Mountain Bike Drivetrain & Groupsets Guide

A drivetrain is what gives your mountain bike the ability to transfer the power from your legs and covert it to forward momentum. The drivetrain is made up of multiple components and requires all its individual pieces to be in working in unison. In this article, we explain what the drivetrain on your bike is and how it works, how to maintain it, how to pick a drivetrain for your mountain bike, and what brands make the best drivetrain components.

Once you have a better understanding of mountain bike drivetrains and what type of drivetrain is best for you and your bike, head into JensonUSA and checkout our huge selection of mountain bike drivetrain components.

In this article, we’ll teach you about:

• What Is Drivetrain on a Mountain Bike?
• Maintaining & Replacing the Drivetrain
• What is the Best Mountain Bike Drivetrain?
• How to Pick a Mountain Bike Drivetrain
• Mountain Bike Drivetrain FAQs

What is Drivetrain on a Mountain Bike?

A mountain bike drivetrain is made up of multiple components that work together to make the bike shift gears and provide power to your wheels. Everything from your gears themselves to the shifters and chain are considered part of the drivetrain and without one of them the whole system fails.

What is Included in the Drivetrain?

• Cranks The metal arms that are connected to your pedals and chainring.
• Chainring The gear at the middle of the bike, close to your feet and connected to your cranks and bottom bracket. 1X drivetrains have one chainring and typically have 30-36 teeth, while 2X drivetrains have two chainrings of different sizes providing you with more gearing options. The higher the tooth count the more difficult, but more powerful the gear will be.
• Chain The metal links that connect the chainring to the cassette in the rear of the mountain bike.
• Cassette The large gears in the rear of the bike. In mountain biking, cassettes can be found with seven gears (speeds) to twelve gears with a range most commonly found in 11-32 teeth to 10-52 teeth. Unlike the chainring, the higher the tooth number on the cassette's cog, the easier of a gear it is to pedal in.
• Derailluer(s) The brain of the drivetrain. This mechanism receives the input from your shifters and moves the chain onto the correct gear at the cassette, allowing you to shift between gears when the terrain changes. Bikes with more than one chainring will also have a front derailleur to change between gears on the chainrings.
• Shifters The levers on your handlebar that are connected to your derailleur by cables. The shifter has two levers, one for shifting up and one for downshifting and allows you to change gears at the press of a button. If you have a front derailluer you will have two shifters on your handlebars, one on each side of your bars.

What is a 1x drivetrain on a mountain bike?

A 1X drivetrain has one chainring, no front derailleur, and is usually paired with a wide range cassette in the rear. Most modern mountain bikes, and usually all newer ones, will have a 1X drivetrain due the advancements in gearing technology of cassettes; making the need to have additional gears up front at the chainrings obsolete. 1X drivetrains are simpler to use and save a lot of weight compared to 2x drivetrains due to the absence of a front derailleur, shifter and extra chainrings.

What is a 2x drivetrain on a mountain bike?

2X drivetrains have a second chainring, a front derailleur, and a second shifter at the handlebars. Having two chainrings allows the rider to have a wider gear range than having just one chainring. 2X drivetrains typically are heavier and not as simple to use than 1X drivetrains, but are more efficient. 2X drivetrains have more gears than 1X drivetrains because the addition of the second chainring essentially doubles the amount of gears you have. A 1X drivetrain with a twelve-speed cassette will have twelve gears, while a 2X drivetrain with a ten-speed cassette has 20 gears. 

Is 1x drivetrain better than 2x?

There are pros and cons of both 1X and 2X drivetrains. Factors such as the availability of the components, the simplicity of operating the drivetrain, the gear range you are looking for, and the overall weight of your drivetrain all play a huge factor is determining which type of drivetrain is best for you. Here we briefly break down the pros and cons of 1X and 2X drivetrains.

Maintaining & Replacing the Drivetrain

Properly maintaining your drivetrain will help it last longer, perform better, and shift smoother. In this section, we will go over how to clean and maintain your drivetrain, general information on the longevity of drivetrain components and how and when to replace drivetrain components. 

