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Setting Up Your Air Suspension Fork

Features covered: Air chamber, Damper & Rebound

Air Fork Settings

Setting up the suspension on your bike comes after learning what features your suspension products come with. We're going to run down the features of a Fox Factory 34 Step-Cast 120mm fork and explain the setup approach each feature offers. Many suspension forks offer similar features with slight to moderate variations of use and adjustability.

Suspension + Tuning = Traction

Air Chamber

The air chamber is located on the non-drive side of the bike. The cap twists off to allow access to the valve, but remains on the fork during use to prevent debris from getting into the valve. 
You need a shock pump to adjust the air pressure, and it's a good idea to study your fork before adding air because it has a maximum air pressure by design that you don't want to exceed. 

Some forks include a chart to help you visualize proportionate pressure values by rider weight. 

We recommend setting sag to achieve fork pressure starting point and adjusting from there.

The air chamber can also be adjusted by adding or subtracting volume spacers, affecting mid-stroke and bottom out performance. This is to be done after correct sag has been set. Air pressure provides support early in the stroke, and volume spacers provide more or less linearity in the air-spring rate later in the stroke. 

Forks are linear by nature, so volume spacers help 'ramp up' the air-spring rate as the fork compresses further into its travel.

The Damper

The damper is the most complicated component in the fork and is located on the drive side of the bike. Given the complexity of its operation, the damper is one of the best examples why suspension forks are priced where they are. 

Damper performance is usually what distinguishes forks from one to another in ways that can be discerned by riders with enough experience. The damper controls oil flow to actuate the suspension leg and provide favorable compression and rebound characteristics. 

The compression adjustment dial is located at the top of the fork, and the rebound adjustment dial is located at the bottom of the fork on the same leg.

The Fox Factory 34 Step-Cast 120 fork has Fox's Fit4 damper, which is incredibly simple to understand and adjust. The blue dial selects the compression mode (oil flow rate) that includes 'open' (highest flow rate), 'medium' (reduced flow rate), and 'firm' (completely restricted flow rate with bump threshold). 

The firm setting essentially locks-out the fork, but a threshold valve opens slightly to allow oil to flow upon big enough impact to prevent internal pressure damage to the small components in the damper. 

When you need the suspension to track changing terrain but prefer more pedaling platform, select the medium setting. If you don't mind additional suspension actuation while pedaling and want the plushest setting available, select the open setting. 

The black dial further adjusts the fork's compression performance during weight shifts, G-outs, and slow inputs when the blue dial is in 'open' mode.

The Rebound

At the bottom of the leg containing the damper is the rebound adjustment knob. Adjusting rebound makes an adjustment to the damper. The rebound controls the rate of speed that the fork extends out, or recovers, after a compression before another compression. Rebound allows the fork to keep up with the terrain that the wheel is tracking over. 

Rebound set too slow will cause the fork to pack-up and sit in the mid stroke during multiple compressions, leading to a feeling of harshness for the rider. Rebound set too fast will cause the fork to eject the wheel off the ground or cause a violently irregular oscillation that unsettles the rider.

Rebound will vary based on the terrain you are riding. 

Trails with a lot of small to medium impacts close together (rock gardens/tree roots/lumpy or chunky dirt) will usually ride better with faster rebound settings, and trails with big impacts further apart (drop offs, jumps, smooth dirt) will usually ride better with slower rebound settings. 

Flow trails are an example where running slower rebound will keep the bike settled in to the smoother transitions generally attributed to their design. 

Naturally 'busy' terrain with lots of compressions are an example where running faster rebound will keep the bike floating over the chaos of constantly changing features.

Featuring the Pivot Trail 429