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What Is a Mountain Bike Drivetrain?

The mountain bike drivetrain is a cluster of parts that work together to get the bike moving forward. As your legs press into the pedals, they add pressure to the cranks (the shafts that connect the pedals to the front gear). This spins the front gear (called a chainring), pulling on the chain connected to the back gears (known as the cassette). The rear cassette is connected to the rear wheel via a freehub, which gives the pedaler momentum. Sounds pretty simple, right? Well, there are a lot of little pieces of technology working in unison to maximize efficiency, and we still haven’t even brought up the derailleurs that allow you to move through different gears. Before we shift things into high gear, let’s start with a quick breakdown of the components that make up the drivetrain and the two main manufacturers of these components, SRAM and Shimano. There is a third manufacturer, Campagnolo, but they make up a tiny percent of the mountain-biking components market in North America.

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Drivetrain Components

** First, a note on mountain biking jargon: All of the components listed below as part of the drivetrain collection are known as the groupset, groupo/gruppo, or group. Occasionally brakes are included in the groupset, but we are only discussing the drivetrain and not including any information about the brakes in this article. 

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Crankset

The crankset consists of the crank arms, the bottom bracket, and chainring(s). The crank arms connect the pedals to the chainring(s). This is where all of your leg power is directed to be transferred to the rest of the system. Cranks are made with a variety of materials such as aluminum, steel, and carbon fiber. The higher-end models are lighter and stiffer, with some manufacturers hollowing out the crank arms to save additional weight. Crank-arm lengths can also vary and be customized to fit individual riders.
SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Mountain bike chainrings have seen some change lately, from having two or three rings—also known as 2x or 3x, which would be verbally expressed as “2 by” or “3 by”—to now only one front chainring (1x/“1 by”). This is mainly due to improvements in the rear cassette, which is the next component we will discuss.

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Cassettes

This key component in any drivetrain can completely change how a bike pedals, depending on the style of cassette you choose. The cassette is the collection of gears on the back tire of your bike. They have changed a lot recently thanks to improvements in machining as well as weight reductions in bike design. Mountain bike cassettes can be found in 7- through 12-speed variations. The speed means the number of chainrings, like gears in a car. Cassettes are often referred to by the number of teeth on their smallest to largest cogs to indicate their range, e.g., 11-32t (the “t” is the number of teeth on the cog). Essentially, the higher the number of teeth on the rear cassette cog, the easier it is to pedal.   Bikes with multiple front chainrings will most often have fewer rear speeds, as the front chain rings offer versatility (e.g., 3×7 – 11-32t). With the new age of single-gear cranksets, the rear cassettes have gone up to 12-speed to keep you pedaling (1×12 – 10-52t).
SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Chains

These are the unsung heroes of the groupset that keep everything together. Chains come specific to the number of gears on the bike, so make sure you buy the correct chain for your drivetrain. The more expensive the chain, the smoother, more durable, and lighter it becomes. They are also the first item to wear out, so keep that in mind when purchasing a chain. With 1x systems, you don’t need to worry about stress resulting from cross chaining, which is when the chain undergoes diagonal pressure from being on opposing front and back chainrings.
SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Shifters

These are the controls located in the bike cockpit that enable you to change gears. With a 1x crankset, there will only be a single shifter for the rear cassette, which saves some space for all of the other gadgets that will come into play, like dropper post controls.

The technology behind the shifter has rapidly evolved throughout the years. Some of the newest shifters can now be controlled entirely by your thumb, allowing your index finger to remain on the brake. There are also grip shifters that change the gears as they’re rotated, but this system is quickly losing popularity. Higher-end shifters also allow for faster gear changes by offering multiple gear drops with one thumb push.

One of the hottest pieces of new technology is the electronic shifter or “controller.” First created by Shimano, their Di2 electronic drivetrain was impressive but still required wiring throughout the system. SRAM quickly responded with their own electronic shifter, the wireless AXS system. Both systems can be customized via their individual apps. While relatively expensive, some affordable options are sneaking into the market (check out the SRAM GX AXS upgrade package).

