Welcome to BikeRadar's buyer's guide to mountain bike groupsets. A group, gruppo or groupset are all ways of describing the collection of parts that make up a bicycle's drivetrain.
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're going to stick to the items that comprise the drivetrain.
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It is more common to see complete groups on road bikes. When it comes to mountain bikes, however, brands usually mix and match parts from various groups — and in some cases different brands — to suit the bike's intended use and meet a specific price point.
This article was last updated May 2018.
Components of a groupset
Mountain bike cranksets can be divided into three categories by their number of chainrings.
The first is the triple — the old classic. As the name implies, it consists of three chainrings, the largest often being a 42- or 44-tooth outer ring.
The middle ring is usually a 32 or 34 and the smallest, inside ring, is often a 22- or 24-tooth.
This setup offers the largest range of gears, but there is significant redundancy in terms of gear ratios. Cross-chaining is also a concern with a triple.
While Shimano still offers high-end triples, cranksets with three chainrings are rarely found on modern high-end mountain bikes. They are disappearing from the entry-level market as well.
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.
They use a smaller inner ring (22- to 28-tooth), while the larger outside cog offers a gear that’s generally well-suited to faster riding (34- to 36-tooth). Double cranksets are found from entry-level bikes through to high-end models.
The most significant trend in mountain bike drivetrains over the past five years has been the movement toward wide-range drivetrains with a single chainring.
Commonly referred to as a '1x', this arrangement has been popular on downhill mountain bikes for years, where large gear ranges aren’t needed and chain security (that is, no dropped chains) is very important.
Following SRAM's launch of XX1 and the introduction of subsequent wide-range 1x11 and 1x12 groups, the single-ring drivetrain is becoming the norm on high- to mid-level mountain bikes.
Chainring size ranges 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 fatbikes. Most bikes with 1x drivetrains come with 32- or 30-tooth chainrings.
One key attribute of 1x drivetrains is the use of a chainrings with tall, unramped teeth (since there's no need to shift between chainrings) and alternating widths that match up with the inner and outer links of the chain. Both of these features are designed to keep the chain in place without the aid of a front derailleur or chainguide.
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.
A crankset won't get you very far without bearings to spin on. These bearings are pressed or threaded into the mountain bike's bottom bracket shell.
Bottom brackets are available in a staggering array of configurations — you might find our complete guide to bottom brackets useful.
Cassettes come in a wide range of sizes and speeds. Like the crankset, cassette choice is often determined by the bike’s intended riding style and price.
Mountain bike cassettes can be found in 7- through 12-speed versions. They are often referred to by the smallest and largest cogs to provide an indication of the total range, e.g. 11-32t or 10-50t.
Aside from downhill bikes, which often use very narrow-range cassettes, most mountain bikes favor 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.
Single-ring drivetrains go much wider, with SRAM's XX1 and X01 Eagle 12-speed drivetrains providing a 10-50t spread, while Shimano offers an 11-46t range on its 1x11 SLX and XT groups and a 10-51t option on its latest XTR group.
The groupset brand and the number of gears dictate the type of chain you need. In general, as the number of gears increases, the spacing between the cogs shrinks and so the chain becomes narrower as well.
Because of this, you should only run a chain designed specifically for the number of cogs on your cassette — don't use a 9-speed chain on a 10-speed drivetrain, or an 11-speed chain on a 12-speed drivetrain.
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's often best to invest in a mid-level chain.
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.
When pressed, the shifter pulls or releases a cable, which moves the derailleur, derailing the chain and repositioning it in a different gear.
Cables are no longer the only way to control derailleurs. Shimano now offers electronically actuated derailleurs on XTR Di2 as well as XT Di2. Both these groups use wires to send electronic signals from the shifters to the derailleurs to shift gears.
As previously mentioned, shift levers are used to operate a bicycle's derailleurs. Shimano and SRAM use different designs, and while they all shift gears, they each have a particular way of doing it.
While mechanically different, both SRAM and Shimano offer 'trigger shifters'. This name is a bit misleading, as both companies have refined the lever ergonomics to shift both levers with the thumb, rather than also relying on the rider's index or 'trigger' finger.
The benefit of this approach is that it allows a rider to shift while also keeping their index fingers on the brake levers.
SRAM offers two systems, 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 popularity 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.
Shimano's Di2 electronic shifters also throw a spanner into the mix as technically they're electronic switches, rather than mechanical components. This means Di2 levers can be customized and programmed to behave in ways that aren't possible with conventional shifters.
