SUSPENSION
101
Introduction
Unfortunately there is no literature that
can give you the perfect machine setup. Also suspension
setup is individually dependent on the rider (style, preference)
and track conditions, which vary from race to race. We can
therefore only try to give you guidelines and ground rules
for the chassis setup of your machine.
General guideline
The general guideline in road racing is
that the suspension has to support the tires to create the
best possible grip. For this reason suspension plays it's
most important role in corners, chicanes, acceleration and
braking. In the straight line the suspension works satisfactory
if it can absorb the bumps without causing instability.
Suspension stroke
A road race bike should normally not use
its full suspension stroke, although on some circuit one
or two big bumps or hollows can cause the suspension to
bottom. Also landing of front wheel after wheelies can cause
excessive use of the front fork stroke. If suspension bottoms
in big bump or hollow, it should not automatically mean
that the suspension should be set harder. However, if suspension
bottoms at the place were the maximum grip is essential
the tire cannot create the best traction, because it also
has to perform as spring. Adjusting the setting is necessary.
During every riding session the suspension stroke should
be carefully checked. When tire grip and lap times improve,
the suspension has a harder job. So, setting must be set
harder. On the opposite, when it starts raining tire grip
and lap times go down, in that case a softer setting should
be applied.
Suspension setup
Before starting suspension setup, read
the owners manual!
A tip, do your changes in suspension setup
one by one, try to learn what effect each individual adjustment
has on your bike and take notes!
Static sag without rider
Hold the bike upright on a flat surface.
Independently lift front and rear until the suspension is
fully extended, the value should be approximately:
Type Front sag Rear sag
Super Bike 20-30 mm 5-10 mm
Super Sport 20-30 mm 5-10 mm
RR 250 15-25 mm 0-5 mm
RR125 15-25 mm just top out 0 mm
Note: An RR 125 cannot afford
to loose the momentum that the sag would give in a straight
line (loss of top speed). The static sag is adjusted by
the spring preload. The procedure is the same for the front
fork and rear shock.
Static sag with rider
The accepted manner to adjust the spring
ratio is to measure how much stroke is used with the rider
sitting on the bike in straight line position (behind fairing)
after you have set the correct static sag without rider.
Normally 1/3 of the full stroke is a good starting point
for all machines. This is only a guideline for the right
spring ratio. The final check must be done on the circuit.
Note: Ohlins racing shocks features a "top-out"
spring to prevent the shock from extending to quickly, causing
the rear wheel to jump under braking. The top-out spring
also affects the negative sag, making it difficult to adjust
the sag with the shock on the bike.
Your Ohlins shock is delivered with the
correct spring preload set and we recommend you to use this
value for the basic setup. Ride height should be adjusted
with the ride height adjuster on the bike or on the shock.
Rebound damping
*Rear suspension
Too much rebound damping can cause:
- The rear "jumps" on the bumps
instead of following the surface.
- The rear "jutters" under braking.
- It holds the rear down with the result that the bike will
understeer!
- It can cause overheating in the hydraulic system of the
shock absorber and make it fade, in other words, it will
loose damping when hot.
Too little rebound damping can
cause:
- The rear "tops out" too fast
under braking, causing the rear wheel to jump
- The bike feels unstable.
*Front suspension:
Too much rebound damping can cause:
- Oversteering!
- It will give poor grip of the front tire.
- It feels like the front wheels will tuck under in corners.
Too little rebound damping
can cause:
- Understeer!
- The front can feel unstable.
Compression damping
Rear suspension
Too much compression damping can cause:
- The rear wheel to slide under acceleration.
-It can give a harsh ride over bumps.
Too little compression
damping can cause:
- The rear wheel starts to bump sideways
under acceleration out of the corner.
- The bike will squad too much (rear is too low), that will
cause the front to loose grip.
Front suspension
Too much compression damping can cause:
- Good result during braking.
- Feels harsh over the bumps.
Too little compression damping
can cause:
- Strong diving of the front.
Adjustment advice:
Compression damping should be adjusted
together with front fork oil level.
Spring ratio
Rear
Too hard spring ratio:
- Gives easy turning into corners.
- Makes the rear feel harsh.
- Create poor rear wheel traction.
Too soft spring ratio:
- Gives good traction in acceleration.
- Creates understeer in entry of corner.
- Makes too much suspension travel, which will make it difficult
to "flick" the bike from one side to the other
in a chicane.
- Will give a light feeling in the front.
Front
Too hard spring ratio:
- Good under braking.
- Creates understeer.
- It feels harsh in the corners.
Too soft spring ratio:
- Gives easy turning into corners.
- Creates oversteer.
- Can cause front to tuck under.
- Bad under braking (diving).
