It's Time to Think Inside the 'Box

Build your GTRO

Innovative Design

Developed and hand-built in the UK, the GTRO was designed to be quickly installed to any bike frame, and work seamlessly with most rear hub motors. All 3 gears are sealed into the crank assembly, making the GTRO fully weather resistant.

Belt & Chain Compatible

Want chain-drive or belt-drive? You have the freedom to choose. The GTRO is compatible with any 5-arm 130mm BCD chain/beltring. Eliminate dropped chain, unlike a traditional derailleur gear systems there's zero lateral movement in the drive-train when shifting, creating a smooth seamless ride.

Seamless Shifting

Effortlessly shift instantly, both when in-motion or whilst stationary. Our patented shifting mechanism allows the GTRO to seamlessly shift between all 3 of its perfectly spaced gears with ease.

Engineered with simplicity

Combine multiple components of your traditional derailleur groupset into one compact unit. The GTRO replaces the below, all while weighing less.

Traditional Derailleur

Free-Wheel Cassette

Right Crank

Rear derailleur

Total Weight - 1,350kg

GTRO Gearbox

GTRO Gearbox (Right Crank)

Total Weight - 1,300kg

Simple Installation

The GTRO is designed to be easily installed to almost any bicycle frame. In 5 simple steps, you can instantly upgrade your bike with 3 gears and unlimited riding capabilities.

Fit your chain/belt-ring to your GTRO, using the five included bolts.

Remove your existing bottom bracket and install the included GTRO bottom bracket.

Fit both left and right (GTRO) cranks, and tighten to 40Nm.

Route your shifter cable, and install the 3-speed shifter to your handlebar.

Install your chain/belt to your drive-train, ensuring the chain-line is correct.

Unlimited Possibilities

Designed and developed to fit almost any bike for any rider, the GTRO seamlessly integrates to any style of bike frame, from compact folders, to cargo workhorses, and everything in-between. You can easily retrofit the GTRO to your existing frame without any modifications or changes to your frame. See our case studies for more examples of the GTRO's flexibility.

Case Studies

We revolutionise how you ride.
See what sets us apart from the pack

Gear Ratios

GTRO internal gear ratios are fixed with a 79% overall increase. The gear size and cadence can be tuned by selecting a belt ring and sprocket for your intended rider experience. Choose from a light gear set for casual riding up to 25kph or a higher set for speed pedelecs.

1st gear is a neutral gear (1:1). Second and third gears are incremental.

Here is an example for a 24in wheel with a Gates Carbon belt drive system with a 46T Belt ring and 28T rear sprocket.

Gear

Ratio

Teeth Equivalent to 28T Chainring

1st

1:1

46T (1.64 ratio)

2nd

1:1.43

66T (2.35 ratio)

3rd

1:1.79

82T (2.94 ratio)

Shifting Cable

Shifting cable inner 1.2 mm.

Shifting cable outer 4mm.

Left mounted handle bar shifter.

After GTRO installation, the shifting cable can be pulled internally through the frame using our cable pre-tensioner system, or externally using exterior cable management. Our cable can be routed along the down tube, seat tube, or even towards the rear wheel (depending on the position of the reaction lever).

Maintenance

The GTRO requires just 1ml of official gearbox maintenance oil for every 1000 miles, no mess or disassembly required!

Compatibility

Frame Compatibility

The GTRO can be fitted to almost all frame geometry, this includes touring, city, folding, fat-bikes, E-bikes, cargo bikes, and everything in-between.

The reaction lever can be orientated to fit against your chainstay or any other locally fixed point.

Transmission

Compatible with any rear transmission (geared or single speed rear hub motor)

Works with chain-drive or belt-drive.

Will fit any standard 5-arm 130BCD beltring & chainring.

Bottom Bracket

GTRO Gearbox is supplied with its own Bottom bracket (B.B), compatible with the industry standard English thread B.B shell.

B.B widths are available in multiple sizes to fit any bike.

Shell diameter cannot exceed 45.6 mm. Custom length axle widths available with MOQ

Note: The GTRO will not work with torque sensing bottom brackets, however, is fully compatible with PAS sensors.

Dimensions & Weight

Gearbox (Right Crank) Weight - 1300g

Belt-Line - 42.5mm (For belt drive)

Crank Length - 170mm

GTRO 3-Speed Gearbox

Gears - 3 Speed

Weight - 1300g

Price - £499

Installation - Easy

Maintenance - Easy

Belt-Drive Compatible

Fixed Chain-line

Rear Motor Compatible

Broad Frame Compatibility

Wide Avaliability

Rear Hub Gearbox

Gears - 3-12 Speed

Weight - 1700g~

Price - £450~

Installation - Moderate

Maintenance - Difficult

Belt-Drive Compatible

Fixed Chain-line

Rear Motor Compatible

Broad Frame Compatibility

Wide Avaliability

Centre-Drive Gearbox

Gears - 6-18 Speed

Weight - 2700g~

Price - £900-£2000~

Installation - Difficult

Maintenance - Difficult

Belt-Drive Compatible

Fixed Chain-line

Rear Motor Compatible

Broad Frame Compatibility

Wide Avaliability

Mid-Range Derailleur Groupset

Gears - 7-12 Speed

Weight - -1100-1400g~

Price - £200-£400~

Installation - Moderate

Maintenance - Moderate

Belt-Drive Compatible

Fixed Chain-line

Rear Motor Compatible

Broad Frame Compatibility

Wide Avaliability

Disclaimer: Product comparisons reflect general industry markets and do not refer to any specific competitor or brand.

What people are saying about the GTRO

"The gear system is easy to use. The extra ratios add to the efficiency, especially up steep slopes, meaning you don't need to use maximum assistance"

"With the improved performance and the neat addition of the gearbox, there are not many places that aren't conquerable with this great little bike"

"The gear unit is housed within the chainring body, and manages to get a planetary gear set up into a space only around 15mm deep; with the diameter the same size as a medium sized chainring. In short, a miraculous piece of engineering"

Driven by innovation. Committed to service.

At G3ARED, we push boundaries without losing the human touch. Our support extends beyond checkout; we personally reach out after every purchase to verify compatibility and offer technical advice. From browse to build, we’re here to ensure you have exactly what you need to get moving at every step of the way.