1957 Triumph Thunderbird

1957 Triumph Thunderbird

1957 TRIUMPH THUNDERBIRD IS THE COOKING VERSION
The 1957 Triumph Thunderbird was fast becoming the ‘ugly sister’ to the hot new Triumph TR6 and the already red-hot Triumph Tiger T110. With its full fenders, headlight nacelle and milder tuning, the 6T was really the basic commuter of the Triumph 650 line. In England, they would call this ‘the cooking version’.

WILD NEW COLORS FOR 1957 TRIUMPH THUNDERBIRD
In the biggest market for Triumph motorcycles, the US, things were getting wilder by the day in the automotive scene. Carmakers were putting bigger and bigger fins, more and more chrome and wilder and wilder colors on their products, and the scary part is that it seemed to be working. Triumph jumped on board with a whole raft of cosmetic upgrades, to make their bikes more flamboyant. This was actually right up Edward Turner’s alley, as this was his original marketing plan with Triumphs line of singles, when he first arrived at Triumph in 1935. He took stale old models and gave them bright new paint and brightwork. It worked then, could it work now?

BOLD NEW TANK BADGE ON 1957 TRIUMPH THUNDERBIRD
A new chromed tank badge appeared, recognizable by the striking chrome-grille ‘mouth organ’ look, with the Triumph name picked out in white against a black background (and a new tank was needed to accommodate it). This large badge, in conjunction with a chrome trim strip allowed 2-tone paintjob in the best tradition of late 1950’s decadence. Triumph Motorcycles probably did better in this area (picking better colors and finishing them better) than just about anyone else in the British Motorcycle Industry at the time. The fenders were painted to match also, with a gold-lined stripe running down their centers. A very handsome color scheme.
RUNNING GEAR
A new chain guard was introduced across the entire line, offering better enclosure and more solid mounting (to the lower rear shock bolt). The lower exhaust bracket, always prone to cracking from vibration, was beefed up. The “hole-in-the-frame”, (a cast lug in the frame behind the engine that allowed a single carb to run a straight tube trough it to a large air cleaner under the seat) actually trickled-up to the TR6 line.

TRICKLE-DOWN IMPROVEMENTS
The 7-inch front brake was improved greatly with the fitment of a full-width finned hub and a modified backing plate. The brake shoes themselves were actually the same as before. The humble T-Bird’s high-performance stablemates, the Tiger T110 and TR6 got a new 8-inch front brake. This seemed to be the pattern at this time. The T110, then later the T110 and TR6, would get all the best parts first, then as they moved on to yet more new features, the old ones would trickle down to the 6T Thunderbird. The alloy Delta head still had not made the journey, as the T-Bird still used the old cast iron head, although with some modifications.

GEARBOX
Changes were made inside the gearbox. These included a new kickstart cotter, in an effort to stem a well-known oil leak. New sleeve gears with bushings were fitted, and the mainshaft high gear bushing now extended through the primary case oil retainer plate into the chain case itself, again all in an effort to combat oil leaking. And it was not altogether successful. The rubber compound of the clutch shock absorbers was again remixed.


1957 Triumph Thunderbird SPECIFICATIONS

Engine type

Displacement

Bore & Stroke

Compression

Carburetor

Ignition

Engine output

Primary drive

Primary sprockets

Clutch

Gearbox

Ratios, overall:

1st, bottom

2nd

3rd

4th, top

Final drive

Final drive sprockets

Frame Type

Suspension, front

Suspension, rear

Brake, front

Brake, rear

Tire, front

Tire, rear

Wheelbase

Seat Height

Ground Clearance

Fuel capacity

Dry weight

Air-cooled OHV vertical twin, non-unit

649cc / 40.0 ci

71mm X 82mm / 2.79″ X 3.23″

8.5:1 (US & export); 7.0:1 (UK)

1-Amal Monobloc

Lucas magneto

34 bhp @ 6500 rpm

1/2″ X .335″ X 5/16″ chain, 70 links

24T X 43T

Multi-plate, wet

4-speed constant mesh, right foot shift

 

11.9:1

8.25:1

5.81:1

4.88

5/8″ X .400″ X 3/8″ chain, 101 links

18T X 46T

Brazed lug, rigid

Telescopic fork, hydraulic damping

Swing arm, 2 Girling dampers

7″ SLS drum

7″ SLS drum

3.25″ X 19″

3.50″ X 19″

55.75″ / 141 cm

31″ / 77.5 cm

5″ / 12.7 cm

3 Imp gal (US); 4 Imp gal (UK & export)

395 lbs / 179 kg