Front fork oil
level
First see manual. The modern front fork
of cartridge type is very sensitive for oil level changes,
because of the small air volume Air inside the front fork
works as a spring. The different level of oil affects the
spring ratio from the middle of the stroke and has a very
strong effect at the end of the stroke.
When the oil level is
raised:
The air spring in the later half stage
of travel is stronger, and thus the front forks harder.
When the oil level is
lowered:
The air spring in the later half stage
of travel is lessened, and thus the front forks are softer.
The oil level works most effectively at the end of the fork
travel.
Note: Adjust the oil level
according to your manual.
BASIC SETUP
- Check the following first:
Forks/Rear Shock - Race
sag 25-30 mm, 1 - 1 3/16 inch
Forks/Rear Shock - Street sag 30-35 mm, 1 3/16 - 1 3/8 inch
Check chain alignment. If not correct, sprocket wear is
increased.
Proper tire balance and pressure. If out of balance, there
will be vibration in either wheel
Steering head bearings and torque specifications, if too
loose, head will 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.
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TROUBLESHOOTING
FORK DAMPING PROBLEMS
Fork Adjustment Locations:
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
Forks are plush, but increasing
speed causes loss of control and traction.
The motorcycle wallows exiting the turn causing fading traction
and loss of control.
When taking a corner a speed, you experience front-end chatter,
loss of traction and control.
Aggressive input at speed lessons control and chassis attitude
suffers.
Front end fails to recover after aggressive input over bumpy
surfaces.
Solution
Insufficient
rebound - Increase rebound "gradually" until control
and traction are optimized and chatter is gone.
Forks - Too Much Rebound:
Symptoms
Front end feels locked
up resulting in harsh ride.
Suspension packs in and fails to return, giving a harsh
ride.
Typically after the first bump, the bike will skip over
subsequent bumps.
With acceleration, the front end will tank slap or shake
violently due to lack of front wheel tire contact.
Solution
Too much rebound - Decrease rebound "gradually"
until control and traction are optimized.
Forks - Lack of
Compression:
Symptoms
Front-end dives severely,
sometimes bottoming out over heavy bumps or during aggressive
breaking
Front feels soft or vague similar to lack of rebound.
When bottoming, a clunk is heard. This is due to reaching
the bottom of fork travel.
Solution
Insufficient compression
- Increase "gradually" until control and traction
are optimized.
Forks - Too Much
Compression:
Symptoms
Front end rides high through
the corners, causing the bike to steer wide. It should ride
in the middle of suspension travel.
Front wheel bounces over bumps while ripples and bumps are
felt directly in the triple clamps and through the chassis.
Ride is generally hard, and gets even harder when braking
or entering turns.
Solution
Too much compression -
Decrease compression "gradually" until the bike
neither bottoms or rides high, and control and traction
are optimized.
Symptom
Front end chatters or
shakes entering turns. This is due to incorrect oil height
and/or too much low speed compression damping
Solution
First, verify that oil
height is correct. If correct, then decrease compression
"gradually" until chattering and shaking ceases.
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TROUBLESHOOTING
SHOCK DAMPING PROBLEMS
Shock Adjustment Locations:
Rebound adjustment (if
applicable) is located at the bottom of the shock.
Compression adjustment (if applicable) is located at the
top of the shock or on the reservoir.
Spring preload is located at the top of the shock.
Shock - Lack of Rebound:
Symptoms
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.
Loss of traction will cause rear end to pogo or chatter
due to shock returning too fast on exiting a corner.
Solution
Insufficient rebound - Increase
rebound until wallowing and weaving disappears and control
and traction are optimized.
Shock - Too Much Rebound:
Symptoms
Ride is harsh, suspension control
is limited and traction is lost.
Rear end will pack down, forcing the bike wide in corners,
due to rear squat. It will slow steering because front end
is riding high.
When rear end packs in, tires generally will overheat and
will skip over bumps.
When chopping throttle, rear end will tend to skip or hop
on entries.
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
The bike will not turn in entering
a turn.
With bottoming, control and traction are lost.
With excessive rear end squat, when accelerating out of
corners, the bike will tend to steer wide.
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
Ride is harsh, but not
as bad as too much rebound. As speed increases, so does
harshness.
There is very little rear end squat. This will cause loss
of traction/sliding. Tire will overheat.
Rear end will want to kick when going over medium to large
bumps.
Solution
Too much compression - Decrease
compression until harshness is gone. Decrease compression
until sliding stops and traction is regained.
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Front
Fork Problems Possible Cures
Race sag too small - Reduce
preload.
Race sag too great - Increase
preload.
Forks compress too far
on smooth turns - Stiffer springs, increase preload.
Forks dive too far (bottom
out) - Stiffer springs, reduce air gap, possibly increase
preload.
Always losing front end
on corner entry - Softer springs, adjust weight distribution.
Front end chatters coming
out of corners - Softer rebound springs or main springs,
reduce damping.
