The Dennis RS/SS series was a range of fire engine chassis built by Hestair Dennis (later Dennis Specialist Vehicles), produced from 1978 until the early 1990s.
Internally codenamed Retained, Steel, the Dennis RS series was first launched in 1979, initially not offered with a tilting cab due to a belief that few fire stations at the time could accommodate a tilting cab. A lower-cost alternative named the Standard Specification, or SS series, was launched shortly afterwards, however at the request of the London Fire Brigade, this would be fitted with a tilting front cab as standard to improve ease of maintenance. The all-steel cab, designed by Ogle Design, replaced the older fibreglass and wood construction of the previous appliances it succeeded, such as the Dennis D and Dennis R, increasing the strength of the cab overall in the event of a collision.
The first of the Dennis RS/SS fire appliances were fitted with Perkins V8 diesel engines, either the V8-540 or the V8-640, with or without turbochargers; by 1987, the RS and SS could be specified with Cummins C-series engines. Early appliances were bodied in-house by Dennis at their Woodbridge factory, but when in-house fire engine bodying was discontinued in 1985, the bodying of the Dennis RS/SS series and derivative products was outsourced to other coachbuilders, primarily to Carmichael Fire. The RS could also be fitted with a variety of bodies by other coachbuilders including HCB Angus, Fulton Wylie and Saxon Specialist Vehicles.
Over 1,750 Dennis RS/SS fire engines would be produced, being sold to nearly all fire brigades across the United Kingdom as well as being exported to various fire brigades worldwide. As the appliances aged, RS and SS series appliances were known to suffer from corrosion particularly around the cab doors, nicknamed "Dennis Disease" by mechanics.
