Bicycle Suspension - Rear Suspension

Perhaps because front suspension has been easier to implement and more readily adopted, it is often assumed that a bicycle with rear suspension has full suspension.

Mountain bike technology has made great advances since first appearing in the early 1990s. Early full suspension frames were heavy and tended to bounce up and down while a rider pedaled. This movement was called pedal bob, kickback, or monkey motion and took power out of a rider's pedal stroke — especially during climbs up steep hills. Input from hard braking efforts (known as brake jack) also negatively affected early full suspension designs. When a rider hit the brakes, these early suspensions compressed into their travel and lost some of their ability to absorb bumps. This happened in situations where the rear suspension was needed most.

The problems of pedal bob and brake jack began to be solved in the early 1990s. One of the first successful full suspension bikes was designed by Mert Lawwill, a former motorcycle champion. His bike, the Gary Fisher RS-1, was released in 1990. It adapted the A-arm suspension design from sports car racing, and was the first four-bar linkage in mountain biking. This design solved the twin problems of unwanted braking and pedaling input to the rear wheel, but the design wasn't flawless. Problems remained with suspension action under acceleration, and the RS-1 couldn't use traditional cantilever brakes. A lightweight, powerful disc brake wasn't developed until the mid 1990s, and the disc brake used on the RS-1 was its downfall.

Horst Leitner began working on the problem of chain torque and its effect on suspension in the mid 1970s with motorcycles. In 1985 Leitner built a prototype mountain bike incorporating what became known later as the "Horst link". Leitner formed a mountain bike and research company, AMP research, that began building full-suspension mountain bikes. In 1990, AMP introduced the Horst link as a feature of a fully independent linkage rear suspension for mountain bikes. The AMP B-3 and B-4 XC full-suspension bikes featured active Horst link/Macpherson strut rear suspensions and optional disc brakes. A later model, the B-5, was equipped with both the Horst link and a four-bar active link suspension featuring up to 125 mm (5 inches) of travel on a bicycle weighing around 10.5 kg (23 pounds). For 10 years AMP Research manufactured their full-suspension bikes in small quantities in Laguna Beach, California, including the manufacture of their own cable-actuated-hydraulic disc brakes, hubs, shocks and front suspension forks.