Evolution Rear Shock

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Early Rear Shock Systems

Image taken from US Patent 91,682 with emphasis added to rear shocks[1].
The evolution of the bicycle rear shocks began as a gradual process. The earliest suspension system that received a US Patent was in 1869. Suspension systems like this one were used for some of the earliest bicycle designs like the Velocipede. The rear suspension systems for these bikes were simple in design and consisted of just springs and a wood or metal casing. Although these suspension system were primitive, they served an important purpose in the overall function of the bike. Since early bicycle were made of only wood and iron, they gave the rider a rough and jarring ride because all the bumps and edges from the road would translate directly to the rider.
The image was taken from US Patent 3,133,748. In this image the plungers that damping the spring forces are visible. [2]

Through the late 19th and early 20th century the advances in rear suspensions systems was limited to variation of springs to absorb the jarring of the ride. A variety of different springs were developed for use on the rear fork and on the bike stem to achieve this shock absorption. Other developments in the rear suspension system included shock absorption applied to the bottom bracket. These were complicated designs with lots of different parts and where incorporation with the front cog. Also, attempts to apply shock absorption was incorporated directly into the frame. These unique bike frames would absorb the shock because the rear fork bowed outward and where made of a flexible metal in order to absorb some of the road jarring. These frame would have been effective because it reduced the weight of heavy springs and casing but the frame were expensive and difficult to built.

It was not until the 1960's when a big advancement was made in the rear suspension system. This was the time when a suspension system began to incorporate a damping feature along with the springs. The shocks with the damping not only absorbed the jarring but also soften the force applied by the springs. This combination of springs and damping was popular on other vehicles like motorcycles and automobiles but it was not until this time that bicycles first added this type of suspension system. This was a big step in the rear shock evolution but it was still another 20 years, after invention of the mountain bike, that rear shock became popular and began to change rapidly.

Full Suspension Frames Hit The Market

Mountain Bike Frames that coupled front and rear suspension systems first became commercially available to enthusiasts in the early 1990's. These early designs were heavier than the proven traditional hardtail mountain bike frame, and their functionality was largely compromised by pedal bob, chain torque and hard braking situations. The industry turned to the motorcycle and motocross racing industry to improve these designs.

Motorcycle Champion Mert Lawwill and motorcycle designers Horst Leitner and Karl Nicolai had worked on similar problems in racing motorcycles in the past. Their first resulting design was incorporated in what was to be name the Gary Fisher RS-1. This four-bar linkage system was a cousin to that used in motorsports. It greatly overcame pedal bob and braking input, but required the use of a rear disk brake. This became a problem because at the time no commercially available disk brakes were readily available for use on mountain bikes.

RS-1.jpg Gary Fisher RS-1

The bike manufacturer Specialized also worked with these designers and eventually developed a variant of the original four bar linkage system that was first featured on the Specialized FSR frame. This system quickly became the most popular rear suspension system and proved to be a benchmark in the industry for years to come.

Specfsra.jpg Specialized FSR

After the introduction of the FSR much parallell development was done to produce better rear suspension systems. Today, in addition to the Four-Bar Linkage system, there are a few commonly seen basic rear shock designs in use on bikes today. These include the Single-Pivot, the Soft-Tail, The Unified Rear Triangle, and a new smart Suspension system introduced by Specialized called the Brain which is an active part time suspension system that is only activated as the rear wheek of the bike is given upward motion from the riding surface.

URT.jpg Unified Rear Triangle Suspension SPP.jpg Single Pivot Point Suspension

The Brain has become the modern pinnacle of rear bicycle suspension. It elminates pedal bob, chain torque effects hard braking influence when needed and activates on rough surfaces when better control, ride and traction are needed. It is also tunable to adjust the rate and response of the activation of the shock.

Brain.jpg Specialized Brain

Full-Suspension Bicycles have come a long way since some of their early patents and the continuing evolution in technology and manufacturing ensure more impressive designs to come in the future.


1. Patent 91,682. US Patent Office Full-Text and Image Database. Retrieved on February 14, 2008.

2. Patent 3,133,748. US Patent Office Full-Text and Image Database. Retrieved on February 15, 2008.

3. www.wikipedia.org Bicycle Suspension . Wikipedia. www.wikipedia.org

Related link: bicycle