| Diagram | Fig. 14 — SWINGING FORK, SUSPENSION UNITS AND CHAINGUARD · ref 40 |
| Subsystem | primary |
| Listed in parts books | 1965–1967 |
BRK SW 54-59 PTRI 6468 50
Lucas-type rear brake light switch, PN 31383, used in the rear suspension/brake linkage area on pre-unit and early unit Triumph twins.
This is a Lucas-type brake light switch, PN 31383, also cataloged under SPX016. Our records show it appearing in the SWINGING FORK, SUSPENSION UNITS AND CHAINGUARD figure, which puts it down in the rear suspension area rather than up on the bars — this is a rear brake switch, not the front lever plunger type.
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The switch closes the circuit to the stop light when the rear brake is applied, so the wiring routes back from the switch body to the tail lamp. It's a mechanical trigger tied to brake pedal or rod movement, and like most Lucas switches of this era it's a simple, replaceable unit rather than something worth rebuilding.
Our catalog entries for this one span the mid-1960s. If you're matching this to a specific machine, bring your parts book number or ask us to check before you order — pre-unit and early unit twins used a few variations of these switches and we want to get you the right one.
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