DH setup 101
Correct bike setup for DH racing
Let’s face it, everyone is different. Different types of people and different types of bikes. But, there are particular ways we can set up our bikes to maximize the benefits of these highly evolved machines while traveling downhill at high speed.
The first thing you will notice about a bike used for DH is they are longer, stronger and have larger amounts of suspension travel than XC style mountain bikes.
One of the easiest things we can change on our bikes to make them more DH friendly, is the rider positioning. By this we mean, handlebar position, seat height and angle, brake lever reach and position, and if possible frame geometry can be adjusted to increase stability.
The most suitable position to run your handlebars is, to ensure the up-sweep of the bar is somewhere between horizontal to the ground through to rolled forward. In doing so, the sweep should be rolled upwards. This will ensure your arms remain slightly bent at all times and you’re encouraged to use your arms to absorb impacts. It also helps to keep your body low which improves your stability. Your handlebar height should be at a comfortable height but as you gain more experience it is beneficial to lower your handlebar height to lower you centre of gravity.
Seat height and angle.
In order for your body to be able to slide easily over the back of the seat in steeper sections, it is best to run your seat at a lower height. It is a personal comfort factor, but as a guide your seat should be set so when you are sitting on it, both feet should be able to comfortably touch the ground with flat feet. It should also be angled with the nose slightly upwards so you are encouraged to sit slightly behind the saddle.
Brake lever position.
When riding, it’s best to use one finger, your index finger, on the each brake lever. Most brakes are powerful enough to do this but for some younger riders it can be difficult to have enough strength to stop. Especially on rough tracks. If you set your brake levers so when your first finger is extended, the curve at the end of the brake lever rests comfortably under your index finger. It’s important to adjust the reach on each brake lever towards the handlebar so it’s easy to reach any time. It is also very helpful to adjust your brake lever so when your brakes are fully applied, the lever finishes just before touching the handlebar. This will help to greatly improve your grip on the handlebar in rough terrain as your hands are wrapped around the handlebar more completely. Again, this is personal choice but it is very helpful for beginners and will greatly reduce arm pump. Attention should be made to the angle of your brake levers also. It’s widely accepted that the best position for your brake levers is at an angle that will follow the angle of your arm when seated on the bike. As a side note, run your brake levers so they are not completely tight on the handlebar. Just tight enough so they don’t move with normal riding forces but loose enough so they move in the event of a crash and thus won’t brake. Hydraulic brake levers are not cheap!
Frame Geometry setup.
On some bikes, there is the ability to change frame geometry, suspension setup and travel and even wheelbase length. Some very important aspects of frame geometry are head tube angle and bottom bracket height. The general rules are; the lower your bottom bracket height the more stable the bike will be at speed and through corners, and the slacker, or more raked out the head tube angle, the better the bike will handle at speed. Obviously, sometimes different types of courses require bikes and angles to be changed to suit, but generally it is best to find a comfortable setup that works for you and stick with it. Sometimes you can also change the amount of suspension travel the bike has front and the rear. Some smoother courses may only require shorter travel and courses with big bumps may need more travel. If the course requires you to maintain speed through flat turns and berms, it may be best to run with shorter travel to allow your bike to stay more firm and nimble to keep speed high. Wheelbase length relates directly to courses with high or low speed. A long wheelbase is best for fast wide open courses and shorter wheelbases are best for coursed with lots of tight turns and slower speed sections.
Some things can be a little more technical to set up on your bike but will greatly improve the performance of your bike.
Bikes of all shapes, sizes and weights require different suspension setup. Bikes with only front suspension (hardtails) rely heavily on the suspension that is inside the riders elbows and knees. Keeps these pivots (your joints) well oiled and use them as much as possible, they are priceless. Make sure that your front suspension is set up so that you can maximize the travel. Your pre-load, or pressure of the downward motion of the suspension should be set so under the riders weight and with a big, hard push down on the handlebars the forks, while riding, should use about 85% of the travel available. While riding downhill the forks should bottom-out slightly when you ride off a large drop or jump. This way you are maximizing the full travel of the suspension.
The rebound damping, or speed at which the suspension returns to its top position, is also very important. Make sure your forks are not rebounding so fast they top out. This can damage forks and be very off-putting and unstable while riding. As a guide, have your rebound adjusted so that if you compress your forks very quickly and pull up quickly while not on the bike, the rebound damping is set so the forks have some resistance in the rebound motion and the front wheel will momentarily bob off the ground.
For bikes having front and rear suspension, it’s important to have both fairly evenly balanced. Within reason, if you have 10 inches of rear wheel travel you won’t need 10 inches of front travel. 8 inches is fine..
The most important factor for rear suspension travel is rebound. Incorrectly set rear rebound adjustment will make your bike ride very awkwardly and can be dangerous. It is best to have you rebound adjusted relatively slowly. Again, if you were to compress the rear suspension quickly and then lift the bike quickly off the ground the rear wheel should stay off the ground momentarily. Less than half a second before returning to the ground. Most importantly, don’t allow the suspension to rebound at the same rate that it compresses.
Also important in the setup of rear suspension is air pressure.
NEVER RUN YOUR REAR SHOCK WITH NO AIR IN IT!!!
The manufacturer will have minimum and maximum air pressure limits for their suspension and it’s important to stay between these limits. You will damage your shock if you don’t, and always use a correctly fitting, specific suspension pump with a good pressure gauge on it. Never use a auto or tyre pump. For more in depth suspension setup, we highly recommend that you contact TeKin Suspension, in Melbourne.
Getting flat tyres is a pain! It can ruin the fun of a good ride, and can mean your entire race experience was wasted on one rock.
For downhill riding, always use a good quality two ply tyre. This will mean you can lower pressure in your tyres and are less likely to get flats. As a very general rule, tyre pressures should be between 18psi and 30psi. Basically, try to run your tyre as soft as you can without getting a flat. You won’t know what pressure this is without a bit of trial and error. After some time, you will learn what the best pressure is for different tracks. In general, for courses with lots of sharp rocks and objects you will hit hard, run your pressure harder. For smoother tracks you can run your tyre pressure.