Bike Forums

Bike Forums (http://www.bikeforums.net/forum.php)
-   Bicycle Mechanics (http://www.bikeforums.net/bicycle-mechanics/)
-   -   Why Would my Shifter Cable Tension INCREASE? (http://www.bikeforums.net/bicycle-mechanics/929518-why-would-my-shifter-cable-tension-increase.html)

SPiN 360 01-11-14 10:43 PM

Why Would my Shifter Cable Tension INCREASE?
 
Problem Solved... see Post #29.



My Giant Hybrid has a triple in the front cassette.

In the last ride in Fall 2013, everything was fine. The bike has been stored indoors at room temperature for all Winter. The bike has not moved, no derailleur adjustments made since Fall 2013.

Now I've noticed that the shifter will not shift into the granny gear (smallest cog in front). You press the shifter lever and it does not click and the derailleur does not move. The other 2 cogs can still be reached.

Based on my research on forums and watching many YouTube derailleur videos, it appears the cable tension must be reduced. But this brings up a better question: What caused the tension to mysteriously INCREASE?! I could see cable stretch over time causing a tension reduction, however, the tension increase at constant temperature and no adjustment makes no sense to me.

Any ideas on how this increase happened? Could it point to a larger issue that must be fixed?

Derailleur: Shimano Deore LX
Shifters: Shimano SLX

fietsbob 01-11-14 10:47 PM

Bent the housing ? Corrosion of the cable, perhaps, ?

buy new die drawn Stainless steel cables , greasing them is also a decent Idea.

FBinNY 01-11-14 11:47 PM

It's probably not related to cable "shrinkage" t all, but rather to corrosion and friction.

You might get away with running some light oil into the cables from the ends and working the mechanism back and forth helping the spring move it in with some hand pressure applied directly to the FD. If this reestablishes the range of travel, continue to shift back and forth until it works freely without help.

BTW- some oil of the FD pivots also will probably help, but be sure to wipe off excess.

digibud 01-11-14 11:57 PM

Cable tension may not have increased at all. It's more likely that it is not being allowed to retract fully due, as fietsbob mentioned to poor grease or something else that is causing friction. If, for instance, the cable in the brifter moved out of its slot/area the cable would not be able to fully detension. If the housing became dirty or the got a bend it in it would similarly fail to retract fully. A cable might be frayed internally. Someplace within the cable routing may be contaminated. All sorts of things could be involved. Chances are if you clip the end of the cable and release the cable you'll find it is not moving freely and smoothly. Time for new cables and/or housing. That's a project I just finished on two bikes.

catonec 01-12-14 12:31 AM

Quote:

Originally Posted by fietsbob (Post 16403315)
.....greasing them is also a decent Idea.

is it? wont that allow dust and dirt to stick to them? wouldnt a dry graphite be better?

Kimmo 01-12-14 07:30 AM

My money's on misdiagnosis and a sticky pawl in the shifter preventing it from dropping into first.

Quote:

Originally Posted by catonec (Post 16403439)
is it? wont that allow dust and dirt to stick to them? wouldnt a dry graphite be better?

Grease on cables, I wouldn't recommend, at least for anywhere cold. A few drops of any kind of oil (except edible stuff) inside the housing is a good idea. You'll probably want to wipe any excess off the bare parts of the cables, but dust sticking to them there doesn't matter, obviously.

I'd say it's riding in the wet that gets crap up inside the housings more than anything, and if you find that an issue in particular, grease may be worth a try as a means to minimise it.

Retro Grouch 01-12-14 07:43 AM

Easy enough to troubleshoot:

1. Disconnect the shift cable from the derailleur. Does the derailleur move inward on it's own? If so, it's not the derailleur.
2. Hold the shift cable with your finger and cycle the shifter. Can you feel all 3 positions?
3. If the shifter doesn't want to move to the granny position (my bet) then that's it! Find a way to shoot some WD40 into the shifter innerds and cycle the shifter a few times while you pull on the shift cable with your other hand.
Reconnect the shift cable, readjust the cable tension and you're dont.

Andrew R Stewart 01-12-14 09:15 AM

OP should check for a bent der hanger or cage too. Andy.

fietsbob 01-12-14 10:57 AM

Quote:

buy new die drawn Stainless steel cables , greasing them is also a decent Idea.

Quote:

Originally Posted by catonec (Post 16403439)
is it? wont that allow dust and dirt to stick to them? wouldnt a dry graphite be better?

inside the housing its not an issue , open runs you can leave it bare ..

Cheaper and more easily soldered where I cut the end, Zn Treated Cables Greases Is what I often use.. greased, in fully housed cable Runs.

LBS buys that sort in Bulk, SS as an each package.

SPiN 360 01-12-14 11:24 AM

Some very good suggestions here. I'm not ruling out misdiagnosis.

Considering that I still have the original 1 year guarantee on it from the LBS, I don't want to go monkeying around.

Tension is just a twist knob, but I have never actually disassembled anything on a bike before, so I prefer to do that when it's out of warranty.

Quote:

Originally Posted by Andrew R Stewart (Post 16403884)
OP should check for a bent der hanger or cage too. Andy.

I think the bent hangar is an unlikely chance since it is the front derailleur. :)

Jeff Wills 01-12-14 11:44 AM

Quote:

Originally Posted by SPiN 360 (Post 16404167)
Some very good suggestions here. I'm not ruling out misdiagnosis.

