Sway
Sway is the side-to-side oscillation of a towed caravan about its vertical axis. Poor load distribution, low tow hitch load, high speed and crosswind are the main triggers. Because the oscillation can amplify itself, it threatens control of the vehicle if it is not dealt with early.
A caravan is a mass that can rotate about the tow ball. When a disturbance pushes the caravan sideways, the resulting forces may throw it the other way instead of bringing it back. The further the centre of gravity moves behind the axle, the more unstable this behaviour becomes.
- Load distribution: put heavy items in line with the axle and low down; piling them at the rear end feeds sway.
- Hitch load: too low a hitch load is the most common cause of instability.
- Speed: every combination has a speed at which it loses stability; the margin shrinks as speed rises.
- Response: when the oscillation starts, the generally accepted approach is to lift off the throttle and reduce speed without sudden steering or hard braking.
Sway is a phenomenon of travel and must not be confused with levelling while parked. Their common denominator, however, is load distribution: loading the vehicle in a balanced way both reduces sway on the road and, when parked, evens out the leg loads and prevents body twist.
Context in which this term is used: Guide to automatic RV levelling