Rebound & Compression: What's What in MTB Suspension

Modern suspension components for mountain bikes feature numerous external adjustment options and offer you the possibility to adjust your suspension precisely to your personal preferences, your riding style, the route or the weather. The first step toward finding the right setup is to know the different options and understand how they impact your bike. Not every suspension fork or every shock offers every adjustment option. It is best to first check what applies to your chassis before you start setting up your MTB!

From Suspension Stiffness to Volume Spacers: The Adjustment Parameters 

How Do You Determine the Right Suspension Stiffness and Find the Optimal Sag?

Suspension stiffness – or "spring rate" in physical terms – describes the ratio of a force acting on the spring to its deflection. In other words: how far does a spring compress when you load it with a certain force? The suspension stiffness is the most important adjustment parameter of every suspension component. It has a direct effect on the driving dynamics and an indirect effect on all other setting options. The suspension stiffness is used to set the sag, which is so important for riding dynamics, i.e. how far your suspension component compresses due to your body weight plus equipment. The correct sag ensures that the suspension works optimally in both directions, i.e. can compress and rebound. Rebound is important to keep your tyres in contact with the ground, even on potholes in the trail. Depending on the area of use and the available suspension travel, you usually choose a sag of 15 to 30 percent. The more travel you have, the greater the sag values usually become. For full-suspension bikes, make sure that the amount of sag on the fork and shock do not differ dramatically. This easily leads to a front- or rear-heavy riding behaviour.

With an air suspension, you simply adjust the stiffness via the air pressure. In any case, use a special suspension fork or shock pump. Steel or titanium coils allow you to install springs of varying hardnesses – depending on your weight. Don't forget to consider the weight of your equipment, such as clothing, shoes or backpack. You can also preload the suspension to a certain extent. However, you should know that a higher preload is not the same as a harder suspension. Too much preload can have a negative effect on the response, which is why we advise against using preload to adjust the suspension stiffness.

If your fork has an external travel setting, make this and all other adjustments in the extended position.

Tip: Manufacturers such as Fox Racing Shox or RockShox provide setup tips for their suspension forks. Often they stand directly on the dip tubes of your fork. This is not possible with shocks because of the different gear ratios on different rear triangle designs.

Perfect Grip Thanks to High-Speed and Low-Speed Compression

The compression stage is the opposite of the rebound stage, namely the load on pressure. This setting allows you to control the compression of your suspension component(s) on the MTB. The higher the compression damping, the slower the suspension component compresses, both when pressure is applied from above (for example, in the saddle) and when riding over bumps. Less compression damping means an active chassis, but it can also feel jumpy. More compression damping reduces the sensitivity of the spring component, but provides more counterpressure.

A special feature of a compression damper is a platform damper, which is in addition to or instead of a fine-grid adjustment. Usually a platform damper has a few, strongly differing stages, e.g. "Open - Pedal - Lock" by Rock Shox or the "Climb Switch" by Fox or Cane Creek. Unlike a real lockout, the closed mode here also does not completely block the oil flow in the damper.

As with rebound, particularly high-quality suspension components also differentiate between high- and low-speed compression and thus allow your MTB suspension system to be finely adapted. A stronger low-speed compression damping with less high-speed would, for example, ensure that the suspension does not sag on smaller impacts, but immediately releases the necessary suspension travel on larger impacts. Unlike rebound, compression damping has a relationship between the speed of suspension movement and the low- or high-speed setting. Low-speed compression dampens the compression against slow movements such as pedalling while standing or pedal input. High-speed compression is responsible for the fast strokes that mean high piston or shaft speeds.

Tip: Closing the compression damping almost completely on a mountain bike uphill is fairly common, but often inefficient and uncomfortable. As soon as you leave the smooth-as-a-baby's-bottom asphalt, an active chassis that ensures that the tyres follow bumps and do not lose contact with the ground is usually the most energy-saving and best solution – especially for uphill riding.