Transparent Ohlins shock shows cavitation in action and reveals the importance of IFP

If you are an experienced mountain biker and enjoy changing your suspension settingsYou’ve probably come across the term cavitation. So what does this mean and why do suspension manufacturers go to such lengths to prevent this from happening? Thanks to a new and ingenious transparent shock manufactured by Ohlins USA, it’s easy to see how cavitation occurs and why it has such a negative impact on suspension performance.

The Ohlins team based their transparent shock absorber on a motorcycle unit, but the design, construction and effects are basically the same as what you’d find in a modern mountain bike shock absorber. It uses standard shock internals housed in a Perspex body, which is then mounted on a shock dyno used to replicate the forces encountered when hitting a bump or making a jump.

In the video you can see the main piston moving up and down inside the shock body, pushing oil through the valve. You can also see the volume of damping fluid fluctuating in the far reservoir on the right, regulated by what is known as the Internal Floating Piston. As the name suggests, this is a floating piston pressurized by a gas (usually nitrogen) inside the tread. The gas can be compressed, causing the liquid volume to change under pressure, so air cannot enter the damping circuit.

Fox Float X is in shock. IFP is in remote reservoir

When the technician releases the air pressure in the IFP, turbulence immediately begins to occur in the damping fluid and small bubbles begin to form within the main piston. This makes damping performance inconsistent and unpredictable. Adjusting the IFP pressure (10 bar in this case) will also have an effect on the damping curve; higher pressures increase the spring pressure of the system and make it harder to initially compress the shock. Of course, a lower IFP pressure runs the risk of allowing cavitation. Suspension has several solutions to help solve this; one of these is the RockShox Countermeasure, which is a negative coil spring that puts pressure on the IFP.

Another takeaway from this video is that there’s a lot going on inside your shock. Such action for a year or more will inevitably cause wear and tear on the seals and damping fluid; because, get your suspension serviced regularly.