Bike difficult to turn
in - Softer springs, reduce preload or compression damping,
alter steering geometry
Front wheel skips on bumps
- Softer springs, reduce compression damping, increase air
gap.
Forks judder when braking
on a straight - Reduce compression damping.
Forks dive too fast -
Increase compression damping.
Forks pump down on fast
bumpy corners - Reduce rebound damping.
Excessive pogo action
through chicanes - Slightly increase rebound damping.
Front end shakes (not
chatters) in corners - Increase rebound damping.
Front end shoots up too
fast after braking - Increase rebound damping.
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Rear
Shock Problems Possible Cures
Race sag too great - Increase
preload.
Race sag too small - Reduce
preload.
Rear squats on acceleration
- Stiffer spring, increase anti-squat angle, slightly increase
compression damping.
Very harsh ride over ripples
- Reduce compression damping.
Bike wallows - Increase
rebound damping.
Rear jacks up too fast
on braking - Increase rebound damping.
Rear end chatters exiting
slow corners - Increase rebound damping.
Bike kicks off ripples
or bounces on bumps - Increase rebound damping.
Rear end pumps down on
bumpy corners - Reduce rebound damping.
Symptoms
LACK OF COMPRESSION
DAMPING (Front Fork)
Front end dive while on
the brakes becomes excessive.
Rear end of motorcycle wants to "come
around" when using front brakes aggressively.
Front suspension "bottoms out"
with a solid hit under heavy braking and after hitting bumps.
Front end has a mushy and semi-vague feeling,
similar to lack of rebound damping.
TOO
MUCH COMPRESSION DAMPING (Front Fork)
Overly harsh ride, especially
right at the point when bumps and ripples are contacted
by the front wheel.
Bumps and ripples are felt directly - the
initial hit is routed through the chassis instantly, with
big bumps bouncing the tire off the pavement.
The bike's ride height is affected negatively
- the front end winds up riding too high in the corners.
Brake dive is reduced drastically, though
the chassis is upset significantly by bumps encountered
during braking.
LACK OF REBOUND
DAMPING (Front Fork)
The fork offers a supremely
plush ride, especially when riding straight up. However,
when the pace picks up the feeling of control is lost. The
fork feels mushy, and traction "feel" is poor.
After hitting bumps at speed, the front
tire tends to chatter or bounce.
When flicking the bike into a corner at
speed, the bike will tend to "porpoise" or wallow
a bit, before settling down. Getting aggressive with the
controls makes it worse. As speed increases and steering
inputs become more aggressive, chassis attitude and pitch
become a real problem, with the front traction feedback
going numb after the bike is countersteered hard into a
turn.
TOO MUCH REBOUND
DAMPING (Front Fork)
The ride is quite harsh
- just the opposite of the plush feet of too little rebound.
Rough pavement makes the forks feel as if they're locking
up with stiction and harshness.
Under hard acceleration exiting bumpy corners,
the front end feels like it wants to "wiggle"
or "tankslap." The tire feels as if it isn't staying
in contact with the pavement when on the gas.
The harsh, unforgiving ride makes the bike
hard to control when riding through dips and rolling bumps
at speed. The suspension's reluctance to maintain tire traction
through these sections erodes rider confidence.
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LACK OF COMPRESSION
DAMPING (Rear Shock)
Too much rear end "squat"
under acceleration - bike wants to steer wide exiting corners
(since chassis is riding rear-low/nose-high).
Hitting bumps at speed causes the rear
to bottom, which upsets the chassis.
Chassis attitude affected too much by large
dips and "G-outs" - steering and control become
difficult due to excessive suspension movement.
TOO MUCH COMPRESSION
DAMPING (Rear Shock)
Ride is harsh, though
not quite as bad as too much rebound - however, the faster
you go the worse it gets.
Harshness hurts rear tire traction over
bumps, especially during deceleration.
There is very little rear end "squat"
under acceleration.
Medium to large bumps are felt directly
through the chassis - when hit at speed, the rear end kicks
up.
LACK OF REBOUND
DAMPING (Rear Shock)
The ride is plush at cruising
speeds, but as the pace increases, the chassis begins to
wallow and weave through bumpy corners.
Poor traction over bumps under hard acceleration
- rear tire starts to chatter due to lack of wheel control.
Excessive chassis pitch through large bumps
and dips at speed - rear end rebounds too fast, upsetting
chassis with a pogo-stick action.
TOO
MUCH REBOUND DAMPING (Rear Shock)
Very harsh ride - rear
suspension compliance is poor and "feel" is vague.
Poor traction over bumps during hard acceleration
(due to lack of suspension compliance).
Bike wants to run wide in corners since
the rear end is "packing down" - this forces a
nose-high chassis attitude, which slows down steering.
Rear end wants to hop and skip when the
throttle is chopped during aggressive corner entries