A great example is Shimano's Synchroshift technology, which allows the rider to use a single shift lever to control the front and rear derailleurs. The system's computer shifts into the optimal chainring and cassette to keep the rider's cadence relatively constant.
Choosing an MTB groupset: price versus performance
Like most components, groupsets vary in price a great deal. So what benefits do more expensive groupsets bring?
Keith Bontrager famously said of bicycle parts: "Strong. Light. Cheap. Pick two."
A lighter bike will always accelerate, climb and brake better than a heavier one, but without sacrificing strength, something has to give. Whether you're looking at mountain bike drivetrains, wheels or even complete bikes, reduced weight is often the major factor in increased cost.
Generally, with mountain bike groups, the more you spend, the lighter they get. Often the performance of the groupset plateaus at the second tier from the top, with reduced weight being the reason for the extra expense.
For example, the difference between Shimano's top two tiers, XT and XTR, is around 230g (excluding brakes and bottom bracket), while the difference between SRAM's flagship XX1 Eagle and second-tier X01 Eagle drivetrains is closer to 46g (excluding brakes and bottom bracket).
These weight differences are the result of more expensive materials and refined, or more time-consuming, manufacturing processes.
In addition to further machining, hole-drilling and high precision, more expensive components often use materials such as carbon fiber, titanium, lightweight aluminum and ceramic bearings to achieve class-leading low weights.
If you're spending more money on a mountain bike group, you'd expect it to outlast a cheaper option.
Durability does improve with price, but our experience is that durability also plateaus at the second-tier options. XT in the case of Shimano and XO1 in the case of SRAM.
In some cases, component durability can actually decline at the most expensive option, where absolute weight savings sometimes trump product longevity.
The more expensive technical components are built with greater precision, refinement and materials that lend themselves to greater longevity. This is apparent in derailleurs and shifters, where the cheaper options will develop play and slop overtime, whereas better parts often remain like new for many years of use.
Wear items, such as cassettes and chainrings, however, are often the reverse of this. Cheaper options are made of heavier, but more durable steels, while the more expensive versions are made with lighter, but softer, aluminum and titanium metals.
In addition to the benefits of reduced weight, more expensive MTB groupsets find other ways of increasing performance.
Most noticeably, higher priced options provide a smoother, more precise and quicker shift between gears.
This includes reduced effort at the lever, something that becomes apparent once you've been on the bike for a few hours. It's an area where electronic gears are going to set a new benchmark — ultimate precision and speed at the simple push of a button.
Another performance example is increased crankset stiffness to provide crisper shifting and more efficient power transfer from the pedals to the rear wheel. This is achieved with more complex designs and materials that increase strength and stiffness without adding weight.
Besides offering extra gears, it's common for the more expensive groups to offer additional features.
Clutch-equipped rear derailleurs, such as Shadow Plus from Shimano or Type-2 from SRAM are an example of a technology that is offered on these company's mid- and high-end groups.
The clutch keeps the chain taut, which improves shifting over rough terrain, keeping the drivetrain quieter, and reduces the likelihood of dropping a chain.
In reverse of this, gear indicators are a feature often lost as the groupset price increases. The theory being that more experienced riders use gears based on ‘feel’ and don’t need numbers or indicators to help them.
With mountain biking spanning so many individual disciplines, it shouldn’t be too surprising to find that what works perfectly for climbing steep hills in cross-country may not be ideal for descending cliff faces in downhill.
This is why discipline-specific groupsets now exist for the more extreme riding styles. We’ll cover these below in the individual brand hierarchies.
Shimano's mountain bike groupsets
Japanese manufacturer Shimano offers the widest range of groupsets for mountain biking.
The range starts with Tourney, which is usually found on department-store bikes.
While it's included in the mountain bike groupsets, we don’t consider Tourney to be off-road worthy.
Tourney is available in 6-, 7- and 8-speed systems combined with a triple crankset.
Next is Altus, this the group you're likely to find on entry-level mountain bikes.
The latest version of Altus offers a 9-speed cassette with a triple crankset with 40/30/22t chainrings.
The Altus rear derailleur doesn't use Shimano's Shadow Plus clutch technology for chain stability, but it does use the Shadow design, which refers to a lower-profile to reduce the likelihood of damage from obstacles on the trail.
Acera follows next. This group starts to introduce corrosion-resistant materials such as stainless steel on certain components.
It's a 9-speed group that can be used with a 40/30/22 triple crankset or a 36/22 double crankset. It offers a wider range 11-36 cassette.
Shimano Alivio sits just above Acera. Like Acera, this 9-speed group is available with a triple or double crankset. We consider Alivio Shimano’s starting point if you’re seeking a trail-worthy mountain bike.
