circumstances require; 3. Reduce weight.
Rear-Wheel Suspension
After the front-wheel suspension systems gained acceptance, it was only a matter of time before
engineers designed a suspension system for the rear-wheel. This was considered to be an ambitious
undertaking, because it meant jeopardizing the stability of the rear frame, a vital part of the frame structure.
At the end of 1990, Cannondale, Offroad, and Gary Fisher introduced the first rear-wheel suspension.
Cannondale and Offroad used similar systems. They both have elevated chain stays providing lateral sway,
with the pivot point located in the front of the seat tube. Cannondale uses an oil-pressure suspension, the
Offroad rear frame is protected against shocks by plastic devices. These suspension systems are well made
and designed, but they also contribute to some problems: Stiff wishbone construction at the rear frame
lessens lateral stability; interference with the important geometry of the rear frame by adding shock
absorbers will also cause considerable loss to the bike’s lateral stability, changing the ride of the bike. Gary
Fisher installed plastic devices to absorb shocks. They’re located behind the bottom bracket. Chain tension,
however, makes the rear frame more rigid (due to the lowered seat-stay position); traction is not affected.
Rear-wheel suspension is great for riding downhill, because potholes are smoothed out, and tires
are protected from severe punishment. However, uphill riding can be an ordeal when the rear of the frame
bounces with every pedal stroke. This can drain the energy from the rider quite rapidly. A bike equipped
with rear-suspension is also heavier. At this time no satisfactory solution has been found; the many
different versions are all still in the experimental stages. This technology is still recent and still has room for
improvement. A rear-wheel suspension that is standard to most bikes has not yet been found.
Gears
Shifting and drivetrain have undergone enormous evolutions. Today four different methods of
shifting gears are available: single shift, double shift, rotation-grip, and grip shift. All four of the systems are
different. The one thing that they all have in common is that they are all indexed. The functions of the front
and rear derailleurs have reached high standards, technologically and functionally. In combination with
numerous gear positions this is (at this time ) the most perfect gear shifting system. The only disadvantage
is that it needs frequent attention and adjustment.
To shift gears smoothly and silently before the invention of the indexed system was truly difficult.
It was a process of slow learning, and only professionals knew how to do it properly. The indexed system,
however, made it possible for even a novice rider to master the art of shifting gears properly and with ease.
The indexed system has a built-in mechanism that enables the derailleur to move in such a way that the
chain rests securely on the chain ring as well as on the sprockets.
Single Shifter
Today, as in the past, the single shifter is the one that most bikers prefer. It is close to the
handgrip, and top mounted, this one is the lightest (51/4 oz or 150 g) and reaches every sprocket within a turn
of 90.. This system also makes it possible to disengage the indexed system, so that in case of difficulties,
the gears and derailleur can be used manually, using the friction system. The only disadvantage is that the
position of the lever isn’t ergonomically perfect. The thumb has to move up above the handlebars each time
the gears have to be shifted. However, the single shifter system is preferred for all racing bikes.
Double Shifter
For ergonomic reasons, a few of the professional mountain bike racers, moved the shifter below
the handlebars. The lever worked well of the biker pushed the lever away from himself. It was pulling it
back that was the problem. To solve this problem the double shifter was introduced in 1989. The shifter
was split into two separate levers. The lower lever moved the chain to a larger sprocket and the upper lever
moved the chain to a smaller sprocket. The whole procedure became more complicated; instead of one
movement in two directions, using one lever; now two movements, using two levers in two directions,, was
necessary. To shift gears it was necessary, even for trained bikers, to learn the whole new procedure.
despite the improved position of the shifter the double shifter system has a disadvantage; although by using
the lower lever the largest sprocket or chain ring can be reached, to shift to a smaller sprocket (to the right),
it’s necessary to push the lever six or seven times, causing a slight slowdown. Although it is a minor
inconvenience for the recreational biker, it is a concern for mountain bike racers.
Rotation-Grip Shifter
Handle bars with a diameter of 7/8″ (22.2 and 22.7 mm) are equipped with a 61/4″ (16 cm) long
rotation grip with two or three mechanisms inside. The springs, activated by pressure, cause a mechanism
either to tighten or to loosen the gear cable. In order to shift to another gear, the grip must be rotated. A
dial lets the rider know on which sprocket the chain is riding on. Every sprocket can be reached within a
90. turn of the shifter. Later a lever inside the rotation grip was made that prevents the gears from jumping
when riding in rough terrain. Despite the perfect ergonomical placement of the shifter, it does have two
disadvantages; the increasing number of handlebar accessories leaves little room for mounting new ones,
and accidental shifting can’t be totally eliminated.
Grip Shift
The “Grip Shift” is a system that can be mounted at several different places on the handlebars. A
21/8″ (5.5 cm) wide by 13/4″ thick rotation ring can be mounted on either the inside or outside of the grip and
used on any handlebars that have a 7/8″ diameter (22,2 and 22.6). This system has an intricate system
consisting of three ring-cups that turn within each other that tightens and loosens the gear cable by pulling it
across a wedge. The only disadvantages is that a 270. turning radius is needed to reach all the sprocket.
The greatest advantage is its light weight. At only 2 oz (66 g) the “Grip Shift” is even lighter than the single
shifter. Other handlebar accessories may also be added if desired.
