SunTour - Frank Berto and the curse of Duopar

SunTour AG Tech derailleur (5000) main image SunTour Trimec black derailleur (4600) main image SunTour Superbe Tech GTL derailleur (5400) main image

This group of derailleurs tell a story of the best people, with the best of intentions, striving for perfection and, in the process, destroying the very thing that they love. It is a genuine tragedy in the Greek tradition.

By the mid 1970’s a new breed of cyclists was emerging. We were typically young, middle class and often graduates. We had a vague interest in cycle racing, but no history of riding in the chain-gang, we did not point out potholes as we cycled past them, or sprint for speed limit signs. We cycled for pleasure, for environmental reasons, to travel in a way that connected with the landscape and/or the cityscape and (most important of all) we cycled in order to be pointedly different from the car driving masses. Making your protest by riding a bike seemed so much easier than joining the Red Brigades or signing up with Andreas Baader and Ulrike Meinhof, so much more peaceful than shooting Aldo Moro in the back of your car, or helping Joschka Fischer to bludgeon Frankfurt policemen. We were physically fit, but not into breaking through the pain barrier - we needed low gears and lots of them - and because of all this we were interested in quality touring derailleurs.

The high priest of this movement to low, low gears was Frank Berto, a California-based mechanical engineer. He brought a certain rigour to the subject of bicycle gearing, clearing the shrouds of myth and legend in which the European derailleur manufacturers so loved to hide. Frank Berto had first become interested in very low gears in 1971, had written a seminal article on low gears for Bike World magazine in 1973, and had become a regular contributor (mainly on the subject of gearing and derailleurs) to Bicycling magazine from 1975 eventually becoming engineering editor. Famously, Frank Berto built a derailleur testing machine, and used it ruthlessly to assess how ‘early’ or ‘late’ a derailleur shifted, and how much ‘overshift’ and subsequent correction were required. His tests consistently showed that Japanese designs, and particularly SunTour designs, were measurably superior to those of the more prestigious European brands, including Campagnolo, Simplex and Huret. We ‘new cyclists’ loved a bit of scientific rigour - and loved it even more when that rigour was used to overturn the established order. We lapped up every word that Frank Berto said. I remember waiting with bated breathe for the latest edition of Bicycling to appear so that I could read Frank Berto’s article on whichever new gear had just hit been released.

Suntour and Frank Berto were symbiotic. SunTour was not into myth and legend, it had little interest in gaining prestige by sponsoring Tour de France teams. SunTour’s ‘thing’ was excellent, affordable, engineering. By the mid 1970’s SunTour had established itself as the derailleur brand of choice for the ‘new cyclists’ and their wide range gears. SunTour Cyclone GT’s, SunTour V GT’s, and SunTour GT’s were everywhere, coping valiantly with the new 14 to 34 freewheels that we so loved.

Everything in the garden was lovely - until a niggling doubt wormed its way into our world. In 1975 Huret released its Duopar derailleur. This was a very interesting design, with a third pivot that allowed the pulley cage to float up and down, maintaining a small chain gap even with very wide ratio freewheels. The Duopar was also constructed out of exotic materials with titanium pressings as knuckles, in the style of the Huret Success. Because of all this complexity and exoticism the Duopar was fiendishly expensive - and therefore only sold in small numbers, posing no threat to SunTour’s business. However, when tested on Frank Berto’s machine the Duopar turned in the best results yet achieved. Frank Berto himself started to use the Huret Duopar on his own bikes. This sent a shiver through the derailleur world, and particularly through SunTour, which felt that its technical supremacy was threatened.

All this was deeply mysterious to British bicycle mechanics. I hated the Huret Duopar in much the same way that I hated the earlier Huret Allvit. The Duopar was a bit like a Meccano construction kit to fit, with the hanger bolt and washers loose in the bag, it had Huret’s ridiculous plastic ‘styling’ parts. It was a fragile design made up of easily bent flimsy plates. But most of all it worked fantastically when new - but in British conditions at least, it then wore out almost immediately. Many are the hours I have spent wrestling with Duopars with loose pivots, with the pulley cage slightly out of line with the main body, with slightly bent pulley cages etc. etc.. I referred to these bikes as suffering from the ‘curse of Duopar’. The Huret Duopar was great for Frank Berto, who probably religiously cleaned and oiled his gears and lived in sunny California - and disastrous for the everyday British cyclist, who went light on maintenance and rode in filthy, muddy, rain. The customer’s expectations of the Duopar were always extremely high (partly fuelled by Frank Berto) - but the reality was so distressing poor. It was incomprehensible to me that anyone would want to copy such a dog.

However SunTour and, to a much lesser extent, Shimano were obsessed with the idea that they had to come up with a design that would out perform the Duopar on Frank Berto’s famous test rig. Both decided to introduce designs incorporating a third pivot. SunTour went first, initially with their 1982 SunTour Trimec (an alarmingly literal copy of the Huret) and then with their first mountain bike specific derailleur - the 1982 SunTour MounTech. The MounTech, in particular, had everything, it was a slant parallelogram design, it was affordable, it had its three pivots and, most crucially of all, it reclaimed the crown for SunTour when tested on Frank Berto’s machine.

However the MounTech had two flaws. Firstly it had a very complicated and fragile guide pulley that quickly wore out or sometimes even broke into pieces - thereby causing expensive warranty problems for the bicycle brands that used the MounTech as original equipment. Secondly it had some of the flaws of the Duopar - it was simply too complex and easily bent. Several of the ‘Tech’ series derailleurs in this collection are well used examples in which the pulley cage is no longer properly aligned with the main body. Crucially SunTour used Duopar-like designs on all of its early mountain bike derailleurs. Shimano, always more cautious about the idea, did offer the Duopar-like Shimano Deore XT Superplate, but was also careful to offer (and encourage the adoption of) the standard Deore XT.

The problems with the MounTech were a terrible blow to SunTour, and they made every effort to correct the design - and did so with a new guide pulley and third pivot design for 1985. However the market had discovered that the conventional two pivot Deore XT worked just fine, and that the extra complexity of the three pivot design had never been necessary after all.

In his article ‘Sunset for SunTour’ Frank Berto identifies the MounTech fiasco as one of the crucial events that destroyed SunTour, precipitating their decline from technical and market dominance in the early 1980’s to total irrelevance by the 1990’s.

As I said at the beginning, the whole story is a tragedy. Excellent Frank Berto, with his scientific rigour, contributed to the well-merited rise of the excellent SunTour V GT derailleurs to world dominance. Then by praising the quick-shifting but fragile Huret Duopar, the still excellent Frank Berto inadvertently provided the spur for SunTour, a company he much admired, to launch the quick-shifting but fragile SunTour Mountech - a mistake from which the company never recovered. And, most galling of all, it was all completely unnecessary - today’s Shimano Deore XT M772 uses the same basic geometry as the 1970 SunTour V GT, without a third pivot anywhere in sight.

SunTour was a great company - but was laid low by the ‘curse of Duopar’.