See also also bike pic for other bike-related technical discussions and more failed parts.

SunTour Superbe Tech Rear Derailleur

Some derailleurs have interesting mechanisms but which are subtle or hidden and are easy to overlook. In contrast, the SunTour Superbe Tech uses a conventional parallelogram, but it looks highly unusual.

There are no gears in the design, but it might seem that way — from the outside, the operation is a mystery. Also, disassembling it is risky: you might never get it together again! Indeed, the first one I saw was damaged and disassembled; it was unclear if it was damaged before or after disassembly, but by the time I saw it, it was permanently damaged, and several mechanics opined reassembly was not possible, or at best difficult and not worth-while.

Many photos follow, but the key observation is that the mechanism is an parallelogram, The parallelogram is odd because it is assembled inside a box: the box is one "long side" of the parallogram. A bent wire is the other "long side" of the parallelogram. Finally, two triangular segments are the two short sides. It looks odd, but the operation is entirely conventional.

Overview: the derailleur in pieces:

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Picture below: the upper and lower sub-assemblies. The upper sub-assembly is bolted to the frame. The lower sub-assembly holds the cage with the jockey pullies. Both pivots have springs. The upper assembly has a spring under the rounded dark gray plate; it is not visible in the picture. The lower assembly has a spring that sits above the rounded dark gray plate, it is shown sitting off to one side. For both springs, one end of the spring goes in a hole in the dark plate; the other end presses against the upper case. The dark wire on the righ to fhte lower plate is the "long side" of the parallelogram which sits inside the case:


Below: lower plate and linkage holds the cage spring and cage with jockey pulleys. The first photo shows the parts as they would be with the chain on the smallest/outboard sprocket; the second photo shows the parts as they would be with the chain on the largest/inboard sprocket:

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The upper plate/case. The first photo shows the parts as they would be with the chain on the smallest/outboard sprocket; the second photo shows the parts as with the chain on the largest/inboard sprocket:

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Below: more perspectives on the linkage. The wire that makes the "long side" is a very wide and not-tall "U", where each end fits in one of the dark-gray plates. Each dark gray plate has a "nub" that sticks up from the plate and contacts the limit adjustment screw:

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Many modern derailleurs use a parallelogram with a spring on the bolt which attaches the derailleur on the frame. That upper spring allows the whole derailleur to "float" vertically and so the upper jockey pulley can closely follow the sprockets — and thus give good shifting.

In this derailleur, there is no such spring, so the derailleur has a fixed location relative to the frame. A fixed location allows a cable to run without housing from the frame to the derailleur, except for a short (approx 1 cm) and smooth bent tube mounted on the chainstay. This "housing-free" approach nearly eliminates cable friction and problems with the housing getting clogged.

Made briefly then disappeared

The Superbe Tech was made briefly but withdrawn. [Disraeli Gears as of 2016/11] shows it as having been made in only 1983, with a GranTech variant offered in maybe 1985.

Several retrospectives say the derailleur design had problems and SunTour was having financial problems which kept them from investing more in improving the design.

The Superbe Tech was offered in mid-cage (Superbe Tech L 4800) and long-cage (Superbe Tech GTL 5400). They use use a conventional spring attached the lower parallelogram assembly, plus another spring inside the upper jockey pulley. The paired springs allow the upper jockey pulley to closely track the sprockets. However, to fit the spring inside the pulley, it uses a design which has high friction and wears quickly. (The spring-in pulley design was introduced in 1982 on MounTech derailleurs; presumably it took a bit over a year for SunTour to realize the extent of the problem.)

There is also short-cage version which uses normal pulleys. The short cage uses a conventional design where the upper pulley is offset from the cage pivot. The upper pulley thus follows a pre-determined path, rather than tracking the sprockets. If you have the right mix of rear sprockets and the front chainrings are close in size, then shifting can be good; but many common gearing combinations cause the upper pulley to move far away from the sprockets in some gears, leading to poor shifting.

Another reportedproblem is the parallelogram breaks. As shown above, the parallelogram's "long side" which is inside the box is made of a bent piece of where, which is about 1 mm diameter. It has been reported that this sometimes would break or the U would straighten. [Disraeli Gears as of 2016/11] shows an example where this has happened. It may be that the wire failed only under duress -- e.g., in a crash that would also have broken other derailleurs -- but the unusual design means the design gets blamed rather than the crash.

Parallelogram Durability

It is (perhaps) interesting to speculate about the durability of the "sealed" design. In principle, the pivots are protected from the elements, but the two main parallelogram pivots pierce the top of the "case" and so gravity may tend to carry in debris which can cause wear.

Also, it appears the bearing surfaces are thin (the thickness of the case) and made of aluminum, both of which probably contribute to faster wear.

Finally, there is no obvious lubrication port to flush out debris which does get inside; and as noted above, reassembly is challenging.

These are probably all solvable problems — a slightly more complex casting might allow construction where the lower main parallelogram pivot only exits the bottom of the case. A slightly more complex casting would allow the upper main parallelogram pivot has a "skirt" over the place it enters the top of the case. A lubrication port of some sort is clearly feasible.

Pulley Durability

It also seems likely that the fast-wearing upper pulley could be replaced with a conventional pulley plus an "external" spring placed next to the pulley.

Indeed, SunTour had such a design in the MounTech II GTL (1985). An example at [Disraeli Gears as of 2016/11] shows the secondary pivot also wore quickly, but likely that problem can be solved farm more easily than solving the spring-in-pivot problems. But again the design was scrapped, rather than continue to invest in improving it.

As an aside: the "spring in pulley" design is fundamentally flawed because it uses a large-diameter bearing and large-diameter seal to the outside world. Both are problems:

In The Time Since

The Superbe Tech addressed at least two problems; the design did not work out, but the problems did not simply go away:

How have we progressed?

To summarize: derailleurs today are more resistant to wear, and somewhat less likely to clog. However, the pivots are still exposed to wear debris and not easy to clean/relubricate. Also, open parallelograms are still subject to mud/snow clogging.

So we have made progress in the (2016 - 1983) = 33 years since the Superbe Tech, but there is still an obvious improvement ... and we're not using it!