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Triumph Bonneville

(by Ian Falloon, Feb 2022)

              Bonneville 1969



Falloon picks the best of the Meriden vintages


A great wine, such as a Grange Hermitage or Chateau Lafitte, will always have a vintage year, that particular year where the weather conditions were just perfect, and the grapes at their peak.


The same can be said about certain motorcycles, and the 650cc T120 Triumph Bonneville is a particular case in point. Rather than the variability of climactic conditions, motorcycles can suffer from poor managerial decisions, or the demands of the marketplace.


This is especially appropriate to the T120 Bonneville that, along with the single carb Trophy, was Triumph’s production mainstay from 1959 until 1974.


Ask any Triumph enthusiast for an opinion on the vintage years for the Bonneville and inevitably the years from 1968 until 1970 will be mentioned. Before 1968 the Bonnie was afflicted with marginal electrics, handling and brakes, and after 1970 there was the debacle of the Umberslade Hall designed oil-in-the-frame version.


If one bike typifies the sixties it is undoubtedly the Bonnie. Because they were so ubiquitous, to so many older enthusiasts today it is the one bike that epitomises youth. By 1972 it was reckoned that 250,000 Bonnevilles had been built - at least three times as many as any comparable Norton or BSA twin. The Bonneville also offered an unparalleled balance between looks and performance at a competitive price, and a timeless appeal, and the ones to have were from that pinnacle period, 1968 to 1970.


Yet it was considerably earlier that the Bonnie was conceived. In recognition of the speed records at Bonneville, Triumph boss Edward Turner decided to make the most of this association, and in 1959 Triumph released the T120 Bonneville. This was intended to be the performance flagship, but initially still very much a 650cc T110 Thunderbird hybrid.


Performance was boosted over the 110 through the use of a splayed-port alloy cylinder head, higher compression, and twin Amal monobloc carburettors without air filters. With 46 horsepower at 6,500 rpm, the Bonneville was claimed to be the fastest production bike available, a claim substantiated in 1961 when the British motorcycle press tested a T120R at 188 km/h.


The first unit construction Bonneville appeared in 1963, and at first wasn’t as highly rated as the pre-unit predecessors. While there were gains in the frame, which reverted back to the classical Triumph single downtube, the unit construction engine lost out in smoothness and electrical reliability.


However, where the new T120 really scored over the pre-unit 650’s was in compactness and weight. At 165kg it was nearly 14kg lighter, and this contributed to much brisker on the road performance. Every year saw a range of detail improvements, in particular from 1966 onwards, but with 1968 came one of the three top years. A new 8-inch twin leading shoe front brake, two-way damping in the front fork in light of racing experience, and a stronger race-bred swinging-arm, contributed to superior on-the-road performance.


This was a particularly trying time at Meriden, both financially and politically, and most resources were being poured into developing the new triples. By now the 650cc engine had reached the zenith of its development as a competition unit, and the Umberslade oil-in-the-frame models were waiting in the wings.


But the late sixties were real boom years for sales in the US, with over 30,000 Triumphs sold in 1969. While Meriden was flat out meeting demand, with production up to about 900 machines a week, quality varied considerably, and the factory never really mastered the high volume/high quality equation that ultimately contributed to their downfall.


After 1970, just as the T120 seemed to represent the distillation of everything that was right about motorcycle styling, the expensive new R&D facility at Umberslade Hall gave birth to the inferior oil-in-the-frame replacement. When it appeared, enthusiasts were mortified.


Gone were the classic mufflers, gaitered forks, bullet-shaped headlights, and rounded side covers that epitomised Triumph. What’s more the new double cradle frame was so tall that the seat height was a towering 876mm, and a series of initial production problems got them off to a very shaky start. Eventually the oil-in the-frame twins became solid and rideable motorcycles, but looking back now Triumph enthusiasts lament that the 1970 models were “the last of the good ones”.


Given some of the reliability problems of the late sixties, the use of the word “good” is dubious, but what is undeniable is that they were the last of the “classic” Triumphs, and among the best-looking motorcycles ever made.


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