atm vsProtected against: 1 ATM: Can withstand depths of up to 10m (33ft) Wet weather conditions and splashes: 3 ATM: Can withstand depths of up to 30m (98ft)The difference between ATM and GTM – 200kg in this case – is the amount being supported by the jockey wheel or towbar of the tow vehicle, otherwise known as ball weht. Therefore, payload capacity of a trailer is