If you’re new to mountain biking—or simply cycling in general—you’ve probably already been bombarded by a huge lexicons of terms that make absolutely no sense to you. It seems like cyclists speak an entirely unique dialect of English, especially mountain bikers. One minute your new riding buddies sound like surfer dude transplants from southern California, the next they go all geeky on you and start throwing out a slew of mechanical and technical terms about bikes.
First up, take a deep breath and relax. There’s no need to learn everything you’ll eventually pick up over time right this moment. The more you ride your bike along the trails and hang out with other MTBer’s the more you’ll learn naturally. Like your riding skills, there’s a natural progression to your knowledge that will increase with time and experience.
So, if you have no clue about the difference between gears, sprockets, cranks, and cassettes, it’s not that big of a deal. It’s good to learn all that stuff, and we’re here to help. Check out this basic guide to mountain bike parts and components. Don’t try to memorize all of this at once. Come back from time to time to refresh your memory.
Mountain Bike Frames
As you can see in the illustration above, the parts of your bike are not really all that complicated. Whether you’re looking at a hardtail bike—one without a rear suspension—or a full suspension bike, one of the things you’ll notice right away is that a bike frame forms two triangles. In fact, the terms front triangle and rear triangle are often used to describe the two major sections of a bike’s frame.
Let’s look at the front triangle first. As you can see, it has four major parts—the top tube, down tube, seat tube, and head tube. Taking a look at these parts, the names become rather obvious. A bike frame is essentially a grouping of metal tubes that have been welded together to create a cohesive body. The head tube is at the very front of the bike, and it’s where the cockpit and front fork come together. The top tube is, well, at the top of the frame, while the down tube goes down from the head tube to the bottom bracket. While not specifically labeled here, the bottom bracket is the hole you see at the bottom of the frame into which the spindle for the crankset is inserted. (We’ll cover cranksets later.) Finally, the front triangle is finished by the seat tube—the tube into which the seat post is inserted.
The rear triangle can be said to consist of either two or three major parts—depending on your point of reference, and whether or not you’re looking at a hardtail or full suspension bike. Those parts are the chain stay, seat stay, and (again) the seat tube. The chain stay is the portion of the frame nearest the chain—it runs essentially parallel to the upper side of the chain loop. The seat stay generally runs from the seat tube down to the join the chain stay where the back wheel is mounted. The reason why the rear triangle may have two or three parts is basically because on a full suspension bike, the rear triangle is not welded to the frame, but rather mounted at pivot points to allow the rear triangle to move independently and utilized a rear shock.
Not sure what some of the words in this article mean? Be sure to check out our Glossary of MTB Terms and Slang.
Mountain Bike Components
Moving on to bike components, take a look at the illustration of a hardtail bike above. Let’s step through the parts one by one.
First up are the obvious pieces such as pedals, handlebars, tires, wheels, and the chain. Anyone with even the most basic exposure to cycling knows what these parts are. You may not understand how they work or how to repair or replace them yet, but they should be familiar enough to not need laborious explanations.
The handlebars and everything mounted to them are often referred to collectively as the cockpit. Handlebars should have a good pair of grips for your hands to hold onto through various environments and conditions. On most bikes, you’ll find the back brake lever and rear shifter mounted to the handlebar near the right-hand grip. The front brake lever and front shifter (if present) is typically mounted to the handlebar near the left-hand grip. You may not find a front shift on a modern mountain bike since many feature only a single gear up front—this is called a 1x drivetrain. NOTE: On bikes in Europe, and some other parts of the world, the cockpit controls are reversed. This makes sense if you think about it—they do drive on the opposite side of the road!
Handlebars on a bike are connected to the front fork with a piece called the stem. The stem is tightened around both the handlebars and a part of the front fork called the steerer tube, which is inserted through the bottom of the head tube. Then a top cap is tightened down on top of the steerer tube to help hold it all together. The front fork of a mountain bike most likely has a pair of shock-absorbing tubes that make up the front suspension. We’ll cover suspensions and how they work in a future post.
The front wheel is mounted to the front fork with an axle that is either a quick-release skewer or a thru axle. This axle is inserted through the wheel’s hub and tightened down by hand. The hub is that part of the wheel in the center where all of the spokes running from the wheel’s rim are laced into place. A disc brake system is mounted in two parts here—the brake actuator (containing brake pads) is mounted to the front fork, and the disc brake itself is mounted to the hub. Either a mechanical wire or hydraulic tube filled with mineral oil runs up from the brake actuator to the brake lever.
Quickly reviewed, the seat—also called a saddle—is mounted to the seat post which is then inserted into the seat tube of the bike frame. One of the newest and best innovations in recent memory is the introduction of a dropper post, which is a seat post whose height can be adjusted on the fly via a lever attached to the bike’s handlebars. We’ll talk more about dropper posts in a future article.
Moving on to what is possibly the most complex system of components on any bicycle, let’s look at the drivetrain. (A drivetrain is sometimes called a groupset.) Starting with your body’s final points of contact—the first two being the handlebars/grips and the seat—look at how the drivetrain is an interconnected mechanism meant to propel you forward.
The pedals are mounted to two long pieces of metal (or sometimes carbon) called the crank arms. The crank arms are connected together by a spindle which is inserted through the frame at the bottom bracket. The front gears, often called the chainrings (or collectively the crankset, chainset, or cogset) is mounted to the spindle via either a separate or integrated spider—the arms you see running from the center of the spindle and bolted to the chainrings.
The chain is threaded around the chainrings and runs through a pair of derailleurs found at the front and back. Derailleurs simply move the chain inward and outward as necessary depending on the gear chosen. Front derailleurs may not be present on many modern mountain bike setups.
Rear derailleurs are more complex, consisting of a mechanism that not only shifts the chain inward and outward but also changes the amount of tension placed on the chain depending on the size of the rear gear currently in use. A rear derailleur has a cage apparatus holding two pulleys—sometimes called jockeys. The lower pulley is the tension pulley, and it accomplishes its job by pulling backwards or forwards on the chain, so it’s often called the tension pulley or tensioner. The upper pulley guides the chain to the sprockets, so it is often called the guide pulley. Rear derailleurs are fitted with limit screws which can be adjusted to limit how far inward and outward the derailleur can shift. The derailleur is mounted to the frame with a small piece of metal called the derailleur hanger, which is meant to bend or break under pressure in order to prevent damage to the bike frame.
Collectively, the rear gear set, or sprockets, is usually called the cassette. The cassette is mounted to the rear wheel at the hub. As with the front wheel, the rear wheel also has a disc brake.
To wrap this up, let’s take a quick look at all of these parts on a full suspension bike, and note the major differences.
Right way, you can see that the parts and components are basically the same. The major difference is what gives a full suspension bike its name—the rear shock. As mentioned above, the rear triangle on a full suspension bike is not a welded-on piece, but rather the chain stay and seat stay are bolted to the main part of the frame at pivot points. Connected in various ways by different bike manufacturers you’ll find the rear shock, which is the main piece that gives a full suspension bike all of its cushiony goodness. We’ll go more in-depth about both front and rear suspensions in the future.
There you have it! Those are all the basic components you’ll find on pretty much any modern mountain bike. There’s a lot more we can go into, such as all the stuff mentioned above that we’ll dive into more deeply in the future, as well as discussion about the different sizes of wheels and how much travel some suspensions have compared to others. We’ll leave all of that for another time and place.
Do you have any questions or comments about frame parts and bike components? Is there anything we missed or said wrong? Let us know in the comments.
Have fun, ride smart, and keep shredding!