1972 Triumph Bonneville

1972 Triumph Bonneville Background & History

The 1972 Triumph Bonneville was mostly carried over from 1971. So many changes were made in the 1971 Bonneville that little new was needed, but some brushing up of its finer points was in order. And just about every part of the bike was looked at and changed as needed. 1972 was also the year when Triumph's parent company, BSA collapsed, leaving Triumph in the hands of their old rival Norton. Whatever was going to happen next was bound to be interesting. And it was, but that’s another story.

The 1972 Triumph Bonneville was certainly a handsome machine.

1972 Triumph Bonneville gets an Optional 5-Speed

Minor revisions were made to the clutch actuator mechanism for the 1972 Triumph Bonneville. And of course, the 5-speed Quaife gearbox became available as an option. These 5-speed bikes received a “V” after their model designation (ie: T120RV) and a Roman Numeral “V” on the black side covers under the “Bonneville” transfer.  Improvements were also made to the gorgeous front conical brake designed to improve braking performance.

The 1972 Triumph Bonneville engine was largely carried over without change.

1972 Triumph Bonneville gets a Lower Saddle

The excessive seat height of the 1971 Bonnevillewas the main change to the chassis for the 1972 Triumph Bonneville. By reworking the seat rails and the seat itself, they dropped it from a towering 32-1/2 inches down to a much more reasonable 30 inches. But stocks of the old, taller frame were used up first, so the lower seat height began with Engine #CG50414. Some dealers couldn’t wait and came up with ‘quick fixes’ themselves, like shortening the forks and shocks, and removing padding from the seat. The frame changes required alterations to the Girling rear shocks, the seat, battery box, air filters, coil mounts ands side panels. Most everything else carried over relatively unchanged.

The big news for the 1972 Triumph Bonneville was the availability of the optional Quaife 5-speed gearbox.  The 5-speed bikes got a "V" under the Bonneville decal on the side covers, like this one.

This is the paint combo of the early 1972 Triumph Bonneville.

1972 Triumph Bonneville Color Combos

The 1972 Triumph Bonneville color scheme was Tiger Gold over Cold White, with black pinstriping separating the two colors.  Early 1972s saw the white start under the tank badge and ran forward from its leading edge to the front of the tank, and ran rearward from the bottom-rear corner of the badge, curving down and running horizontally under the knee grip rubber.  Late 1972s had white flashes, from the top and bottom of the tank badge, curving backwards.  The later design was probably the better-looking.  All of the above applied to US-market bikes with that pretty teardrop tank.  The larger, squarer UK-market tanks got a white center stripe and lower side borders.  Same colors, same pin striping.

Lowering the seat height of the 1972 Triumph Bonneville required reworking the seat rails of the frame, shortening the shocks and removing some foam from the seat.

Improvements to the Conical Brake

When the 1971 Bonneville launched, just about everything (except the engine) was new; frame, suspension, running gear, bodywork, and brakes. And those brakes! Conical brake hubs front and rear give the 1972 Triumph Bonneville an exotic, race bike-look. While some Triumph traditionalists opposed the ‘new look’ of the oil-in-frame 650s, they were very handsome bikes. The new-for-1971 twin leading-shoe conical front brake used a simple system to actuate the two brake cams. The rear arm anchored the outer casing of the brake cable, and the front arm held the inner cable, so that when the brake lever was depressed, the outer and inner parts of the cable would pull toward each other, thereby actuating the two arms. Simple, but maybe a little too simple. First off, the two arms didn’t always exert the same force, sometimes one pulled harder than the other, hurting brake performance. But, the biggest problem was that the 1971 brakes used actuator arms that were too short, and so didn’t have the mechanical leverage needed to apply the brakes hard.

When you compare the brake arms from this 1972 Triumph Bonneville those of the <A href='1971-triumph-bonneville.html'>1971</a> you'll see that the 72s are longer, giving them greater leverage.

So, the 1972 Triumph Bonneville got a set of longer arms, which mostly eliminated the weak braking for the earlier models. However beautiful to look at, the 8-inch conical brake never performed as well as the 8-inch TLS (1968 through 1970) that it replaced. The TLS had the actual mechanical linkage between the two brake arms that the conical hub lacked, assuring even pressure. And the TLS had a full-width drum, where the conical hub obviously couldn’t do that. But, the looks of the conical hubs were radical for the time, and still very attractive and rather exotic today. Custom bike builders (of both choppers and cafe racers) love them because there’s nothing else like them, and they’re fairly cheap and easy to find. In 1973 Triumph replaced this gorgeous front hub with a disc brake. A welcome improvement, practically speaking, but not as pretty as the conical hub setup. The rear brake was also conical, starting in 1971, and remained in use through the 1975s model year, replaced in 1976 by a rear disc brake, when the switch was made to left-foot shifting.

This is a UK-spec 1972 Triumph Bonneville with the larger 3.5 Imperial gallon "bulldog" tank.  Note the low bars, typical of British bikes.  Americans liked them taller.

1972 Triumph Bonneville Specifications

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Triumph Bonneville Books

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More Triumph Bonneville Pages

1959 T120 Bonneville

1960 T120 Bonneville

1961 T120 Bonneville

1962 T120 Bonneville

1963 T120 Bonneville

1964 T120 Bonneville

1965 T120 Bonneville

1966 T120 Bonneville

1967 T120 Bonneville

1968 T120 Bonneville

1969 T120 Bonneville

1970 T120 Bonneville

1971 T120 Bonneville

1972 T120 Bonneville

1973 T140 Bonneville

1974 T140 Bonneville

1975 T140 Bonneville

1976 T140 Bonneville

1977 T140 Bonneville

1977 T140J Silver Jubilee

1978 T140 Bonneville

1979 T140 Bonneville

1980 T140 Bonneville

1981 T140 Bonneville

1982 T140 Bonneville

1983 T140 Bonneville

1983 TSS Bonneville

1983 TSX Bonneville

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