Understanding dirt bike suspension terminology

Dirt bike suspension is tricky business, and it's one thing to understand how it works, and it's a totally different thing understanding the terminology. 

In this guide, we cover common dirt bike suspension terminology so you can wrap your head around motocross bike set-up.

Static sag: Static sag is the amount your off-road bike compresses under its own weight. Sag is seat via the rear suspension.

Suspension travel: Travel relates to how much suspension is 'available'.

Race sag: Race sag, which can also sometimes be referred to as rear ride height, is the amount your motocross or enduro compresses with you seated on it.

Rebound damping: When your suspension compresses, it needs to return to its initial starting point. This is called rebound. A fast rebound may see your dirt bike kick up over braking and acceleration bumps, while a slow rebound may not allow the suspension to return far enough in time for the next bump or obstacle, causing it to bottom out.

High-speed compression: High-speed compression relates to how fast the suspension moves, not the motorcycle. You can adjust the rate of the high-speed compression for different conditions and how the suspension is reacting.

Low-speed compression: Low-speed compression is the same as high-speed compression in that it relates to how fast or slow the suspension moves. Low-speed compression changes the flow of oil, and comes into effect on more mellow obstacles or impacts.

Preload: Preload is what it sounds like - the load before the load. More preload generally means the suspension will have less compression when a rider's weight is added.

Headshake: Headshake is when the front-end is somewhat uncontrollable and the handlebars will 'shake' from side to side. This generally happens at speed and over braking bumps, and is usually a result of poor suspension setup.

Plush: Plush is a word to describe a comfortable suspension set-up that handles impacts with ease and doesn't send any harsh forces through the bike.

Harsh: Harsh is the opposite to plush in that the suspension set-up is generally not comfortable, and hard impacts can be felt rather than the suspension soaking it up.

Linkage: The linkage is the link arm that connects the rear shock to the frame, allowing it to pivot.

Air fork: An air fork is the latest in fork technology and used by many manufacturers, with Showa, KYB, and WP all offering air fork variations. Most air forks contain compressed air in favour of a spring in just one of the two forks.

Spring fork: A spring fork is a traditional motocross fork that is still used as standard on many motocross and enduro bikes. 

Bottoming out: Bottoming out means the suspension has used all of the travel available, and as a result, has bottomed out.

Fork leg height: Fork leg height is how far the fork has been pushed through the triple clamps.

Spring rate: Spring rate relates to the stiffness of the shock spring in the fork spring.