The Smiths and Jaeger instruments fitted to the MGB are mechanical units driven by cables, and their condition is one of the most immediate indicators of a car’s overall state of care. The instruments were originally marked British Jaeger with a small ‘British’ above a larger ‘Jaeger’, later replaced by Smiths branding. Speedometers are available on exchange across a comprehensive range of calibrations, covering 1040, 1020, 1060, 1216 automatic, 1280, and 1000 mph units in both mph and kph specifications. Correct calibration identification is essential as the drive ratio differs between gearbox types, axle ratios, and overdrive applications.
Speedometer cables are available in five specifications reflecting the different cable lengths and fittings across the production run, pre-1967, four-synchro standard, pre-1976 overdrive and V8, post-1976, and post-1976 LHD overdrive. Tachometers are available on exchange in Smiths and Jaeger specifications, with positive earth, negative earth converted, and standard negative earth versions covering the full production run including the early positive earth cars to 1967. The ammeter and voltmeter are available as Smiths units. Chrome gauge rims are available in three diameters for refinishing the gauge surrounds.
Gauge failure is most often a fuse or sender unit issue rather than the gauge itself, always check both before replacing a gauge.