How to choose your suspension oil?

MTB suspensions are highly technical components that are put under great strain in the field. Regular maintenance of your suspensions is essential to guarantee their proper functioning over time. This upkeep helps preserve not only your comfort and safety, but also your riding feel.

Choosing the right suspension oil is a mandatory first step to ensure the maintenance of your fork and shock absorber. This oil, which you will use in particular to drain the hydraulics of your suspension, must comply with the manufacturer's recommendations.

Why replace your MTB suspension oil regularly?

Suspension oil is essential for the proper functioning of MTB forks and shock absorbers. It must be renewed regularly to maintain a consistent level of performance.

The role of oil in the operation of MTB suspensions

It is important to understand that the operation of forks and shock absorbers on mountain bikes relies on 2 main elements: a spring a(pneumatic or coil) and a damping system b(hydraulic). The role of the damping system is to control and compensate for the action of the spring, so that the bike does not bounce with every contact with the ground.

The damping of an MTB suspension is always managed by a hydraulic system. A fork uses an open or closed cartridge (right side in general). For a rear suspension, the hydraulic system is integrated into the body of the shock absorber or partially offset in a reservoir (piggy-back). The hydraulic shock absorber works through the circulation of oil through a piston. This fluid is called damping oil or working oil. With continued use, this fluid will wear out and lose its qualities, ultimately affecting the performance of the suspension.

MTB suspensions also need a lubrication oil to facilitate the sliding movement. This lubrication oil is present inside the lowers (fork) and inside the air chamber (shock absorber). This oil helps protect the various components from wear (stanchions, seals…).

Draining the suspension oil

Suspension oil plays a fundamental role in the proper functioning of your shock absorber or MTB fork. A quality oil allows you to exploit the full potential of your suspension and preserve its original sensitivity. Conversely, worn oil weakens the suspension's hold during the compression/rebound phase and compromises the precision of the adjustments.

In the case of a fork, if you do not take care to clean the stanchions and regularly replace the lubrication oil, the lowers risk drying out and accumulating dirt inside. These deposits can scratch, or even grind down the stanchions and cause leaks. Similarly for a shock absorber, the lubrication oil and seals must be renewed regularly.

A complete suspension service includes cleaning the parts, draining the lubrication oil, renewing the seal kit and bleeding the hydraulic damping system.

Respecting maintenance intervals is all the more important for high-end MTB suspensions, as they use advanced technologies and components that are very sensitive to wear. The cost of a repair resulting from neglected maintenance is considerably higher.

To avoid reaching that point, we strongly advise you to strictly follow the manufacturers' recommendations regarding the maintenance frequency of MTB forks and shock absorbers.

You can also let our MTB fork maintenance advice guide you, or contact our technical advisors.

MTB fork and shock absorber oil: how often should you change it?

Instructions vary from one manufacturer to another. Please note that intensive use in harsh conditions (dust, moisture, mud) encourages dirt to penetrate your suspensions. Depending on the intensity of your riding, you may consider shortening or extending the intervals between maintenance operations.

It seems worthwhile to adopt the following schedule for the general maintenance of your fork:

Probikeshop tip: A full service including the hydraulic oil change is a fairly involved operation. We recommend entrusting it to a professional.

MTB suspension oil: which viscosity to choose?

MTB suspension oil is classified according to its viscosity. You will find the following values: 2.5WT / 3WT / 4WT / 5WT / 7WT / 7.5WT / 10WT / 15WT / 20WT / 30WT.

If the viscosity grade is low, the oil is fluid and your damping system is more sensitive to the terrain. An oil with a higher grade is thicker: it corresponds to damping that is harder to activate. If you are an experienced Enduro/DH rider, a high viscosity level seems better suited. Conversely, a low-viscosity oil is more suitable if you ride more occasionally for leisure and prioritise comfort and sensitivity.

You can adapt the type of oil to your riding style and discipline, but it is above all preferable to follow the manufacturer's recommendations. Please note that any modification not recommended by the manufacturer will void the warranty.

Listed in your service manual and available on the manufacturer's website, the type of oil compatible with your suspension model is easy to find. Brands may specify the volumes required for each operation (right/left lower bleed, hydraulic drain).