At their core, shocks are simply about giving you comfort and helping you maintain control of your vehicle or mountain bike. They do this by controlling the way oil flows inside the shock. In this video we take a look inside a few types of FOX shocks and talk about how they work.
Having knowledge about how shocks work is integral to understanding why, when, and how to adjust them.
What’s the deal with damping and damping force?
In simple terms, damping is control of the shock and vehicle.
Technically speaking, damping restrains vibratory motion. It is a decrease in the amplitude and frequency of oscillations by dissipating energy from the system.
Damping force is how the oscillations (movements) of the shocks and vehicle are controlled. It is generated when oil flow is restricted by the main piston and the base valve. This restricting of the oil flow converts the kinetic energy of the moving shaft and main piston into thermal energy that is transferred through the oil and dissipated into the atmosphere.
Every single compression and rebound stroke involves energy being converted and dissipated. This conversion and subsequent dissipation of energy is what allows bumps and obstacles to be absorbed by the shocks instead of being translated directly to you.
Is there another way to explain oil displacement and how base valves control it?
Think of a ball being dropped into a full glass of water. When the ball contacts the surface of the water, water flows over the edges of the cup and onto the surface the cup is resting on. This is because the ball entering the cup consumes space previously occupied by the water and it pushes the water out of the way.
If you’re interested in learning more about oscillations and the need to control the motion of your vehicle via shocks, check out “Why You Need Shocks”.
Shocks function similarly. When the shock shaft enters the shock body, it consumes space that was previously held by the oil. This volume of oil that is displaced by the volume of the shaft does not pass through the main piston.
In order to control the displaced oil and utilize additional damping force, shocks use base valves. Base valves control how quickly this displaced oil moves out of the way of the shaft. If the displaced oil moves out of the way slower, the shaft moves slower. If the displaced oil moves out of the way faster, the shaft moves faster.
But which adjustment should I make to…?
We’re getting there. We promise. Like we said earlier, knowing how your shocks work will make it much easier to understand why, when, and how to adjust them.
In the meantime, go back and take a look at the segment in the video discussing low vs. high shaft speeds starting around 5:03. Because adjusters are usually described in terms of “low speed” and “high speed”, you’ll want to be able to understand how the movement of the shock shaft translates to practical experience:
- Grip 2 has high-speed and low-speed adjustments for both compression and rebound;
- X2 has high-speed and low-speed adjustments for both compression and rebound;
- DSC has a high-speed and low-speed adjustment for compression;
- QS3 adjusts low-speed compression and has a predetermined high-speed compression setting;
- iQS electronically adjusts low-speed compression and has a predetermined high-speed compression setting.
Low-speed shaft speed event examples:
- Front end of the vehicle or bike diving during braking;
- Back end of the vehicle squatting during acceleration;
- Shock and fork on a mountain bike bobbing (oscillating) during pedaling;
- Vehicle body rolling to the outside during a corner (ex: vehicle body rolling left while turning right);
- Slowly crawling over square edged obstacles like rocks.
High-speed shaft event examples:
- Landing a jump or drop, particularly on flatter ground;
- Blasting through whoops;
- Moving quickly through square-edged obstacles like rocks;
- Driving over a pothole in the road;
- Riding or driving through medium to large braking bumps at a higher speed.
Next time you’re riding or driving, see if you can identify which types of shaft movements your shocks are experiencing. This will prepare you for learning how to effectively adjust your shocks.
Like what you see? Check out all the FOX Academy videos for powered vehicles and mountain bikes here.