1953 Triumph Thunerbird

1953 Triumph Thunderbird Background & History

The 1953 Triumph Thunderbird was largely carried over from the 1950 through 1952 Thunderbirds.  Rigid frame, front forks, wheels and brakes, bodywork and seat were all very similar to the previous models.  Paint colors and minor trim varied.  However, some significant mechanical changes were made for the 1953 model year.

New 1953 Triumph Thunderbird Electrical System

The 1953 Triumph-Thunderbird benefited from the switch to alternator electrics, points and coils for ignition. Gone were the old magneto (spark) and dynamo (lights). The new electrics appeared first on the 500cc 5T Speed Twin, then began appearing on other models throughout the model year.

The new Lucas RM12 alternator lived in the primary chaincase on the outer left end of the crankshaft. Changes to the primary cases were made to accommodate and a large, elegant bulge appeared on the outer primary case that would evolve into the lovely Triumph logo that would appear on later Unit Construction twins. The points were located in a distributor which occupied the space behind the cylinders where the magneto used to live, and was driven by the same method: gear-driven off the inlet cam gear.

The 1953 Triumph Thunderbird had no means of voltage regulation, just a simple full-wave, 2-plate rectifier under the seat for converting AC to DC current. In case of a dead battery, an “Emergency” switch brought the alternator’s full output into the ignition circuit, making it easier to start. The old magnetos were self-sufficient & would start no matter what. These new-fangled alternators & coils were suspect in the eyes of the public. Engine mounting plates were modified to deal with the absence of the dynamo.

1953 Triumph Thunderbird Loses its Shock Absorber

One nice feature that pre-unit Triumph twins had prior to the alternator was a very neat engine shock absorber that occupied the place at the left end of the crank now taken by the new alternator. This shock absorber was really an ingenious contraption. It was comprised of two pieces cammed to one another with ramps and pushed together with a spring. One was hooked to the crank and the other to the primary engine sprocket. It allowed a certain amount of “give” in the form of some controlled slippage in both directions between the two pieces along their ramps, against the spring tension attempting to clamp them together. This served to quell engine vibrations so effectively that it made everything last longer: engine bearings, primary chain, gearbox, even the final drive chain were reputed to last longer due to the smoothing effect of the shock absorber. Unfortunately, this brilliant innovation had to be dumped to make room for the alternator. Attempts were made to accomplish the same task with a shock absorber inside the clutch hub, but nothing worked as well.

1953 Triumph Thunderbird Teething Problems

The early alternator systems had problems. The distributor was inaccessible, the wiring much more complex. The only way to get full power out of the alternator was to turn on the headlights. This triggered the alternator to go from 4 stator windings to 6. The critical air gap between alternator rotor & stator was proving vulnerable to play in the bottom end. Many fixes were tried, but not until the resin-encased the stator in 1968 did the problem truly get solved. Loose primary chains would also eat into the alternator wiring.

The distributor too was fraught with problems. It had one set of points and one coil, with a rotor and distributor cap, car-style. The small dimensions of the bushings also caused excessive wear.

While there were some early problems with the new electrical system, for the most part, the change was progress. And the good thing about alternators and points was that, when they did fail, the were much less costly than replacing a magneto or dynamo. However, magnetos were retained on some pre-unit sport models, as racers preferred them and Triumph didn’t want to lose their business to BSA or Norton, who were still offering the mag.

A young Marlon Brando rode a black 1950 Triumph Thunderbird in the 1953 movie "The Wild One".  Soon after Triumph started offering black paint on their Thunderbird, which became known by the nickname "Blackbird".

1953 Triumph Thunderbird Specifications

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1953 Triumph Thunderbird Books

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More Triumph Thunderbird Pages

1950 Triumph 6T Thunderbird
1951 Triumph 6T Thunderbird
1952 Triumph 6T Thunderbird
1953 Triumph 6T Thunderbird
1954 Triumph 6T Thunderbird
1955 Triumph 6T Thunderbird
1956 Triumph 6T Thunderbird
1957 Triumph 6T Thunderbird
1958 Triumph 6T Thunderbird
1959 Triumph 6T Thunderbird
1960 Triumph 6T Thunderbird
1961 Triumph 6T Thunderbird
1962 Triumph 6T Thunderbird
1963 Triumph 6T Thunderbird
1964 Triumph 6T Thunderbird
1965 Triumph 6T Thunderbird

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