Rear Suspension Race Sag - Honda CRF450R 2009 Owner's Manual & Competition Handbook

Rear Suspension Adjustments

Rear Suspension Race Sag

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 pre-
load 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
center of the rear fender mounting bolt to the
center of the chain adjuster lock nut as illustrated
here — for three different situations:
124
Adjustments for Competition
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.
REAR FENDER MOUNTING BOLT
UNLOADED MEASUREMENT
(without rider)
EXAMPLE: 23.6 in (600 mm)
CHAIN ADJUSTER LOCK NUT
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.
REAR FENDER MOUNTING BOLT
LOADED MEASUREMENT
(with rider)
EXAMPLE: 19.7 in (500 mm)
CHAIN ADJUSTER LOCK NUT
Example:
= 23.6 in (600 mm)
Unloaded
= 19.5 in (495 mm)
– Loaded
= 4.1 in (105 mm)
Race Sag
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: 4.1 in (105 mm)
Adjust spring pre-load as necessary to obtain
the desired handling results.
Decreasing the race sag dimension (example:
3.7 in, 95 mm) improves turning ability for
tight terrain at the cost of slightly reduced
straight line stability.
Increasing the race sag dimension (example:
4.5 in, 115 mm) 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.