Groupsets are the collections of parts that makes up a bike's gearing and braking. This comprises the shifters, crankset, front and rear derailleurs, chain, rear cassette and brakes.
Just like our buyer's guide to road bike groupsets, this guide is designed to explain the components of a groupset, and the different options offered by the two main manufacturers: Shimano and SRAM.
Where its more common to see complete groupsets on a road bike, the multiple extra tiers in mountain bike components mean bike brands usually mix and match parts from various groups, and in some cases, different brands too.
Because of the wildly varying prices and mix-matched groupsets of hardtail and dual suspension bikes, we’ve decided to leave out estimated price ranges for this guide. With that in mind, it’s worth pointing out that a mountain bike is a technical product and we don’t recommend choosing a bike based on its drivetrain components and/or groupset. Rather, use this as a guide to help educate yourself on the key differences between the groups.
Components of a groupset
Crankset
There are three types of front crankset found on mountain bikes. Commonly, the type of crankset fitted will depend on the bike’s designed use, pricepoint and even wheel size, with bigger wheeled bikes (such as 29ers) often having lower gearing available.
The first is the triple – the old classic. It consists of three front rings, 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 some noticeable cross-over of available gear ratios.
The second type of crankset and, and one's that common on modern mountain bikes, is a double. This uses a smaller inner ring (24- to 28-tooth) to allow for a lighter bottom gear to make climbing steeper slopes easier, while the larger outside cog offers a gear that’s generally well-suited to faster riding, this is usually between a 36- and 42-tooth size. It’s lighter than a triple and offers a better angle for the chain in order to use all the gears. A double features less gear ratio cross-over compared to a triple.
There's also a more recent trend toward a simpler setup, with just a single ring of the front. This was already popular in gravity-based mountain biking such as a downhill, where large gear ranges aren’t needed and chain security (that is, no dropped chains) is more important, but the trend has expanded and now even some cross-country bikes use a single chainring. This is generally between a 30- and 38-tooth chainring size and is matched to a larger gear range in the rear. By removing the front derailleur and relevant shifter, a single-ring setup (often referred to as 1x or ‘one by’), offers a greatly simplified, lighter setup.
The crankset spins on bottom bracket bearings that are housed or threaded into the bicycle frame. Bottom brackets are available in a staggering array of configurations – you might find our complete guide to bottom brackets useful.
Cassettes
Cassettes come in a huge range of sizes and speeds. Like the crankset, cassette choice is often determined by the bike’s intended riding style and price.
Aside from for downhill riders, who often use road bike cassettes, most mountain bikes favour a cassette with a wide spread of gears to make climbing easier. The most commonly found ratio range on standard bikes is an 11- to 32-, 34- or 36-tooth count.
Generally speaking, the large 36-tooth cassettes are reserved for 10-speed drivetrains; the 32 and 34t setups more commonly appear on 8- and 9-speed drivetrains respectively.
Recently, SRAM has released an 11-speed cassette designed to work specifically with single-chainring cranksets. This provides massive gear ranges – the smallest cog is a 10-tooth and the largest is a dinner-plate sized 42.
Chains
The groupset brand and number of gears dictate the chain. The more expensive chains often have smoother, more durable and corrosion-resistant coatings than their cheaper counterparts.
Additionally, some more expensive chains have the pins and plates drilled to remove weight. A chain is a wear item though, and is cheap to replace, so the one included with a bike isn’t worth stressing about.
Derailleurs
Derailleurs are the components that move the chain between rings at the front and across the gears of the rear cassette. Each brand offers its own design, but the principle is generally the same, with a cable connected to the shifters doing the pulling.
There’s an exception to this – Shimano now offers electronically-actuated derailleurs at the top level, XTR Di2.
Shifters
Mountain bike gears are changed using gear levers that sit next to the brake levers at the handlebar. Each company offers its own design, and while they all shift gears, they each have a particular way of doing it.
There's three common shift options these days, one from Shimano and two from SRAM.
By far the most common is Shimano's RapidFire – a design that uses two levers, one on top of the other.
Push the larger (bottom) thumb lever away from you on Shimano and the rear mech shifts the chain upwards on the cassette (to a lighter gear). When the smaller, inner lever is pulled with either your index finger or pushed with your thumb (it can go either direction), the chain is shipped down the cassette (to a harder gear). RapidFire is designed to allow multiple upshifts at one time, so the further you push the larger thumb lever, the more gears you'll shift (to a maximum of three).
The left-hand shifter operates the front derailleur. The larger thumb lever moves the chain onto the larger chainring, the small lever moves it to the smaller ring. Cheaper Shimano shifters, such as those below Alivio offer a slightly simpler setup, in which the small lever only works by pulling it towards you with your index finger.
