Mountain Bike Suspension

How to get the most out of your forks and shocks!
Your mountain bike's suspension plays an outsized role in how your bike feels. Its sag, pressure, rebound, and compression will significantly affect the way it rides. Properly set up, even entry-level mountain bike suspension will lead to miles of smiles as your bike aids your pedalling, steering, turning, and hucking. Unfortunately, even top-tier bikes can't make up for poorly set-up suspension. So, do your performance, your safety, and your enjoyment a favor: spend a little time tuning your suspension to suit your weight and preferences.

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SAG

"Sag" is the distance of your suspension's stroke taken up by your weight while you sit on the bike in your normal riding position. Sag is measured without any impacts or other stimulus upon the suspension. Usually, forks and rear shocks will have a rubber o-ring around their stanchions to help you set sag. Standing beside your bike, place the o-rings against the top of the stroke. Now, carefully mount, then dismount, your bike. The distance your o-ring traveled AWAY from the top of the stroke denotes your current sag.

Rear Sag

Follow these quick steps to tune your rear sag:

  1. Make sure your rear shock is fully opened by adjusting its dial toward the (-).
  2. Have a friend hold your bike steady while you carefully climb on.
  3. Sit in place for a few seconds, and make sure your rear shock's o-ring is against the rubber wiper seal at the top (or bottom) of the stanchion.
  4. Dismount the bike without disturbing the o-ring.
  5. Measure the distance between the o-ring and the wiper seal. Divide this measurement by the total stroke of your shock, then multiply the quotient by 100 to determine your current sag percentage (e.g. 25mm distance on a 125mm shock. 25/125 = 0.2 x 100 = 20% sag).
  6. Consult your shock's specifications for ideal sag (usually around 30% for rear shocks), and incrementally adjust the air pressure in your shock to increase or decrease your sag.

Front Sag

Once your rear shock's sag is tuned, you will repeat the process for your fork:

  1. Fully open your suspension dampening by adjusting its dial toward the (-).
  2. Have a friend hold your bike steady while you carefully climb on.
  3. Sit in place for a few seconds, and make sure your fork's o-ring is against the rubber wiper seal at the bottom of the stanchion.
  4. Dismount the bike without disturbing the o-ring.
  5. Measure the distance between the o-ring and the wiper seal. Divide this measurement by the total stroke of your shock, then multiply the quotient by 100 to determine your current sag percentage (e.g. 25mm distance on a 125mm shock. 25/125 = 0.2 x 100 = 20% sag).
  6. Consult your fork's specifications for ideal sag (usually around 20% for forks), and incrementally adjust the air pressure in your shock to increase or decrease your sag.

Rebound

Rebound is the speed at which your suspension recovers from a hit. If your rebound is under-damped, usually denoted by the (-) on your damping control, your suspension will extend too fast and your bike will feel bouncy and out of control. If your rebound is over-damped (+), your suspension will not recover quickly enough after repeated hits and it will sink lower and lower into its travel. This is called "packing down," and it will result in temporary changes to your bike's geometry, poor performance, and potential damage to your suspension if it repeatedly bottoms-out.

Rear Rebound

Adjusting rebound is a bit more involved than adjusting sag, as your rebound will be at least partly determined by your personal preferences.

  1. Adjust your rear rebound by adding full damping to your shock by turning its dial toward (+).
  2. Choose a small drop to ride off slowly (e.g. a tall curb), and focus on how the shock springs back after the impact.
  3. Reduce your shock's rebound damping by turning its dial toward (-) by one click, then repeat the test. Feel how the shock starts to recover faster with each click?
  4. Once your shock recovers from your test drop so quickly it overshoots by a small amount, you've reached a good starting point for fine-tuning.
  5. Go ride a full section of familiar trail and see how it feels. Adjust your suspension by a click or two to either side of your base setting, and choose the setting that gives you the best control, grip, and feeling!

Front Rebound

Adjusting front rebound is a lot like adjusting the rear.

  1. Adjust your fork's rebound fully closed by turning its dial toward (+).
  2. Stand next to your bike and compress the fork with your body weight, then release it to let the fork bounce back.
  3. Open the rebound by turning your fork's dial toward (-) until the fork rebounds as quickly as possible without it causing the front wheel to jump from the ground. This is your starting point for fine-tuning.
  4. Go ride a full section of familiar trail and see how it feels. Adjust your suspension by a click or two to either side of your base setting, and choose the setting that gives you the best control, grip, and feeling!

Compression

In the same way you can adjust how your suspension dampens its rebound, you can also adjust how it dampens compression. Where rebound is your suspension's recovery stroke, compression is its impact stroke; it is the speed and characteristics of your shocks' movements during a hit or other forces' stimuli.

Low-Speed Compression Damping

Sometimes, even when you've successfully set up your sag and rebound, your bike still sinks deep into its travel during normal riding. If you're braking hard, cornering hard, or coming fast into quick rises, and you notice your bike suspension is sitting in its mid-stroke, then it's time to adjust your low-speed compression damping:

  1. Start with no low-speed compression damping added on your shock.
  2. Ride your test trail, focusing on how your suspension feels during bigger impacts.
  3. Repeat your test ride, adjusting your compression by turning the dial one click toward (+) with each repetition. Ideally, your suspension will still feel supportive in the middle of its stroke during rapid braking, corners, quick rises in terrain, and weight shifts.
  4. Repeat for your fork.

High-Speed Compression Damping

Other times, you might find your suspension bottoming-out even when you aren't subjecting it to especially large impacts. If this happens even when your sag and rebound are set up correctly, then it's time to adjust your high-speed compression damping (note: some shocks do not have adjustable high-speed compression):

  1. Start with no high-speed compression damping added on your shock.
  2. Ride your test trail, focusing on how your suspension feels during bigger impacts.
  3. Repeat your test ride, adjusting your compression by turning the dial one click toward (+) with each repetition. Ideally, your suspension will still feel supportive (i.e. not "dead") during the bottom of its stroke at the end of its maximum travel.
  4. Repeat for your fork.
As you make these adjustments, seek balance fore and aft. A fast front end will clash with a slow back end, and vice versa. Ultimately, suspension is designed to make your bike handle in a predictable way over harsh terrain--when in doubt, seek a feeling of balance.