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

Derailleurs

This component moves the chain from cog to cog and is controlled by the shifters (or controllers). For the most part, the derailleurs are controlled by cable tension that is changed as you shift through the gears. With the advent of electronic and wireless shifters, cables are going the way of the dodo bird in place of electronically actuated derailleurs. However, most of us will still be relying on cables for now as both electronic systems are around $1,200 alone or come on bikes with price tags that retail for $10,000 and beyond!
SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

How To Decide?

As you will see later in the article, for the most part, as the price tag of the groupsets increase, the weight will decrease. This is because the higher-end components are made of more expensive components and more refined, time-consuming manufacturing.   Durability is always a concern when berm bashing on your mountain bike. Again, generally speaking, durability improves with price, but it seems to plateau around the midrange options. The durability can also decline in the super high-end offerings where weight saving is more crucial than longevity.   SRAM and Shimano produce incredible drivetrains that are exceptional at all price points. The technology that was once only in the super high-end pieces of kit is slowly making its way down to the more affordable options, which is a win for everyone. The key when buying a drivetrain is finding one that you can afford. For most cyclists, saving roughly 500g of weight is not worth a $600 jump in price.

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker

SRAM versus Shimano

Time for a bit of a history lesson. Shimano has now been in the cycling game for a century. The company was founded in 1921 by Shozaburo Shimano to produce freewheels for bicycles. Shimano didn’t make it into the US market until the ‘60s. In the 1980s, Shimano introduced indexed shifting, which is now the basis for all mechanical shifters on bikes to this day. They also created “Total Integration,” allowing riders to brake, shift gears, and steer without taking their hands off the handlebars. This game-changer is something we all take for granted now.

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker
Shimano also created the first electronic mountain bike groupset in 2014—the XTR Di2 M9050, though it was still a wired system. As a company, Shimano makes up approximately 80% of the global road-biking components market, but only 20% of the global mountain-biking market. So, who controls the other 80%? This is where SRAM enters the game.
SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker
Chicago-based manufacturer SRAM was founded in 1987. A year later, they revolutionized the road-bike market by introducing the Grip Shift. Found on the bottom of drop handlebars for road bikes, it made for more effortless shifting. They brought in several road-bike innovations throughout the years and brought the 1×12 group back to the mainstream in 2012, which of late has become the market standard. In response to Shimano’s electronic shifter system, SRAM released Red eTap, a wireless road bike groupset. Their mountain bike electronic group system AXS, released in 2019, became the first wireless mountain bike gruppo.   SRAM is considered the more innovative of the two companies. While Shimano may be slower to innovate, they have been around for a long time. Many riders trust the quality that goes along with their storied history.   It would be impossible for us to pick the ultimate winner between SRAM and Shimano. In an industry where the technology is practically the same, it truly comes down to individual “feel” and preference. It is a call we don’t want to make. The best thing you can do is test drive some setups at a local bike shop and see what you prefer. Even at Gear Hacker HQ, there is friendly debate over which company reigns supreme, and it comes down to the style of riding and the day of the week.

Notable Differences

Drivetrains from the outside can all look very similar, but there are enough differences between SRAM and Shimano groupsets and technology for us to break down some of the more substantial contrasts.
    • Shifters

      Both Shimano and SRAM have shifters that can downshift multiple gears in a single stroke. The main difference is that Shimano’s Rapid Fire trigger shifter features “2way-release,” allowing the upshift lever to move in both directions. This gives the rider the choice to upshift using either the thumb or index finger. Personally, I have this on my bike and rarely use the index-finger shift, but it is always nice to know that I have some options.

    • Crank Arms

      Fabrication material is the main divergence here. Shimano does not use carbon fiber on their crank arms. What they are known for is HOLLOWTECH, a very durable and lightweight setup that employs hollow aluminum crank arms. SRAM, on the other hand, offers carbon fiber on higher-end models. Carbon fiber does have a higher strength-to-weight ratio, but the trade-off is overall durability.

