A groupset is simply the collective term for the mechanical parts found on your bicycle and its role is one of two things, either to make you GO or to make you STOP. Your groupset comprises gears and gear levers, brakes and brake levers, chain, cassette, chainset and in some cases the bottom bracket as well as hubs and wheels.
Campagnolo, Shimano and SRAM, offer different levels of groupsets from entry-level groupsets, all the way up to professional level groupsets which are used by the pros in the big races such as the Tour de France for road and the World Cup for MTB. There are also mechanical and electronic groupsets.
All the parts of a certain groupset are designed to work best when with other components of the same range. Meaning, for example, a Shimano XT rear derailleur/mech will work best with XT shifters, an XT cassette and an XT chain. Some manufacturers now produce different variations to their groupsets such as 2x10, 2x11, 1x10 or 1x11 (‘1’ being the number of chainrings on the chainset and ‘x 11’ being the number of gears or cogs on the cassette). A further high-end option is a groupset which offers electronic gearing, which is currently available from Shimano, Sram and Campagnolo.
A cassette is a cluster of sprockets or cogs at the rear of your bike. The cassette slides onto the freehub body and is held in place by a lock-ring. Depending on what ‘speed’ your groupset is you may have between 5 and 11 sprockets on your cassette.
Road bike cassettes can be found in a huge range of sizes. Professional riders and time triallists favour a rear cassette with as little difference between gears as possible. Having close ratios between gears makes it easier to maintain a consistent pedalling cadence as you accelerate or climb. Cassettes can be found as low as an 11-23, which will only have a maximum jump of two teeth between gears
These close ratios are most commonly 11 to 25. That means that in an 11-speed cassette, the lowest gear (easiest to turn) has 25 teeth, while the hardest gear has 11.
Most people will favour a road bike cassette with a wider spread of gears to make climbing easier. The most commonly found on standard bikes is 11 or 12 to 27 or 28. Recently, all of the gear component companies have released even wider cassettes designed for serious mountain climbs.
SRAM have their WiFli cassettes which go as large as 11-32, Shimano offer a 32 in their 10-speed systems and a 30 in 11-speed, while Campagnolo offer up to 30-tooth options.
Mountain biking requires a broader range of gears to cope with changes in terrain, one minute you might be powering along a flat track and the next minute having to tackle a short, super steep climb. As mountain bikers are more concerned with range there can be big steps between each sprocket, although this is minimised by having a larger number of sprockets on a cassette.
A 10-speed cassette could be in 11-32, 11-34 or even 11-36. There are now 10, 11 and even 12-speed cassettes available, so mountain bikers have been able to do away with the inner-ring and run double or single chain rings up front, reducing both weight and the chance of malfunctions.
A chainset comprises the large front chain rings and the cranks. It attaches to your bike via the bottom bracket and uses a chain to connect the front chain rings and rear cassette. It drives the bike forward when the pedals are pressed in a clockwise direction. It is worth nothing a chainset includes the chain rings where as a crankset does not.
You need to decide on your crank length when buying a chainset. Cranks come in a range of sizes starting at 165mm, 170mm, 172.5mm and 175mm.
There is a lot of debate around crank length as longer cranks allow greater leverage and shorter cranks make it easier to spin the pedals faster. A simple rule of thumb is to buy depending on your height and leg length with taller people requiring longer cranks. To check what you currently use the length is written on the rear of the crank.
Chainsets need to be compatible with your bottom bracket, which attaches the chainset to your frame, or you can replace both together. See bottom brackets for more information.
Road bike chainsets are available in a few different configurations. The first is called a double and consists of two front rings – the 53-tooth outer and the 39-tooth inner ring. The second (and most common) is a called a compact. On a compact the outer ring is a 50-tooth, but it uses a smaller 34-tooth inner ring to provide a lower bottom gear to make climbing steeper slopes easier.
You can also get a front road bike chainset that’s a halfway house between standard and compact, called a semi-compact, which uses a ring combination of 52 and 36.
The remaining front chainset setup, and one that has fallen a little out of favour since the introduction of the compact is the road bike triple chainset. Road triples usually combine a 50-tooth outer ring with a 39-tooth middle, and an inner ring that’s just 30 teeth. Road triples offer the easiest possible bottom gear, but nowadays are only really found on lower priced entry-level road bikes, though they are still highly favoured by touring cyclists riding bikes laden with the extra weight of luggage.
