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lube in rear derailleur arms

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lube in rear derailleur arms

Old 05-12-15, 06:16 PM
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lube in rear derailleur arms

my bike's rear derailleur springs aren't doing their jobs tensioning the chain. (see picture) the bike is shifting very poorly as a result, especially in the smaller sprockets. pedaling is a nightmare on the small ring. I recently took apart the arm to grease the spring. But there seems to still be a lot of friction. I used white lithium grease. should I use a different grease, or did I put the spring in the wrong way? I did wind up the spring one turn to tension it.

I haven't tried to take apart the joint near the derailleur hanger yet. But I imagine whatever I have to do to the arm joint, I should do the same on the other one.
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Old 05-12-15, 06:24 PM
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Usually I just hit up all the moving pivot points with a drop of chain lube while lubing the chain, wipe clean.
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Old 05-12-15, 06:31 PM
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There's an adjustable screw on the top of the rear derailleur that fits into a notch in the derailleur hanger to adjust chain tension but its a compromise between various front and back combinations and so requires attention to all those possibilities, so for example you should choose to ignore a slack chain when the chain is on the smallest ring in front and smallest cog in back because you shouldn't be using that combination anyway. This is what's called "cross-shifting" and it will wear out your chain and sprockets. What you're aiming for is something like adequate tension when the chain is on the small ring in front and medium sized cog in back.

As for lube on the derailleur light penetrating machine oil as for sewing machines is what you need, or just any thin viscosity oil. No grease will get into the spring-pivots unless you dismantle them. Alternately, maybe your chain is too long? Consult Sheldon Brown's website for chain length. As I recall he recommends testing the length by removing the chain from the rear derailleur and looping it around the largest ring and largest cog, than adding one 'complete link' defined as both the inner and outer chain plates or two apparent links. You'll need a chain tool to remove links.

I really doubt you have a problem of binding in the spring-pivots. More likely your chain is too long, worn and stretched out, and perhaps your cassette in back is worn out too. Consider that chains are made to fit huge 53-toothed rings. If your big ring is smaller you have to remove links.

Last edited by Clem von Jones; 05-12-15 at 07:42 PM.
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Old 05-12-15, 06:32 PM
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Derailleurs come in two basic types. Those with a fixed angle upper body which use tension from the lower body spring to pull the unit forward to the stop. And those with a floating upper body, which uses balance between springs in the upper and lower body to change angles as chain tension varies.

The key to the second design is freedom of motion in both pivots so it floats to the balance point consistently. The springs must be properly balanced to start with, but there has to be low or no friction or the system will not float to neutral balance properly.

The type of grease shouldn't make a difference, but something binding when it's tightened does matter. Use a hex hey in the pivot bolt to confirm smooth action, and do the same with the cage. If both are perfectly free and smooth, odds are you wound too much or too little tension onto one of the springs.

BTW- there's usually a spring adjuster of some kind, like a B-screw that bears against the spring leg instead of the stop cam.
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Old 05-12-15, 10:06 PM
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Originally Posted by FBinNY View Post
Derailleurs come in two basic types. Those with a fixed angle upper body which use tension from the lower body spring to pull the unit forward to the stop. And those with a floating upper body, which uses balance between springs in the upper and lower body to change angles as chain tension varies.

The key to the second design is freedom of motion in both pivots so it floats to the balance point consistently. The springs must be properly balanced to start with, but there has to be low or no friction or the system will not float to neutral balance properly.

The type of grease shouldn't make a difference, but something binding when it's tightened does matter. Use a hex hey in the pivot bolt to confirm smooth action, and do the same with the cage. If both are perfectly free and smooth, odds are you wound too much or too little tension onto one of the springs.

BTW- there's usually a spring adjuster of some kind, like a B-screw that bears against the spring leg instead of the stop cam.
the guy at the shop pointed out that both springs seem to be bad. maybe the spring slipped out of its socket after I put it back together. I'll open it up tomorrow and update.
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Old 05-12-15, 10:39 PM
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It's pretty rare for those pivots to be taken apart. It's also rare to have problems with them. Maybe there's a correlation there.
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Old 05-13-15, 04:11 AM
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Originally Posted by AnkleWork View Post
It's pretty rare for those pivots to be taken apart. It's also rare to have problems with them. Maybe there's a correlation there.
It's also pretty rare for springs to "go bad" unless they are severely overstressed (unlikely in this situation) or heavily rusted. I'd put my money on excess friction or improper assembly/adjustment. Also check to be certain that your chain is not too long, but it must be long enough to engage the big chainring/big cog combination without straining anything.
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Old 05-13-15, 08:18 AM
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not the chain's problem. I should be able to sprint in my big ring and shift smoothly in my smaller cogs, and I'm not. spring looked fine when i took it out. going to take a look aggain
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Old 05-13-15, 04:08 PM
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opened up both joints. turns out the hanger joint was a little gummed up, which I cleaned up. not sure if the brown stuff is rust or hardened lubricant, but wiping it off made the movement a lot easier. the derailleur arm joint spring popped loose somehow, which explained why the derailleur wasn't tensioning. putting the spring back in is a huge pain in the ass because the spring keeps popping out of its socket when you're putting it back in, as you're winding it up. and because the spring is steel and the cage is aluminum, each time it pops out takes out some material from the cage, so popping out becomes progressively easier. funny how shimano didn't think of putting a steel washer in there to mitigate this, but then again I guess they weren't expecting anybody to play around with their ****. anyway, it's doing fine now. used some wax chain lube on the bolts. there are two holes for the spring to sit in, and I used the lower tension hole. hopefully that keeps it from popping out in the future.
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Old 05-13-15, 05:29 PM
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Originally Posted by spectastic View Post
. . . spring looked fine when i took it out. going to take a look aggain
Not sure the spring rate is visible.
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