    • 1x Drivetrains

      • SRAM brought the 1x drivetrain back into the mainstream with the XX1 group. Single chainring drivetrains are now the most popular option in modern mountain biking for many reasons. Shimano resisted initially, sticking to the 2x drivetrain, which has a greater gear variety. 
      • SRAM conquered the reduced gear-range problem when they introduced their Eagle 1x drivetrains in 2016. These drivetrains offered a 500% gear range, eliminating the need for 2x front chainrings. 
      • Shimano now offers 12-speed cassettes with a 10-51t range in their top three drivetrain setups. SRAM has a 10-52t cassette, so they still sneak ahead with a slight advantage over the Shimano updates. 
    • Electronic Drivetrains

      • Shimano introduced the first electronic drivetrain—the Di2 system—in 2009 (for road bikes only). They now offer it for all of their bike ranges. The Di2 electronic drivetrain is still wired. The single rechargeable battery the Di2 system uses has 1,000-2,000km (621-1,242mi) of battery life. 
      • SRAM released the eTap Red system in 2015 for their road bikes. The AXS system for mountain bikes was introduced in 2019. The AXS drivetrain is wireless and very easy to set up. The downside is that you need separate batteries for each derailleur. These batteries have a life of about 20 hours, so make sure you charge them before every ride! 
    • Freehubs

      • While not officially included in a groupset, it is vital to know which freehub you have on your bike before switching to a new groupset or cassette. For the most part, Shimano created the “standard” freehub called Hyperglide way back in the 1990s. Hyperglide (HG) has become an industry standard for every 8-10 speed Shimano or SRAM cassette; Shimano 11-speed cassettes will also work on an HG freehub. 
      • With the advent of larger rear cassettes, there’s now a need for different freehub setups. To fit SRAM’s GX Eagle and above drivetrains, you’ll need SRAM’s proprietary XD freehub body (10-50t/52t). This freehub is available on many higher-end wheels and is something to note before making a big switch and revamping your gruppo.
      • Shimano also had to create a new freehub to fit the larger cassette sizes. Their new freehub Micro Spline uses a 23-spline interface and will work with a selection of their 11- and 12-speed cassettes. It is essential to know what is on your bike and what the cassette you’re upgrading to will require. 

The Bottom Line

As mentioned early, there is no way we can choose a “Best Drivetrain.” Each company and individual groupset will work better for different riders, on different trails, with different budgets. We looked at dozens of other reviews and comparisons to see if they chose winners, and they all basically took the same stand. One reviewer did say that if they could have the SRAM AXS controller and derailleur paired with the Shimano XTR hardware, it would be the perfect system. So as you can see, there is really no way to choose a winner—both companies bring incredible technology to the table with no signs of slowing down.

Groupset Comparisons

SHIMANO
Altus, Acera, Alivio
DEORE
SLX
Deore XT
XTR
XTR Di2
BASIC
ENTRY-LEVEL
MID-LEVEL
HIGH-END
RACING
PRO-LEVEL
SRAM
X3, X4, X5, X7
X9, SX, NX
GX
X01
XX1
X01 Eagle AXS, XX1 Eagle AXS

Shimano Groupsets

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker
Shimano has three subsets of mountain bike groupsets: Downhill, Daily Drivers, and Mountain Biking. For this article, we specifically looked at the mountain biking groupsets.   To further clarify, their downhill-specific group sets are called Saint and Zee. These are purpose-built for going downhill fast and are not really made for pedaling at all. The Daily Driver range is called Tourney and is made for commuting or flat trails, not something you’d want to take up a Forest Service Road (FSR) or into the bush. Finally, the mountain biking family of drivetrains comes on a long list and with a more diverse range of groups.
There is one important thing to note before moving forward. While researching this article and comparing setups, we noticed that Shimano’s website does not include their drivetrains as a “package.” That means if you want to buy a full XTR groupset, you need to go through each component and pick individual parts. While it does make sure you are getting precisely what you want, it does not offer an easier way to buy a groupset.   Here is a friendly chart so you can quickly compare the weight and cost of each major groupset in the Shimano lineup. We did not include the Altus, Acera, or Alivio as it is very unlikely that riders will be “upgrading” to these systems. For the most part, bikers are going to be looking at the main Shimano mountain biking groupsets.
GROUPSET
Deore
SLX
Deore XT
XTR
Di2
PRICE
$296
$388
$604
$1,351
**
CRANKSET
Weight
780g
624g
634g
541g
SHIFTERS
Weight
133g
133g
133g
130g
66g
DERAILLEUR
Weight
320g
310g
282g
241g
290g
CASSETTE
Weight
598g
533g
477g
376g
CHAIN
Weight
277g
279g
278g
269g
TOTAL WEIGHT
2,108g
1,879g
1,804g
1,557g

