Sluggo

I recently made some modifications to an older bike, and in a nod to modernity (and steep hills and aging legs), I converted from a 7-speed freewheel to a Harris cyclery custom 13-34 9-speed cassette. All went reasonably well, except the Huret duopar (arguably the best-shifting touring derailleur of the mid 1980's) shifted very badly on the new cassette. Or maybe it shifted too well -- it changed gears very easily, but it wanted to keep shifting, and it was nearly impossible to find stable spots for any gear (for those of you coming in late, bear in mind that none of this equipment is indexed). I tried a shimano lx (robbed from a early 90's mountain bike that I don't ride much) and it worked just fine.

The duopar has worked just fine for twenty-odd years, although the last time I put on a new chain and freewheel I began to have hints of this problem.

Has anyone had a similar experience? Any ideas about how to make the duopar work better on this setup? Or am I stuck with Shimano?

robo

kind of odd... i wonder if the parallelogram mechanism is getting worn out and has developed some slop?

I've also heard that friction shifting gets kind of iffy above 8 speeds, but if the LX worked ok...

I was also going to suggest that you face the fact that we're now living in the '80s, and get used to using a Japanese derailleur.

HillRider

Actually, by the mid-80's both Sun Tour and Shimano made rear derailleurs that shifted much better than the Duopar.

Sluggo

The Huret is remarkably lacking in slop.

It can be a little touchy, but perfectly acceptable. The barcon ratchets could be a little finer.

I am still resisting bowing down to Shimano world domination.

I worked in a bike shop almost all the way through the 80's and tried pretty much everything available in touring-range derailleurs. Both Suntour and Shimano made good ones. I would argue that the duopar was the best.

Retro Grouch 

So what are you trying to accomplish? Are you fixated on using the Duopar derailleur or do you want a bike that you can ride?

You've got a 20 year old derailleur that doesn't want to hold the tolerance that's necessary for a 9-speed cassette. Is it the Duopar geometry or has 20 years of use simply worn out the parallogram bushings?

well biked

Since in the OP you say you were having hints of the problem even with the seven speed setup, I'd venture to guess the Huret has seen it's last hurrah. Maybe scour ebay for another Duopar, or if it's just Shimano you don't like I'd recommend something like a Suntour Cyclone MkII GT or XC Pro for a top notch vintage derailleur capable of handling a wide range of gears, you should be able to find those on ebay. Or a modern SRAM mtb rear derailleur. But anti-Shimano sentiment aside, if the old LX you've got on the bike works fine, I'd leave it-

JunkYardBike

A Suntour Cyclone MKII GT won't handle an 8-speed cassette, let alone 9 speed. I tried it on 8...too much travel for it to handle; it bottoms out before it can shift to the low gear. Or is a 9 speed cassette more narrow overall than an 8 speed?

robo

You say the Huret is the best, but the issues you are describing are indicating the opposite...

well biked

Good to know about the MkII GT not having enough travel to move over a modern cassette (I don't know if you remember, but I have one; at one point you were interested in buying it I think). I stand by my recommendation of the other derailleurs I mentioned, though..............As for the overall width of nine speed and eight speed cassettes, they're the same; the nine speed just has more gears crammed on there. That's the reason nine speed chains are narrower-

top506

This may be a silly question, but did you also go with a nine-speed chain?
Top

Sluggo

RetroGrouch: Slop, as I said before, is not the problem. This particular derailleur is not actually the original. And what I want is a trick to make the duopar work well again, because it is a lot cooler than anything shimano has made in the last 20 years. Some retro grouch you are.

Well biked: Hints of the problem occurred with a new chain and freewheel, but not (I think) as a symptom of age. I think all those candyass ramps and stuff that make indexed systems work are not only not necessary but counter-productive for a derailleur that works well without them. At least that is my current theory.

Robo: I said that the duopar was (arguably) the best shifting in the mid 1980s, not now, obviously.

And yes, top506, I am using a nine-speed chain. Otherwise the shimano would not work well. Although I can imagine that the system would work as badly with a wider chain as it does with the duopar.

Just for reference if anyone is contemplating the same type of conversion (since junkyard brings it up): travel is an issue. Both of these derailleurs (duopar and 7-speed shimano) are pretty close to their maximum travel, as are the shifters. I would not have tried 9 speed if I could get the gears I wanted in 8. Even the Harris custom 8-speed cassettes have big jumps at the bottom end that I did not want.

well biked

I really don't have an answer for why your Duopar doesn't work well with your nine speed setup. But in my opinion shift ramps on the cogs are beneficial, even for friction shifting. Good luck with getting it sorted out-

Road Fan

Other than slop, which the OP says he does not have, what tolerance are you talking about, recalling that he is not indexing?

Road Fan, who can get significantly grouchy himself.

Road Fan

I wonder if the vertical parallelogram and the cage pivot is working smoothly or if there is stiction in the lateral parallelogram when under tension. I have seen ssytems where the rear mech (or other Bowden operated device) will not move in precise small increments due to stiction. You might want to clean the Duo and its cables/housings, re-lube as necessary, and try it again.

Love these derailleurs! I use them on narrow 7-speeds, no problem whatsoever as long as I don't undershift or over shift. Needs a different touch than a Campy Racing Triple or the classic campys.

Road Fan

Retro Grouch 

Uh - holding the chain in line with the cog?

Retro Grouch 

So there you are. That's why I asked what your objective was. It appears that your objective is to use the Duopar.

I resist making changes just to make changes but, when it comes to making the bike functional, I'm a pragmatist.