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Your mountain bike can only perform as well as its suspension set up. When you know how your bike’s suspension adjustments work, and how to change them to suit you and the terrain, your riding will be more fun and safer too.  

The suspension adjustments on a mountain bike are:

  1. Sag  
  2. Rebound 
  3. Compression 
  4. Volume spacers 

1. Sag

mountain bike Sag adjustment ring on a rockshox zeb

Sag is the starting point for your suspension set up. It's defined by how much your suspension sinks when you have your full weight on the bike. To measure sag push the rubber O-ring against the top of the shock (or shocks if your bike has dual suspension), then sit in the saddle and slowly lift your feet until they are floating, all without bouncing – it’s good to use a handy friend to steady you. Get off your bike and measure the distance between where the O-ring ends up and the dust wiper on the shock – that's your sag. 

Sag on your rear shock should be no more than 25-30% of the full amount of suspension travel. Front fork sag is generally less at 15-20%. So if the fork has 120mm of travel, your sag should be between 18 and 24mm. 

To adjust sag on air springs you’ll need a shock pump. With coil shocks or forks, you might need to change the springs to achieve the correct amount of sag.

2. Rebound 

detail of rebound adjustment on a fox mountain bike fork

Rebound is the setting that controls how fast or slow your suspension recovers from a hit. Your rebound adjustment is usually a red dial at the bottom of the fork leg and rear shock body. Some higher-end suspension components have high and low speed rebound settings. 

If your rebound is set too fast, you’ll feel like you’re riding a pogo stick. On the other hand, a rebound setting that is too slow won’t allow the suspension to recover and will feel stiff. 

A faster rebound – that means less damping - is good for small, chattery bumps where the suspension needs to recover quickly to keep the tyre on the ground. A slower rebound - with more damping – will cause the suspension to settle lower in its travel and offer a more predictable ride. The idea is to find a happy medium for the terrain you’re riding on. 

Adjusting Fork Rebound 

Start by turning the rebound dial to the fastest setting with least damping. While standing next to your bike, push down on the bars then release your hands and watch the front tyre bounce up off the ground. Continue to add more damping until the front wheel no longer leaves the ground.  

IMPORTANT: Your fork should always have a faster rebound setting than your shock to keep you from being pitched over the handlebars on hits to the front wheel. 

Adjusting Rear Shock Rebound 

Having adjusted your fork, it’s time for the rear 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 safer to start with a slower setting and then gradually remove damping if you think your shock is sitting too low in its travel and feels stiff. 

3. Compression

detail of Compression adjustment on mountain bike suspension

Most forks have high-speed compression adjustment to firm up the fork - typically the blue dials or levers at the top of the fork and shock body. Compression levers are also known as lock-outs or pedal switches. Low-speed compression is seen on higher end forks and is used to fine-tune their feel. Note: speed in this context refers to the speed the suspension moves at, not how fast the bike is going.

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. 


4. Volume Spacers 

Mountain bike front fork volume spacers

There’s another adjustment available to you, if you have air suspension. It can be adjusted by adding or reducing the number of volume spacers inside the air chamber. In the image above green spacers are being dropped into the fork.

More spacers will add progression, providing better resistance to bottoming out on hard hits. Reducing the number of spacers makes it easier to use full travel. Given the same bike a heavier rider might want to add spacers and a lighter one might need to remove them to give better suspension compliance over rough terrain. 


So that’s your introduction to suspension settings. Getting it dialed in is a process of trying out little differences and seeing what feels best to you for where you’re riding. Running a suspension log that records your sag, rebound and compression settings can be really handy when you want to return to a setting you liked for a particular trail. 

By the way, it pays to take care of your suspension. It’ll perform better and last a lot longer if it’s serviced at least once a year (more frequently if you ride a lot) and gentled cleaned with a soft microfibre cloth after every ride. Never use a pressure washer on suspension as dirt can get forced into the seals. 

Any questions? Just drop into our bike shops in Queenstown and Wanaka or give us a call. Everyone here is a super keen rider and we love helping other riders out. 


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