Detailed Guide on Mountain Bike Drivetrains

Mountain bike components are some of the most important aspects when it comes to your mountain bike. Regardless of the bike, they will have a drivetrain that propels the bike forward, while giving you a variety of different levels of tension.

The mountain bike groupset is commonly referred to as the collective name that describes the various components around the drivetrain. Mountain Bike Drivetrains might seem intimidating, but we have broken it down for you.

Mountain Bike Drivetrain

In the following article, we will be looking at some of the components of the drivetrain. We will also look at the finer features of the mountain bike drivetrain. We will collectively discuss the groupsets, which are commonly designed by the big names in the industry. A brief internet search will reveal Shimano and SRAM as two of the main brands for mountain bike groupsets.

What is a Mountain Bike Drivetrain?

The drivetrain can be seen as the engine room of any mountain bike. Without a decent drivetrain, your mountain bike will remain stationary and you will eventually need to push it to move forward. The mountain bike drivetrains consist of a couple of components, with each of these playing an important role in the overall bike design. Here are the different components that make up the drivetrain:

Crankset

Without the crankset, the mountain bike will have no means of moving forward. Generally located at the side of the bike, the crankset is where the pedals will attach to the bike. Not all cranksets are the same and they have different chainrings that attach to the component. These chainrings will dictate how many front gears the mountain bike has. For most bikes, you will have 1-3 chainrings depending on the crankset.

mountain bike drivetrain crankset

The crankset also features an arm, but the arm is pretty standard when it comes to the bike. The arm affects the bikes that are used. Smaller brakes will have a crankset arm of around 170mm, with 175mm being reserved for the medium-sized brakes. Downhill bikes will make use of the 165mm arm, which lifts the bike. The more lift a rider has the better clearance below the bike.

Bottom Bracket

One of the smaller components of the mountain bike is the bottom brackets. The bearings are fitted to the frame and the crankset will generally attach to them. A threaded bottom bracket is commonly found on most mountain bikes. However, the pressed bottom bracket relies a lot more on tight tolerances. Either way, your bike will need one.

Cassette

Another big word you might hear is the cassette of the mountain bike. Fortunately, it is not as complicated as it sounds and only refers to the cogs at the back of the drivetrain. These cogs vary in numbers and will refer to how many gears the mountain back has at the back. For mountain bikes, the rear gears will often vary between 8 and 12 like the Shimano HG50 10 Speed Mountain Bike Cassette.

mountain bike drivetrain cassette

Chain

The chain is probably the most common of the lot and often the part that can be the most frustrating. The chain will sometimes come off the gears, which could be dangerous. However, it simply refers to the chain that connects the front and rear gears. Most chains are made from solid steel with interconnected links. The links make it possible to shift gears and give you smooth transitions on trails. Chains like the SRAM PC-830 MTB Bike Chain will be a good choice.

Derailleurs

If you have read any of our other articles, you will find the derailleurs are often one of the main components that we mention. The derailleur is a small metal component that is operated by the shifters. The SHIMANO Deore is a popular derailleur on mountain bikes. It shifts the chain into the desired direction and will be the main force of what allows you to change gears successfully.

Mountain Bike Rear Derailleur

Shifters

To finish up with the mountain bike drivetrains components, one also needs to have a look at the shifters. When you buy a mountain bike, you will notice that the shifters are important as well. Generally, Shimano and SRAM provide the best shifters on the market today, which makes them some of the leading sponsors of the Tour De France.

While there are numerous forms of the shifter, the most common options are the trigger shifters. With these shifters, you will simply need to flick a lever and the mountain bike will switch to a different gear. The SRAM NX Eagle Shifter are a good option. However, the twist shifters are also comfortable, but they can be tedious when you want to shift back to a different gear.

mountain bike trigger shifters

Understanding The Gears, Ratios, And Numbers

With all the basic knowledge now at your disposal, we can dive into some of the more intricate components. Many people have been asking about the gears and ratios that will best suit their needs. While it is hard for us to give you a specific number, we can give you a break down of the numbers and rations, and what they mean.

Higher And Lower Gear Ratios

As you might have guessed, not all gear ratios are the same and you will have a variety. Whether your mountain bike has 50 gears or 11 gears, the difference between the highest and lowest gear will be the same. However, the smaller intricate gears will not be as many with the 11-gear drivetrain, reducing the options you have available.

  • Lower Gear Ratios: Lower gear ratios refer to a tire that will give you fewer revolutions for each revolution you perform on the pedal. Since there is less friction on the tire from the surface, it becomes easier to scale up mountains at a slower pace.
  • High Gear Ratios: These gear ratios are the opposite of the low gear ratios and will provide more revolutions for each time you turn the pedal. However, they allow the bike to build up more momentum.

Unfortunately, there is no precise option for mountain bike enthusiasts and you will need to find the gear the suits your riding style the best. For the top mountain bikes, the drivetrain is generally on the lower end of the scale. This means that you are bound to have a 1X drivetrain to make it more comfortable for riding up and downhills. 

Crank Speed

Another big word you see a lot from the experts is the crank speed. Unfortunately, no crank speed is perfect for everyone, but you will notice that 21-speed mountain bikes are designed for some of the younger riders. The speed number refers to the number of chainrings at the front, which is multiplied by the chainrings at the back.

The 3 chainrings at the front do not necessarily mean that the bike will have more unique gears and while it might be a 27-speed Shimano drivetrain, you might find that only 18 of the gears are unique. As we have mentioned, the ratio from the highest to the lowest will remain the same with less jumping in between.

When it comes to selecting the right mountain bike drivetrain, it is less about what seems the best and more about what you feel the most comfortable with riding. All of these components might seem confusing at first, but a mountain bike with a 1 front chainring is often best for beginners. The 7 or 9-speed drivetrains require far less maintenance.

Wrap-Up

Mountain bikes are some of the best tools one can use when you want to enjoy the outdoors. While it is not always easy to understand all of the components, you will find that many experts are always willing to help. Mountain Bike Drivetrains might seem a bit confusing to the untrained eye, but we hope this article has helped.

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