Mountain Bike Spring Or Air Suspension - Mountain Bike Zen
Spring or Air suspension.
Mountain bike suspension front or rear can be spring suspension or air suspension.
Both types of front fork suspension are basically a couple of overlapping tubes of metal capped at each end with a spring or air inside. When you push down on the top tube it pushed onto the spring or air and compresses it against the bottom tube, the two tubes slide over each other and this allows some movement. Inside the mechanism there will be lubricant for the springs/tubes and oil for damping the rebound of the springs. The rebound is how fast the spring will force the suspension back to its original position. Too bouncy and the bike will be more like a pogo stick, too little and the suspension will not recover from one bump quickly enough to allow for full travel on the next.
Sprung forks can be relatively cheap but prices can range skywards to more than the cost of most complete mountain bikes. The front forks can be the amongst the most troublesome part of the bike and often the most prone to failure, so buying wise is important.
The benefit of spring forks is that they are generally a little cheaper than air forks and relativiely easier for a user to maintain. Spring suspension is also often better for heavier riders, although the spring can usually be substituted to allow for a stiffer or lighter suspension. Air forks can be adjusted by pumping more air in, occasionally this will require a specialist pump and will definitely need a pump with a good accurate pressure gauge to avoid contant guesswork.
In terms of travel you will want an absolute minimum of 80mm any less and you don't want to be travelling on anything more than the lightest and simplest of trails, 100mm is usually adequate for novice to intermediate mountain bike trail riding, but for riding large drops and jumps you will definitely want much more travel than this.
In a similar manner to v-brakes/disc brakes you will get a better spring fork than air fork for the same money.
For your rear/frame suspension the mechanism is a little different and design can vary from bike to bike. Rear air suspension will need more care and is definitely more expensive, in terms of the suspension they provide there is not a great deal in it although they are almost always more accurately adjustable to your personal preference and they will be significantly lighter.