Shifters are there to change gear and apply the brakes. Although the shifters from the three major manufacturers work slightly differently (and we’ll come on to the intricacies of each), braking remains the same as you only have to pull the brake levers back towards you.
Shimano introduced the STI (Shimano Total Integration) system in 1990, effectively integrating the shifting mechanism and brake lever into one unit. To change to an easier gear on the cassette, the rider is required to push the right-hand brake lever inwards, while to flick into a harder gear, there is a separate paddle behind the brake lever. The left-hand shifter operates the front derailleur; press the inner paddle to move the chain onto the inner chain ring.
Most road bikes are fitted with cable-operated caliper brakes with pads which squeeze up against the wheel rim to slow you down and stop. Direct mount calipers, which attach directly to the frame and fork by two bolts, rather than by a single, central bolt, are increasingly popular and offer improve braking performance, but only work with compatible frames.
Disc brakes are becoming more popular and are seen fitted to many endurance and sportive bikes; these can be either cable-operated or hydraulic depending on the price and specification of the bike. Hydraulic discs not only offer greater stopping power and modulation but the wheel rim itself may be lighter as there is less need to reinforce the rim against braking forces.
Road chainsets come in two main categories: double and triple, referring to the number of chainrings.
While doubles adorn race and sportive bikes, triples are normally (but not exclusively as they can be found on some road bikes) reserved for heavy audax or touring bikes, which require an especially low gear. However, the advent of the compact double chainset has seen the popularity of triple chainsets fall, with riders able to achieve a similarly low gear but without the added weight.
While road racers favour the classic double chainset, using chainrings with 53 and 39 teeth, compact chainsets use a combination of 50-34t. The larger the number, the bigger the gear, so a compact allows for a lower gear, ideal for climbing, and compacts are now fitted as standard to most sportive and endurance road bikes. A third option growing in popularity is a ratio of 52-36t, known as a mid or semi-compact and thus bridging the gap between a standard and compact. Shimano and Campagnolo’s upper-level chainsets now have a universal BCD (Bolt Circle Diameter), which enables you to change the chainrings without replacing the whole chainset.
Crank lengths vary and, when buying a bike, are usually directly related to the size of the frame. For example, a 160mm crank will be fitted to a very small bike, while a 172.5mm crank will be found on 56cm frame. 175-180mm cranks will be fitted to larger frame sizes.
The cassette is the collection of sprockets (and so effectively the gears) fitted to the rear wheel and cassettes come in a vast array of sizes.
Unlike chainrings, when it comes to the cassette, the larger the number, the easier the gear. Professional riders and time trial specialists may prefer a close 11-23t or 11-25t ratio for super-smooth gear changing and only small gaps between each sprocket, while hill climbers may prefer a wider 12 to 27 or 28-tooth cassette.
All three component manufacturers now offer even wider cassette, up to 32-teeth with Shimano and SRAM, and 30-teeth with Campagnolo, but be careful before you upgrade as these cassettes will often require a ‘long-cage rear’ to work. Check with your local bike shop first.
The type of chain fitted to your bike is totally dependent on the number of gears on your bike. A ten-speed groupset must run a ten-speed chain, and so on.
Wheels have not got wider to accommodate wider cassettes, so the sprockets themselves have got narrower and so have the chains. An eight-speed chain is much wider than a ten or 11-speed chain.
Sadly most of us neglect our chains and they often wear out significantly quicker than other groupset components, so check the length of your chain regularly and change it when required to reduce wear and tear on more expensive components and to prolong the life of your cassette and chainset.
Often known as mechs, the derailleurs are responsible for moving the chain from one sprocket to another, or one chainring to the other. The front mech takes car of the chainrings and the rear mech looks after the cassette.
Cable-operated mechs are the most common type (the shifter ‘pulls’ the cable to move the derailleurs) but electronic shifting such as Shimano’s Di2 and Campagnolo’s EPS systems do away with cables and use wires and battery-operated motors to refine the shifting. Electronic groupsets come with a weight penalty over cable-operated systems but offer super-smooth shifting, especially under load. While initial setup can be tricky, long-term maintenance should be trouble-free thanks to the superb reliability of electronic systems, particularly as the front mech will self-align to avoid chain rub. SRAM currently only offer cable-operated groupsets but are expected to launch a wireless electronic setup in 2015.
Front mechs are fitted to a bike in either band-on, which is a clamp system that fits around the frame near the bottom of the seattube, or braze-on. The braze-on system employs a small bracket that’s either brazed, bolted or riveted to the frame depending on the frame shape and material from which it’s made. Whether you need a band-on or braze-on front mech will depend on your frame.
Now you know what each component is responsible for, it’s time to consider the intricacies and hierarchies of Shimano, SRAM and Campagnolo’s systems.