Looking for a new front suspension fork?

Looking for a new suspension fork for your bike? It's a nightmare isn't it? There are loads of front forks on the market in fancy colors, made from exotic materials with different amounts of travel and unlikely names. But which is best if what you really want to do is a bit of trail riding?

What is a Trail Fork?

A trail fork is a medium-travel single-crown suspension fork, and we reckon the majority of Mountain bikers would be better off with a fork of this kind and not an air-sprung race fork, which are too lightweight, not reliable enough and cost a load of money. Nor a 16 centimeter travel downhill triple-clamp either, because they reduce turning radius, put more stress on the head tube and you can whack your knees on the upper crown when negotiating tricky terrain.

How much travel should the fork have?

It's a subjective point, but we reckon a trail fork should have between 75mm to 100mm of travel – enough to absorb the biggest bumps but not so much as to effect the geometry of your bike.

More travel means a long fork and most bikes should be suspension-corrected and designed to take forks with about 75mm of travel. Some bikes can take more but to find out you'll need to measure the distance between the dropout and the bottom race of the headset. If this is 420mm or more you should be able to run a front fork with 7 to 8 centimeter of travel with no trouble at all. Not that there's anything stopping you fitting a longer-travel fork, it's just that the extra length will slacken the head angle, raise the top tube and effect you bike's handling.

These changes will make the steering a bit sloppy, but then we've ridden plenty of bikes set up like this and you can get used to the ride. At the end of the day a lot depends on the type of riding you're doing.

Springs and Things

All forks have a spring inside, it's what supports your weight. Without them the fork would just compress and stay there. Ideally a spring should be matched to your body weight but you don't have to abide by this rule – you can fit lighter or heavier springs if you want.

Springs are either compressed air, steel coils, elastomer or a combination of steel coils and elastomer.

Air springs are popular in race forks because they weight nothing but the downside is air leak out and it also has a lot of initial friction so needs a negative spring to help it out at the beginning of the stroke, although some manufacturers have tried to get around this problem with new technology.

Steel coils have a smooth linear action, which feels very plush. They're also consistent performers over time because they don't wear out. The downside is they're heavy.
One of the most popular and lightest spring is elastomer and it's either solid or micro-cellular. It is why it's used without a damper. But the problem is elastomer forks don't perform very well on big hits – they tend to recoil violently. This limits their use unless they're used with a damper. Other problems with elastomer's is they go hard in cold weather, soft on hot days and shrink with use.
Combination elastomer / steel springs are an attempt to get a lot of the above features in one spring.

Should it have damping?

Damping controls the speed of the fork and most forks have some sort of damping, be it air-, friction- or oil-damping. However, the majority use oil-damping. When the fork compresses or rebounds oil is either squeezed through holes or past a stack of thin plastic or metal washers (shims). Changing the size of the holes or thickness of shims measures the amount of oil flowing through the fork -0 this is how you alter the damping rate. Most of the midrange forks have a factory-set damping rate but there are forks with external damping adjusters – these cost obvious more. The most expensive forks have both compression and rebound adjusters.

An easy way to effect the damping rate is by changing the oil weight (viscosity) and nearly every fork has this adjustment. It's not as precise as the adjuster, and does effect compression and rebound, but it's better than nothing.

The oil is either sealed inside a cartridge or allowed to flow freely in the legs, the latter is called an open bath. Both systems have pros and cons but the companies who use them have perfected them to such a degree so that we wouldn't recommend on over another.