Long ago, I removed a Huret rear derailleur from a used Trek. I like that they didn’t inscribe on it the model name. Duopar? Read the text at the link. Titanium! Two parallelograms, hence duo-par! I need to mount this on a bicycle and give it a try!
When I first met this derailleur, it didn’t properly tension the bicycle chain. I didn’t want a sloppy chain on such a terrific bicycle, so I installed another derailleur and put the Huret in the parts bin. There it remained for a decade or so. Today I needed a project so I decided to make it work again.
Most of the work was obvious, but taking apart the top jockey wheel was anything but. At this point in the project I was ready to toss the thing, but it was too nice, or at least too old, so I kept at it.
The assembly had what appeared to be three lock nuts and the order of operations was a mystery. I tried one locknut, then the next, then the last. All my efforts seemed to put me further from the goal. I did a quick search, zippo, so I took the time required to solve the riddles of this Huret derailleur. I will share what I learned below.
For this tutorial, I’ve mounted the derailleur on a frame. The frame at hand didn’t have a hanger, so I added one, but let’s pretend the derailleur is being removed from a hanger (as there is one not obvious step to share in this regard).
I wasn’t at first sure how to remove the plastic cap covering the hex head bolt that secures the derailleur to the hanger (the plastic thing with an “H” in the picture below). It was pretty flush so I couldn’t see where to insert a pry tool. Glad I used my eyes before diving in–the plastic cover is easily pushed out from the back (it is held in place with a plastic post that is pressure fit into the hollow of the hanger bolt). Next remove the locking nut on the back of the hanger bolt.Finally remove the derailleur from the hanger with a 6mm hex key.We now begin disassembly. Remove the nut and bolt that secures the derailleur cable. The cable securing nut and bolt are covered by the two wrenches in the picture below. Use a nut driver to remove the bolt that holds the cage support bracket parallelogram (the second of the two parallelograms–read the text at the link–referred to here as the “CSBP”) and the cage support bracket (which I’d call a jockey wheel carrier but out of deference to the maker I will refer to it here as the “CSB”) as a single assembly (I will refer to the CSBP and the CSB, together, as the cage support bracket assembly, or “CSBA”). If you don’t have a Hozan 8-9-10 mm Y nut driver, get one here. With that bolt removed, pull the CSBA free (the bolt securing the CSBA to the derailleur body is pressed tightly into the hole in the derailleur body so some force is required). Note the nylon washer remaining on the derailleur body (see below). This is the first of many of which you should keep track, treat carefully and reinstall.Now we will remove the CSB from the CSBP. Using a 13mm cone wrench, turn the locknut under the black arm clockwise (to tighten) so that the locking force is released. This is the step that confounded me. With this locknut released, the rest is pretty easy. Now flip the CSBA over and use a large flat blade screw driver to loosen the main bolt as shown below. You can see that I marred the flats when I tried to turn it without having the correct locking nut released. Luckily, this should never need much force to be properly adjusted when you’ve released the proper locknut, such that the marring won’t negatively impact future maintenance.Once the bolt is fully loosened, lift the black metal arm. There is another nylon washer resting on the locknut that was tightened a bit in the second step above.Set aside the nylon washer and remove the 13mm nut.With that nut off, lift off the chromed arm of the CSBP shown in my right hand in the photo below. Easy as it is just sitting there. Next remove the spring. Again, it is just sitting there.Remove the bolt that holds the two arms of the CSB together and acts as a spring stop. I’ll refer to it as the spring stop bolt.Remove the lower jockey wheel. There’s the trusty Hozan Y wrench again. All that remains is the top jockey wheel attached to the outside arm, the long arm, of the CSB. A bit of a trick here. The center bolt, the one with the marred flats, should be loose as there are no threads holding it in. Mine wasn’t lose so I assumed it was threaded. I eventually secured the long end of the bolt in an axle vice and turning the arm. It eventually turned without rising, so I thought I had stripped the threads. I was happy to find there weren’t any threads–it was merely seized. I gave it a rap from the back side and it popped free. Once cleaned, it moves very freely inside the hollow axle supporting the top jockey wheel. A good place for a little grease during reassembly. To remove the jockey wheel, loosen the hollow axle shown below by pushing on the detents with a screw driver. This axle is threaded into the jockey wheel arm. Mine was really tight. Maybe seized. I had to hold the arm in a vice and lightly tap the screw driver with a mallet. The right tool would have made this easier, but who has such a tool?Once the axle clears the short stack of threads, the jockey wheel comes free.The top jockey wheel has bearings–fancy! Loosen the cone with a 13mm wrench (or fingers if your derailleur was well cared for).That’s it. All apart and ready to be cleaned.I’ll leave the cleaning to you and your collection of used toothbrushes.