It's the first of Shimano's mountain groups to use a two-piece crankset with an external bottom bracket for increased stiffness — Acera uses an Octalink bottom bracket, while Altus and Tourney rely on square-taper bottom brackets.
Deore is widely considered to be the Japanese company's first performance-ready mountain bike groupset. It's a 10-speed group that shares many of the technologies found on Shimano's higher-end 11-speed groups. The 10-speed cassette is offered in a wide-range 11-42t version.
Deore is offered with double and triple crankset options. It's also the first group to use Shimano's Shadow Plus clutch-equipped rear derailleur.
SLX is a very important group in the Shimano hierarchy. This is the first group to share the same number of speeds as XT and XTR in a more budget-friendly package. Generally speaking, SLX offers the same features and function as the upper-end groups at a higher weight and marginally lower shift quality.
Standout features include an 11-speed cassette offered in 11-40 and 11-42t cassettes for use with the SLX double crankset. SLX is also the first Shimano group to offer a 1x drivetrain with an 11-46t cassette.
There is no triple version of the SLX crankset.
The first of the discipline-specific groups, Zee, is Shimano’s entry-level gravity groupset. It's a more affordable version of Saint (see below).
Available only with a 1x crankset, Zee is designed for downhill and freeride. It’s built heavier (and sturdier) than the similarly-priced SLX group.
Unlike SLX, Zee is a 10-speed group.
Saint is positioned as a top-level option for those who race downhill.
Saint, like Zee, is a gravity-focused 1x10 group built to handle the abuse of freeride and downhill.
Deore XT M8000
Shimano Deore XT sits one rung below the professional-grade XTR group. This 11-speed group has nearly all the top-end design features as XTR and offers all the performance most riders will ever need, but with a slight weight penalty.
XT is available with either single, double and triple-ring cranksets. Like SLX, Deore XT is available with a wide range 11-46t cassette for 1x drivetrains.
XTR is the pinnacle of Shimano's range and is often used for racing purposes. XTR combines top-end design with lightweight materials, such as high-grade alloys, carbon fiber and titanium. It’s common for XTR to offer features that no other groupset level receives, such as multi-shift release when downshifting.
The latest M9100 group has four different drivetrain options to choose from. There's a wide-range 1x12 drivetrain with a massive 10-51t cassette, a tighter range 1x12 drivetrain with a 10-45t cassette, a 2x12 drivetrain with a 10-45t cassette, and a 1x11 option designed to save weight with a 10-45t cassette.
In the past, XTR was split into Race and Trail categories. The latest M9100 series sees many parts of the group condensed into one line. However, there are still Cross-Country and Enduro categories for brakes as well as pedals.
Cross-Country is all about weight savings, where features such as tool-free brake levers adjust and Ice-Tech brake cooling fins are removed in favor of saved grams. Enduro is the more ‘everyday’ and feature-packed option, where a few additional grams get you greater brake power and adjustability.
This latest XTR group also uses an entirely new freehub design that's not compatible with previous Shimano mountain bike groups.
Deore XT and XTR Di2
Shimano also offers XT and XTR in electronically-operated Di2 variants.
These drivetrains do away with traditional cables in favor of a system that's actuated by motor-driven derailleurs powered by a battery, which can either be frame mounted or hidden within the seatpost, seat tube or steerer tube.
The advantage of the electronic system is consistent gear shifts and very low maintenance. Another perk of Di2 is sequential shifting, AKA SynchroShift, whereby both the front and rear derailleurs are operated with a single control, and the system decides whether to shift at the front or rear for the next closest jump.
The downsides are the high cost and remembering to occasionally recharge the battery.
These Di2 groupsets share the same crankset, cassette, chain and brakes of the respective mechanical groupsets. Note that the latest XTR M9100 mechanical series does not have a Di2 counterpart, so the current XTR Di2 group on the market is one generation behind.
SRAM's mountain bike groupset range is divided into two families, with single-chainring groupsets (many of which get a ‘1’ featured in the name) separate from the double and triple options. Like Shimano, SRAM offers a discipline-specific option too, in the form of X01 DH.
While SRAM’s recent success story is its dedicated single-chainring groupsets, the brand was also a strong advocate of doubles over triples. We'll run through the 2x and 3x groups followed by SRAM's ever-expanding 1x family.
The X3 level of components is the most basic level of SRAM's componentry.
Designed for 7-speed drivetrains, the shifters and derailleurs make heavy use of plastics. These components are suitable for light recreational riding, but not trail use.
Next in the line is X4. Like X3, these components are often found on budget bikes.
