The ability to jump obstacles is one of the many attractions of mountain biking. An XC mountain bike is designed for nimble handling and to be relatively lightweight for climbs, and it is equipped with shocks that will soak up moderate bumps and holes and even absorb the landing of some jumps. The maximum height of a jump is determined by the combination of your skill and the bike's design.
Jumping
XC mountain bikes are designed to be responsive and versatile in moderate terrain. Cross-country terrain typically includes natural and artificial obstacles such as log jumps, rock gardens and even some ramped jumps. The geometry of the bike frame is intended to give you maximum control with both tires in contact with the trail surface. The angle of the front fork and top tubes are such that the bike's ability to absorb impact is fairly limited.
Different Types
XC bikes are one of many types. When it comes to jumping, freeride and all-mountain bikes are probably the best suited, with greater front fork travel and a broader wheel base for more stability. Trail bikes are intended for a specialized style of racing that involves extreme obstacles. Regulation jump heights range from .8 m to 1.8 m. By comparison, the average high-quality XC bike can typically handle jump heights of 1 m.
Front Fork Travel and Rear Suspension
A front fork with shocks is standard equipment on modern XC bikes. XC forks are generally angled so the handlebars are behind the front-wheel hub, but forward of the rim. Most successful jumps are landed front wheel first. The geometry of the front fork limits jump height. The angle places the impact under your handlebars, potentially disrupting bike control and limiting maximum height to about 1 m. The longer fork angles on freeride and all-mountain bikes place the impact farther out in front for better absorption. Rear suspension can also limit jump height by absorbing your launching power. The stiff frame of hardtail bikes can provide better platforms for takeoff.
Wheel Diameter
Mountain bikes weren't always available with 29-inch wheels. Standard mountain bike wheels were originally available in 26-inch diameters. The larger diameter increases the ground clearance of your bottom bracket, which is useful in making it over lower obstacles but does not contribute to jumping heights. The larger wheels can, however, be inflated to lower pressures and contact a greater area of the ground. This can improve your traction and control on landing.
References
- "Mastering Mountain Bike Skills"; Brian Lopes and Lee McCormack; 2005
- Mountain Bike World: Buy a Mountain Bike
- UCI: Cycling Regulations
- "Mountain Bike Like a Champion"; Ned Overend; 1999
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