A group or groupset are all ways of describing the collection of parts that make up a bicycle\u2019s drivetrain<\/a>.<\/p>\n The components include the shifters, crankset, bottom bracket, front and rear derailleurs, chain, and cassette. Brakes are sometimes included in component series, but, for this article, we\u2019re going to stick to the items that comprise the drivetrain.<\/p>\n Just like our buyer\u2019s guide to road bike groupsets<\/a>, this guide is designed to explain the components of a groupset and the different options offered by the two main manufacturers:\u00a0Shimano<\/a> and\u00a0SRAM<\/a>.<\/p>\n It is more common to see complete groupsets on road bikes. When it comes to mountain bikes, however, brands usually mix and match parts from various groups \u2013 and in some cases different brands \u2013 to suit the bike\u2019s intended use and meet a specific price point.<\/p>\n Mountain bike cranksets can be divided into three categories by their number of chainrings.<\/p>\n The first is the triple \u2013 the old classic. As the name implies, it consists of three chainrings, the largest often being a 42- or 44-tooth outer ring.<\/p>\n The middle ring is usually a 32 or 34 and the smallest, inside ring, is often a 22- or 24-tooth.<\/p>\n This setup can offer the largest range of gears, but there is significant redundancy in terms of gear ratios. Cross-chaining is also a concern with a triple if the lowest or highest chainring is selected with the opposite lowest or highest sprocket on the cassette.<\/p>\n Cranksets with three chainrings aren\u2019t found on modern high-end mountain bikes. They are disappearing from the entry-level market and double- and single-ring drivetrains are quickly becoming the most desired setup and the new normal.<\/p>\n Cranksets with two chainrings overtook the triple as the most popular mountain bike crankset when SRAM and Shimano introduced 10-speed drivetrains. Double cranksets offer a narrower gear range with less overlap than a triple.<\/p>\n They use a smaller inner ring (22- to 28-tooth), while the larger outside cog offers a gear that\u2019s generally well-suited to faster riding (34- to 36-tooth).<\/p>\n Double cranksets are found from entry-level bikes through to high-end models but their popularity is on the wane too.<\/p>\n The most significant trend in mountain bike drivetrains over the past five years has been the movement toward wide-range 1x drivetrains<\/a> with a single chainring.<\/p>\n Commonly referred to as a \u20181x\u2019 (one-by), this arrangement has been popular on downhill mountain bikes for years, where large gear ranges aren\u2019t needed and chain security (that is, no dropped chains) is very important.<\/p>\n Following SRAM\u2019s launch of XX1<\/a> and the introduction of subsequent wide-range 1\u00d711 and 1\u00d712 groups, the single-ring drivetrain has now become the new norm on high- to mid-level mountain bikes, and is increasingly found on entry-level bikes too, thanks to the introduction of SX Eagle<\/a>\u00a0and NX Eagle 12-speed<\/a> drivetrains.<\/p>\n Chainring size ranges vary widely, depending on the intended use, from 38-tooth chainrings for strong cross-country racers down to 28- and even 26-tooth chainrings on some fat bikes. Most bikes with 1x drivetrains come with 32- or 30-tooth chainrings.<\/p>\n One key attribute of 1x drivetrains is the use of a chainring with tall, unramped teeth (since there\u2019s no need to shift between chainrings) and alternating tooth widths that match up with the inner and outer links of the chain.<\/p>\n Both of these features are designed to keep the chain in place without the aid of a front derailleur or chain guide.<\/p>\n By removing the front derailleur and corresponding shifter, a single-ring drivetrain is less complex as well as lighter. Many novice riders find 1x drivetrains easier to operate as well.<\/p>\n A crankset won\u2019t get you very far without bearings to spin on. These bearings are pressed or threaded\u00a0into the mountain bike\u2019s bottom bracket shell.<\/p>\n Bottom brackets are available in a staggering array of configurations \u2014 you might find our\u00a0complete guide to bottom brackets<\/a>\u00a0useful.<\/p>\n Cassettes come in a wide range of sizes and speeds. Like the crankset, cassette choice is often determined by the bike\u2019s intended riding style and price.<\/p>\n Mountain bike cassettes can be found in 7- through 12-speed versions. They are usually referred to by the smallest and largest cogs to provide an indication of the total range, e.g. 11-32t or 10-50t.<\/p>\n Aside from downhill bikes, which often use very narrow-range cassettes, most mountain bikes favour a cassette with a wide spread of gears to make climbing easier. The most commonly found ranges on bikes with double or triple cranksets are 11- to 34- or 36-tooth.<\/p>\n Single-ring drivetrains go much wider, with SRAM\u2019s 12-speed Eagle-branded drivetrains providing up to a 10-52t spread<\/a> (11-50t on SX and NX Eagle), while Shimano offers an 11-46t range on its 11-speed SLX and XT groups and a 10-51t option on its latest 12-speed XTR, XT and SLX groups.