How to set up a suspension fork - video

Air pressure, sag and damping adjustments explained

Most suspension forks will have a set of dials that allow you to adjust how they work.

Getting these settings correct is essential to maintaining your fork's performance and ensuring you have the most comfortable ride possible.

Suspension fork controls

There are three main controls you’ll see on mountain bike suspension: preload, rebound, and compression, which is sometimes split into low-speed and high-speed compression on high-end forks.

Preload

Preload is the resistance the fork gives against your weight. So the heavier you are, the more preload you’ll need. For a fork with a coil spring, this would equate to having a stiffer spring, but for an air fork it’s simply a case of pumping in more pressure.  

Compression damping

Compression damping comes from the internals of the fork and works by regulating the flow of oil through small holes. Compression damping only affects the fork when it is compressing – this doesn’t affect the preload but can appear to have a similar effect on the fork.

The more compression damping you dial in (+) the slower the fork will move through its travel – this is good if you want a bike to pedal without bobbing for instance, but the negative effect will be the limitation of the fork’s movement when you hit a bump, making it feel a bit like it’s locked out. In fact a fork’s lockout is simply an extremely high amount of compression damping.

Rebound damping

Rebound damping is a similar internal system to compression and only affects the fork when it is returning to its natural position after an impact.

The more rebound damping you dial in (+) the slower the fork will return to its natural position after an impact. A slower return, or more rebound compression is required if the bike feels as though it’s trying to buck you off, especially after corners or when you land a jump – but if repeated hits are causing the fork to feel like it’s ‘packing down’ and not returning to it’s natural position, you’ll need less damping.

CTD/lockout

Your suspension might feature settings that are designed to give it a different ride characteristic. Lockout is the most common of these, and when activated it will use the compression damping system to effectively stop the fork from working. Lockout is useful when you encounter prolonged climbs.

CTD (climb, trail, descend) is a slightly more advanced form of lockout that gives a ‘tune’ that’s better suited to the type of terrain you are riding on. CTD is a Fox term, but other manufactures have similar systems.

A climb mode would pretty much act as a lockout, although typically will allow more movement; trail or ride mode is a slightly stiffened setting to allow movement, but with some resistance in order to give a good pedaling platform with a stiffer compression setting; descent means the suspension is fully active and would offer little compression damping during use.

How to adjust a suspension fork

In the video below, BikeRadar's James Tennant shows you how to set up and tune your front suspension. Knowing how to get air into your fork and exactly how much you need is vital.

Video: How to set up a suspension fork.

This video is part of the Park Tool Maintenance Monday series. You can purchase the Park Tools used in the video at a number of dealers across the UK and internationally. For more maintenance videos, subscribe to the BikeRadar YouTube channel.

Tools for the job

  • Shock pump
  • Ruler
  • Full set of riding gear

It’s important to have your full riding kit to hand – as the weight of what you wear will need to be factored into the ‘rider weight’ and the suspension sag will need to be set accordingly. So it might be a good idea to make adjustments just before you ride, and take the shock pump with you so you can make further adjustments.

Set preload sag

It’s a good idea to have someone to help, but it’s possible to set sag yourself by leaning against a wall or solid object.  

Start by measuring the stanchion of the fork, the shiny bit that moves inside the larger leg. Divide that length by four to calculate a 25 percent sag distance. Some more aggressive forks, such as those found on downhill bikes, can be set with up to 30 percent sag, but if you’re not sure, use 25 percent.

Get on the bike and assume the riding position. Most forks will have a small rubber ring on one of the legs which will allow you to see the amount of sag – if yours hasn’t, you can tie a rubber band around the leg.

Don’t be tempted to use a cable tie and don’t leave the rubber on the stanchion, as the it collects dirt, which can damage the stanchion.

Get on the bike and try not to bounce it as you mount it – you’re looking for a standing weight. Slowly get off the bike and measure the amount of sag.

Adjust the air pressure or preload dial and try again until the desired 25 percent is achieved. If you have an air fork, take it up or down by 10psi at a time, or for coil forks, a full turn at a time should give the right increments.

It’s worth noting that for coil-sprung forks, you might need a heavier or lighter spring depending on your weight – these should be available from any good bike shop.

Compression and rebound

Start by working out how many ‘clicks’ of adjustment you have with the compression and rebound – to do this, wind the dial in clockwise, then wind it back out. As you wind it out, count the clicks.

If you aren’t sure what you need, or have a new fork set the dials to the middle. You can then experiment by one or two clicks at a time until the desired setup is achieved.

Different trails and terrain will have difference setup requirements. So it’s a good idea to get a feel for what the dials are actually doing in terms of suspension action, so you can fine tune to your own preference.

Also, be aware that it’s quite rare that taking either compression or rebound to the extremes will have much benefit, so as a rule of thumb it’s usually better to stay near the centre of the available range.

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