Squat. Wallowing. Damping. What does it all mean? Sometimes the biggest disconnect between riders and tuners is a simple understanding of terminology. Below are suspension terms that riders will hear when talking with a suspension tuner.
- AIR GAP
The space between the fork cap and top of the oil inside a fork. Used as a tuning variable to help with bottoming and harshness.
The effect of the rear end being “held up” during acceleration.
The phenomenon of the suspension oscillating up and down uncontrollable. Compared to riding on a square wheel.
Suspension movement when the wheel hits a bump and compresses.
Fluid resistance to movement. Damping turns mechanical energy into heat.
Excessive compression of the front suspension, normally seen during braking. Normally cause by too soft springs or lack of compression damping.
- FREE SAG
The amount the suspension compresses under the bikes weight from fully extended.
- FREE LENGTH
The length of a spring in a relaxed state.
When the forks/handlebars oscillate back in forth rapidly and sometimes violently.
- HIGH-SPEED COMPRESSION
Compression damping created by fast vertical wheel movements. Examples would be things like rolling over pot holes, curbs, whoops, etc.
Serious harshness that actually throws the wheel off the ground. Generally caused by too much high-speed compression and/or severe bottoming.
When the suspension compresses over a bump and returns too slowly to its normal position. This normally causes the suspension to ride at the bottom portion of the stroke and causing possible bottoming. Cause by excessive rebound damping.
When a spring is compressed, normally mechanically or hydraulically.
Uncontrollable rebound. Can feel like a figure 8 motion in turns or riding over marbles, caused by lack of rebound dampening.
When the bars are easy to turn but the bike doesn’t turn. Normally is a lack of traction.
The angle of the steering axis from vertical, measured in degrees.
Suspension movement when a wheel extends.
- RIDER SAG
The distance the suspension compresses under the weight of the bike and the rider fully geared. The following are general guidelines for rider sag.
FRONT SAG REAR SAG STREET 30 – 35 mm 30 – 35 mm TRACK/RACE 25 – 30 mm 25 – 30 mm DIRT 60 – 75 mm 95 – 100 mm
A thin metal washer, normally made out of spring steel.
- SHIM STACK
A combination of shims of varying diameters and thickness that are stacked in a certain configuration to provide a certain damping curve.
A mechanical device, normally in a coil design, that stores energy as it displaces.
- SPRING RATE
A measurable amount of force applied to a spring to make it compress a certain distance.
- STATIC FRICTION (STICTION)
Friction where there is no movement between surfaces.
The effect of the rear end being “pulled down” during acceleration.
The distance between the center of the contact patch and the steering axis measured along the ground.
The mechanical hardware that creates damping.
When the rear end feels loose or wanders. Normally caused by too much rebound.