SRAM offers two systems, trigger and Grip Shift. The trigger system is the more common, and features two thumb levers that sit in a similar position and work in a similar way to Shimano’s RapidFire. Where RapidFire gives you the option to use your index finger, SRAM’s triggers are operated by pushing of the thumb only.
The other system from SRAM is Grip Shift which has lost mainstream popularity over recent years, but still holds a loyal following in cross-country racing where multiple shifts without moving your hands are considered benefits. Grip Shift is a handlebar grip (or throttle) that twists in either direction to change the gears.
Brakes
Over a decade ago, brakes were simple items – cable-operated rim brakes were the common option, but now they're a rare sight, kept for the very cheapest machines. Most mountain bikes now feature disc brakes, in either mechanical or hydraulic (fluid-based, like a car or motorbike) formats. Mechanical disc brakes are found at the entry-level, while hydraulic discs area staple on any enthusiast or performance-level mountain bike.
Disc brakes place a rotor (a disc rotor) at the wheel’s hub, with a brake caliper that clamps onto this rotor. There are many benefits to disc brakes on mountain bikes, such as improved stopping power (especially when wet), improved brake control (modulation), less maintenance and no issues with buckled or worn rims.
While most groupsets do offer brakes, it’s common for mountain bikes to have brakes that don’t match the rest of the groupset. This is occasionally done because of price or the perceived ‘best option’ from the brands.
Price vs benefits
Like most components, groupsets vary in price a great deal. So what benefits do the more expensive groupsets bring?
Weight
Keith Bontrager famously once 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 giving up strength, something has to give. Whether you're looking at groupsets, wheels or even complete bikes, reduced weight is often the major contributor to increased cost.
Generally with mountain groupsets, the more you spend, the lighter they get. Often the performance of the groupset plateaus at the second tier, 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), while the difference between SRAM's top-range XX1 and second-tier XO1 single-ring options is closer to just 30g (excluding brakes).
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 fibre, titanium, lightweight aluminium and ceramic bearings to achieve the pinnacle in low weight.
Durability
If you're spending more money on a groupset, 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, and in some ways, actually starts to decline at the very most expensive option.
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.
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, aluminium and titanium metals.
Performance
In addition to the benefits of reduced weight, more expensive 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, but don't add weight.
Braking raises an entire new list of benefits as prices goes up. Simply put, the more expensive brakes are stronger, offer better feel and control, stop you with less hand force required and will be more consistent when used for long periods of time.
Additional features
Besides offering extra gears, it's common for the more expensive groupsets to offer additional features, however subtle they may be. An example of this is the tool-free adjustable brake lever position on Shimano's SLX, XT and XTR.
Both Shimano and SRAM offer clutch-equipped derailleurs – look for these on any performance-level bike
Clutch-equipped rear derailleurs, such as Shadow Plus from Shimano or Type-2 from SRAM, are another example. The clutch offers enhanced control of the chain, keeping the drivetrain quieter and with less chance of a dropped chain over rough terrain.
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.
Discipline-focused options
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.
The major brands and their groupset hierarchies
On the trails there are two major brands making these parts, the first, biggest and most widely used is Shimano, the second is SRAM.
Shimano
Japan's Shimano offers the widest range of groupsets for mountain biking.
The range starts with the most budget Tourney, which is usually found on kids’ and entry-level bikes. While it's included in the mountain bike groupsets, we don’t consider Tourney to be off-road worthy outside of occasional and light use. Tourney is a 6- or 7-speed system (six or seven gears at the rear) combined with a triple crankset.
Next is Altus, which is sold as a 7-, 8- or even 9-speed system. No matter how many gears are featured out back, this group is always supplied with a triple crankset.
Acera follows, and starts to introduce corrosion-resistant materials such as stainless steel on certain components.
For 2015, Shimano Alivio is looking like a respectable entry option in regular off-road riding
Shimano Alivio sits just above Acera and introduces a few performance features such as RapidFire Plus shifters with push/pull trigger action. Like Acera, this 9-speed group is available with a triple ring crankset only. We consider Alivio Shimano’s starting point if you’re seeking a focused mountain bike.
Next in line is Shimano Deore, widely considered to be the Japanese company's first performance-ready off-road groupset. It's 10-speed and shares many of the designs and technology of the higher priced groupsets. Deore is offered in both double- and triple-crankset options and also spells the introduction to the clutch-style rear derailleur.
Long considered the workhorse group in Shimano’s mountain offerings, SLX is a third-tier offering from the Japenese giant. Generally speaking, SLX offers many of the features and function as the upper-end XT, but at a higher weight and marginally lower shift quality.
The workhorse of Shimano's mountain line-up, SLX is arguably the best value option
The first of the discipline-specific groups, Zee, is Shimano’s entry-level gravity groupset, a cheaper version of Saint (see below). Available only with a single-chainring crankset, Zee is designed for fast and rough downhill riding. It’s built heavier (and sturdier) than the similarly-priced SLX offering.
