Mountain bike components

You might have been riding a bicycle from a very young age, but have you ever given any thought to how exactly it works and what each part does? Every part of the bike needs to do its job properly so you can ride safely, efficiently and achieve the most enjoyment. In this section we’ll take a look at all the components you find on a mountain bike and what they’re there for. We’ll also discuss the different choices you have in design and materials, which can have a huge impact on the way the bike performs. Don’t worry though, it's not rocket science!

FRAME

The central part of a mountain bike is its frame. Every other part is connected to it, so it needs to be sturdy. There are two main aspects when studying a bike frame; material and geometry.

There are two common choices for material: an aluminium alloy or carbon fibre. Carbon fibre sounds very advanced and expensive and that’s because it is. Here are some of the benefits of carbon over aluminium:

It is lighter, which means less weight to drive forward.

It dampens better than aluminium, which means you’ll feel less of the shocks from riding over rocks and roots.

It's sturdier and more flexible, which means it is more durable and will break less quickly on a hard impact.

That being said, a carbon fibre frame is more expensive, sometimes it will cost over €1000,- more than the same aluminium frame. Buying a bike with an aluminium frame is not a bad choice at all. It will be heavier (0,5 to 2 kilograms), but save you a lot of money.

Now the more complicated part of the frame design: geometry. The geometry of the frame is very important to the performance of the bike. Luckily, bike manufacturers do a great job at designing the frame for its specific purposes so we don’t need to go into all the details. However, there are a few things you should keep in consideration when choosing a frame.

First of all cross country bikes are designed to be lightweight and go fast on relatively smooth terrain, so don’t use them when riding technical downhill tracks with big drops as this will severely affect the durability of the frame and it might even break.

Second, there is the size of the frame, perhaps the most important aspect. Again, the manufacturers have made it easy for us. Go to their website, find the size chart for the specific bike you had in mind and find the right match for your height. Yes, there is much more to it, which is why the size chart of each specific bike or bike manufacturer can be different, but 99% of the time the given size will be correct for you. Most bike shops will also help you find the right size and offer you a test ride, just to be sure.

Some retailers sell their frame separately so you can make a custom bike.

WHEELS

Wheels are what keep your mountain bike rolling and they come in various sizes. The sizes refer to the diameter of the wheel and are usually measured in inches. For many years every mountain biker was riding 26 inch wheels as it was the only option. Then came along the 29 inch wheels and not much later the 27.5 inch wheels. As almost no one rides the 26” anymore, we’ll compare your remaining two options.

In comparison, 27.5” are more agile, they will accelerate faster, handle better and they have a lighter weight since they’re smaller. 29” wheels are more of a power house, they provide more traction, roll easier over obstacles and are more efficient on longer rides. It’s up to you to decide what advantages you prefer, but there’s something else to consider, your height.

The wheel size has a large impact on the geometry of the bike. To keep things simple, 27.5”is better for shorter riders and 29” for taller riders (over 180cm). It’s not uncommon to see a bike manufacturer fit 27.5” on smaller sizes and 29” on bigger sizes by default. If you’re not sure what wheel size you need, it is generally recommended to new mountain bikers to get 27.5” as it gives you more control over your bike. Alternatively, you could even combine both options with a 29” wheel on the front and a 27.5” wheel on the back, known as a mullet.

TYRES

The piece of rubber attached to your wheels are your tyres. Along the edges of the tyre you’ll find the bead which sits in a small groove in the rim of the wheel. When the tyre is properly inflated, the air pressure within the tyre keeps the bead in this groove.

Your bike probably already has a suitable set of tyres, provided by the bike’s manufacturer. But just in case you’re curious, we’ll explain some of the information you may find on the side of the tyre:

Brand & tyre name: use this to look up more details about your tyre online.

Size & width: what wheel size the tyre fits and how wide the tyre is (both measurements usually in inches).

PSI: the maximum air pressure (in PSI) the tyre can hold.

All of these aspects influence how your bike handles out on the trails. Remember that the tyres are the only part of the bike that touches the ground. Having the right tyres for the terrain you ride is therefore crucial. Here’s a rundown of three key aspects when looking to buy a new set of tyres:

Width

Wider tyres will give more grip needed for technical terrain (as they make more contact with the ground), while narrow tyres will increase speed (less contact equals less rolling resistance). Tyre width is usually measured in inches. Check the image below to see what tyre width matches your style of riding.