Front Derailleur
The front derailleur transports the chain rings. This is done by a chain guide, which can be moved
from side to side by a cable, and is moved back with a retracting spring. Indexed systems also function
with the derailleur, but still need further refinement. All too often the chain rubs against the cage and must
be adjusted at the shifter. While it is quite easy at the shifter, it’s much more complicated with the rotation-
grip shifter. Adjustments don’t last, and frequent attention is necessary. This is a main complaint about the
rotation-grip shifter.
Rear Derailleur
In order to accommodate the wide arrangement of the gears, the mountain bike’s chain housing has
to be much longer than that of a road bike. The chain housing has to accommodate the largest sprocket.
The most popular type of mechanism is the “slant” mechanism, almost all rear derailleurs are built according
to this model. With the slant mechanism, a much better functioning shifting system has evolved because
the guide pulley “wanders” back and fort at the same distance over every sprocket.
Brakes
Brakes are the only components that haven’t significantly changed in the evolution of the mountain
bike. Today, the simple cantilever brake system has proven the most reliable for off-road riding. The
future, however, belongs to disc brakes, which at this time, are still going through a trial and error period.
The concept of the disc brake is of interest for mountain bikers, because mountain biking makes such great
demands on the brakes. These demands are best served by disc brakes for three reasons: First, the amount
of space that disc brakes allow for the fat tires, so that mud accumulation won’t create problems; second,
the brakes should weigh as little as possible; and third, they must function under both wet and dry
conditions. But first we have to the learn the basic, and still the most common type of brake system.
Cantilever Brakes
The best system is also a simple one, and one that works. The cantilever brake is a perfect
example. Two moveable brake arms with brake shoes are mounted on bosses that are soldered to the seat
stays, or to the chain stays. On many models both brake arms are connected by cables. At the end of the
cable, which originates at the brake lever on the handlebars, are cable carriers to which a linking wire is
attached. The link cable can be disconnected either at the left or right brake carriers. This release the
tension and allows the rear of front wheel to be removed. On newer models the brake cable, which comes
from the brake lever, is attached directly to one of the brake arms, and guided by a round cable carrier,
connected to the other brake arm.
On traditional cantilever brakes, brake arms extend rather far to the outside for the best possible
leverage. Sometimes this causes the rider’s feet to come in contact with the brake arms. This problem was
solved by “Low Profile” brakes. Brake arms became longer, but the angles became much tighter. The
Pedersen cantilever brake makes use of the direction of the rim rotation to give more power to the brake
shoes. The brake shoes are pulled in the direction of the wheel’s forward movement, creating a
correspondingly higher brake action. When releasing the brake shoes, a spring action pulls them back into
the neutral position, which results in an energy saving of 20%.
Brake Shoes
Most brake shoes are made from a hard, friction-resistant, special material consisting of vulcanized
rubberlike plastic, which has been constantly been improved over the years. New combinations made from
synthetic rubber and pheol ressin have increased deceleration, but overall they lose an enormous amount of
effectiveness when the rims are wet. Effectiveness when the rims are wet is the big disadvantage of all rim
brakes.
Since the rim becomes part of the brakes in cable-carrying systems, the effectiveness of the brakes
very much depends on the surface condition of the rim. The most recent rims have a layer ceramic on the
outside which have improved the effectiveness of the brakes under all weather conditions.
Hydraulic Brakes
Hydraulic brakes operate by an enclosed oil tube made from polyamide. Pressure applied to the
brake lever is transferred to a cylinder and the brake shoes. In spite of many advantages, these brakes are
being used less and less, even though the last disadvantage has been eliminated. The disadvantage was that
in order to remove the wheels, you would have to let the air out of the tires. This was solved by designing a
brake so that the brake arms could be opened up so that the wheel could be taken off with out letting the air
out.
Disc Brakes
Despite the good track record of the cantilever brake, the search for an effective disc-brake system
has started. A new bike company in California, Mountain Cycles, introduced a hydraulic “Pro Stop” disc-
brake system in 1990. Aluminum discs (located at the hub of the wheel) have brake shoes made from a
low-temperature fibre material. These brake shoes grip the disc in a “pinching” fashion. The brake shoes,
together with the aluminum disc, don’t lose power under wet conditions. Power from hand pressure is
perfectly transferred to the brake shoes. These disc brakes were developed in conjunction with a front-
wheel suspension system. Their weight including fork is 53/4 lbs (2.6 kg). This system can also be mounted
on conventional Unicrown forks.
Brake Levers
The brake lever has been used ever since the mountain bike was invented. It has gone through
improvement over the years in ergonomics, size, weight, and the way it performs. The lever pulls a brake
cable, which transfers the pulling action of the brake arm of the cantilever to the brake shoe. The lever was
shortened after it was discovered that it can be operated with only two fingers. There is also a brake lever
with a roller mechanism, called the “Servo Wave”. When this lever is used, the pivot point changes the
relation to the cable carrier, which causes the brake shoes to come closer to the rim. The closer the brake
shoes get to the rim, the more effective the transfer of power from the lever to the brake shoes. All
accomplished with a minimum amount of pressure applied to the brake lever at the handle bars.