The transmission, or drivetrain, parts on a bicycle are the moving gear and associated parts round the centre and rear of a bike. These are the parts that when force is used to move them they the propel the bike forward. Transmission parts include: chainset, bottom bracket, chain, front mech, rear mech and cassette. Usually when people talk about transmission in a workshop setting they are referring to the chain, chainset and cassette as you will hear mechanics saying that your transmission or drivetrain is worn and will need replaced if the gears are not working properly or are badly worn.
There are three main companies which produce road transmission systems; Shimano, Campagnolo and SRAM, which although may look and operate very similar, are unfortunately incompatible with each other’s gear systems. This is because each gear system has a certain amount of movement from gear levers and differs slightly with each manufacturer. As an aside, they do work with each other to a certain degree but it is not as slick and not recommended for long term use.
Each manufacturer also recommends only using similar groupset components as some mechs may not work with differing numbers of gears, i.e. Shimano Dura Ace 11 speed must use an 11 speed rear or front mech as it is different in size to some of its lower tier groupsets.
Shimano are the world’s biggest cycle groupset manufacturer making components for Tour de France riders to shopping bikes and everything in between.
The hierarchy of Shimano road groupsets from professional to entry level is as follows:
Campagnolo are the world’s oldest manufacturer of cycle gears and the company which actually invented the rear derailleur. They produce professional level components for some of the world’s top cycling teams down to weekend warrior suitable gears with prices to suit
The hierarchy of Campagnolo groupsets from professional to entry level is as follows:
SRAM are the newest groupset manufacturer and have come up with a series of ingenious inventions which have quickly gained a wide fan base from professional to recreational with their alternative view on operating systems.
The hierarchy of SRAM road groupsets from professional to entry level is as follows: