Universal Transmissions GmbH

Headquarter, R&D, Production
Külftalstraße 18
D-31093 Lübbrechtsen

What is this site for?


What are the goals of the G-Con Standard?

Definition Of the G-CON Standard


Connecting the gear box and the frame

Manufacturing / preparations / frame building


Techtalk / FAQ's



Special rear wheel hub



Bikes / History



CAD data / FTP Download


What is this site for?

Over the course of the past 40 years bicycles have seen the adoption of a chain drive based rear wheel gear change system (drivetrain). To accomplish this, engineers invented a system whereby the main component of the bicycle, the frame, contains a mounting system for a free spinning bottom bracket, to which different sized sprockets can be mounted. The aft system contains a rear hub which houses the cassette assembly, providing up to 9 different gearing ratios. Attached to the right side dropout of the rear wheel is a derailleur, which accomplishes gear change by moving the chain from one cog set to the next. Complementing the system is a front derailleur which typically mounts on the seat tube, to facilitate gear changes in a similar manner on the front dual or triple chain rings. The end result is a mechanical system which allows for the driver to adjust gear ratios according to varying riding conditions. In an effort to simplify this derailleur based drivetrain system, engineers invented a hub based drivetrain, whereby the rear hub contains a planetary style internal transmission system. In this case, the cassette, front chain ring assembly and both front and rear derailleurs are not necessary, thus providing for a more simplified gear change mechanism.

All the major disadvantages and caracteristics of these systems are discussed in the Tech talk/Faq 06 link.

"Gearboxx-Bikes" or also called "Internal Transmission-Bikes" on the other hand contain a transmission mounted inside the main frame - the classic bottom bracket housing is replaced by an integrated transmission. Similar to previously described gear change mechanisms, a chain or belt drive system is used to provide power to the rear wheel. In this case, the chain (or belt drive) does not have any shifting duties.

This page should be a plattform and showcase for all gearboxx bicycle related issues. If you would like to add something important to this page please contact the editor ( editor@g-boxx.org ).