Glossary

Sag

How much your suspension compresses under your body weight when in a neutral riding position on the bike.

Damper

The part of the suspension that controls the suspension's behaviour through the restriction of the flow of oil through a set of valves.

Compression damping

How much your suspension resists being compressed. High compression damping means your suspension will compress slower; low compression damping means it will compress faster.

Rebound damping

How quickly your suspension will extend back to its neutral position after being compressed.High rebound damping means the suspension will rebound slowly; low rebound damping means it will rebound quickly.

Bottom out

Using the full travel of your suspension and hitting the bumper at the end of the suspension stroke. Some RockShox suspension has adjustable bumper heights that change the bottom out feeling and progression.

Suspension packing

Suspension packing occurs when the suspension doesn't have enough time (or has too much rebound damping) to recover in between subsequent hits/compressions, resulting in the suspension sitting lower in its travel and/or the suspension feeling more firm.

Air spring

A chamber of compressed air that acts as the spring in your suspension. Air spring suspension has become the more common suspension type found on mountain bikes. Air springs are known for adjustability, weight savings, and their progressive feel.

Coil spring

Traditional steel spring used in some suspensions. Coil springs are known for durability, small bump sensitivity, and linear progression.

Spring rate

The stiffness of a spring, measured in pounds per inch, or how many pounds of force it will take to compress the spring one inch.

Preload

When using a coil spring, the amount of load or amount the spring is compressed with no weight on the bike. Changing the preload will have effects on the initial compression force needed at the top of the suspension stroke, and will allow you to fine tune the sag.

High speed circuit

The set of valves in your damper that are engaged when the suspension is moving quickly through its travel. The high speed circuit is engaged when your suspension is compressed the most on bigger hits like drops, flat landings, and square edge rocks.

Low speed circuit

The set of valves in your damper that are engaged when the suspension moves slowly through its travel. The low speed circuit will control the suspension during cornering, compressions, braking, and generally moving your body around on your bike, as well as smaller terrain impacts like roots and small rocks at slower speeds (smacking a root going Mach 1 will be the high speed circuit's job).

Adjusting your suspension

Most suspension/bike manufacturers have some sort of suspension setup guide like the RockShox TrailHead App or Fox Tech Help Center, or will print a handy little chart right on your fork for quick reference. It's important to note that the values suggested by any of the setup guides are just starting points and shouldn't be taken as gospel. It's at this point that you should think about where and how you're going to be riding your bike. A cross country race bike ridden on flat ground will sacrifice some small bump compliance in favour of efficiency, and an enduro rig set up to chase KOMs in the burliest terrain will want to use as much of its travel as possible to provide as smooth a ride as possible.

Sag

As stated earlier, sag is how much your suspension compresses under your body weight when in a neutral riding position on the bike. Sag is measured as a percentage of the total suspension stroke. As a starting point, weigh yourself with all your riding gear on and plug the weight into the relevant sag chart. Using a shock pump*, fill up your suspension to the suggested value. If you can't find a sag chart for your suspension, use your weight in kg for the starting psi for your fork, and your weight in pounds for the psi in your rear shock.

Now it's time to check our work:

1. On a flat surface using a tree, wall, work bench, or other solid structure for balance, stand on your bike in a neutral riding position. Make sure you have both your suspensions "open" and not in climb/firm mode.
2. Bounce on the suspension a couple of times to ensure you've overcome any seal stiction.
3. This part is easier with a friend: reach down and push the O-ring on the suspension all the way against the seal without bumping the suspension. To avoid the awkward reach, having a friend move the O-ring is suggested.
4. As gently as you can, get off the bike while moving the O-ring as little as possible.
5. Get out a ruler if needed to measure the distance between the O-ring and seal. Divide that number by the travel and multiply by 100 to get your sag percentage. RockShox conveniently prints the sag measurements right on their suspension.
6. Add or remove air as needed in 5 psi increments until you get to your desired sag.

As a general rule of thumb, you're aiming for 15-25% sag in your fork and 25-30% sag in your rear shock, though this varies by manufacturer. We always recommend erring on the side of having slightly less sag in your fork compared to your shock as more of your weight is over the shock when descending, where sag really matters.

A properly set sag will allow your suspension to extend into any small holes and crevices, have enough support to keep you from bottoming out on every rock and root, and have enough small bump compliance to keep you from rattling your fillings loose. This is where a little bit of personal preference and terrain knowledge will come in. If you know you only ride high speed roots, you may want to run more sag for more small bump compliance. If you're planning on hitting 40-foot booters as a chill after work ride, then less sag will provide more support on harder landings.

Setting the sag on a coil shock is pretty much the same as air, with the caveat that you should put your information into a spring rate calculator from your shock manufacturer's website and ensure you have the correct spring rate.

*A tire pump typically moves too much volume to get the exact pressure that you want, and very rarely will be able to handle the high pressures needed for rear shocks.

Rebound damping

Rebound damping will control how fast your suspension will bounce back after compressing. Most suspension will only have low speed rebound control, with higher end dampers having a separate control for high speed rebound. Rebound will typically be adjusted by the red knob on your fork lowers or rear shock. Manufacturers will give you a recommended rebound in the form of number of clicks from fully closed (all the way to the turtle on RockShox, all the way to the + on Fox). Now that we have a starting position, let's check our work:

• Hop on your bike and ride slowly around your driveway/in a parking lot. Compress the suspension a few times. If it feels like you're getting bucked one way or another, your damping is too low. If your suspension isn't fully rebounding between bounces, your damping is too high.
• Grab your phone and find a nice curb. Set up your phone on its slow motion video mode with a side-on angle of the curb and a good view of your suspension. Now ride off the curb at a gentle pace. Your suspension should extend to meet the curb, compress to absorb the impact slightly past your sag point, and return to sag. If your suspension doesn't move past the sag point, open up the rebound a click or two. If your suspension bounces around the sag point a couple of times before settling into its sag, then slow down your rebound by a click or two.

Compression damping

Compression damping is the most subjective/personalized variable on your suspension. There's no simple test or method you can do to dial in your compression; it's all based on how your bike feels on trail.

Compression damping will control how quickly your suspension will be able to compress, and like rebound, is split into high speed and low speed compression. Similar to rebound, low speed compression is how your suspension will respond to rider inputs like braking, pumping, and cornering, as well as terrain impacts at slow speeds. High speed compression controls how your suspension responds to large terrain features and big impacts.

It's easiest to think of compression as a spectrum of trade-offs: at the end with high compression damping, your bike will feel supportive and efficient, especially while pedalling, but will also feel stiff and unable to track the ground, bouncing off terrain instead of absorbing it. On the other end of the spectrum, low compression damping will make your bike feel supple and comfortable on trail, but can feel like it's diving while braking.

Finding the right compression setting is finding the right trade-off between having your suspension support you when braking and cornering, and smoothing out the trail with small bump compliance. This will depend on your riding style, the terrain you ride, and personal preference. An easy way to break this down is to do some bracketing.

Bracketing

Photography nerds will already be familiar with this concept: if you're taking a photo of a scene that has a really bright part like the sky midday, and something darker like a person sitting in the shade of a tree, cameras will have a hard time capturing both the bright and dark parts. The solution is to take multiple photos, one where the sky is exposed correctly, one where the subject is exposed correctly, and one where the shadowy parts are exposed correctly. You can then take all the parts that are correctly exposed from each image and combine them.

Bracketing your suspension is the same in a way. Find a trail or section of trail that has features that you ride most often or want your suspension to perform the best on. Bring some materials:

• Your shock pump
• A ruler (if needed)
• A way to record your suspension settings (your notes app on your phone will w