Traxxas Fiesta ST Rally BRUSHLESS Owner's Manual page 26

26 • FIESTA ST RALLY
ADJUSTING YOUR MODEL
Wheels and Tires
Many types of aftermarket tires and wheels can be adapted for use
on your model. Most will affect the overall width and the suspension
geometry of the model. The offsets and dimensions designed
into the model's wheels are intentional; therefore, Traxxas cannot
recommend the use of other non-Traxxas wheels with different
specifications. The diameter of the wheels is an innovative design,
and there is a variety of different tires available for you to experiment
with in addition to the included tires on the model (listed in
your parts list). Experimentation with different types of tires is
recommended to see which ones work the best on the terrain where
the model is run. When selecting tires, consider the overall diameter
and the rubber compound (hard or soft). If the overall diameter
of the tire is significantly increased, you will need to use a smaller
pinion gear to compensate for the larger tire. Soft compound tires
with many short spikes generally work better on hard, dry surfaces.
In loose dirt, a tire with large spikes should perform better. See your
parts list for accessory wheels and tires.
Tuning the Sealed Gear Differentials
The action of the model's front and rear gear differentials can be
tuned for different driving conditions and performance requirements,
without major disassembly or removal of the suspension system.
From the factory, the differentials are sealed to maintain consistent
long-term performance. Changing the oil in the differential with
either lower or higher viscosity oil will vary the performance
characteristics of the differentials. Changing to a higher viscosity oil
in the differential will reduce the tendency for motor power to be
transferred to the wheel with the least traction. You may notice this
when making sharp turns on slick surfaces. The unloaded wheels
on the inside of the turn have the least traction and tend to spin
up to extremely high rpms. Higher viscosity (thicker) oil causes the
differential to act like a limited-slip differential, distributing more
equal power to the left and right wheels.
Your model will generally benefit from higher viscosity oil when
climbing or racing on low traction surfaces. Note: Heavier oil will
allow power to be transferred even with one or more tires off the
ground. This can make the vehicle more likely to overturn on high-
traction surfaces.
From the factory, the front and rear differentials are filled with grease,
but can also be tuned with silicone differential oil.
Only use silicone oil in the differentials. Traxxas offers SAE 10,000W,
30,000W, and 50,000W viscosity oil (see your parts list). The
differentials have to be removed from the vehicle and disassembled
to change/replace oil.
Follow these steps to access and refill the front and rear differentials.
Front differential:
1. Remove the two 3x15mm button-head screws that secure the
upper bumper/body mount to the differential case.
2. Turn the chassis over and remove the three 4x10mm
countersunk screws that hold bumper/skid plate to the
bulkhead. The two rear screws do not need to be removed.
3. Slide the bumper/body mount assembly off of the chassis.
4. Remove 3x15mm button-head screw from the differential tie bar.
5. Slide the tie bar off of the vehicle.
6. Remove the two 3x15mm button-head screws from the
differential cover. DO NOT remove the two screws that secure the
shock tower.
7. Use a 1.5mm hex wrench to remove the two screw pins that hold
the driveshaft yokes to the differential output shafts. Remove the
differential cover and slide the differential out of the front of the
case.
8. To reinstall the differential, reverse the steps.
Front Differential Removal
1. 3x15 BCS
6. 3x15 BCS
4. 3x15 BCS
7.
2. 4x10 BCS