Downhill Mountain Biking: Gravity Is Your Weapon

While cross-country mountain biking tests your endurance, and enduro makes use of your technical, climbing and downhill skills in a timed race, downhill mountain biking uses gravity and requires agility and quick reflexes when descending some of the highest hills and mountains. Downhill mountain biking is considered the most extreme of any type of mountain biking because of the dangers involved in this sport. It’s also the most popular kind of mountain bike racing; it has the biggest sponsors, coverage and number of spectators. If you want speed, technical skills, brave riders and high-tech bikes then downhill MTB is for you.

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Image credit:

Downhill Mountain Biking Defined                 

DH or downhill mountain biking is a type of mountain biking that is practiced on steep and rough terrain that often features jumps and other obstacles. Downhill bicycles are stronger and heavier as compared to cross-country mountain bikes and enduro mountain bikes. All downhill mountain bikes are built with front and rear suspension with over 20cm or 8 inches of travel. Long suspension travel provides the ability to glide over rocks, stumps, tree roots, crevices, mountainsides and other terrain that a normal mountain bike could not handle.

In downhill races, a continuous course is defined by a strip of tape or flag markers. Riders have a single or double attempt to reach the finish line as fast as possible without going out of the designated course. Downhill racers must choose their line strategically; finding the shortest lines possible could mean travelling at a faster speed and therefore winning the race. If a rider goes out of the designated course, they are required to go back to the point of exit (unless they don’t gain a time advantage, in which case, the rider can go on and continue with their downhill run). Downhill riders usually start at intervals from the slowest to the fastest. The average downhill course may take 2 minutes to complete. Winning time margins are often less than a second. Downhill races are timed with a FAT (fully automatic time) like that which is used in downhill skiing.

Downhill Bike Setup

If you’re a newbie, these tips can help you set up your bike, go faster, have more control and be more stable during downhill runs. Keep in mind that different body types will have different bike setups, so this is only a guide. But there are some specific things you can do when setting up your DH bike to take full advantage of the fast speeds you’ll no doubt encounter.

Aaron Gwin's Prototype 2014 Specialized Demo DH Race Bike - Andorra World Cup. Image credit:
Aaron Gwin’s Prototype 2014 Specialized Demo DH Race Bike – Andorra World Cup. Image credit:

One of the first things that you will notice about DH bikes is that they are stronger, longer and have longer travel suspensions as compared to XC or enduro. One of the easiest things that you can change to make your bike more DH friendly is to change the rider’s position and the frame’s geometry to increase stability.

1. Handlebar position

Most pro DH riders agree that the most suitable position for your handlebars is horizontal to the ground and slightly rolled forward. This position will ensure the arms remain slightly bent every time and will encourage you to use your arms as additional shock absorbers. It will also keep your body low, creating a lower the center of gravity and giving your ride a more stable feel. The handlebar height should be comfortable for your height. Once you gain some experience, you can lower your handlebar height to achieve an even lower center of gravity. Wider bars  give more leverage and offer better control. DH bars are between 730-780mm wide.

2. Seat height and angle

It’s best to lower your seat height in order for you to slide easily over the back of the bike when doing your runs. Comfort is a personal choice but as a proven guide, both feet should comfortably and flatly touch the ground when you are sitting.

3. Brake lever position

The best advice is to use your index finger on each lever when riding. While most brakes out in the market today are powerful enough to do this, newbies and younger riders might find this position difficult. It’s essential to adjust each lever toward the handlebar for an easy reach. It’s also essential to adjust the brake lever when the brakes are fully applied. It should finish just before it touches the handlebar. It is also widely accepted that the best position for the brake levers is at an angle that follows your arm when seated on the bike. Bigger brake rotors will dissipate heat faster and are less likely to make the brake pump up. 180-200mm rotors are generally used in downhill mountain bikes.

4.  Frame geometry

Some of the essential aspects of DH frame geometry are the head tube angle and the bottom bracket height. Some bikes have the ability to change frame geometry, suspension travel and setup and the wheelbase length. In general, most DH riders follow this rule – the lower the BB height, the more stable the bike will ride through corners and at high speeds. The slacker the head tube angle, the better the bike will handle at fast runs. Different courses will require different bike setups, but you need to find a general comfortable setup that will work for you. A long wheelbase is suited for fast, wide and open courses while shorter wheelbases are suited for courses with tight turns and slower speed sections.

5. Suspension setup

Rear shocks should be in between 30-35% sag. To set the sag, push the bottom out bumper up the shaft of the shock until it meets the body of the shock. Stand on the pedals with all your weight (including all your riding gear) and check how far the number will displace. Just change the spring air pressure to decrease or increase the shocks sag. Check your user manual for any base settings and the right spring rate for your weight. For your dual fork crowns, 25% is the ideal sag. Tie a string on the stanchions and then stand on the pedals with your full gear and check how much compression occurs. Check the user’s manual and contact the fork manufacturer for the base fork settings. Also take note of the rebound rate of your fork and rear shock. Make sure that your shocks are not rebounding to fast because it can damage the suspension. The manufacturer will have a minimum and maximum air pressure limit for their suspension so it is essential to stay between the suggested limits.

6. Tire pressure

Softer compound tires may roll slowly as compared to harder compounds, but the grip and traction they offer is far superior. Soft compound tires can also run on high pressure without compromising the tire’s grip. It will also offer better braking when needed. Pro riders use 2 ply tires because they can still lower the pressure and it’s still less likely to go flat. Tire pressure should be between 18-30psi. As a basic rule, try to run your tires as soft as you can without getting any flats. As always, this will be a trial and error sort of thing. At some point you will learn the best tire pressure needed for different downhill courses. For any courses with sharp rocks and any objects that you may hit hard, tire pressure should be harder. For smoother courses, low tire pressure is best.

Downhill riders are a different breed of bikers; they have balls of steel, enjoy the thrill of attacking hills and mountains and are not afraid of gravity. Kill the hills and conquer every obstacle on your way down the mountain. Ride hard, pedal hard and win!


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