Straightening a RD cage
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Straightening a RD cage
I noticed the cage on my old Sachs Huret DuoPar eco is a bit bent. From what I’ve read, this was a common complaint back in the 80’s when this derailleur came out. Should I bend it back while on the bike or take the derailleur off and apart, then bend it against something flat?
also, is heat needed? I believe it is steel.
it shifts fine, but gets stuck when back pedaling.
also, is heat needed? I believe it is steel.
it shifts fine, but gets stuck when back pedaling.
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Personally, I'd try to do it on the bike--you'll get more leverage that way. I wouldn't heat it.
Be advised--sometimes cages can take weird compound curves--they might be fairly difficult to straighten perfectly.
Be advised--sometimes cages can take weird compound curves--they might be fairly difficult to straighten perfectly.
Last edited by smd4; 07-18-22 at 10:35 AM.
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If you do it on the bike, I would be concerned about bending the integrated hanger and not the RD cage.
John
Edit added: As far as bending it off a bike. Get an inexpensive universal/claw type hanger and mount it in a vise.
John
Edit added: As far as bending it off a bike. Get an inexpensive universal/claw type hanger and mount it in a vise.
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Bending it against something flat will not help, you have to overbend the metal to get it to deform and take a new shape.
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You think the thick hanger will bend before the thin cage?
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I’ve straighten the hanger and a steel frame with a large crescent wrench and a square. It doesn’t take a lot of effort.
Whether or not straightening the RD will tweak it I can’t say. If it were me I’d take it off the bike. It might even be necessary to remove the outer plate.
It looks substantially out of line. I will say that the cage will break before the hanger.
John
Whether or not straightening the RD will tweak it I can’t say. If it were me I’d take it off the bike. It might even be necessary to remove the outer plate.
It looks substantially out of line. I will say that the cage will break before the hanger.
John
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I’ve straighten the hanger and a steel frame with a large crescent wrench and a square. It doesn’t take a lot of effort.
Whether or not straightening the RD will tweak it I can’t say. If it were me I’d take it off the bike. It might even be necessary to remove the outer plate.
It looks substantially out of line. I will say that the cage will break before the hanger.
John
Whether or not straightening the RD will tweak it I can’t say. If it were me I’d take it off the bike. It might even be necessary to remove the outer plate.
It looks substantially out of line. I will say that the cage will break before the hanger.
John
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Well, a vice is a good idea too. It'll take some time before the cage breaks, if it's steel.
But anyway, if it can't be straightened, replacements are on eBay. Although I'd be inclined, myself, to upgrade to something more modern (i.e., a slant parallelogram).
But anyway, if it can't be straightened, replacements are on eBay. Although I'd be inclined, myself, to upgrade to something more modern (i.e., a slant parallelogram).
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Taking it apart and getting the plates flat in isolation is what I'd do.
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The hanger probably won't bend but there is a lot of flexion in the RD body that will occur when you
start to bend the cage if mounted on the bike. Best to remove from bike and dismantle the cage so only the inner cage
is exposed, then you can clamp in a vise and precisely bend it back. No heat needed.
start to bend the cage if mounted on the bike. Best to remove from bike and dismantle the cage so only the inner cage
is exposed, then you can clamp in a vise and precisely bend it back. No heat needed.
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...that's one of the few rear derailleurs I routinely replace with something that works better.
I know thee are people who like them, but I never could get them to work as well as the long cage alternatives.
The ones I've encountered seem to wear out at all the various pivot points...I don't imagine bending and straightening will help that.
...that's one of the few rear derailleurs I routinely replace with something that works better.
I know thee are people who like them, but I never could get them to work as well as the long cage alternatives.
The ones I've encountered seem to wear out at all the various pivot points...I don't imagine bending and straightening will help that.
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How valuable is the bike vs your time? I bend a lot of old RDs back into shape on bikes donated to non-profits. But I don't care about the bikes. If this is your baby, treat is as such and enjoy the process. Get out the old toothbrush and shine it as you go.
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Maybe because the bent cage throws the angle off a bit but it looks like the guide pulley is not aligned either.
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I would chunk it, I bet your bike has a lot of clattering.
If you want to give it a shot, align the dropouts, align the hanger, reinstall rd examine the top pulley align that to the cogs, then attack the cage align to the cogs. In fixing bends I try to reverse engineer the bends.
If you want to give it a shot, align the dropouts, align the hanger, reinstall rd examine the top pulley align that to the cogs, then attack the cage align to the cogs. In fixing bends I try to reverse engineer the bends.
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I would chunk it, I bet your bike has a lot of clattering.
If you want to give it a shot, align the dropouts, align the hanger, reinstall rd examine the top pulley align that to the cogs, then attack the cage align to the cogs. In fixing bends I try to reverse engineer the bends.
If you want to give it a shot, align the dropouts, align the hanger, reinstall rd examine the top pulley align that to the cogs, then attack the cage align to the cogs. In fixing bends I try to reverse engineer the bends.
Last edited by Lbxpdx; 07-19-22 at 09:43 AM.