1958 Triumph Twenty-One

1958 TRIUMPH TWENTY-ONE HAS BATHTUB STYLING.
The British home market had been hungry for cheap transportation after WWII, and commuter motorcycles helped fill that role. But England being...well, England, was wet and rainy and to prevent rust an owner needed to wipe his bike down each night after getting home from work. This was a chore that most came to hate. The British motorcycle industry responded with what are now called "enclosed bikes" as a way to make them easier to clean. Unfortunately, the gunk still found it's way into the new enclosures and rusted them from the inside out. Triumph had its swing at this fad, and it started with the 1959 Triumph 3TA Twenty One (350) and its big-sister-bike, the 1959 5T Speed Twin (500). Both had bulbous sheetmetal enclosures over the entire rear section of the bike, along with a huge full-valance front mudguard (fender) and old fashioned headlight nacelle. The look quickly spawned the nickname "Bathtub Triumph" and the name stuck. 55-odd years later, that's still what we call them today.
1958 TRIUMPH TWENTY-ONE HAS UNIT CONSTRUCTION
Unit construction was all the rage in England back in the 1950s. Essentially, non-unit construction is when the engine, primary case and gearbox are all separate components that are bolted together in the frame. It was the old way of doing things, but it was time to move on. Unit construction meant taking all these separate component and "unitizing" them, that is placing them all in one common casing. Hence the term "unit construction". The first bike to benefit from this was the 350cc Twenty One, which converted over in 1957. Next up was the 500 twin (5T , TR5 and T100) in 1959. Their big 650 twin, once sharing components with the smaller non-unit 500 twins, was now a stand-alone engine design. It took until the 1963 model year to redesign the 650 twin into unit-construction.

1958 Triumph Twenty-One SPECIFICATIONS

Model designation
Engine configuration
Displacement
Bore & Stroke
Compression Ratio
Fuel system
Primary drive
Clutch
Gearbox
Shifter
Final drive
Horsepower @ RPM
Frame
Rear Suspension
Front Suspension
Brakes, front
Brakes, rear
Tire, front
Tire, rear
Wheelbase
Overall length
Seat height
Curb weight
Fuel capacity
3TA
OHV air-cooled vertical twin
348cc / 21 ci
58.3mm x 65.5mm
7.5:1
1- Amal Monobloc
Chain
Multi-plate, wet
4-speed constant mesh
Right-foot
Chain
18.5hp @ 6500 rpm
Single down tube
Swing arm w/2 Shocks
Telescopic forks
7-inch SLS drum
7-inch SLS drum
3.25 X 17
3.25 X 17
53.5in / 1360mm
87in / 2115mm
28.5in / 724mm
340 lb / 154.4 kg
4.4 US gal / 16 L

Check out these TRIUMPH BOOKS




2018 Classic Triumph Calendar


Triumph Motorcycles: The art of the motorcycle


The Complete Book of Classic and Modern Triumph Motorcycles 1937-Today (Complete Book Series)


Triumph Motorcycles: From Speed-Twin to Bonneville


Triumph Bonneville and TR6 Motorcycle Restoration Guide: 1956-83


British Motorcycles Triumph (Little Books)


Triumph Motorcycles in America


McQueen's Motorcycles: Racing and Riding with the King of Cool


Triumph Motorcycle Restoration


Illustrated Triumph Motorcycles Buyer's Guide: From 1945 Through the Latest Models (Illustrated Buyer's Guide)


Tales of Triumph Motorcycles and the Meriden Factory


Hinckley Triumphs: The First Generation (Crowood Motoclassic)

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Last updated 12/1/17

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