Shimano Altus

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano Altus Groupset - Gear Hacker

The Altus is the groupset that you will find on entry-level mountain bikes. With a 2x or 3x crankset (40/30/22t) and a 9-speed cassette, this is a low-cost, low-technology build. The derailleur doesn’t use Shimano’s Shadow Plus clutch but uses similar technology to reduce the chance of damaging the derailleur on the trail. The whole setup is mainly made of steel. It does not even begin to consider weight-saving technology or corrosion resistance.

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Shimano Acera

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano Acera Groupset - Gear Hacker

An Altus step up, the Shimano Acera is built to handle the “rigors of teenage trail riding and continue to perform with minimal maintenance.” Odd to point out the teenage demographic so specifically, but it is a burly gruppo that will work well under harsh conditions and won’t break the bank if something happens.   The Acera group is lighter because it uses a hollow axle compared to the solid Altus axle. There is also a greater variety of materials used for this group compared to the Altus. The shifter is the same, coming with Shimano’s Rapidfire Plus, which offers multiple gear shifts in a single motion.

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Shimano Alivio

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano Alivio Groupset - Gear Hacker

A final step up in the hierarchy before getting into the “real deal” drivetrains is Shimano’s Alivio. Even though the Alivio still sports a 9-speed 2x or 3x drivetrain, it is lighter and shifts better than the Acera or Altus. The steel cassette options range from 11-28t to 11-36t and use Shimano’s Hyperglide technology. This tech helps with the tooth positioning on the cog to make shifting smoother and more efficient.

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Shimano Deore

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano Deore Groupset - Gear Hacker
    • Deore M6000

      This is where Shimano drivetrains start to get serious, and we see these groups as stock parts on pre-made bikes. The Deore M6000 is only available in 2x or 3x groups, but the cranks get Shimano’s Hollowtech II technology, providing lighter components compared to the previous three. The bottom bracket is integrated with the right crank arm providing more stiffness, weight saving, and more efficient power transfer. The cassette is all steel and is a 10-speed with either 10-36t or 11-42t, and it comes with a rear derailleur clutch that can be turned on or off.
    • Deore M6100

      12-speed performance makes its way into the more economical drivetrains with the Deore M6100 series. The Deore 12-speed is a 1x only groupset but is also available in 2×11 or 2×10-speed. The front chainring is directly mounted to the crank and is available with 30t or 32t. The 12-speed cassette has 10-51t cogs made entirely of steel, not alloy, but does get the Hyperglide+ technology for smoother shifting. The shifters come with Rapidfire Plus and 2way-release; these are technologies that are found on the more expensive pieces of kit as well. Both are great examples of the trickle-down technology that more budget-friendly bike components receive after the work goes into their more expensive counterparts.

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Shimano SLX

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano SLX Groupset - Gear Hacker

The Shimano SLX group is most commonly found on reasonably priced mountain bikes. You will save a little weight from the Deore groupset with the alloy cassette. The SLX can be purchased as a 1×12 or 2×12 drivetrain. The 2×12 options are a 36-26t chainring with either a 12-speed 10-45t cassette or a 12-speed 10-51t cassette. The 1×12 uses the 10-51t cassette, and options for the front chainring range from 28-34t. The addition of the 1×12 cassette has also introduced the need for Shimano’s Micro Spline freehub, so it will no longer fit on the fairly standard Shimano Hyperglide freehub.   The cranks are directly mounted to the chainring and are hollow-forged with HOLLOWTECH II. The chainring uses Shimano’s Dynamic Chain Engagement for chain retention to deliver smoother pedaling along uneven terrain. The shifters on the SLX come with I-SPEC EV, enabling the rider to join the shifters and brakes on one clamp for a cleaner cockpit and dial in your riding setup. Shimano has done lots of work to offer a high level of customization to suit each rider’s preferences and terrain.

