Product Introduction
The Kappstein Doppio is a compact 2-speed gearbox system integrated into the bottom bracket, designed to provide an additional gear ratio without the need for a conventional multi-sprocket drivetrain.
Positioned within the bottom bracket shell, the system enables riders to switch between two gear ratios while maintaining a straight chainline and minimal drivetrain complexity. The gearbox is designed as a self-contained transmission unit, combining compact packaging with functional simplicity.
Why This System Is Different
• Integrated 2-speed gearbox inside the bottom bracket
• Maintains straight chainline (no derailleur required)
• Adds gear range without increasing drivetrain complexity
• Compatible with standard bicycle frames (no modification required)
How the Doppio System Works
The Doppio operates as a two-speed planetary gearbox integrated into the crank/bottom bracket area, allowing the rider to switch between two defined gear ratios.
• Gear 1: Direct drive (1:1)
• Gear 2: Overdrive with a ratio of 1:1.57
Shifting is controlled via a Bowden cable system connected to a minimal handlebar shifter. The cable is secured using a dedicated clamping mechanism developed specifically for the Doppio system.
Because the chainline remains fixed, the system avoids lateral chain movement, contributing to:
• Reduced drivetrain friction
• Improved chain stability
• Lower wear compared to derailleur systems
Technology Inside
The Doppio gearbox incorporates key Kappstein drivetrain engineering principles:
• Integrated Bottom Bracket Gearbox Architecture – the entire transmission is contained within the bottom bracket shell, eliminating the need for external gearing systems
• Compact Mechanical Design – the gearbox adds only approximately 200 g compared to a conventional bottom bracket, maintaining a lightweight system profile
• Patented Mounting System – enables installation into standard frames without modification, ensuring compatibility and structural integrity
• Cable-Actuated Shifting Mechanism – simple and robust control via Bowden cable and minimalistic handlebar shifter
• System-Based Drivetrain Integration – designed to work in coordination with chainring, chain, and rear drivetrain components rather than as an isolated unit
Learn more:
Real-World Performance
In practical use, the Doppio system is engineered to deliver:
• Two usable gear ratios in a compact drivetrain format
• Stable and predictable chain behaviour due to fixed chainline
• Reduced mechanical complexity compared to derailleur systems
• Efficient power transmission through direct drivetrain alignment
• Increased efficiency is subtly felt by the rider through a precisely tuned drivetrain
This makes the Doppio particularly suited for urban riding, commuting, and simplified drivetrain setups.
Applications
Ideal for:
• Urban and City Bikes
• Commuter Bikes, E-Bikes
• Minimalist drivetrain setups
• Integrated drivetrain system builds
Important Usage Note
The Doppio system is designed specifically for urban and city bike applications and is not intended for high-impact or off-road use such as MTB, downhill, or freeride riding.
Technical Specifications
System Type: 2-Speed Bottom Bracket Gearbox
Gear Ratios: 1:1 (Direct Drive) or 1:1.57 (Overdrive)
Drivetrain: Chain or belt
Chainline: 43.5mm
Q-Factor: 185mm
Bolt Circle Diameter: 4 x 104mm
Weight: 1250g (complete set)
Crank: Kappstein JIS square, 175mm
Chainring: Kappstein 32T
Bottom Bracket Mounting: BSA/BSC (68/73mm)
Shifting Operation: Bowden cable with Kappstein 2-speed shifter
Gears: 6 CNC-shaped planetary gears
Material: High-quality steel and aluminum components
Origin: 100% Made in Germany
Recommended Setup
For optimal performance, the Doppio system is designed to be used with:
• Kappstein Doppio-compatible chainring (e.g., 32T)
• Singlespeed or fixed gear rear drivetrain
• Proper cable setup and alignment for smooth shifting
Easy Purchase Options
The Doppio is now available in our online shop, complete with a detailed manual/installation guide in the download area to ensure a smooth setup. Choose the purchasing option that suits you best:
· Direct Purchase: Order directly from our online shop for convenience and fast delivery.
· Indirect Purchase: Connect your local dealer or bicycle workshop with Kappstein, and we’ll handle the rest. Contact us via email to inquire about authorized dealers in your area.
Before buying, consider whether a direct purchase or working through a trusted dealer is the best fit for your needs. Our team is here to support you every step of the way.
About Kappstein
Kappstein is a German engineering company specializing in high-efficiency bicycle drivetrain systems and components. Through precision machining and applied mechanical research, the company develops drivetrain solutions that focus on geometry, system interaction, and efficient power transmission.
Learn more about Kappstein and the company’s engineering philosophy.
Manufacturer:
Kappstein GmbH & Co. KG
Südstraße 15, Gebäude 14
99867 Gotha
Germany
info@kappstein.de