How to Clean Mountain Bike Drivetrain

There are many methods to cleaning a bike's drivetrain. Whether you are looking to have a cassette and chainring you can eat off of, or do just enough to restore proper performance, there are numerous methods out there.

We recommend having a consistent cleaning routine to ensure gunk doesn’t build up. If you have a regular routine, you can get away with a five-minute cleaning before every other ride or so. This doesnt have to be much, just wipe away all the old lube, grit, and mud, reapply new lube, and wipe again.

Check out our How To Clean a Bike Chain article in our blog for more information and tips to getting a clean drivetrain.

How Long Does a Mountain Bike Drivetrain Last?

How long your drivetrain will last is based on a few factors. How well you maintain your drivetrain, replacing your chain when it becomes stretched, shifting properly, and how often you ride will all effect the performance and longevity of your drivetrain.

A few tips to keeping your drivetrain in proper working order and extending the lifetime of your drivetrain are:

• Replacing your chain When it becomes stretched. Use a chain wear indicator to see if your chain has stretched. If it has, you should replace it or it will cause damage to your cassette.
• Maintaining your drivetrain Properly cleaning your drivetrain and lubing your chain goes a long way. Not only will your shifting be smoother and your bike will ride better, but your drivetrain components will last longer.
• Mileage Your chain will be the first to go. If your chain is stretched greater than 1/16" then it is time to replace it. Your cassette should last at least 1500 miles. Once your chain starts skipping on your cassette and shifting starts to suffer, inspect the cassette for worn or missing teeth.

How to Tell if a Mountain Bike Drivetrain is Bad?

If you are unsure if your chain or cassette are worn, there are three signs to tell if your drivetrain is worn out and you should replace it. 

• Chain wear A chain wear indicator is your best friend here. Since your chain will be the first component of your drivetrain to wear out, it is important to check your chain for signs of wear before it gets too late. Chain wear indicators can have different measurements to tell you if your chain is worn. Some use millimeters, where if your chain is stretched beyond 0.4mm you should replace it. Some chain indicators use inches, where a stretch of more than 1/16 of an inch requires replacing. Finally, some chain wear indicators use a percentage and require that a chain above 75% wear should be replaced. Each chain wear indicator will have directions and markings on the tool itself.
• Tooth wear Inspect the teeth on both your cassette and chainring. If the teeth on the cogs or chainring are worn, they will be mishaped, missing pieces of metal, or resemble a shark's tooth. Once your teeth on the cogs or chainring are mishaped, your chain might skip while under load or will not line up properly with the cogs, resulting in poor shifting perfomance.
• Bad shifting If you have waited to replace your chain, cassette, or chainring and you are now experiencing poor drivetrain performance, then you may have to replace your chain and cassette, if not your chainring as well. Chain skipping, chain drops, and late or missed shifts are all results of a worn out chain and cogs.

How Much Does It Cost to Replace Drivetrain?

How much it costs to replace the drivetrain on your mountain bike depends on what level of components you are replacing the existing ones with. There are many drivetrain groupsets that range from entry-level to high-end and the price and performance will vary greatly depending on the level of components you are looking for. Also, the price goes up with th amount of gears you are looking to get, so twelve-speed drivetrains are more expensive than eight-speed drivetrains. Lastly, if you dont have the tools and know-how to replace the drivetrain components yourself, then you are going to need to take your bike to your local bike shop and have them install your new drivetrain for you, which means you will have to pay for labor as well.

The good thing about most drivetrain components are that they are compatible with other drivetrain components of different tiers from the same manufacturer. For example, SRAM's GX Eagle derailluer can be paired with SRAMs X01 Eagle cassette and XX1 chain. Many other brands do this and this means you can mix and match drivetrain components from the same manufacturer as long as they are compatible with each other to help save money on some parts, while upgrading a few specific parts. 

How to Replace Drivetrain on a Mountain Bike

There are certain steps you should follow when replacing your drivetrain to ensure it all goes smoothly.