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Shimano Deore XT

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano Deore XT Groupset - Gear Hacker

The Deore XT is similar in setup to the SLX drivetrain but again with overall lighter weight. The Deore XT 32t chainring and crankset claim a weight of 620g while the SLX crank and chainring weigh 638g—already 18g of weight saving in a similar component. The technology is very much the same in the XT compared to the SLX, so you’re really just seeing the weight savings. The XT 10-51t cassette is 64g lighter than the SLX cassette. The 10-51t cassette does require Shimano’s Micro Spline freehub, so keep that in mind when making the upgrade or switch. Many riders have noticed a more refined feel to the shift in the Deore XT compared to the SLX. With the technology you get for the price, it is hard to argue with the value.   With the Deore XT, we also see the first compatibility with Shimano’s Di2 electronic groupset. The Di2 groupset is 11-speed only and uses the Deore XT 11-speed parts with the addition of specific shifters and the handlebar-mounted display.

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Shimano XTR

SRAM vs. Shimano: The Ultimate Drivetrain Review: Shimano XTR Groupset - Gear Hacker

The XTR is Shimano’s top-of-the-line group for mountain bikes. It’s similar to the XT but with an added R (which stands for racing). Suffice it to say, you are looking at some serious kit. Shimano did everything possible to lighten the XTR groupset without compromising quality or performance. The cranks are two-piece alloy that are bonded together for a lighter weight. The chain is directional and has a slight curve to better follow the profile of the teeth.   The shifter comes with a non-slip rubber face and 20% quicker engagement, as claimed by Shimano. The double upshift is still possible, and with the two-way shifting, you can shift up with either your thumb or index finger. The lever itself is adjustable as well, allowing the rider to choose their preferred starting point.   The cassette uses the same ranges as the SLX and XT but features an alloy “beam spider” carrying 3 alloy, 5 titanium, and 4 chromoly sprockets—saving weight and adding a cool aesthetic to the rear cassette at the same time. If you are looking to get XTR’s 12-speed cassette, you will have to upgrade to Shimano’s Micro Spline freehub to accommodate the larger cassette. The front chainring is available in sizes from 30 to 38t for the single and 28/38t for the double. The cranks are interchangeable between the 2x or 1x chainrings, so you can switch without getting a new set of cranks. The XTR is also compatible with the Di2 but again, only in the 11-speed version.

