REFRESHER COURSE: MOUNTAIN BIKE SUSPENSION TUNING FOR DUMMIES
Get your bike's suspension dialed
SUSPENSION TUNING FOR DUMMIES
Have you ever looked at your suspension and asked yourself, “What do all these dials and doohickeys do?” If the answer is yes, this article is for you. And, even if you do have a basic understanding of how your suspension works, this article may still help. Follow along as we break down suspension tuning into easy-to-digest tidbits.
It’s important to always use sag as the starting point for suspension setup. Sag is simply the amount of suspension used when you place your body weight, including riding gear, on your bike. Long before you touch any of your hydraulic adjustments, you must first set your sag or spring rate.
The majority of mountain bike suspension components use an air chamber; however, it’s not uncommon to have a coil spring instead of air. On coil shocks or forks, the rider may need to swap out springs to achieve the correct amount of sag. In an air fork or air shock, riders use a shock pump to achieve the correct sag setting.
Whether air or coil, a shock should generally be set between 25- and 30-percent sag.
To set sag (on a common air shock), start by pushing the o-ring to the top of the stroke and then carefully sit on your bike. It’s best to have a friend help support you while doing this but it can be done while leaning against a wall with to help balance with all of your weight on the bike. Reach down and pull the O-ring up gainst the air can of the shock and gently slide off the bike without compressing the suspension. Where the O-ring lands is the amount of sag you have. Let’s say your bike has 100mm of travel. This means that 25 to 30mm of stroke should be used by your full body weight with gear on the bike. Finding sag with a coil shock requires a slightly different approach, but the basic principles are the same.
Next, move to your fork and set up its sag. Recommended fork sag varies from 15 to 20 percent. To measure sag in your fork, it’s often best to stand up out of the saddle and have a friend help support you. If you don’t have a friend around at the moment, try riding on a flat surface and doing your best to place your weight on the fork without bouncing. Again, use the O-ring to help measure sag. If the fork has 120mm of travel, then your sag should be between 18 and 24mm. If necessary, use a calculator to find the correct measurements for your amount of suspension travel.
Rebound is the setting that controls how fast or slow your suspension returns. It’s a critical component of your suspension that allows it to recover from hits. On the majority of suspension components, rebound is marked by a red dial that can be found at the bottom of the fork leg as well as on the shock body. Some higher-end suspension components have both high and low rebound settings; however, most suspension components only offer control over the low-speed rebound.
When setting rebound, it’s important to not just take a buddy’s settings and think they will work well for you, too. Changes in air pressure, suspension design or riding style will determine how your rebound should be set. If your rebound is set too fast, you’ll feel like you’re riding a pogo stick. Meanwhile, a setting that is too slow won’t allow the suspension to extend completely after hitting a bump, causing it to pack up and feel stiff.
When setting your rebound, keep in mind that less rebound damping (turning it counter clockwise) equals a faster return speed, while more rebound damping (turning it clockwise) will cause it to slow down. generally speaking, faster rebound (with less damping) is good for small, chattery bumps where the suspension needs to recover quickly to keep the tire planted to the ground. A slower rebound (with more damping) is going to cause the suspension to settle lower in its travel and offer a more predictable ride quality. A properly valved shock from the factory can achieve both. The idea is to find a happy medium with your external settings.
Finding Fork Rebound
Start adjusting the rebound of your fork by turning it to the fastest setting with minimal damping. While standing next to your bike, push down on the bars and watch the fork quickly return back to your hands and bounce the front tire off the ground. Continue to add damping to your fork to slow down its rebound so that the front wheel no longer bounces off the ground.
Setting Shock Rebound
Now that you’ve dialed in your fork, move back to your shock. The shock’s rebound needs to be set quick enough so that the suspension has time to recover, but not so fast that it kicks the rear end of the bike around. It’s often safer to start with a slower setting and remove damping if you feel your shock is sitting too low in its travel, causing it to become stiff.
Compression adjustments are often blue dials or levers at the top of your fork and on your shock body. Compression levers can be referred to as lock-outs or pedal switches. These types of compression adjustments quickly firm up the suspension in order to reduce movement during pedaling. Other forms of compression adjustments, such as high-speed compression, are used to fine tune suspension. When talking about high-speed compression, it’s important to note that it’s referring to high shock shaft speeds and not high riding speeds. High-speed compression adjustments deal with things like braking bumps or square edge hits and big impacts that cause the shaft to move quickly. By adding compression, riders can firm up the suspension to stay higher in its travel and offer a more supported ride. Less compression offers a plusher or softer suspension feel.
Another popular way to adjust suspension settings is to add or remove air-volume spacers or tokens. A rider might do this to make the fork or shock more progressive or more linear. A progressive suspension component will better resist bottom out by becoming more firm towards the bottom of the stroke. A linear rate will create an equal amount of force throughout the travel.
Air forks and shocks are progressive by nature; however, some riders find the added resistance during bottom-out is helpful for harsh hits. On the other hand, lightweight riders or mellower ones who are having trouble reaching full travel, even with the correct amount of sag, may find it helpful to remove spacers in order to reach the bottom. Keep in mind that once a volume spacer is added or removed, this whole process reverts back to setting sag again.
The End Result
A bike can only perform as well as it’s set up to. You might have a $10,000 bike, but with a poor setup, you won’t get close to the performance your bike is capable of. The same is true with an inexpensive bike. So, if you truly want to get the most out of your steed, you would be wise to spend quality time getting to know how its suspension adjustments work.