Now let’s put it back together. Add grease to the cup and replace the bearings. Replace the hollow axle (with the detents in the head). The axle is placed through the side of the jockey wheel that doesn’t have the chrome bearing retainer visible (the underside in the picture above). Then screw on the cone, make it finger tight, and back it out a quarter turn.
Next thread the jockey wheel bolt into the long jockey wheel arm. Note the orientation of the jockey wheel arm (the wheel goes on the side of the arm with the pressed valleys). When the jockey wheel is finger tight in the arm, use a 13mm cone wrench to lock the cone against the arm. This is tricky because all of my Park cone wrenches were too thick. I have the chromed two ended ones and wonder if the black single ended cone wrenches are thinner. With my too thick cone wrench, when I tightened the cone onto the arm, the wrench would be stuck in the assembly. I was lucky to find a thinner cone wrench in an Eldi travel repair kit. Before I found the Eldi cone wrench, I considered grinding the chrome off of a Park cone wrench to make it thinner. Glad to not have to do that. Lightly grease the jockey wheel axle. It will rotate inside a hollow axle on the CSBP. Install the lower jockey wheel and the left jockey arm. Install the spring stop bolt and nut. Remember to replace barrel that rests between the arms (and assures proper distance between the two arms).Lightly grease then replace the bolt that goes through the top jockey assembly. Mine seemed like it should have been put in before I installed the left arm, but I could push it passed the left arm. Looks like I forgot to grease it. Oops. Maybe I’ll have to take this derailleur apart a third time (I’ve disassembled then reassembled it once for the sake of the derailleur and then again to get the pictures shown here).Flip over the CSB and replace the spring. Long tension arm of the spring on the bottom. Replace the chrome arm of the CSBP. Replace the nut. Finger tight for now.Remember the nylon washer.Place the unthreaded end of the black arm of the CSBP (note correct orientation shown below) over the unthreaded post shown in the lower left corner in the photo below (remember to grease the post) and hold the threaded end of the black arm over the bolt end shown in the center of the photo. While holding the arm in place, turn the CSBA over. Lightly tighten the bolt (the one I marred) with a flathead screw driver. Too tight and the jockey arm assembly won’t rotate freely. Don’t worry about it coming loose. It is locked in place in the step below. Note: When half way tight, make sure all the parts of the CSBP are properly lined up and operating freely. There is a post on the black arm and two stops on the chromed steel part below it. Make sure the post is between the two stops before tightening it completely. Now lock it in place by loosening (counterclockwise) the locking nut with a 13mm cone wrench (this one is thick enough for my Park cone wrench).Install the nylon washer. Replace the derailleur body. Tighten the nut with a nut driver until secure.Replace the cable holder in the hole to the right of the cable holder in the picture below. Spin the CSBA counterclockwise to seat the ends of the springs on the respective spring tension arm stops. When the derailleur is laid on a table, Huret logo up, the top spring end can be seen peeking out just above the black arm and the bottom spring end is seen to the left of the spring stop that holds the two jockey wheel arms together. This sounds confusing, but if it is together correctly and the jockey wheel arm is rotated counterclockwise, the spring tension arms should find the stops. Phew! A lot of work, but it is wonderful that this derailleur is user serviceable.
As I mentioned above, I’ve only done this twice (and I don’t have any formal training in bicycle mechanics–trust me at your peril!). If I got something wrong, please let me know. For balance, if you find this post helpful, please let me know.