Racing bikes and mountain bikes fill different niches for the cyclist, with design differences that tilt toward speed or durability. Even so, elite mountain bike riders look for a light bike with good speed, and racers who do grueling staged races, such as the Tour de France, need a bike with durability. For triathlon racers and mountain bikes, high-end models costing $5,000 or more, from leading manufacturers such as Trek and Cannondale, will feature carbon frames, a Shimano or SRAM drivetrain and Bontrager stems and saddles.
Function
Differences between racing bikes and mountain bikes stem from their radically different purposes. Racing bikes are designed for speed in a triathlon, time trial, road race, a criterium or short race on a circuit, or a stage race. Racing bikes have lightweight frames and minimal accessories, notes the online bike comparison site PedalsMonkey. Mountain bikes are designed for bumpy trails and uneven terrain, with design features to offer the rider control.
Features
Depending on frame size, a mountain bike may weigh 22 lbs. to 23 lbs., while a racing bike may be lighter at 17 lbs. Racing bikes feature downward-curving handlebar ends that provide the rider with an aerodynamic tuck similar to that of an Alpine skier. Mountain bikes feature straight handlebars with upward-curving bar ends, allowing the rider to sit up more, see what's coming ahead and to stand up on the pedals with good control when climbing. Mountain bike gears range from very low to very high, typically with 16 to 30 gears, while racing bikes have medium to very high ratios, distributed across 18, 20, 27 or 30 gears, notes PedalsMonkey.
Considerations
The tires of racing bikes often inflate to 80 to 120 psi, to lessen the tire's "contact patch" with a smooth road and thus its rolling resistance on a smooth road. Mountain bike tires often inflate between 35 and 50 psi, writes Vic Armijo in "The Complete Idiot's Guide to Cycling," to allow more sidewall deflection and "give" to avoid bouncing off roots and rocks.
Effects
Most mountain bikes feature a front-fork suspension, and allow 2 to 3 inches of travel and a rigid frame, Armijo notes. Some also have a rear shock absorber for greater comfort and control. Racing bikes feature a rigid frame.
Expert Insight
Mountain bikes typically end up on the road almost as much as racing bikes do, Armijo notes. The upright riding position and cushiony tires of the mountain bike are more comfortable, and the suspension forks make the bumps and irregular surface of a rougher paved road disappear. But cyclists at times switch from mountain bikes to racers after realizing how much slower a mountain bike is on the road, mainly due to its increased tire drag. Knobby tread has more rolling resistance than smooth tread, Armijo writes, and the tires are also twice as wide and more softly inflated.
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