<\/p>\n The groupset brand and the\u00a0number of gears dictate the type of chain<\/a> you need. In general, as the number of gears increases, the spacing between the cogs shrinks and so the chain becomes narrower as well.<\/p>\n Because of this, you should only run a chain designed specifically for the number of cogs on your cassette \u2013 don\u2019t use a 9-speed chain on a 10-speed drivetrain, or an 11-speed chain on a 12-speed drivetrain. Some chains are even directional and need mounting in a specific orientation, so check upon install.<\/p>\n More expensive chains often have smoother, more durable and corrosion-resistant coatings, and save weight with hollow links and pins. With that in mind, chains are the first part of a drivetrain to wear out, so it\u2019s often best to invest in a mid-level chain.<\/p>\n Derailleurs are the components that move the chain between cogs on the cassette and chainrings on the crankset. Each brand offers its own design, but the principle is generally the same.<\/p>\n When pressed, the shifter pulls or releases a cable, which moves the derailleur, derailing the chain and repositioning it in a different gear.<\/p>\n Cables are no longer the only way to control derailleurs. Shimano offers electronically actuated derailleurs on XTR Di2<\/a>\u00a0as well as\u00a0XT Di2<\/a>,\u00a0which use electrical wires connected to the shifter(s). SRAM\u2019s AXS groupsets<\/a> are completely wireless.<\/p>\n As previously mentioned, shift levers are used to operate a bicycle\u2019s derailleurs. Shimano and SRAM use different designs, and while they all shift gears, they each have a particular way of doing it.<\/p>\n While mechanically different, both SRAM and Shimano offer \u2018trigger shifters\u2019. This name is a bit misleading because both companies have refined the lever ergonomics to shift both levers with the thumb, rather than also relying on the rider\u2019s index or \u2018trigger\u2019 finger.<\/p>\n The benefit of this approach is that it allows a rider to shift while also keeping their index finger on the brake lever.<\/p>\n SRAM offers two systems for its mechanical shifters, Trigger and Grip Shift. The trigger system is more common. Grip Shift functions like a throttle, twisting back and forth to shift. This system has lost\u00a0popularity in recent years but still holds a loyal following in cross-country racing, since the system is very light and allows riders to shift across the cassette quickly.<\/p>\n SRAM AXS<\/a> introduced a new design with three buttons, two of which are operated by a paddle that rocks up or down, with the third being a button on the back \u2013 the buttons\u2019 operation is customisable in SRAM\u2019s dedicated app.<\/p>\n Shimano\u2019s Di2 uses electronic switches too and can also be customised via its app.<\/p>\n Di2 can, for example, make use of Shimano\u2019s Synchro Shift technology, which allows the rider to use a single shift lever to control the front and rear derailleurs. The system\u2019s computer shifts into the optimal chainring and cassette sprocket to keep the rider\u2019s cadence<\/a> relatively constant.<\/p>\nComponents of a mountain bike groupset<\/h2>\n
Mountain bike crankset<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/xt-cranksets-1485802410506-1s5pza78zyje5-9ad8194.jpg?quality=90&resize=620%2C349"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Triple<\/h4>\n
Double<\/h4>\n
Single<\/h4>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/08\/SRAM-x-sync-chainring-3884a2e.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Mountain bike bottom bracket<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/bottom-brackets-1485803363454-1eluxqs2zgb3h-341cae6.jpg?quality=90&resize=620%2C349"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Mountain bike cassettes<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/shimano-and-sram-cassettes-1527264235860-fvc8xwlwis90-1357d9f.jpg?quality=90&resize=620%2C349"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Mountain bike chains<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/03\/chains-1485805298402-1u4nwgbqac32c-7b277f1.jpg?quality=90&resize=620%2C349"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Mountain bike derailleurs<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/08\/Front-mech-comparison-bf1b2ee.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/08\/Rear-mech-comparison-ce67c99.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Mountain bike shifters<\/h3>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/08\/Mountain-bike-gear-shifter-types-b141683.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>Choosing a mountain bike groupset: price versus performance<\/h2>\n
![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/21\/2019\/06\/Shimano-SRAM-mech-9c2ef39.jpg?quality=90&resize=620%2C413"\" "\\"\"\"\\"\/")
<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>