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SRAM Groupsets

SRAM vs. Shimano: The Ultimate Drivetrain Review - Gear Hacker
SRAM, while only being in the bike industry since 1987, has taken a firm hold of the mountain-biking component market with its relentless innovation. This innovation has brought about some exciting technologies that have shaped the industry and are setting new standards for how people ride and kit out their bikes. One of SRAM’s most notable influences was the reintroduction of the 1×12 drivetrain to mountain biking. With Shimano steadfast on 2x systems, the 1x quickly became a favorite among mountain bikers, and Shimano had to play catch up to SRAM’s innovation.   SRAM’s range of mountain-biking drivetrains is truly impressive. With the introduction of their Eagle line, SRAM’s options for riders have almost doubled. The SRAM Eagle line takes all of their previous drivetrains and makes them 1×12-speed. Initially released in 2016, Eagle technology was only available on their higher-end drivetrains, but in the last 5 years, the technology has trickled down to essentially every other mountain-bike drivetrain in their arsenal. SRAM was so confident in the 1x drivetrains that they disbanded their entire front derailleur division after releasing the new Eagle systems. That’s a pretty confident move if you ask me, but what do I know? Initially released as a 10-50t cassette, the Eagle cassette offerings increased to 10-52t, creating a 520% gear range. For those keeping score at home, this range is better than 2×10 drivetrains can offer and has fewer moving parts to worry about.   The updated SRAM Eagle family, ranging from SX – XX1, also has cross-compatible technology, so you can easily mix and match components as you see fit. The various drivetrain components are available in a selection of colors from gold to rainbow, offering serious customization to show off to your friends as you cruise past them on the uphills.   A fun fact is that SRAM still offers grip shifts with their high-end products. It was the first product they brought to the market back in the late ‘80s, and they have refined it to be used with their most expensive products. Grip shifts have found a home with riders who like to fire through their gears crazy fast, often in racing situations. The grip shift allows you to travel through your entire range of gears in a single motion, so there’s that.   Take note: as mentioned before, the SRAM Eagle drivetrains from GX to XX1 now require SRAM’s proprietary XD freehub body (10t-50t/52t). The SX and NX cassettes still fit the standard Shimano HG freehub. This list is long, so prepare yourself (listed from least expensive to most expensive):
We’ve included a helpful chart so you can quickly compare the weight and cost of each major groupset in the SRAM lineup. For simplicity’s sake, we only show the Eagle groupsets as they are the benchmark, and everything else is cheaper and heavier (basically).
GROUPSET
SX Eagle
NX Eagle
GX Eagle Alloy
GX Eagle Carbon
GX Eagle AXS**
X01 Eagle
XX1 Eagle
X01 Eagle AXS
XX1 Eagle AXS
PRICE
$212
$380
$545
$685
$600**
$1,285
$1,500
1,900
$2,000
CRANKSET
Weight
694g
700g
649g
555g
463g
424g
463g
424g
SHIFTERS
Weight
129g
101g
122g
122g
77g
117g
112g
71g
71g
DERAILLEUR
Weight
337g
337g
300g
300g
462g
285g
269g
364g
350g
CASSETTE
Weight
615g
629g
451g
451g
372g
371g
372g
371g
CHAIN
Weight
271g
271g
271g
271g
262g
262g
262g
262g
TOTAL WEIGHT
2,046g
2,036g
1,793g
1,699g
1,499g
1,438g
1,532g
1,478g

SRAM X3, X4, X5, X6, X7, X8 and X9

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM X3 X4 X5 X6 X7 X8 and X9 - Gear Hacker
These are most commonly found on budget bikes or recreational bikes. These are big-box-store bike drivetrains and aren’t likely to be found on the more robust bikes. The X3 is solely a 7-speed setup, with the X4 offering a shifter and derailleur capable of working with 7- to 9-speed drivetrains. The X5 is where the drivetrains become slightly more trail-worthy, and it provides a 10-speed drivetrain with 2x or 3x chainring options.   The X7 is a 10-speed drivetrain, again with 2x or 3x configuration, but it gets a clutch and the rear derailleur to stop the chain from popping off. The X9 is similar to the Shimano SLX with respect to quality; it is a 10-speed drivetrain with 2x and 3x cranksets while lighter than the X7 thanks to hollow crank arms. For the most part, people are not “upgrading” to these components—we just didn’t want them to feel excluded.

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SRAM SX Eagle

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM SX Eagle Groupset - Gear Hacker
The SX Eagle is the most budget-friendly Eagle drivetrain offered by SRAM. The cassette does not use the new and improved ratio but has an 11-50t range. This allows the cassette to fit the Shimano HG freehub, so you do not need to replace your entire wheel to accommodate the 12-speed cassette. The cassette itself has a clean black finish. As mentioned earlier, all of the Eagle components can be mixed and matched to dial in for either performance or the desired look.   The SX is where you get into the serious business when it comes to SRAM’s drivetrains. They are all designed very well. Again, the trickle-down technology sharing only helps make SRAM’s gear perform well across the board. Riders with smaller budgets are afforded the ability to own a high-performing piece of kit without having to eat ramen for the rest of the year (we’ve all been there).   Some of the drawbacks of the low-cost SX gruppo are that the cranks are a three-piece set, which is heavier and not as durable or stiff as the NX and above gruppos that are two-piece. The SX is entry-level and is known as original equipment (OE), which means that it is more often found on fully built-out bikes. Only three parts of the drivetrain are sold aftermarket— cranks, derailleur, and shifters.