Mountain bike chainsets need to withstand a lot of force as well as a few knocks and scrapes. You also need to make some choices based on your style of riding and the terrain you ride. Whilst many mountain bikes still come fitted with triple chainsets, increasingly riders are running just a double or even single ring upfront, with a chain guide. Large range cassettes allow a similar spread of gears to a triple chainset but a double or single front ring reduces weight and also reduces the chance of a malfunction.
This is because the chainline is better and there is less travel required from the front mech to shift from inner to outer ring. For downhill and enduro riding the simpler 1x 10 or 1 x 11 is the most reliable set-up.
Derailleurs, also called mechs, are the components that move the chain between rings at the front, and across the gears of the cassette at the rear of the bike. The left hand moves the front mech and the right hand moves the rear mech - if you are riding in the UK - in other parts of Europe and the rest of the world it is the other way round.
When customising your bike and buying a groupset, you cannot mix and match brands. Your drive train including chain rings, cassette and mechs must all be from the same brand to be compatible. If you have any questions or concerns about which components would best suit your bike, you can always seek advice from an expert.
When it comes to choosing your rear mech you need to identify what cage length you require. Larger range cassettes and triple chainsets generally require long cage mechs. A rear mech must have the capacity to cover the cassette size and the chain ring difference. Most mountain bike cassettes will require a long cage rear mech to accommodate gear range. If you are running a single ring up front you won’t require a front mech but you should consider a chain device instead to stop the chain jumping or slipping off.
Each different brand offers their own design of road bike derailleur with Shimano and Campagnolo both offering versions that are actuated electronically. Always match your component brands i.e. all Shimano or all Campagnolo to avoid compatibility issues.
SRAM and Shimano have introduced clutch derailleurs to prevent chain slackness and bounce. Shimano’s Shadow Plus range of clutch derailleurs has a chain stabilising switch so you can choose whether to shift with or without the clutch mechanism engaged and it can be disengaged to allow easy wheel removal.
Bike shifters are the levers on your handle bars which control the front and rear mech to allow gear selection on the move. On mechanical groupsets this is done by the travel of the lever pulling on your gear cable. On newer electronic shifters it is done with the use of a microswitch on the levers.
The most common is Shimano's STI system. The Shimano design uses two levers – a brake lever and another lever that sits just behind it. The brake lever doubles as a gear shift lever - swing the right hand brake lever inwards and the rear mech shifts the chain upwards on the cassette (to a lighter gear). When the inner lever is pushed inwards, the chain is shipped down the cassette (to a harder gear).
Shimano is designed to allow multiple shifts at one time, so the further you push either lever, the more gears you'll shift (up to a maximum of three). The left hand shifter operates the front mech - the brake lever swings inwards to move the chain onto the larger chainring, the small lever moves it to the smaller ring.
Shimano Di2 - Shimano’s electronic gear system uses micro switches in the levers to allow smooth, fast shifts between gears. The shape and feel of the levers feels very similar to mechanical gears but the shift only requires a feather light touch.
SRAM’s system called is called DoubleTap - you only have one lever on each side, which sits just behind the brake lever. Push the right hand lever in until its first click and the chain will drop into a smaller gear on the cassette, but keep pushing the lever until it hits a second click (or double tap) and it'll rise up the cassette to a lighter gear. One the left-hand lever, moving it until the first click will shift the chain to the smaller front ring, while two clicks moves it up onto the bigger chainring.
Sram’s electronic system is simply called E-Tap. Sram E-Tap uses the same shifting principle as DoubleTap but by utilising a micro-switch not a mechanical movement of the lever.
Campagnolo's Ergopower system uses a combination of a lever (which sits behind the brake lever) and a small button on the inside of the brake hoods (the rubber coated housing is referred to as the hood). The right hand lever swings inwards to make the chain rise up the gears, while pushing the button shifts the chain into harder gears.
Pushing the lever further or the button through more clicks allows Campagnolo, like Shimano, to shift multiple gears at a time. The left hand lever lifts the chain onto the bigger chainring and the button trigger drops it onto the smaller chainring.
Mountain bike shifters come in three key styles; twist shift, trigger-shifters and electronic shifters. Twist shift is activated by twisting part of the grip on the bar to tighten or relax the cable. With this style of control, you can keep all of your hand in full contact with the bar at all times. Trigger-shifters have two levers to control going up and down the gears. You need to use your thumb and forefinger to shift. Electronic gearing uses micro switches instead of cables to shift.
Sram’s GripShift is the most common for twist shift but other brands do similar styles. Shimano specialises in both trigger-shifter systems and electronic gearing systems. Shimano’s trigger-shifter system is known as Rapid-Fire and the electronic XTR Di2 system makes shifting quick and accurate. You can also do multiple shifts across the whole cassette by holding down the lever.
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