Bicycle Mechanics - Is this rear derailleur ok?
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I've noticed that when in the two lower gears, the derailleur seems to "sit" on the gears. Not sure if this is something I need to look into or what?
There's probably a way to fix that, it's called b-screw adjustment; http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur , http://sheldonbrown.com/derailer-adjustment.html , https://www.google.com/search?hl=sv&q=b+screw+adjustment&safe=active
No B-screw on that derailleur...
Should prolly get a better one.
08-28-12, 10:14 AM
While we're on this topic, is there any way to adjust the pulley position on a rear derailleur that has no B-screw? Removing links? Shims?
Take a careful look at the photo, and see that the stop cam hasn't come up to the stop on the hanger. That means that there's nothing keeping the RD from coming forward more. Odds are that the opposite tab on the stop cam is either sheered off, or the cam is mispositioned on the RD, so it isn't doing anything to set the angel.
Pull the RD off, and look for a tab engaging the cam to the RD, If it's sheered off you need to replace the cam. If there is a tab or other stop, but it's in the wrong place, you should be able to remove and rotate the cam so it works properly when remounted.
So it's either a 1 minute repair, or you're probably SOL
There definitely something wring with maybe the way the derailleur was installed as that Huret rear derailleur should easily be able to handle those big low gear cogs with no problem. Forum members with the same or similar Huret RDs on their bikes should be able to help as soon a they start chiming into this thread. Try changing the thread title to something that mentions "Huret rear derailleur" on it to snag those guys into this discussion.
08-28-12, 02:43 PM
Huret did offer a version of the mounting plate that allowed "B-screw" adjustment:
Unfortunately, they're rare as hen's teeth these days.
Is it possible the OP is using the wrong mounting plate for the dropout, i.e. a Huret plate on a Campy-type dropout or vice-versa?
More pictures would help, like a straight-on side view to see the "angle of the dangle."
Ok, I'm still pretty new so I'm still trying to get up to speed on terminology. It is correct there is no B-screw. However, the two pulley's do seem like they can be moved up and away from the gears, there's just nothing to set or adjust to keep them there.
I got this bike from a guy who had it hanging in his garage for years, so I haven't changed or replaced anything, and I didn't get the impression the guy did much of anything either.
I'll try to get some more pics, taken outside, later on if possible.
You don't need new pictures. Re-read my earlier post, and look at your fist photo, or at the bike itself.
You'll see that the stop plate's tab isn't engaging the stop position on the hanger, and so is doing nothing to keep the RD from angling farther forward.
There are a few possibilities,
1- everything on the RD is OK, but the stop plate is made for a different hanger as John suggested
2- it's the wrong stop plate for this RD, or mounted wrong so the tab is in the wrong place
3- the corresponding part of the plate that engages the RD is broken off, making the plate useless for setting the angle of the RD.
Another possibility exists. Some RDs of that era had springs in the upper body, that pulled them back with regard to the hanger (or stop cam). Offhand I don't know if your RD is one of these, but if so one leg of that spring is either broken off or dislodged.
If you do post more photos, remove the RD and post one showing the stop plate and upper body from the stop plate side.
Ok here's something I found:
This was one of the best derailleurs of the time - early ‘80s. The paralellogram was horizontal, but the cage moved on a second unsprung parallelogram to let it cope with a very large range of sprockets. This is the steel Eco version - the original Duopar was titanium...
This seems to explain exactly what I'm seeing. There is one spring on there which keeps the two pulleys vertical (if I unhook the spring, they fold back on themselves). The other way the pulleys move, isn't sprung...the unsprung from the quote above...so it seems to me it's meant to do this.
Edit: I also found a page here that talks about it. THIS (http://www.bikeforums.net/showthread.php/505951-Huret-Duopar?p=10343679&viewfull=1#post10343679) post in particular seems to also mention that maybe I'm just being paranoid and the way the RD hangs is how it was meant to be.
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