• Remove the master link from your chain and take your chain off Using chain pliers disconnect the master link and take the chain off of the chainring and pull through derailluer.
• Remove your rear wheel Unscrew the rear axle and remove. Then slide your rear wheel out of the dropouts and clear the derailluer.
• Take off the cassette Using a wrench and a cassette tool. Grip the cassette and unscrew the cassette bolt.
• Install new cassette replace the worn cassette with a new one. Slide it onto the freehub, properly align the gears, and tighten the bolt.
• Remove chainring from cranks undo the four bolts on the chainring. If your chainring is big enough and pedals small enough you can remove the chainring without having to remove the pedals or cranks.
• Install new chainring slide the new chainring over the pedals and cranks and into the correct position.
• Install new chain wrap the new chain around the chainring, through the guides, over the cassette and through the derailluer. Reattach the new chain at the master link.

What is the Best Mountain Bike Drivetrain?

The best mountain bike drivetrains will cost significantly more than some of your base line drivetrains, but with the added cost comes enhanced performance, reliability and style. The best drivetrains on the market are lightweight, have superior shifting, and are built with top-quality materials. 

The best drivetrain components JensonUSA carries are SRAM's XX1 Eagle and Shimano's XTR range. These groupsets are top-dollar, but you get what you pay for. SRAM also offers a wireless verison of some of their best-selling drivetrains, known as AXS, which offers unbeatbale performance, and buttery-smooth, electronic shifting.

How to Pick a Mountain Bike Drivetrain

When shopping for a new drivetrain for your mountain bike you should consider these four factors.

• Compatiability The type of freehub you have limits the type of cassette you can put on your bike, but you can always buy a different freehub. The compatibility of the drivetrain components matters too. With some brands you can run a differnt brand cassette with derailluer but it best to stick to one brand. 
• Wear Chains and cassettes wear out. If you are a newer rider, buying the higher-end casette might not be the most cost effective option.
• Type There are many different types of drivetrains out there a getting the right combination of gears, gear range and performance will play a huge role in your comfort on your bike.
• What are you looking for Are you a seasoned rider looking for the best shifting technology available with the lighestest weight materials? Or are you more focused on a cost effective, durable drivetrain that wont break the bank, but wont have the best features?

Mountain Bike Drivetrain FAQs

How many gears should I have?

Most newer cassettes will have 10-12 speeds. Having more gears provides you with more range to find the perfect gear for the terrain you are riding. However, you can get away just fine with having a lower-end, 8-speed drivetrain, you will just have less range between gears and a harder climbing gear.

What is a gear ratio/range?

A gear ratio is essentially the measure of how powerful each gear is based on the number of teeth on the chainring and the number of teeth on each cog. You calculate the gear ratio for each gear, and from there can tell the spread between gears. To find your gear ratio you divide the number of teeth on the chainring by the number of teeth on the cog and repeat for each gear. This is helpful when experimenting with different chainring sizes and gearing options.

A gear range is the measure of the cassette from its lowest gear to its highest. You take the number of teeth of the largest gear and divide it by the number of teeth on your smallest gear.  For example, a SRAM's GX Eagle drivetrain has a gear range of 520% because it has a top end gear of 10 teeth and a lowest gear of 52 teeth, 52/10= 5.2 = 520%.

Are higher end drivetrains really better?

Higher end drivetrains, such as SRAM's XX1 Eagle drivetrain are some of the best money can buy. Not only do they look sweet, but they are made with lightweight and durable materials and utilize the best mountain biking technology has to offer. With that being said, drivetrains wear out and SRAM's XX1 Eagle drivetrain doesn't offer that much of an advantage over something like SRAM's GX Eagle.

Does having more gears make climbing easier?

Having more gears coincides with having a larger top end gear for climbing. The more teeth in a specific cog, the easier it will be to pedal up a hill. Not only will you have a larger first gear but you will have more gear range and a better chance of having the perfect gear for any given riding scenario.