TRIPLE THOUGHTS
The article on the T160 in RC217 was perfectly timed for me as I’m pondering on purchasing one from a friend. I don’t have a logical reason to buy it, however!
Logic rarely comes into purchase decisions in this household. If it makes you happy…
It’s always good to read a piece about the old Tridents – more so when the discussion isn’t entirely about appearance! I think most would agree that BSA / Triumph could have had a different future if the 1968 T150T had had the specification of the eventual T160.
The future would have been even rosier had the T150T been launched in 1965 – which was apparently entirely possible. It was prevented by both the demand from the BSA sales organisation in the USA for a BSA triple, and the decision to pitch the models to a new market – hence the passing of the design brief to Ogle. The fact is usually overlooked that the T150T was originally intended as a stopgap model pending development of an entirely new modern range.
The introduction by NVT of the T160 (and the rotary models too of course) was a result of its continuation of development that had started prior to the collapse of BSA. In reality the T160 represents a (heroic) failure and a running out of options for reasons well publicised. If nothing else its production allowed the use of the stock of starter motors bought for the cancelled dohc 350 twins! But after a decade the stop-gap model was a living fossil. It says much about Craig Vetter’s styling (created for the Bonneville) that so many T160s were sold.
Further to Frank’s observations about the different riding impressions given by the two Trident versions, his feeling that the T160 is the more stable reflects general comments about the T150 having sharper handling. I think that the oft-quoted statement that the T160 frame is based on the production racing frames is largely marketing guff. The racing frame carries the engine higher and further forward than does the T150 frame. The T160 frame realises this idea to an extent but it is actually a revised assembly of the T150 frame rather than a new racing-derived frame.
Comparison of the two Trident frames shows that the T160 frame uses essentially the same frame tubes and castings as the T150 frame, but there are differences in the position and orientation of the castings and the T160 headstock is machined for taper roller bearings rather than cup and cone. The rear frames of both models are interchangeable (disregarding the lugs/brackets for all the other gubbins).
A significant change is that the T160 swinging arm is mounted higher on the main frame, which together with the shortened fork dampers results in the frame (and hence the C of G of the whole motorcycle) being lowered in relation to the ground. Any benefit from the raising of the engine in the frame is thus cancelled by the lowering of the frame in the rolling cycle – with no obvious improvement in ground clearance. Frank commented about the lower seat height this gives.
The lowering of the C of G of the T160 and at some point the slight increase in the rake of the fork (some feel T160 steering to be somewhat lazy in comparison to the T150) probably account for the different impressions of what are in reality very similar bikes. The standard T150 frame (itself derived from the T120 frame) was good enough to enable Malcolm Uphill to win a Production TT in 1970. However lessons learned led to the appearance of the production race frames later that year.
These are different from the T150/T160 frames in that the standard castings were fettled prior to assembly to remove unnecessary weight, and the frame tubes were both shorter and of a high-spec alloy steel with a thinner wall. The main frame loop, if the axes of the tubes are extended, can be considered to be a scalene triangle. It’s contracted by shortening each side of this ‘triangle’. The racing frame thus carries the engine higher and further forward, resulting in a useful increase in ground clearance. If my T160s had actually had production-type geometry perhaps one of them would have replaced my original T150 (now with added electric start!) but I’ve learned to be wary of pulchritude!
I recall getting fearsome stick some years back when I made an offhand remark about the differences between T150 and T160 frames in an article. I do believe that every single member of the TR3OC contributed (…contradictory…) insights on the subject! It perfectly illustrates how changing one or two apparently minor aspects of a motorcycle’s geometry can radically affect the riding experience. Throw in 50 years of owner adaptations, and it’s hard to generalise about anything – apart, of course, from the fact that the X-75 is better looking than any of them.