Do derailleur springs lose tension?

[frank9755]

I think the spring in my rear mech is getting a bit slack.

It's an LX mech and has done about 6,000 miles, so probably into the tens of thousands of shifts.

I've noticed that the chain rattles a bit, say, when I go over a bump, rather than being pulled taut. It shifts very well, but when shifting up there is quite a slap when the chain drops onto the smaller sprocket. Also I've had the odd instance of chain suck.

Can you replace the spring if they get slack, or do I just replace the mech?

[PW]

Sounds more like the chain than the mech. My XT is well past the 10,000 mark, top jockey roller is starting to get ready, it has needle points instead of teeth, but it still shifts fine.

[reohn2]

I'd expect a rear mech with only 6,000miles on to be no where near ready for changing ,I'm currently running two with atleast 20,000miles on them and apart for some jockey wheel wear to one of them they work like new.
Unless there's something else wrong with the rear mech,I'd check the chain length as it sounds as if its too long.

[prm]

Not quite sure what year/model and cage length you have?? You may be able to adjust the spring tension.

Remove the upper jockey wheel (3mm Allen ?) and check to see if there are two holes on the outer cage plate circling the main swivel pin.
If visible, probe the two holes; these are tensioning points for the cage return spring. Tension can be trimmed to suit cassette block and chainring size.

If the upper hole is occupied – low tension. Dismantle by removing the 2mm Allen securing pin on the lower side of the swivel body. Gently ease out the cage with the main pin from the outer body, just enough to clear the stop tag. Cage will swing back approx 90˚
Hold the main spring into the body and reposition the cage plate to engage the spring into the lower opening (high tension)
Rotate and tension the cage, clearing the stop tag, and then push together. Refit the securing pin.

Once apart, well worth greasing the pin, O rings? and spring.
If removing the spring, check the orientation. The small straight length at each end of the spring may differ.

Regards

[mw3230]

Sorry for being flippant .... but the title of this thread put me in mind of the song - "Do your dérailleur springs lose their tension on the bed post overnight"



Apologies to Lonnie Donegan

http://www.lonniedoneganinc.com/discography.html

[gilesjuk]

What can happen is the pivot gets stiff and then the spring isn't strong enough to push the mech all the way back. So with the chain off try moving it, it should be freely moving.

[frank9755]

Not quite sure what year/model and cage length you have?? You may be able to adjust the spring tension.

Remove the upper jockey wheel (3mm Allen ?) and check to see if there are two holes on the outer cage plate circling the main swivel pin.
If visible, probe the two holes; these are tensioning points for the cage return spring. Tension can be trimmed to suit cassette block and chainring size.

If the upper hole is occupied – low tension. Dismantle by removing the 2mm Allen securing pin on the lower side of the swivel body. Gently ease out the cage with the main pin from the outer body, just enough to clear the stop tag. Cage will swing back approx 90˚
Hold the main spring into the body and reposition the cage plate to engage the spring into the lower opening (high tension)
Rotate and tension the cage, clearing the stop tag, and then push together. Refit the securing pin.

Once apart, well worth greasing the pin, O rings? and spring.
If removing the spring, check the orientation. The small straight length at each end of the spring may differ.

Regards

Thanks,
I'll try this when I have a bit of time next week. It's an LX mech which was fitted to a 2008 Super Galaxy. Not with the bike now so can't check part no.

I meant to say in the original post that I don't believe it is to do with the chain. It has felt the same with a couple of different chains, even when they have been new, and I've shortened them to the normal / correct length.

The mech actually shifts very well (better than it did when it was new!) since I replaced the cables a couple of months ago. There is an argument for leaving it alone, it's just that I'm planning a long tour in Eastern Europe in a few weeks, so want to have everything working perfectly!

[reohn2]

Sorry for being flippant .... but the title of this thread put me in mind of the song - "Do your dérailleur springs lose their tension on the bed post overnight"



Apologies to Lonnie Donegan

http://www.lonniedoneganinc.com/discography.html

Shouldn't that be, ".............on the big ring over night"?

[Edwards]

As somebody has pointed out the mech could be stiff in the fore aft movement. Try a lube eg WD40 and work it backwards and forwards. It should be free.

Do your dérailleur springs lose their tension

on the big ring over night

Great idea for a cycling song.

Not certain but I have heard about the springs getting a set or weak spot if that is done. Truth or old tale I do not know.

[DurableAce]

I read an article a few years ago whereby some professional racers each passed on a good piece of advice they'd been given. One of them (can't remember who) said that they leave their bikes with the derailleurs in their un-sprung state (chain on the smallest cog/chainring) if they're not being used for a while e.g. a race bike over the winter months. That way the spring isn't kept under tension unnecessarily and the shifts remain as crisp as possible.

I've no idea if it's true or not, or even how much benefit it might provide, but it sounds plausible to me. Since then, I've always left my bikes in this state if they're not being used for a while. As they have to be in a gear, I thought it might as well be that one.

[djnotts]

+1 to what DurableAce says - I nearly always leave bikes in a state of least tension!

As to the OP, I DO think that return spring can lose tension over time. My most used/highest miles rear mech while always kept clean (and ditto chain and cassette and recent new cable) has of late been a bit intermittent/slow in moving big to small (and being a normal rise all it has to do is "let go"). Small to big where exerting force on the "spring" indexing is fine.

I think the mech is simply old and tired (must be complying with the Flann O'Brien theory of bike/rider interface!).

[prm]

From an engineering point of view.
Leaving both front and rear mechs set with minimum tension, over any length of time would certainly benefit.

The rear mech torsion spring has a predetermined material life span with preset design parameters to maintain the integrity of the application. Most probably in excess of one million operations at 70-80% of full deflection, then slowly deteriorate with age.
Corrosion and metal fatigue due to lack of lubrication will definitely reduce this period, or …. …. Planned obsolescence strikes first.
.
Regards