How to Adjust the Suspension on a Mountain Bike

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Your mobility and sense of adventure are dramatically increased when you have the mobility and the equipment to get out and explore the world. Mountain bikes are the scratch for your exploration itch but you had better understand how to adjust the suspension or that mountain trail can be pretty painful.

The suspension on your mountain bike determines how efficient your bike will be out there on the trail and you adjust it by first determining and then altering your rate of Sag, Compression, and Rebound.

All three of these are important factors and you want them defaulted to the degree in which it suits your own weight distribution. Once you have the system sagging, compressing, and rebounding based on your own weight, you can fine-tune adjustments accordingly, if that’s something that you want to do. 

Adjusting the Sag

Sag is an obvious term because it is measured by the degree that your bike “sags” or drops in terms of how far your fork travels downward when you sit down on the mountain bike. 

The lower your sag percentage, the more your bike will feel like metal sitting on metal. It equates to a rougher ride while the higher sag percentage means more bounce and give and take in the suspension.

Make sure that all of your adjuster knobs are wide open and use a shock pump to pump up the fork. Make sure you wear everything that you normally would on a bike ride and sit down on the seat. Balance and pick your feet up to apply your whole weight.

You’re going to pay special attention to the O-ring on the fork. Some models have the measuring lines stamped directly on the stanchion, but most will need to be measured by hand. Simply measure how far down the O-ring travels. 

To determine your sag, divide the number that you measured by the length of your shock and then multiply that number by 100. You want to reach something between 25% and 30%.

If your percentage is too high, you need more air. If it’s too low, take some air out. 

Adjusting the Rebound

There’s usually an adjustment knob for this, on mountain bikes that were designed so that rebound can be adjusted. However, most manufacturers have the high-speed rebound set at a default position and it cannot be altered.

Rebound suspension is mostly related to good traction control and maintaining control of the bike as you churn your way through a bumpy trail. You don’t want it to be set too high, because you’ll bounce too much when you go over small rocks or branches.

You want to find that happy medium because setting it too low won’t allow your suspension to recover after each rebound before it is compressed again. The rebound suspension control is located on the fork. 

Adjusting the Compression

As with rebound, you have low-speed compression and high-speed compression. Low-speed compression controls how quickly your fork travels up and down when your bike hits obstacles and experiences an impact force. 

High-speed compression is how quickly your suspension compresses during an impact force, not necessarily how fast it travels. 

Whether or not you can control the adjustments where compression is concerned, depends on the bike and whether or not the manufacturer made that level of control available on your bike. 

Some newer, premium mountain bikes have what is called a “preload” adjustment for changing how the compression factor works to a degree. As far as having a precise level of control over the compression levels on your mountain bike, there’s not much to offer. 

If you want a 100% customized level of precise control over your suspension system—outside of what’s mentioned here—you’re going to have to learn physics to a larger degree than usual. 

The best way to make the adjustments that you can is to get it out on the trail and continually fine-tune your available controls until you get exactly what you want. 

Final Thoughts

Not all mountain bikes have the level of controls that are mentioned here. Some may not even allow you to fine-tune your sag adjustments. However, if you’re heavy into mountain bikes, you probably already know that and know exactly what bikes to get that offer that level of control. 

Suspension is an important factor out on the trail, or wherever you decide to take your mountain bike next. So be sure to fine-tune it and get the most out of every journey. 

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Paul Tuthill
Growing up in Scotland, Paul developed a love for the outdoors and a desire for adventure from an early age.