SDCL § 32-18-3: Trailers, semitrailers, or pole trailers exempt from all-wheel requirement.

Trailers, semitrailers, or pole trailers of a maximum gross weight not exceeding three thousand pounds, and trailers, semitrailers, or pole trailers of a maximum gross weight not exceeding seven thousand pounds manufactured or assembled prior to July 1, 1974, need not be equipped with brakes acting on all wheels, provided that:

(1) The total weight on and including the wheels of the trailer or trailers shall not exceed forty percent of the gross weight of the towing vehicle when connected to the trailer or trailers; and

(2) The combination of vehicles, consisting of the towing vehicle and its total towed load, is capable of complying with the performance requirements of §§ 32-18-8 and 32-18-9.