What is a Downhill Mountain Bike: The Ultimate Guide

Here’s a 4 step guide into the unique capabilities and beauty of Downhill Mountain Bikes
What is a Downhill Mountain Bike: The Ultimate Guide
Trek Session 9.9 (Image Credit: Dirt Mountain Bike Magazine)

So, what is a downhill mountain bike? Downhill Mountain Bikes are often said to be the Formula 1 class of the MTB world. A fitting comparison seeing as both Downhill MTB and Formula 1 are all about speed, using the most cutting-edge technology of their respective industries to find every last sliver of pace.

However, when we hear the question, what is a Downhill Bike, we at Pro Mountain Bike believe Downhill Bikes are more similar to fighter jets. The reason being that both Downhill (DH) Mountain Bikes and fighter aircraft are bad at going slow. A Formula 1 car can go slow just fine but fly a fighter jet or ride a Downhill MTB at low speed and they begin to handle like bricks and become essentially useless. 

Like a fighter jet, Downhill Bicycles transform into precision instruments at speed. Every part of them merges in a triumph of design and begins to sing in unison, giving the rider the ability to sail over all manner of hardcore terrain and obstacles, shooting out the other side ready for more. 

If you think Downhill Bikes sound like a blast to ride, you’d be right. 

Here’s where you will learn what makes a Downhill Bike such a beautiful, extreme, and supremely specific tool.

#1 – What is a Downhill Mountain Bike? Let’s Start with the Why

The reason for Downhill Bikes’ existence is simple; to get from the top of a trail/mountain to the bottom as quickly as possible. It’s that speed that we mentioned in Paragraph 1. That’s the simple and singular goal here, but the second half of the equation is something we mentioned above as well.

For all the parts of a Downhill Bike to work together, they must be designed and tuned to perfection not only as a singular unit, but for the rider as well. There should be nothing about the function of a Downhill Bike that distracts from its descending pedigree. If you balanced the performance in any way, to make the bike easier to pedal for example, it would merely pull away from its downhill abilities and likely add weight!

Now, you may think, “Hang on a second, but every MTB category is designed to achieve its specific goal, why are Downhill Bikes any different?” 

Well, you would be spot on, but every other category is about some sort of balance or compromise to give its bikes the ability to do more than one thing. A Cross Country Mountain Bike climbs exceptionally well but can tackle descents too. An Enduro Mountain Bike shreds in the gnarliest of conditions but still allows its rider to pedal efficiently. 

Downhill does not compromise. It’s for descending and nothing else. Pedaling a DH bike is arduous, and you should just forget about trying to climb a hill with one. That would just be torture.

In that sense, if you are thinking about buying a Downhill Mountain Bike, you should consider it more thoroughly than other MTB types because it won’t take you to a variety of places like the others. It is here to do one thing and one thing only. 

#2 – How Does a Downhill Bike Work?

To perform well, a Downhill Mountain Bike should be:

  • Stable/Controllable at Speed
  • Built for strength and the right weight

Let’s break those points down.

Stable/Controllable at Speed

The faster you go on a bicycle, the more your inputs – whether intentional or unintentional – affect what the bicycle is doing underneath you. 

This is why a Downhill Mountain Bike has:

  • Wide handlebars = smoother inputs and more feel
  • Long-travel full suspension = absorbing both small and large bumps
  • A low center of gravity = no sudden reactions from bike and easier to balance

Built for strength and the right weight

Speed on any mountain bike usually means you will take a beating, so big speeds equal big beating! To make it through Downhill trails unscathed, a DH bike has:

  • Frames built with larger sections and thicker materials
  • Stronger components that will last, everything from pedals to derailleurs 
  • Wider and more robust rims to take the force where rubber meets terrain

Building a DH bike takes more material than bikes of the other classes, which inherently means they are heavier, but this is not necessarily a bad thing. 

Speed in a descent requires a certain amount of momentum and inertia to hit the sweet spot of controllability. More weight means that the rocks, ruts and drop offs you are hitting don’t just bounce you back in the other direction. That extra weight compresses the suspension and transfers the energy efficiently, allowing you to continue forward rather than fighting to keep a light bike on the line you want.

#3 – Let’s See What You’re Made of

Again, like fighter jets, Downhill Mountain Bikes are machines that pretty much anyone can enjoy. A road cyclist would pause as they looked at one in a shop – they may think they are tubs of lard, but you don’t have to want to ride a bike to appreciate how it is made. When it comes to pure eye-candy, DH wins the prize each and every time.

Up front you have the double-crown – a must for DH – beefy suspension with around 200mm of travel, a combination of exotic materials and ingenious fluid mechanics that eat a trail’s undulations like a snack.

Trek Session 9.9 front-end (Image Credit: Trek Bicycles)

Out back you have around 200mm of travel again but this time through a single shock that gleams like something out of a sci-fi film. We’ve been around bikes for decades and still marvel at how shocks take such abuse without coming apart after just one ride, let alone years of downhill madness.

Trek Session 9.9 rear-end (Image Credit: Trek Bicycles)

At each end doing the rolling will likely be two 29” wheels with large heavy-duty tires to work as much grip from the dirt, gravel, mud and rocky trails as possible. While much of the MTB world made a sweeping shift into 29” wheel sets for their advantages over obstacles, Downhill held out for a while with a smaller wheel diameter due to its lower angular momentum, which means easier direction changes. So, you may see a few 27.5”-shod bikes knocking around still, but technology has allowed for the larger wheel diameter to have more pros than cons in the Downhill world and we’d recommend 29” wheels all day long.

Trek Session 9.9 (Image Credit: Trek Bicycles)

Up top you will have a seat set low because while descending you’re going to be standing on the pedals pretty much the whole time.

Drivetrains on DH bikes will almost always be one chainring at the front with 7-8 gears at the rear because you aren’t going to be needing much in this discipline. Still, everything from the crank to the rear derailleur is going to be heavy duty and precision made so that the chain goes and stays where it needs to be, and any shifting done while riding is carried out without a hitch.

Trek Session 9.9 Drivetrain (Image Credit: Trek Bicycles)

#4 – So, Do You Feel the Need for Speed?

Out of all the categories of Mountain Biking, we can say this for Downhill. Try it once and you will know if it is for you.

DH isn’t for everyone. It’s intense and demanding in short stints relative to what you find in other disciplines. And that adrenaline rush will either put a smile on your face or have you trying to unlock the vice grip your fingers have on the bars. 

So, if you:

  • Have ridden other MTB types and find yourself wanting more out of the Downhill sections

    or
  • You always imagined being a fighter pilot

… welcome to Downhill Mountain Biking.


At the other end of the spectrum, check out our introductory guide to Cross Country Mountain Bikes here.

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