By Amit Baweja

It has been a decade in the making, but the mountain bike has become a
passion for many people. Along with this passion it has also become the most
environmental way to get from point A to B. It has gone through a very intense
evolution process over the past decade.
It all started with some guys from California who took their bikes out
for a ride on their day off, they modified their bikes and turned a hobby of
theirs into a worldwide phenomenon. The mountain bike's rapid increase in
popularity was influenced by social and economic situations, and by
technological improvements that had the needs of bike riders in mind. The
introduction of the mountain bike at a bike convention in Long Beach, California,
early in the 1980's coincided with the need for a bike that combined technical
superiority, ease of care, and multipurpose use.
Technological advances came extremely fast after it's introduction into
the world. The advances have made riding mountain bikes easier, which makes it
possible for the rider to explore new terrain. I hope that this report will be
able to provide some information on the subject of mountain bikes and the
advances in technology that the bike has gone through, and what might be in the
future of the mountain bike.
The road bike has taken more than a hundred years to evolve into the
frame that it is being used on todays bicycle. Because of the increasingly
popularity of the mountain bike the demand for advances to be made have come
very rapidly.
The evolution of the mountain bike has been a stormy one over the past
decade. Within one decade the design has changed radically; this is due to three
reasons. First , because geometry and design were copied from the first "Stone-
Age bikes"; second, because off-road riding created different problems ; and
third, because innovative frame design mirrored the "spirit of the times": young,
new, dynamic, and strong. The off-road bike required extra stability.

Frame

It is important to know the basic frame geometry and how to measure it.
The combination of tube length and angle determines not only the maneuverability
of the bike, but also determines the seating position and the transfer of power.
Variances of 1° of the headset angle, or a 1' (2cm) difference in the distance
between the rear-wheel axle and the center of the bottom bracket, can have very
serious consequences.

Frame Geometry

The basic elements of frame geometry are: A- Height of the seat tube; B-
Length of the top tube; C- Seat-tube angle; D- Headset-tube angle; E- Trail, F-
Distance between the rear-wheel axle and the bottom bracket; G- Distance between
the front-wheel axle and the bottom bracket; H- Wheelbase; I- Height of the
bottom bracket; J- Stem angle; K- Length of the headset tube.

A. Height of the Seat Tube

This is determined by the length of the biker's inseam. This measurement
is only of little importance, because of the different frame designs and the
different methods of construction used by different manufacturers.

B. Length of the Top Tube

This length should correspond to the rider's trunk (length from the seat
to the shoulders). With mountain bikes this measurement should be increased by
a few inches. This increases the distance between the two axles, which
increases the riding comfort and makes for a straight and stable ride. Some
times the top tube is slightly slanted, this is because some bike frames are
designed so high off the ground, the slanted top tube makes for an easier
dismount.

C. Seat-Tube Angle

This angle basically determines how the bike will handle. Today the
standard for a seat-tube is to be set at a 72° to 73° angle. At 69° to 71°, it
is a more comfortable ride, but a sharper angle increases the bike's agility and
ability to climb.

D. Headset-Tube Angle

Along with the fork and trail, the headset-tube angle determines the
steering characteristics of the bike. A steep angle together with a curved fork
reacts more sensitively when steering; a flatter angle reacts less sens