/ Tips & Advice

How to maintain your motorcycle's suspension

All you need to know about oil, seals, preload, dampening, and more.

Martin Asuncion Martin Asuncion on Feb 19, 2021
Husqvarna Svartpilen 401 Suspension

For a lot of parts on the motorcycle, maintenance is relatively straightforward – replace your engine oil every few thousand kilometers, replace the battery when experiencing low voltage, among others. However, suspension maintenance is often overlooked and can be a bit difficult to dissect because of the many terminologies and components that can seem a bit alien to the casual rider. As such, we’ve put together a brief overview of how riders should think about suspension maintenance and adjustments. Here’s all you’ll need to know about motorcycle suspension maintenance for the day-to-day.

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Front fork

Husqvarna WP Apex Forks

The fork oil of your motorcycle is responsible for cushioning the upward and downward strokes of your front forks. Most often, front forks make use of a hydraulic fork oil system, and just like engine oil, fork oil has its own viscosity and weight specifications. Fork oil specs typically range from 2.5w to 30w, where higher numbers indicate heavier weights thus creating a stiffer suspension feel. In general, fork oil viscosity must follow the recommended specification of your manufacturer. Advanced riders may decide to customize their fork stiffness by using a different weight—lighter weights are generally better for city and highway riding, while heavier weights are better for more aggressive riding.

Fork seals are the rubber inserts found in between the inner and outer tubes of your motorcycle. They are responsible for keeping the fork oil fully separated from the elements, such as water and dirt. As such, fork seals typically come in sets of oil seals and dust seals, along with accessory o-rings depending on the motorcycle. Fork seals will need to be changed whenever the fork oil is changed for longevity and safety.

In general, fork oil and seals will need replacement every 10,000 to 20,000 kilometers, or when your fork oil starts leaking through the seals. Make sure to follow the recommended specification of the manufacturer for both items in order to achieve optimal performance for regular use.

Rear shock

Husqvarna WP Rear Shock

The rear shock of the motorcycle functions similarly to the front forks. Rear shocks can come in the form of a single mono-shock or a dual-shock system more typically found on older motorcycles. Maintenance for the rear shock is relatively simple—keep the shock clean from dirt using water and soap. Your rear shock will need servicing the moment it starts leaking. More advanced rear shocks can be rebuilt in the same way forks are serviced with oil and seal replacements, however, most regular shocks will require a full replacement. Make sure to use a shock that is designed for your motorcycle in order to maintain performance and safety.

Ride height

Husqvarna Svartpilen 401 Ride Height

Motorcycle ride height is typically adjusted to accommodate the height of the rider, or to provide a different riding characteristic, since altering ride height will inevitably alter suspension geometry as well.

Rear shocks are typically non-adjustable for height directly, however, some motorcycles have preload adjustments which will affect the sag of the motorcycle – the difference in seat height with and without a rider. Other motorcycles have shock linkage adjusters which can raise or lower the ride height to the rider’s liking. This would be the recommended method for height adjustment since linkages are typically engineered by the manufacturer and will not pose any safety risks caused by altering suspension geometry.

Front forks on the other hand are typically much easier to adjust for ride height. Simply loosen the bolts on the triple tree, raise or lower the forks accordingly, align the height of the forks, and tighten. A lowered fork for lower ride height will decrease the fork rake which will make the motorcycle easier to turn into corners—it will feel more agile. However, stability on rough terrain and higher speeds will be sacrificed. The opposite is true for raising the forks for a taller height.

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Preload adjustments

KTM 390 Duke Preload Adjustment

When your motorcycle goes over bumpy terrain, the weight of your motorcycle is pressed and loaded onto the suspension—this is the same concept when adjusting preload. When increasing preload, you’re tricking the suspension into thinking there is more weight being pressed upon the suspension, and the opposite is true for decreasing preload. Preload adjustment is typically adjusted in order to make the suspension feel stiffer, and more importantly to adjust ride height sag when tuning for rider weight.

Cases where adjusting preload for more practical purposes include adjusting for the additional weight of luggage or a pillion rider, and overall ride height. A softer preload will make the motorcycle sag lower, but can also make the bike feel more wallowy and unsure of itself. Stiffer preload will make the bike ride higher and will reduce sag, but can be a bit jumpy over uneven roads. Practical tips would be to first adjust your preload for the rider’s weight and desired seat height, then make adjustments accordingly for various terrain, riding styles, and additional weight.

Dampening adjustments

CFMoto 650 MT Dampening Adjuster

A suspension setup that can be adjusted for dampening typically includes rebound and compression adjustment. The engineering and mechanics behind adjusting these components are a bit technical. In simple terms, however, compression is experienced when hitting a bump and your suspension travel is decreased. Rebound is experienced after the compression stroke is finished, and your springs attempt to straighten out the suspension to return to the resting position.

Adjusting the rebound and compression of your suspension is a bit advanced and would typically need the input of an advanced rider, and the adjustment advice of a dealership service center or trained mechanic. As such, our advice would be to make sure that your rebound and compression are set up for the kind of ride you’re looking for. If your motorcycle has adjustable suspension for rebound and compression, visit your dealership service center or specialized mechanic, discuss your ideal riding experience, rider weight, accessory luggage, and other specifics for proper adjustment – and you’re good to go without any need for further adjustment until necessary.

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