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on the brakes on the approach to the right hander. The front of
the bike dives down viciously, but in a smooth, controlled manner. You
feel that the tyre is on the edge of adhesion. Another millimeter of
brake movement and it's curtains for you as the tyre loses grip and
skids along, dumping you on your face.
You ease off the brakes as you turn into the bend, going to full lean
almost immediately and holding the brakes right up to just before the
apex. Back on the gas as you start to feed in the power and the front
just starts to get light as you progressively open up more and more. The
front wheel and then the back seem to float over the bumps on the exit,
they shrug them off as the suspension works overtime to keep them
following the contours of the road so as to attain maximum grip and
stability.
Sounds like your bike……. not. Most modern bikes have good chassis
with acceptable set up on standard settings. If you've got a basic good
chassis, then you can make your bike handle, without spending loads of
money on steering dampers and aftermarket swing-arms. It's not that
these items do not have their usefulness, but you can often forgo these,
with proper setting up.
Suspension is exactly what it says - the springy bits, suspend the
main part of the bike. In a perfect world, the suspension would see to
it that your wheel follows each and every little contour of the road.
The rubber would not lose contact with the tarmac and your ride would be
as smooth as is you were sitting in the lasy boy at home. All you have
to do is set your suspension up so that it does this. There you have it,
you are now a suspension guru…………….Okay, maybe not, maybe
we'll look into what the different bits do. |
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hanks to
http://www.circuit1.com/circuitone_tuneguide.html for this top guide
Suspension Tuning
Guide
Street Bike or Road Racing Applications
With incorrect suspension setup, tire wear is increased and handling
suffers, resulting in rider fatigue. Lap times can be dramatically
slower and overall safety for both street and race enthusiasts is
another issue. Add the frustration factor and it just makes sense to
properly setup your suspension. The following guide will help you dial
in your suspension for faster and safer riding both on and off the
track.
Basic Setup: Check the
following
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Forks sag 25-40 mm
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Shock sag 25-35 mm
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Check chain alignment. If not correct, bike will
crab walk and sprocket wear will be increased.
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Proper tire balance and pressure. If out of balance,
there will be vibration and headshake.
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Steering head bearings and torque specifications, if
too loose, there will be head shake at high speeds.
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Front-end alignment. Check wheel alignment with
triple clamps. If out of alignment, fork geometry will be incorrect
and steering will suffer.
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Crash damage, check for proper frame geometry.
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Adjustment Locations on
Forks
Rebound adjustment (if applicable) is located near the
top of the fork. Compression adjustment (if applicable) is located near
the bottom of the fork. Spring preload adjustment (if applicable) is
generally hex style and located at the top of the fork.
Forks: Lack of Rebound
Symptoms:
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Forks are plush, but increasing speed causes loss of
control and traction
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The motorcycle wallows and tends to run wide exiting
the turn causing fading traction and loss of control.
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When taking a corner a speed, you experience
front-end chatter, loss of traction and control.
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Aggressive input at speed lessons control and
chassis attitude suffers.
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Front end fails to recover after aggressive input
over bumpy surfaces.
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Solution:
Insufficient rebound. Increase rebound
"gradually" until control and traction are optimized and
chatter is gone.
Forks: Too Much Rebound
Symptoms:
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Front end feels locked up resulting in harsh ride.
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Suspension packs in and fails to return, giving a
harsh ride. Typically after the first bump, the bike will skip over
subsequent bumps and want to tuck the front.
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With acceleration, the front end will tank slap or
shake violently due to lack of front wheel tire contact.
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Solution:
Too much rebound. Decrease rebound "gradually"
until control and traction are optimized.
Forks: Lack of
Compression
Symptoms:
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Front-end dives severely, sometimes bottoming out
over heavy bumps or during aggressive breaking.
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Front feels soft or vague similar to lack of
rebound.
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When bottoming, a clunk is heard. This is due to
reaching the bottom of fork travel.
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Solution:
Insufficient compression. Increase "gradually"
until control and traction are optimized.
Forks: Too Much
Compression
Symptom:
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Front end rides high through the corners, causing
the bike to steer wide. It should maintain the pre-determined sag,
which will allow the steering geometry to remain constant.
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Solution:
Decrease compression "gradually" until bike
neither bottoms or rides high.
Symptom:
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Front end chatters or shakes entering turns. This is
due to incorrect oil height and/or too much low speed compression
damping.
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Solution:
First, verify that oil height is correct. If correct,
then decrease compression "gradually" until chattering and
shaking ceases.
Symptom:
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Bumps and ripples are felt directly in the triple
clamps and through the chassis. This causes the front wheel to
bounce over bumps.
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Solution:
Decrease compression "gradually" until control
is regained.
Sym
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Ride is generally hard, and gets even harder when
braking or entering turns.
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Solution:
Decrease compression "gradually" until control
is regained.
Adjustment Locations on
Shocks
Rebound adjustment (if applicable) is located at the
bottom of the shock. Compression adjustment (if applicable) is located
on the reservoir. Spring prelude is located at the top of the shock.
Shock: Lack of Rebound
Symptoms:
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The ride will feel soft or vague and as speed
increases, the rear end will want to wallow and/or weave over bumpy
surfaces and traction suffers.
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Loss of traction will cause rear end to pogo or
chatter due to shock returning too fast on exiting a corner.
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Solution:
Insufficient rebound: Increase rebound until wallowing
and weaving disappears and control and traction are optimized.
Shock: Too Much Rebound
Symptoms:
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Ride is harsh, suspension control is limited and
traction is lost.
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Rear end will pack in, forcing the bike wide in
corners, due to rear squat. It will slow steering because front end
is riding high.
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When rear end packs in, tires generally will
overheat and will skip over bumps.
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When chopping throttle, rear end will tend to skip
or hop on entries.
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Solution:
Too much rebound. Decrease rebound "gradually"
until harsh ride is gone and traction is regained. Decrease rebound to
keep rear end from packing.
Shock: Lack of
Compression
Symptoms:
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The bike will not turn in entering a turn.
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With bottoming, control and traction are lost.
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With excessive rear end squat, when accelerating out
of corners, the bike will tend to steer wide.
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Solution:
Insufficient compression. Increase compression
"gradually until traction and control is optimized and/or excessive
rear end squat is gone.
Shock: Too Much
Compression
Symptoms:
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Ride is harsh, but not as bad as too much rebound.
As speed increases, so does harshness.
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There is very little rear end squat. This will cause
loss of traction/sliding. Tire will overheat.
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Rear end will want to kick when going over medium to
large bumps.
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Solution:
Decrease compression until harshness is gone. Decrease
compression until sliding stops and traction is regained.
Stock Tuning Limitations
The factories plan on designing a bike that works
moderately well for a large section of riders and usages. To accomplish
this as economically as possible, manufacturers install 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, KYB, 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.
Suspension tuning is an art, be patient.
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