Suspension Terminology - Stop Making Nonsense
With the burgeoning number of full suspension bikes on the market these days there are a huge variety of terms that get thrown around by marketing heads, reviewers, forum-dwellers and riders, allegedly with the intention of describing and analysing the way a particular bike behaves or feels to ride. For the uninitiated, some of these terms might as well be in a foreign language for all the sense they make.
To make matters even worse there’s an overabundance of words that are either misused, misunderstood, or too vague to actually convey anything tangible anyway. In order to help you see through the often nonsensical jargon and extract meaningful information from someone talking about sagging from eye-to-eye whilst post mounting their damper to a full floater, we’ve compiled this not quite comprehensive list of common terms, as well as a not always serious description of what they do, could, or should mean.
Air Can or Air Chamber: The part of an air-sprung suspension unit into which the air is compressed by the piston. The higher the air volume, the more linear the suspension unit will feel; the smaller the volume, the more progressive it will be.
Air Spring: The spring formed when an airtight piston compresses air in a sealed chamber or air can. For everything but dedicated DH bikes air springs have all-but replaced coil springs as they are lighter and the spring rate can be altered by simply adding or releasing air. Air springs are inherently progressive, however by altering the size of the air chamber and/or how far the piston pushes into it, they can be made to feel more or less linear.
Anti-Squat: Not leg extensions at the gym, but rather the ability of a suspension system to resist the tendency to compress when you accelerate forward. Suspension ‘squat’ is caused by the rider’s weight moving rearward as the bike accelerates forward underneath them (because you are not a rigid, fixed part of your bike); this rearward weight shift is generally proportional to the degree of acceleration, so the faster you accelerate, the more your weight shifts rearward, and the more your suspension squats under power. This is one of the main contributing factors to energy wasting, rider-induced ‘pedal bob’, or the tendency for dual suspension bikes to move up and down as you pedal.
Some dual suspension designs overcome this phenomenon by using heavily a damped rear shock that resists compression; however this adversely affects bump absorption, even when the rider isn’t pedalling. There are also shocks that overcome this tendency by using an inertia valve design which has its own pros and cons. Many manufacturers design their bikes so that chain tension from pedalling tries to extend the suspension, and this force resists the squatting effect (hence the term ‘anti-squat’). The biggest benefit of using chain tension to control squatting is that the two opposing forces are proportional, so when you accelerate faster the anti-squat force is also higher. Additionally, this means that the shock doesn’t have to control pedalling forces, and can have a softer compression tune and hence be more supple and absorb impacts better.