achieve. Conversely, more fork offset reduces trail and
should cause the bike to steer lighter and quicker—and
the front end to feel more nervous in a straight line.
Axle offset is how far the axle sits ahead of
the fork centerline. Axle offset affects trail.
More axle offset reduces trail and vice versa.
As a rule, changing trail at the axle is better
than at the clamps. The more offset at the triple clamps,
the more the rider will feel the weight of the fork tubes
when steering. Although there needs to be some offset
at the clamps to give fork clearance for a full turning
radius, the less the better to decrease the fork’s moment
of inertia. The lightest-steering bikes will put as much of
the given offset as possible into the axle clamps.
Weight bias is how much of the bike’s weight
is on the front wheel compared to the rear
wheel. More weight on the front wheel
improves the front tire’s steering bite. More to
the back makes it easier for the rear wheel to follow the
ground. Changing offset changes weight bias.
How can reduced offset make the bike
steer with a much lighter, quicker feel
when the science says it should do the
opposite? Even though the actual
steering geometry is slower-turning and more predictable,
increasing trail is also the same thing as moving the
engine forward and putting more weight on the front tire.
In the end, riders find that clamps with reduced offset
steer better, because altogether it gives the bike a more
stable feel—but with easier steering and with a front tire
that stays more planted. ❏
Less fork offset (20mm as opposed to 22mm)
increases trail and, on paper, should make
the bike steer slower and improve stability.
Yet, for some reason (perhaps the wide number of
factors involved in bike handling), less offset often results
in a bike that turns sharper and is more accurate.
To make a motocross bike stable at speed,
the steering head angle is angled forward.
The degree that the steering axis is angled
forward is called “head angle.” Don’t confuse
it with “rake,” which is a different number that relates to
how the forks are angled in relation to the head angle
(most forks are not raked at a different angle from the
head angle). A chassis with a slack head angle steers
less when you turn the handlebars and wants to remain
in a straight line (think chopper). A steeper head angle
turns quicker and is less stable at speed (think trials
The head angle can be found by drawing
an imaginary line through the steering
stem axis. Now, draw an imaginary line
perpendicular down to the ground at the
same spot where the steering axis intersects it. The
angle created between the two lines is the head angle.
Measuring the angle below the steering-head axis to
horizontal gives the steering-head angle.
Motocross bikes use head angles in the
range of 27. 5 to 26 degrees. A 26-degree
angle means that the steering head is
angled forward less and is at a steeper,
quicker-turning angle. A 26-degree rake is the same
thing as a 64-degree head angle. A 27.5-degree head
angle is a slacker angle and gives a steering-head angle
measurement of 62. 5 degrees. Slacker head angles turn
more slowly and improve straight-line stability.
Trail is a measurement of how far the
contact patch of the front tire is behind the
point where the steering axis hits
the ground. The number is achieved by
extending an imaginary line down the center of the
head angle to the ground. Then, a perpendicular line
is dropped through the center of the front axle to the
ground. The distance between where the two lines hit
the ground is the trail measurement. As a rule of thumb,
it should be between 4 and 5 inches on a motocross bike
(more on a chopper and less on a trials bike).
Trail is what makes it possible for you to
stay balanced on two wheels. Take a
shopping cart as an example. The cart’s
steering axis is vertical—90-degree head
angle and an axle offset of about an inch behind the
axis. When the cart is pushed, the wheels instantly
swing into alignment. The trail on a motorcycle works
the same way. The front end of the bike wants to snap
straight and keep the bike upright every time it is driven
forward. The farther the wheel is behind the steering
axis, the more stable the bike—the closer, the less stable.
To get a bike to turn quickly, like a shopping cart, would
require very little trail.
A longer trail measurement gives greater
caster effect, heavier and slower steering,
and a more stable feel in a straight line.
That is exactly what less fork offset should
ABOUT TRIPLE CLAMP OFFSET