132 Adjustments for Competition
Rear Suspension Adjustments
Setting the proper race sag (ride height) is very
important for competition use.
Race sag refers to the amount of rear wheel travel
used by your CRF at rest, ready to ride, with you
on the seat. As a general rule of thumb, the race sag
dimension should be about one-third of the
maximum travel.
On your CRF, ride height is changed by adjusting
the rear suspension spring pre-load.
Spring Pre-load & Race Sag Adjustment
The following adjustment procedure establishes
the correct starting point for any suspension tuning
— the proper rear suspension spring preload
adjustment for your specific needs.
Your CRF should be at normal racing weight,
including fuel, oil and coolant. You should be
wearing all your normal protective apparel. You
will need two helpers.
To calculate the proper adjustment, it is necessary
to measure between two fixed points — from the
centre of the rear fender mounting bolt to the
centre of the chain adjuster lock nut as illustrated
here — for three different situations:
unloaded: motorcycle on an optional workstand
with rear suspension fully extended, no rider.
loaded with rider: motorcycle on ground, with
rider.
loaded without rider: motorcycle on ground,
without rider
1. Support your CRF on an optional workstand
with the rear wheel off the ground.
2. Measure the unloaded dimension.
3. Measure the loaded with rider dimension.
Remove the workstand. With two helpers
available, sit as far forward as possible on your
CRF’s seat, wearing your riding apparel.
Ask one helper to steady your CRF perfectly
upright so you can put both feet on the pegs.
Bounce your weight on the seat a couple of
times to help the suspension overcome any
situation and settle to a good reference point.
Ask the other helper to measure the loaded
with rider dimension.
Example:
4. Calculate the race sag dimension.
To do this, subtract the loaded with rider
dimension (step 3) from the unloaded
dimension (step 2).
Standard Race Sag: 105 mm (4.1 in)
Adjust spring pre-load as necessary to obtain
the desired handling results.
Decreasing the race sag dimension (example:
95 mm, 3.7 in) improves turning ability for
tight terrain at the cost of slightly reduced
straight line stability.
Increasing the race sag dimension (example:
115 mm, 4.5 in) may improve stability on
faster terrain with less turns, but will reduce
turning performance slightly and may upset the
balance between the front and rear suspension,
producing a harsher ride. This will happen if
the adjustment shifts the effective wheel travel
toward the more progressive end of its range.
Rear Suspension Race Sag
UNLOADED MEASUREMENT
(without rider)
EXAMPLE: 600 mm (23.6 in)
REAR FENDER MOUNTING BOLT
CHAIN ADJUSTER LOCK NUT
Unloaded = 600 mm (23.6 in)
– Loaded = 495 mm (19.5 in)
Race Sag = 105 mm (4.1 in)
LOADED MEASUREMENT
(with rider)
EXAMPLE: 495 mm (19.5 in)
REAR FENDER MOUNTING BOLT
CHAIN ADJUSTER LOCK NUT
CRF450R.book Page 132 Thursday, July 8, 2010 9:34 AM
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