X4 shifters are available in 7-, 8- and 9-speed versions.
This is the first of SRAM's groups you are likely to find on entry-level mountain bikes. It's a trail-worthy group for recreational riding, though it lacks a clutch on the rear derailleur.
This 10-speed group is available with a 2x or 3x crankset. (There is also an older 9-speed version still available.)
The X7 group has a few additional features that make it stand out from X5. The most important upgrade feature of this 10-speed group is the addition of a clutch on the rear derailleur to improve chain retention.
The X7 shifter has a more precise action than the X5 shifter and is also compatible with SRAM's MatchMaker system, which allows riders to use one clamp to secure shift levers and brakes.
X7 is available with a 2x or 3x crankset.
The X9 group is a durable, trail-worthy 10-speed group available in 2x and 3x configurations.
There's more use of aluminum versus plastic on the shifters and derailleurs and the X9 crankset features hollow crankarms to save weight.
Long considered as SRAM’s best option for performance without breaking the bank, X0 is a 10-speed groupset that introduces carbon fiber for weight savings and precision machining for shift accuracy.
While most often found in a 2x version, SRAM does offer a triple crankset for this group.
Until the advent of SRAM's 1x11 systems, the XX group was the company's premier off-road drivetrain.
It's a dedicated 2x10 group and makes extensive use of carbon fiber and titanium hardware to maximize weight savings.
SRAM NX is the most affordable of SRAM's 1x11 groups. This group features SRAM's narrow/wide X-Sync chainring and a wide range 11-42t cassette.
Sharing many designs and internal features of the top-level 1x offerings, SRAM GX components are a popular choice on mid-priced bikes.
Unlike NX, GX is available in 1x11 and 2x11 versions, as well as a dedicated 7-speed downhill group.
SRAM's EX1 group was developed specifically for the growing e-mountain market. Electric assistance and its associated rapid shifts put greater stress on components.
To counter this, EX1 features an 8-speed cassette, with the big cog 7mm inwards of where it would be on an 11spd setup to reduce cross-chaining. This offers an extra-strong chain that's positionally synced with specific teeth to ease strain on the drivetrain while changing gear.
The X1 group is a solid choice for riders wanting a reliable 1x11 drivetrain that won't break the bank. It shares many of the same features of the top 1x11 groups with a slight weight penalty.
The X01 group sits one tier from the top of SRAM's 1x11 family. It's a solid choice for riders who want the performance of the top group but can live with a very minor weight penalty.
X01 DH is a purpose-built groupset for downhill racing and is available as either a 7- or 10-speed setup.
This is SRAM's top 1x11 speed group. It was the group that lead the 1x revolution when it was introduced in 2012.
SRAM Eagle XX1 and XO1
Introduced in 2016, SRAM's XX1 and X01 Eagle 12-speed drivetrains offer a 500 percent gear range through huge 10-50t cassettes. 'Eagle' is the term SRAM uses to denote its 1x12 mountain bike groups.
XX1 Eagle is positioned as the top-end group for cross-country racers. The XO1 Eagle group is frequently used on high-end trail and enduro bikes.
The differences between these two groups are minimal. The XX1 Eagle cassette and chain have gold titanium nitride coatings, which are claimed to increase durability.
The XX1 Eagle derailleur uses a carbon outer plate on the derailleur cage, while the XO1 Eagle has a full aluminum cage. The cranksets are slightly different as well, The XX1 Eagle crankset is hollow, while the XO1 Eagle model has a foam core.
The difference in weight between these two groups is minimal, with a 46g increase in weight on the XO1 Eagle group.
SRAM GX Eagle
The latest addition to SRAM's 1x12 line is the GX Eagle group. It's clear that SRAM was aiming to hammer the final nail in the front derailleur's coffin with the introduction of this budget-minded group.
As you might guess, this affordable 12-speed group does come with an increase in weight. At 450g, the pinned-together GX Eagle cassette 90g heavier than heavily machined XO1 and XX1 cassettes.
Other key differences between the top-tier groups and GX Eagle include a steel, rather than titanium spring in the rear derailleur, an alloy crankset, and a bushing, rather than a bearing used in the shift lever.
Shared features on all these Eagle-level drivetrains that distinguish them from SRAM's 1x11 groups includes the aforementioned 10-50t 12-speed speed cassette, larger, 14-tooth jockey wheels, an improved 'Type 3' clutch mechanism in the rear derailleur, and a redesigned 1x-specific chainring with taller, curved teeth and a new profile intended to improve performance at the extreme ranges of the cassette.
This article was last updated May 2018.