Tread Pattern

Just like with car tyres, the tread of the tyre has a huge impact on how they handle in different riding conditions. Firstly, you’ll notice on your tyres there is a centre line of knobs and a line of knobs on both sides. The knobs on the side are purposed for and only used in cornering. There are two primary aspects when looking at the tread pattern:

The knob profile determines whether your tyre is better at rolling or better at breaking. A high knob profile means the knobs will have more friction with the ground, increasing the braking power. A lower knob profile will decrease friction, which results in a higher rolling speed.

Low knob profile = high rolling speed, less effective at braking.

High knob profile = lower rolling speed, better at braking.

The amount of space between the knobs affects how well your tyres handle different terrain. A tyre with knobs spaced far apart will be able to plough through wet conditions, such as mud. A smaller spacing means more contact with the ground and is therefore more suitable on solid terrain.

Small spacing = better on solid terrain.

Large spacing = better in the mud.

So should you change tyres every time the conditions change? No, most amateur riders will choose an intermediate set of tyres. It will never be the perfect match for the occasion, but it saves a lot of money and effort. Kind of like fitting four-season-tyres on your car. If you do need a new set of tyres, don’t forget the manufacturer will usually make it easy to understand what type of riding the tyre is purposed for. Just check the label.

Tube vs Tubeless

Your tyre needs to be inflated. For most regular bicycles that means there is an inner tube between your wheel and your tyre, but in mountain biking there is another option: tubeless tyres. This basically means the tube is taken out and air is being pumped directly in the space between the wheel and tyre. For this to work it needs to be airtight so no air can escape. Setting up a tubeless tyre is a bit more advanced, so we won’t go into it right now, but here’s a rundown of the pros and cons.

Tubeless pros:

Reduces weight as the inner tubes are removed.
Fewer flats as a tubeless tyre is filled with a sealant that automatically fixes small punctures.
A better feel for the trail as you can ride lower pressure in your tyres, increasing the traction you have.

Tubeless cons:

Costs more money and time to maintain.
Costs more effort to replace tyres or wheels.

SUSPENSION

Suspension distinguishes a mountain bike from any other bicycle and is critical to make rough trails feel smoother. As you hit large rocks, roots or hit a drop, your suspension will compress and as a result reduce the impact on your body. This does not only make your ride more comfortable but also prevents you from being shaken off your bike.

There are two types of suspension. Almost all mountain bikes have suspension at the front, also called fork suspension. Then there are mountain bikes with suspension on both the front and in the rear/middle, also referred to as shock suspension. A mountain bike with only fork suspension is called a ‘hardtail’ and a bike with both front and rear suspension is called a ‘full suspension’ (nicknamed ‘a fully’).

The downside of having suspension on your bike is that it makes it less energy efficient. As you pedal, the suspension will absorb some of the energy, causing it to compress, which means less energy is spent on propelling the bike forward. As a result most cross country riders opt for a hardtail mountain bike, since the trails are relatively smooth.

So how do you know exactly how much suspension a mountain bike has? This is indicated by the suspension travel. It is the maximum distance a suspension can compress before bottoming out. More travel means more absorption of impacts, but usually also more squat. Squat refers to how much the suspension compresses when pedalling, as explained before.

Suspension travel is usually indicated in millimetres. If you’re not sure how much travel you need, here are some guidelines:

80 - 120 mm (short travel): suitable for cross country

120 - 140 mm (mid-travel): suitable for trail riding

150 mm+ (long travel): suitable for All Mountain & Downhill

Exactly how much travel you need depends on the trail, the terrain and the rider. Some riders don’t mind a rougher ride if it means a higher pedal efficiency, while others prefer a smooth riding experience.

As a new mountain biker you’ll want to start with a hardtail. They’re suitable for beginner trails and are generally speaking cheaper than a full suspension bike. It's also said that a hardtail better to learn the basics of mountain biking as you'll have to be more carefull

SEATPOST

Your seatpost can be as simple as a tube that connects your frame to your saddle, but it can be so much more as well. Firstly, you have the choice between aluminium seatposts and those made out of carbon fibre. Just like with the frame the carbon option will be lighter, but more expensive. The more important choice is whether you equip your bike with a dropper post.

Seatposts are adjustable in height as we are not all the same size and want to sit comfortably on our bikes. However, another reason to adjust the height of your seatpost is to get through rough or technical terrain. By lowering the saddle you’ll have more room to move around the bike, which is essential when coming across challenging trails. Previously, that meant hopping off your bike and adjusting the height manually, but since the arrival of the dropper post we’re able to simply press a button attached to the steering handle.

The dropper post works with a hydraulic system and has quickly become very popular among trail and enduro riders who regularly face tough obstacles. When choosing between a regular or a dropper post you should consider what sort of trails you will ride. A cross country rider rides on relatively smooth terrain and therefore doesn’t need a dropper post. Also keep in consideration that a dropper post adds weight to the bike and will increase the price.

