Light and short travel, XC mtb forks are often single crown due to the mild terrain and to save weight so not to make the bike too heavy to rise.

Historically, XC forks will have been spring loaded however the trend is now moving towards air sprung suspension.

The obvious advantages of such a change of keeping the weight of the fork as low as possible and making them simple to adjust this.

Downhill (DH) Suspension Forks

Have you watched the insanity that may be downhill mountain biking?  Massive drops, massive gap jumps and dreadful terrain over a short prtiod of time.  Downhill forks can have big amounts of travel ( ten inches isn’t unhead of ) to make allowance for the stress a DH bike is put under.

Downhill forks are usually coil spring to take on large hits but are also double crowns ; this is where there are 2 legs of the fork close to the top where the fork joins the handle bar.  Double crown forks offer double the suspension of single crown forks.

Dirt Jump (DJ) Suspension Forks

Big airs, giant jumps and massive tricks require forks which can take some punishment forks not designed for this purpose are liable to be damaged, or worse break, causing major injury to a rider.

A dirt jump ( DJ ) bike will typically be a hardtail and front suspension, although some riders do still like rigid forks.  Suspension forks will have tiny travel of 80-100mm and are normally coil sprung as well as being much heavier thanks to the increased strength than those designed for other off-road bike disciplines.

Rigid Forks

Though suspension forks are more and more a common sight on mountain bikes they are by no means the only option left.

For the die hards, those that do not wish to take a position in dear suspension or those preferring something lower upkeep there remain a number of quality firm forks available on the market.

extremely popular in the dirt jump and street MTB scenes as well as singletrack, stiff Forks provide a practicable and often more economical alternative choice to suspension.

A dirt jump ( DJ ) bike will sometimes be a hardtail and front suspension, though some riders do still prefer firm forks.  Dirt jump forks will have little travel of 80-100mm and are typically coil sprung as well as being much heavier because of the increased strength than those designed for other mountain bike disciplines.  

If you know anything about dirt jumping you’ll know the name Marzocchi probably the best known and most generally used make of forks on dirt jump bikes with their infamous dirt jumper range. 

The dirt jumper range starts with the entry level DJ3 fork.  It’s a quick-release fork, but the straightforward forged lowers are very well proved re slam proofing.  The coil-sprung internals get a simple but effective bottom out damper for slam control.  They may also be stiffened up for emergency-only movement ( if that is’s what you are after ) by charging the auxiliary air spring. 
The range then moves up to the Dirt Jumper one & 2 models, which, in the recently asserted 2010 models will utilise the updated Open Bath RV damper, which features outwardly adjustable rebound damping.  The Dirt Jumper one & two models feature a coil spring and a low pressure pre-load system.  

Weighing in at only 2240g for an open bath, coil sprung fork the DJ1 weighs a great 355g less than the 2009 DJ1 while increasing strength by thirty percent.  

If you can’t spring the £190 £500 ( $200 – $1000 ) that the dirt jumper range can cost may want to instead consider a rigid fork.  The advantages are not only cost, stiff forks such as the Charge Nozzle will not only cost you less but will also weight a ton less than suspension forks meaning you are able to save extra weight that may help you with getting some of those technical tricks nailed.

Cross country is probably what most people think about when they imagine mountain bikers a number of terrain across hills and mountains routinely ridden for fun or against each other or the clock.  Whilst this is not the only form of mountain biking today it is definitely very likely the most popular in conditions of numbers.  

Like the frames that they fit, cross country mountain bicycle suspension forks must be lightweight to keep the general bike weight down that may increase rider performance.  They are going to require some suspension ( normally referred to as travel ) but will not be stiff in order to permit some kind of cover against the bumps and knocks a rider will encounter whilst riding on rough tracks.  The quantity of travel normally permitted on cross country suspension forks is around 80mm-100mm.  

Original designs of mountain bike forks used springs like you see on automobiles or elastometers however the design trend is now moving toward air sprung shocks.  This change of direction in the planning of trail bicycle forks has a number of added benefits ; the absence of moving parts keep the weight to a minimum and air sprung forks are simply adjustable.  The disadvantage of this change in design is the parts can frequently be harder to maintain and take less abuse than their coil sprung opposite numbers.  

Costs of cross country mtb forks can alter greatly with the top of the range models such as the DT Swiss and RockShox costing over £400 ( $800 ) to the cheaper Ritchey and Kinesis forks costing slightly over £100 ( $200 ).

Commonly on MTB’s now days you will tend to find that the forks at the front of the bike have an integrated set of shock absorbers, with the blades being made from upper and lower extendable cylinders, called ‘legs’. These telescopic tubes allow the impact of the extreme surface under the wheel to be reduced, thereby making the bike much easier to ride in rough conditions.

The design for MTB Forks can vary greatly, with the forks travel and handling characteristics setup to a specific discipline of mountain biking. For example, the XC mountain bike rider will need a different suspension fork to a DH mountain bike rider, who will have a different setup again to a freeride mountain bike rider. XC bikes will not need as much suspension travel, typically around eighty to 100 millimeters and can be made from lighter metal when compared to the suspension forks used on a downhill bike. This is basically because they won’t receive as much punishment as they might during cross country riding.

When suspension was originally introduced onto mountain bikes, a travel length of the 80 to 100 mm was typical. Now though, downhill forks offer typically around one hundred and fifty to two hundred millimetres of travel. There are some downhill MTB forks though which can offer anywhere up to three hundred millimetres of travel for really harsh terrain!

Some MTB forks may also enable the rider to adjust the suspension travel to fit particular sections of terrain. More travel for DH and extreme terrain, and less travel for the not so extreme cross country or up hill sections. The rider may even want to entirely eliminate suspension movement all together which would be an advantage on a smooth concrete road for example. This lockout ability may even be activated externally from the handle bars using a trigger.

Whichever discipline of mountain biking you do, it benefits you to choose your mountain bike front suspension forks carefully because when you pick the correct ones you will gain a significant change in performance.