K021 Instructions v1.0
Tuning
Page
74
The initial disadvantage of the mid-motor concept was a lack of forward bite out of
corners, especially on slick tracks. X Factory designed the 4-gear transmission to help
solve this problem: by turning the motor so it rotates in the same direction as the
wheels, the motor itself helps transfer weight to the rear under acceleration, dramatically
increasing forward bite. Further, the XF Team has put a lot of work into set-ups,
developing cars that often have more rear bite than our competitors!
The starting set-ups in this manual have several features that add rear traction to help
ease the transition to driving a mid-motor buggy. These include starting with the 4
o
rear
toe-in block, running the rear hubs all the way forward, and using 30
o
front caster
blocks. As you become more familiar with the car, you may find yourself surprised to be
searching for steering. Read through the rest of this Tuning Section; check the set-ups
posted by team drivers on our website, and feel free to post questions in the forum
about your car. We love talking about this stuff!
TIRES
Tires are the most important tuning element by far: they’re the car’s only connection to
the ground, and all other suspension or chassis changes must act through them. That
said, tires are obviously very track- and condition-specific, so there’s not much we can
tell about them here. If you don’t already have the right tires for your local tracks, see
what the fast guys there are running. That’s usually it.
SLIPPER AND DIFFERENTIAL
In previous sections we described breaking in your diff, adjusting it, and how to test your
slipper clutch. Now, a few words about setting them! The diff and slipper can have a
big impact on how your car corners and lays down the power.
The slipper clutch allows some ‘give’ in the driveline, which both protects the rest of the
driveline from shock loads and takes the edge off the car in the high-torque range of the
motor’s rpm. Off the line and out of corners the slipper will slip some, just as its name
implies, which helps prevent wheelspin and lets the car hook up. On slippery or looser
tracks, we generally run a ‘looser’ slipper: back the nut off so that, when checking on the
bench, the front end barely rises off the table. As traction comes up, you can tighten the
slipper accordingly. On super high-bite surfaces, you’ll actually back the slipper off
some to prevent the car from pulling hard wheelies. The nice thing about slippers is the
