Common Terms Explained
for RC Cars Part 2
Here are some of the common terms explained for RC cars. These terms
and abbreviations are commonly used by experts, manufacturers, message
board users, old professionals, racers, club members etc.
Ackerman refers to the angle between the two front (steering) wheels
when turned to full lock. Altering this 'ackerman angle' will alter
the steering characteristics. A greater angle will give you smooth,
predictable steering, whilst a smaller angle will give you more aggressive
steering. The angle for the rear whish bone hinge-pins relative to the
horizontal refers to the term “Anti-Squat”. Increasing the angle gives
more anti-squat, meaning that the car is less likely to squat (drop
at the rear) during acceleration.
Wheelbase is the distance between the front and rear axles of the car.
The angle of the wheels (when looked at from the front or rear of the
car) relative to the vertical is known as Camber. If the wheels lean
inwards towards the car, the angle is said to be negative. If they
lean out the angle is positive, however, positive camber is almost never
used. Basically, zero camber gives the maximum forward traction, whilst
more negative camber gives more grip while cornering. Caster describes
the angle (when looking at the front wheels from the side of the car)
between the kingpin and the vertical. This is part of the car's geometry
which keeps it travelling in a straight line when no steering force
is applied. It is not adjustable on all cars.
The relationship between the speed of the motor and of the driving wheels
is known as the Final Drive Ratio. For example, a final drive ratio
of 8.17:1 means that for every rotation of the wheel, the motor rotates
8.17 times. Lower the number on the left of the colon, the higher is
the ratio i.e. more top speed and less acceleration. Tweak is the difference
between the heights of the wheels relative to the ground (at the same
end of the car). e.g. If the front left is lower than the front right
the car is said to be 'tweaked' usually caused by a distorted or 'tweaked'
chassis or unequal shock lengths
Toe-in is the relative angle between the two front wheels or rear wheels
(when viewed from above). If the wheels point inwards (towards the front
of the car) it is called toe-in, if they point outwards, it is called
When people refer to body roll, they are talking about the way the car
pitches, either from side-to-side (when cornering) or front-to-back
(when braking or accelerating). Ball differential is a design of differential
unique to model cars which use ball bearings instead of bevel gears
to achieve differential speeds at both wheels. It has the effect of
allowing one wheel to slip whilst still delivering power to the other.
It is also known as 'limited slip differential'.
Tires which have a flat ring of ridged material molded into the rubber
to prevent 'growing' at high speeds, an effect that reduces the tires
contact area with the track, resulting in loss of grip. This tires are
known as Belted Tires.
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