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SRAM NX, SRAM NX Eagle

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM NX Groupset - Gear Hacker
At $380 for the 5-piece kit, the SRAM NX Eagle is a value-forward setup that has basically the same technology that every other SRAM group has all the way up to the XX1. As always, the Eagle is a 12-speed (11-50t), with the standard NX coming with an 11-speed cassette (11-42t). The 11-speed cassette is compatible with a 1x or 2x crank and is compatible with all of SRAM’s 11-speed chains. The NX Eagle cassette uses Shimano’s HG freehub, so it will be an easy switchover on most bikes in the market. If you have a Shimano HG hub and want some XX1 components, thanks to the cross-compatibility of SRAM Eagle components, you could use the NX cassette and match it with XX1 cranks and chains. This means you don’t need to switch out your freehub or buy an entirely new wheel to enjoy some of the higher-end SRAM kit options.

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SRAM GX, GX Eagle, GX Eagle AXS

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM GX, GX Eagle, GX Eagle AXS - Gear Hacker
What do you get as you bump up from the NX to the GX? Weight is the main difference, with a minimum drop of 243g (0.5 lbs). That may not seem like a lot, but my weight weenies out there will know this makes all the difference on those rooty uphills. The GX cranks are offered in both aluminum or carbon, a difference of 94 grams. Both are two-piece and provide excellent performance and stiffness.   As of 2021, the GX drivetrain really benefited from the trickle-down technology that SRAM is feeding across its groupset options. Now available with SRAM’s AXS wireless rear derailleur, the GX is a very value-forward—and high-tech—option for those that really hate wire rattle. This update quickly made the GX the most affordable wireless drivetrain bike on the market. An upgrade kit will set you back $600, but it gives you a glance into the world of the super expensive bike market that always seems just out of reach for us ordinary folk. Upgrading from GX Eagle to GX Eagle AXS also lets you stop calling your shifters “shifters” and start calling them “controllers.” Ooh, la la!

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SRAM X01, X01 Eagle, X01 Eagle AXS

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM X01, X01 Eagle, X01 Eagle AXS Groupset - Gear Hacker
We have finally reached the cream of the crop. The SRAM X01 drivetrain and XX1 drivetrain are essentially the same, but SRAM has made a few tweaks to make them better serve their assigned purposes. The SRAM X01 is designed and built for trail and enduro racing, so SRAM beefed up the cranks and the rear derailleur to make them more suited for rougher trails and enduro-style riding. The rear derailleur is made with an aluminum cover that is a bit burlier than carbon fiber and should contend with the abuse it may take in an enduro or trail setting. The cranks are hollow aluminum but are still almost 200g lighter than the cranks on the GX drivetrain.   To get into this world of elite enduro riding, you are looking at a $1,285 investment for the drivetrain (excluding brakes). SRAM X01 is also available in the AXS wireless drivetrain, and it’ll bump up your total cost to $1,900, but golly, those shifts are going to be smooth.

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SRAM XX1, XX1 Eagle, XX1 Eagle AXS

SRAM vs. Shimano: The Ultimate Drivetrain Review: SRAM XX1, XX1 Eagle, XX1 Eagle AXS Groupset - Gear Hacker
On this side of the super-performance drivetrains, we have the XX1, which is slightly more expensive than the X01 because it is lighter thanks to carbon cranks and a carbon casing for the rear derailleur. The XX1 was designed for cross-country biking or for the really serious weight weenies of the world, and why SRAM spared no expense at cutting the weight from this system. The XX1 Eagle drivetrain is $1,500 and, if upgraded to the AXS version, will cost $2,000—a very pretty penny in the biking world. That drivetrain alone probably costs more than most of our entire bikes.   The chainring for the XX1 comes with a large range of teeth from 28-40t, offering the rider lots of options to fit their riding style. The chainring has been updated for improved mud clearing and a quieter ride. All of the cogs on the sprockets and chainring have been tweaked to improve chain retention. Really, everything on this drivetrain is as good as technology will allow it to be. So until the 1×13 comes out, this is as good as it gets. The gold on the cranks does look really good, though!

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