The Armstrong lever-arm damper is the original front damper on every classic MG fitted with a double-wishbone front suspension, the MGA, MGB, MGC, MGB GT V8, and their contemporaries, and is also the rear damper on every classic MG with a live-axle rear end. The damper is built around a hydraulic mechanism inside the body that resists the movement of the arm under suspension travel, the resistance characteristic determined by a set of valves inside the body that control oil flow between the working chambers.
The standard valves produce a damping curve suited to original-specification road use, while uprated adjustable valves produce firmer, tunable damping for owners running modified or competition specifications, and the replacement gasket sets cover the seals needed for any rebuild, as a damper that has lost its oil through aged seals has lost its damping action entirely.
Adjustable Valve Assemblies
The adjustable valves replace the original fixed valves inside the damper body, providing a means to tune the damping characteristic to suit the application, the adjustment typically being a screw setting on each valve that allows the bleed orifice to be opened or restricted, with restriction increasing the damping force and opening reducing it. The result is a damper that can be set to firmer damping for spirited road use, competition specification for sprint and hillclimb work, or kept at standard road specification for normal use, and on some valve specifications different damping rates can be set for bump and rebound, the compression and extension strokes, allowing the damper to be tuned more precisely to the car's spring rates and the owner's preference. Each application has its own valve specification, the front damper valves differing from the rear damper valves and the various models differing in valve dimensions and mounting arrangement, so the valves are matched to the specific damper application at the point of order. The valves are a particularly useful option during a damper rebuild, allowing the rebuilt damper's characteristics to be fine-tuned to the rest of the car's specification, and suit cars where damping requirements may change, fast-road use, occasional track use, or the addition of uprated springs, where the owner wants to optimise the damping without committing to a fixed-rate rebuild.
Replacement Gaskets & Seal Sets
The Armstrong damper body is sealed by a series of gaskets and O-rings that maintain the hydraulic oil pressure inside the working chambers, and aged dampers typically leak through these seals as the rubber compounds harden and the gasket faces corrode, leaving a damper that has lost its oil and consequently its damping action, a frequent cause of damper fluid leaks even when the internal valving is in good condition. The replacement gasket sets cover all of the seals needed for a complete damper rebuild, the body-to-cover gasket that seals the case halves, the shaft seal where the arm exits the body, the filler-plug O-ring, and the various smaller seals at the valve assemblies and external fittings. Renewing the seals as part of a damper service or rebuild restores the original sealing performance and allows the damper to hold its oil through normal service intervals, and a complete gasket set is required for any rebuild work, with service kits containing all the components for a typical rebuild available alongside individual parts for specific repairs.
Rebuild Considerations
A complete Armstrong damper rebuild typically involves the body being dismantled, the valves and pistons being inspected for wear, the seals being renewed, the oil being changed, and the body being reassembled with the appropriate torque settings, the work being methodical but not difficult for an owner with workshop facilities, while alternatively the dampers can be sent away for professional rebuild by specialists who have built up the experience and the tooling to do the work efficiently. Beyond the gaskets and valves, damper rebuilds may need new pistons, seals, fluid, and small fixings, and the correct damper oil to the right specification is important as the oil viscosity contributes to the damping characteristic.
For owners considering whether to rebuild original Armstrong dampers or convert to telescopic damper conversions, the rebuild typically costs substantially less than the conversion and preserves the original lever-arm appearance and behaviour, which matters for cars maintained to original specification, while the dedicated Suspension parent section covers the telescopic conversion options for owners choosing that alternative. The technical team is available to advise on the right valve specification and the appropriate rebuild approach for a specific damper application.