DRIVETRAIN

The name ‘drivetrain’ refers to a set of components which are responsible for driving the bike forward. Depending on who you ask, it can also include the shifters and the brakes. For now, let’s focus on the components everyone agrees are part of the drivetrain:

Crankset
Chain
Cassette
Derailleur

Crankset

It all starts with the crankset (also known as chainset in the UK). It converts the input from the riders pedalling into rotational motion. The crankset itself consists of several parts. The rider pushes onto the pedals which are attached to the crank arms. The crank arms, or cranks, are attached to the chainring(s). A crankset can have one to three chainrings of different sizes. The last few years a one-by (single) chainring is most popular in mountain biking. It weighs less, is simple to operate and prevents breaking a chain caused by bad shifting. Thus, it is advised to look for a one-by drivetrain when buying your first mountain bike.

Chain

The chain sits on the chainring(s) and connects it with the cassette. Thus, by pedalling and rotating the chainring, you also rotate the cassette.

Cassette

The cassette is a collection of different sized sprockets and is attached to the axis of the rear wheel. This is where the rotational movement of the crankset finally converts to the movement of the rear wheel. When a drivetrain is called a 1x11, 1x12 or 3x7 (just some examples) system, the second number refers to the number of sprockets on the cassette and the first number refers to the number of chainrings in the crankset.

Derailleur

A derailleur is responsible for shifting the chain between sprockets or chainrings. So, unless a bike has only one sprocket in the cassette and one chainring in the crankset, it will always have one or two derailleurs. The derailleur(s) are operated with shift levers located on the handlebar of the bike. Shifting is essential in mountain biking as we often ride on irregular terrain.

The rear derailleur is slightly more complex than the front derailleur as it has a secondary purpose: removing the slack in the chain when shifting to a smaller sprocket. This is done by two pulleys guiding the chain in an S-shaped pattern and a spring that increases chain tension if there is too much slack.

BRAKES

Brakes are an essential safety feature, especially on a mountain bike which is used to travel at high speeds, down steep terrain and through switchbacks. Within the mountain bike world there are two distinct options to choose from: rim brakes and disc brakes.

A rim brake uses brake pads on both sides of the rim which squeeze together in order to slow it down. A disc brake has a disc attached to the axle of the wheel where brake pads squeeze it to slow down. Below you'll find an example of a disc brake:

The most affordable mountain bikes will have rim brakes as they are low cost. However, they’re also unreliable in rainy and muddy conditions, can damage the rims and are not very durable. Seeing as brakes are so important to prevent crashing your bike, you can understand why most people prefer disc brakes. They’re just more reliable in all weather conditions. The only downsides are that they’re heavier and cost a bit more (although crashing your bike due to bad brakes is even more expensive).

Professional cross country riders might opt for top quality rim brakes because of the reduction in weight, but every other mountain biker is better off with disc brakes. So if you’re serious about mountain biking, go for a bike with disc brakes.

PEDALS

By now you probably realise there are many different options to choose from when looking at mountain bike components and pedals are no exception. Two of the main contact points with your mountain bike, besides your butt and hands, are your feet. By pushing your feet onto the pedals you transmit power to the bike. The pedals are also used to keep you balanced. There are two main options between pedals: flats and clipless.

Flat pedals are the type of pedals you see on every regular bike. You simply put your feet on them and off you go. Clipless pedals are designed so you can ‘clip-in’ to your pedals with special shoes. Yes, that’s right, clipless pedals actually do have clips. You just can’t see them anymore on the modern models, hence the name. If your feet are clipped in, you’ll be able to transfer more power to your bike and are less likely to be shaken off your pedals on rough terrain.

Because everyone has different preferences when it comes down to pedals, a lot of bike manufacturers will not include any pedals when you buy a mountain bike. The low-budget bikes do have pedals, but they’re usually made out of some kind of plastic compound. Plastic pedals are not optimal as they break more easily and provide less grip than other materials. Most common pedals are made out of an aluminium alloy and can cost anything from €15 to €200+. There are also pedals made out of carbon fibre or titanium which have their own advantages over aluminium, but are more expensive.

If your mountain bike has no pedals or cheap ones made out of a plastic compound, you’ll want to buy a set of ‘flat’ aluminium pedals. As mentioned before, they don’t have to be expensive and fitting a new set of pedals is very simple, which we’ll explain later in this course. Once you’ve bought a new set of pedals it is also very simple to transfer them to any future bikes you might buy. Below you'll find an example of flat pedals (on the left) and an example of clipless pedals (on the right).