Advanced Tuning Adjustments - Traxxas Unlimited Desert Racer Owner's Manual

ADVANCED TUNING ADJUSTMENTS

Roll Center
The Unlimited Desert Racer has provisions for adjusting the roll center
geometry of the rear suspension. Roll center refers to the virtual axis
around which the chassis will roll when subjected to cornering forces.
The rear upper suspension link is set in the upper position, which is
the recommended position for running. Moving the link to either of
the two alternate mounting holes will increase the roll center and
reduce anti-squat.
Gearing
One of the more significant advantages to your model's transmission
is the wide range of available gear ratios. Changing the gearing
allows you to fine tune the speed of the model and control the
temperatures of the battery pack and motor. Use a lower gear ratio
(numerically larger) to reduce current draw and temperatures. Use
a higher gear (numerically lower) to increase top speed. Use the
following formula to calculate the overall ratio for combinations not
listed on the gear chart:
# Spur Gear Teeth
x 9.47 = Final Gear Ratio
# Pinion Gear Teeth
When using higher gear ratios, it is important to monitor the
temperatures of the battery, motor, and speed control. If the battery
is extremely hot (150°F) and/or the motor is too hot to touch (180°F),
your model is probably over-geared and drawing too much current.
This temperature test assumes that the model is close to factory stock
weight and operates freely with no excessive friction, dragging, or
binding, and the battery is fully charged and in good condition.
Note: If not using the pin system, check and adjust gear mesh if a
spur and/or pinion gear is changed.
This model is equipped with a 2200Kv brushless motor. The gear
combination that comes stock on each model provides good overall
acceleration and top speed.
SHOCK TUNING
Shock Pistons
The shock pistons can be replaced with the available optional pistons to
vary the amount of damping. Optional pistons with bypass holes that are
larger or smaller than the factory installed stock pistons can be used to
decrease or increase damping respectively. Change the pistons if you only
have one weight of shock oil available to you.
From the factory, the Desert Racer is
equipped with pistons with 1.7mm
bypass holes (recommended).
Shock disassembly
The shocks must be removed from the
vehicle and disassembled to change
the pistons. Use the shock exploded
views included with the model to aid
in the assembly process.
1. Remove the 2.5x10mm cap screw
from the lower spring retainer.
Remove the lower spring retainer
and spring from the shock.
2. Remove the shock cap (A) and
empty the shock body of shock oil.
3. Remove the lower cap (B) and
the X-ring from the shock body.
4. Use side cutters to grip the shock
shaft just above the rod end (C).
Remove the rod end from the
shock shaft using the suspension
multi-tool (C).
5. Remove the shock shaft with piston
from the shock body out through
the top of the shock body.
Shock assembly
1. Replace the stock piston with
desired optional piston. Be careful
not to lose the small washer
located below the piston.
2. Position the new piston onto
the shock shaft above the small
washer. Grip the threads of
the shaft with side cutters or
needlenose pliers and tighten
the nut with the 4-way wrench to
secure the assembly (D).
3. Insert the shock shaft assembly through the shock body until the piston
bottoms out.
4. Lubricate the shaft and X-ring with silicone oil.
Multi-tool Shock Functions
A. Tighten/Loosen Upper Cap
B. Tighten/Loosen Lower Cap
C. Remove/Install Rod End
D. Piston Installation/Removal
Gearing Compatibility Chart:
The chart below shows recommended
gear combination ranges for your model.
Spur Gear
47 51 55
23 - - 2.39
24 - - 2.29
25 - - 2.20
26 - - 2.12
27 - 1.89 2.04
28 - 1.82 1.96
29 - 1.76 1.90
30 - 1.70 1.83
31 1.52 1.65 1.77
32 1.47 1.59 1.72
33 1.42 1.55 -
34 1.38 1.50 -
35 1.34 1.46 -
36 1.31 1.42 -
37 1.27 - -
38 1.24 - -
39 1.21 - -
40 1.18 - -
Out of Box Setup; recommended for most
running, 4S/6S LiPo.
2S 5000mAh + recommended
3S 5000mAh + recommended
4S 5000mAh + recommended
Usable gearing range for 4S LiPo only.
Increases torque and run time.
4S 5000mAh + recommended
Usable gearing range for 4S/6S LiPo.
Increases torque and run time.
2S 5000mAh + recommended
3S 5000mAh + recommended
4S 5000mAh + recommended
4S LiPo, 40mph running only.
Fits; not recommended.
Does not fit.
DESERT RACER • 29