Motorcycle Suspension Setup: Getting to Grips with a
Black Art
By Mark J Thompson
Suspension Set-up: The basics
Whether you are a road rider or a racer correct suspension setup
is the key to fast smooth riding and consistent lap times. To get
the best out of your bike it needs to be set up for the
conditions in which you will be riding. It is considerably easier
to set the bike up for the Track as you know what conditions will
be like for the next hour or so and thus you can dial in the
optimum settings for the that particular situation.
To what extent you change your suspension settings will depend on
whether your bike will also have to cope with riding on the road.
Unlike Roads Tracks are generally smooth and grippy. So if you
are only going to use the bike on the track you have the luxury
of fitting harder springs and modifying the fork and shock
internals. If you ride on the road as well as the track you will
probably want to keep a certain comfort level and concentrate on
just optimizing the current equipment
With incorrect suspension setup, tire wear is increased and
handling suffers, which in turn can result in rider fatigue. Lap
times can be dramatically slower and in extreme cases safety can
be compromised. Hopefully the following guide will help you dial
in your suspension for faster and safer riding both on and off
the track.
Firstly you will need to check the Fork and Shock sag: this is
the amount the forks and rear shock settle under load. To measure
it do the following: push down on the forks a number of times to
settle them, then mark the stanchion with a felt pen or put a
cable tie where the dust seal is sitting. Next ask some for help
to lift on the bars so the front wheel is just off the ground and
measure the amount the forks have traveled down. This is the
static sag (or unladen sag), This can be changed by adjusting the
spring preload (more preload = less sag). Repeat the same process
for the rear, this time measuring the distance from the wheel
spindle to a fixed point on the tail. Now you are ready to begin
setting up your suspension. The key is to do it a little at a
time and make notes as you go. For road riding start with the wet
track settings and work from there.
Basic Setup: Check the following
Forks sag 18-22 mm for dry track, 23-27mm for rain.
Shock sag 8-10mm for dry track, 10-14mm for rain.
Check chain alignment. If not correct, bike will crab walk and
sprocket wear will be increased.
Proper tire balance and pressure, starting with 30psi front and
32psi rear (both dry and wet).
Steering head bearings and torque specifications - if too loose,
there will be head shake at high speeds.
Front-end alignment. Check wheel alignment with triple clamps. If
out of alignment, fork geometry will be incorrect and steering
will suffer.
Crash damage, check for proper frame geometry.
Stock Suspension Tuning Limitations
Manufacturers plan on designing a bike that works moderately well
for a large section of riders and usages. To accomplish this as
economically as possible, they use valving with very small
venturis. These are then matched to a very basic shim stack which
creates a damping curve for the given suspension component. At
slower speeds this design can work moderately well, but at higher
speeds, when the suspension must react more quickly, the
suspension will not flow enough oil, and will experience
hydraulic lock. With hydraulic lock, the fork and/or shock cannot
dampen correctly and handling suffers. The solution is to
re-valve the active components to gain a proper damping curve. It
does not matter what components you have, (Ohlins, Fox, Kayaba,
Showa) matching them to your intended use and weight will vastly
improve their action. Furthermore, if you can achieve the damping
curve that is needed, it does not matter what brand name is on
the component. Often with stock components, when you turn the
adjusters full in or out, you do not notice a difference. In
part, this is due to the fact that the manufacturer has put the
damping curve in an area outside of your ideal range. Also,
because the valves have such small venturis, the adjuster change
makes very little difference. After re-valving, the adjusters
will be brought into play, and when you make an adjustment, you
will be able to notice that it affects the way the way the fork
or shock performs.
Another problem with stock suspension is the springs that are
used. Often they are progressive, increasing the spring rate with
increased compression distance. This means that the valving is
correct for only one part of the spring's travel, all other is
compromise. If the factory does install a straight-rate spring,
it is rarely the correct rate for the weight of the rider with
gear. The solution is to install a straight-rate spring that
matches the valving for the combined weight of the bike, rider
and gear to the type of riding intended.
Remember!
• Always make small adjustments, more is not always better.
• Always keep notes of what you have done.
• Suspension tuning is an art - be patient
Mark Thompson has spent the last 20 Years Racing motorcycles and
managing Race Teams. He now runs the Trackbikes website.
http://www.trackbikes.co.uk/
<<---------------- End of Free Reprint Article ------------->>
Find More Free Articles
Index of All Automotive & Truck Articles
Index of Motorcycle & Off Road Articles
Index of All Free Reprint Articles
