Weight transfer - RC Handling Guides

In RC cars, as with any race car, when the car accelerates in any direction (acceleration, deceleration, turning), it undergoes load or weight transfer.

When accelerating from a stop, the car's inertia will make it want to stay still. However, with the wheels pulling the car forward, the car's mass will be forced to follow, and much of that load will transfer to the rear wheels. If you could weigh the car as it was driving, the rear wheels would be heavier (and the front wheels lighter) than when the car is at rest.

When you slow down, the opposite happens - the weight shifts to the front of the car, putting more load on the front wheels.

In turns, the car's weight shifts to the outside, putting more weight out the outside wheels and less on the inside wheels.

Tuning

RC car tuning is largely about helping the car respond to this weight transfer. As the chassis shifts (rolls) forward and back, left to right, the steering and handling becomes less and less ideal because the suspension is compressed on one side and extended on the other.

On low-grip tracks, this weight transfer can be helpful because it will help the car generate grip. On high-grip tracks, however, too much weight transfer will make the unresponsive, giving sluggish steering or causing unwanted situations like the lifting of the inside tire or even traction roll.

Controlling transfer

To limit weight transfer generally, thicker shock oil (or pistons with smaller holes) can be used to increase damping. You can also try lowering the ride height or limiting the droop.

Limiting side-to-side roll can be achieved by using thicker anti-roll bars or raising the roll center.

Of course, you can also limit weight transfer by simply reducing the weight of the car! Using lighter parts or electronics, trimming unused material (within reason!), and reducing the amount of wiring can all help to save weight and help your car respond more quickly to changes in direction.

Lastly, you can reduce the load transfer by shifting the arrangement of the weight within the car, moving weight towards the center of the car and as low as possible. Batteries and motors are mounted very low on the chassis for this reason.