A serious mountain bike rider has a long list of desirable attributes, and a finite budget with which to get them. The bare essentials include a rigid, light high-tech aluminum frame, a serious suspension fork, and a drivetrain made to withstand thrashing in the mud.

Different riders will disagree about some of the items that come on the list after this, but one is quickly becoming a must-have in many riders' eyes: disc brakes.

Why should a bicycle have a separate disc brake when conventional rim caliper brakes use the rim itself as a braking disc? To the skeptic, there are disadvantages: a separate disc brake adds more parts, and also requires the braking stresses to be transmitted through the spokes.

But to the rider in the woods, the advantages outweigh these disadvantages: the disc brake stays out of the muck. Rim brakes on mountain bikes are a high-maintenance item, because as abrasive materials get onto the brake pads, they actually grind away the rim surface, sometimes to the point where the rim needs replacing. And the presence of the abrasive materials causes the braking performance to deteriorate. By contrast, the smaller brake disc stays out of the muck and doesn't have these problems.

For these reasons, disc brakes are pretty much universal when you shop for $2,000 mountain bikes. But in this price class, they are much rarer, and the Jamis Durango Sport SX is on the short list. If you want disc brakes for $500, start your search here.

The rest of the Durango Sport SX is pure cost-effective hard-core mountain bike stuff: the gussetted (that means extra strong) frame, the Manitou suspension fork with a full 80 mm of suspension travel, the easily adjusted threadless headset and the Shimano Deore rear derailleur.

One bit of cost-cutting may actually be a plus: this bike comes with plastic pedals. Used hard, they're only good for one season. But if, like many mountain bike riders, you want to choose your own pedal binding system and replace the pedals anyway, you can take comfort knowing that you didn't pay too much for the pedals the bike came with.

You'll hear this bike called a "hardtail." That means it has a front suspension fork but no rear suspension. While rear suspension is available in all price ranges, many riders prefer hardtail because of its mechanical simplicity and because there is no possibility of the rear suspension moving when you don't want it to.

The frame comes in sizes down to 13 inches because dedicated mountain bike riders like a small frame with a fully extended seat post (for weight savings, stiffness, and standover clearance).