Shimano XT sits one below the professional-level XTR. This 10-speed group has nearly all the top-end design features as the range topping XTR and offers all the performance most riders will ever need, but at a weight penalty compared to XTR. XT is available with either double- or triple-ring cranksets.
Shimano Zee and Saint are both designed for gravity-focused downhill and freeride type riding
Sitting as a top-level offering for those who race downhill is Saint. Saint, like Zee, is gravity-focused groupset that is built incredibly strong to handle the abuse of freeride, downhill and other extreme forms of mountain biking. Only offered with a single-ring crankset, Saint also has additional chain retention features.
XTR is the pinnacle of Shimano's range and is often used for racing purposes. For 2015, it offers 11-speed gearing with either single-, double- or triple-crankset configurations. XTR combines top-end design with lightweight materials such as high-grade alloys, carbon fibre, and titanium. It’s common for XTR to offer features that no other groupset level receives, such as multi-shift release when downshifting.
XTR is split into two separate groupset offerings – Race and Trail, with the brakes, rear derailleur and crankset options being the difference. Race is all about absolute weight savings, where features such as tool-free brake lever adjust and Ice-Tech brake cooling fins are removed in favour of saved grams. Trail is the more ‘everyday’ and feature-packed option, where a few additional grams get you greater brake power, adjustability and even chain retention.
Shimano also offers XTR in its latest electronically-operated Di2 design. This system does away with traditional cables in favour of a system that's actuated by motor driven mechs 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 the XTR Di2 is sequential shifting, in that both 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 mainly the cost, but there’s also a minor weight penalty and remembering to occasionally recharge the battery.
The Di2 groupsets shares the same crankset, cassette, chain and brakes of the respective mechanical groupset.
Shimano's groupsets are designed to work with each other (providing they share the same number of gears), so for example, you can easily upgrade Deore with a mix of SLX and XT parts.
SRAM
SRAM's mountain groupset range is split into two, with single-chainring groupsets (with a ‘1’ featured in the name) separate to the double and triple options. Currently SRAM’s highly popular single-ring options are only for performance-level bikes. 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 and still is a strong advocate of double chainring setups over triples. SRAM calls this 2X10.
Another detail to be aware of with SRAM is trickle-down technology. The cheaper components from SRAM are often the same as more expensive options from a few years prior. As well as to this reuse of technology, it’s common for SRAM groups to be very close in function, with material changes accounting for the weight differences. An example of this is that X9, XO and XX SRAM 10-speed shifters all feature identical internal parts.
SRAM’s mountain groups kick off with X3, a 7-speed gear system with technology that’s trickled down from the top. It’s comparable to Shimano Altus in price.
X4 is next in the line-up with 9-speed shifting. Compared to X3, the X4 components feature more metal for better durability. X4 isn’t offered as a complete groupset, and so it’s common to find SRAM X4 parts mixed with those from other brands.
SRAM X5 is the entry point into 2x10 shifting
X5 is the first official groupset in SRAM’s line-up. This groupset is popular with bike brands as it offers upper-level features such as a double-chainring crank and 10-speed gearing.
X7 is a 10-speed group, and like Shimano’s Deore, is SRAM’s first groupset that can handle regular and proper off-road use.
Sharing many design and internal features as the top-level offerings, SRAM X9 is a popular choice on mid-priced bikes. A 2x10 groupset, X9 features plenty of alloy, giving it a substantially lower price compared to X0.
It's going to become a popular choice for 2015 – SRAM X1 is a new lower-priced single-ring option for all forms of mountain biking from cross-country riding to enduro racing
The entry-level into SRAM’s single-chainring groupsets is X1. X1 is an 11-speed groupset that will only work with a single chainring, afforded by the massive 10-42t cassette. Introduced for 2015, X1 offers nearly all the same features as X01 and XX1 but at a higher weight.
Long considered as SRAM’s best option if you don’t race, X0 is a 2x10 groupset that introduces carbon fibre for weight savings, among a few other small features.
Arguably the most popular single chainring groupset on the market, X01 offers all the features of X1, but more expensive materials and manufacturing processes substantially reduce weight.
X01 DH is a purpose-built groupset for downhill racing and is available as either a 7- or 10-speed setup.
SRAM XX1 is the groupset that kicked off the whole single-chainring phenomenon. It remains as SRAM’s pinnacle off-road groupset and is popular among everyone from gravity-seeking enduro riders to gram-counting cross-country racers. With approximately 30g separating X01 and XX1, it’s mainly for those who just want the best.
Sitting as a cross-country race specific groupset, XX is SRAM’s pro-level 2X10 offering. Since the release of XX1, XX isn’t used or seen as often.
SRAM and Shimano groupsets by cost and discipine