In my experience, bikes that sit a while almost always develop friction in the cables, even when stored at room temperature. If your bike has split cable housings, learn how to pull the housing away from the stop so you can expose the covered cable. Many times just wiping them off improved function. You can smear a little lube on the covered portion of the cable before reassembly- light oil for cold climates, light grease in warm. It's part of my "spring tune-up".

I'm about to go out for a ride- the bike's been sitting for a month in the garage. I'll probably have shifting issues. :twitchy:

cny-bikeman 01-12-14 12:56 PM

Quote:

Originally Posted by SPiN 360 (Post 16403307)
... the shifter will not shift into the granny gear (smallest cog in front). You press the shifter lever and it does not click and the derailleur does not move. The other 2 cogs can still be reached.

Although friction is a common issue it does not seem to be the culprit here. For one, the front derailleur spring is fairly strong, so it would take considerable friction for the derailleur not to move at all, especially after working fine on the other two rings. More importantly the lack of a lever click or any derailleur movement at all points to either an obstruction of some sort interfering with further inward movement or a problem with the lever mechanism. Retro suggested the correct approach based on the symptoms presented - isolate the parts of the system to identify the cause. Of course if it's still under warranty and taking it to the shop is practical that would resolve the problem, but it's still good experience to understand how to properly diagnose.

Andrew R Stewart 01-12-14 02:10 PM

Quote:

Originally Posted by SPiN 360 (Post 16404167)
Some very good suggestions here. I'm not ruling out misdiagnosis.

Considering that I still have the original 1 year guarantee on it from the LBS, I don't want to go monkeying around.

Tension is just a twist knob, but I have never actually disassembled anything on a bike before, so I prefer to do that when it's out of warranty.


I think the bent hangar is an unlikely chance since it is the front derailleur. :)

Well, I'll just have to keep my suggestion for another time. :) Andy.

FBinNY 01-12-14 02:19 PM

Quote:

Originally Posted by Andrew R Stewart (Post 16404510)
Well, I'll just have to keep my suggestion for another time. :) Andy.

Though it didn't apply here, bent hangers are the number one (just about only) cause of "cable shrinkage" on RDs. Any time an RD exhibits signs of cable shrinkage, owners and mechanics are well advised to reconfirm limit settings, especially the inner limit, before shifting into spokes.

SPiN 360 01-12-14 02:26 PM

Quote:

Originally Posted by FBinNY (Post 16404525)
Though it didn't apply here, bent hangers are the number one (just about only) cause of "cable shrinkage" on RDs. Any time an RD exhibits signs of cable shrinkage, owners and mechanics are well advised to reconfirm limit settings, especially the inner limit, before shifting into spokes.

Good to know, thanks.

fietsbob 01-12-14 02:43 PM

Un hook the cable , feel it sliding through it's path .. independent of the part it is Operating.

digibud 01-12-14 04:01 PM

By the time you get symptoms the OP describes it is more likely the problem is more than just needing to lube a cable. That said, I agree that a very light lube, graphite or otherwise, is more efficient and less likely to allow further dirt to accumulate. It takes a pretty dirty/rainy/dusty environment to get enough gunk into cables to cause a problem like that described and if it is dirty cables it's probably dirty housing and even more likely frayed housing or cables. This really -is- time to put in new housing and cables unless something obvious and easily cured rears it's head. You can't see inside a worn cable housing so even after removing all the cable housing the problem might not be obvious.

FBinNY 01-12-14 04:08 PM

Quote:

Originally Posted by digibud (Post 16404785)
By the time you get symptoms the OP describes it is more likely the problem is more than just needing to lube a cable......

We could speculate until the swallows return to Capistrano, but it's pointless. The only things we know for sure are that the cable didn't shrink, and that something is hanging up someplace.

The next step, before anything else is to diagnose the problem, and it doesn't have to be taken apart for that. The lever can be wokd against tension by pulling the wire away from the frame like a bow string, to see if it provides three positions, and shifts leanly between them.

The FD can be tested the same way, shifting by pulling the wire directly and seeing if it works smoothly through it's range of travel. (shift to low first).

The actual cause could be the lever, cable, BB turnaround guide, or the FD itself either being sticky or having dirt packed in and hdried there. A proper diagnosis will point out where to look closer, and the direction to a fix.

cny-bikeman 01-12-14 10:37 PM

Indeed, diagnosis is not a guessing game, a competition where people try to be the first to post the right answer, or a "this happened to me once" exchange. It is a simple, logically driven process. Whether it is the OP or a shop mechanic, the best route is to eliminate possible explanations until the correct conclusion is reached.

Kimmo 01-12-14 11:12 PM

Quote:

Originally Posted by cny-bikeman (Post 16405795)
Indeed, diagnosis is not a guessing game, a competition where people try to be the first to post the right answer

It totally is, and I bet I won :p ;)

Seen it heaps.

OP, don't worry about voiding your warranty - just grab a small philips head and some WD40, and remove the two screws holding the cover on the left shifter (which you likely need to do if you wanted to change the cable anyway), and look for a little sprung pawl that moves with the lever - you'll see it sticking and failing to engage when the desired shift doesn't occur. You just need a drop or two of WD40 on its pivot, then just use the screwdriver or something pokey to work it back and forth a bit until it moves freely again; hey presto.

Al1943 01-12-14 11:32 PM

FWIW both Shimano and Camagnolo recommend greasing cables on installation.

FBinNY 01-12-14 11:44 PM

Quote:

Originally Posted by Al1943 (Post 16405906)
FWIW both Shimano and Camagnolo recommend greasing cables on installation.

Yes, and at one time (maybe they still do) Campagnolo used to supply the housings pregreased. OTOH, back when I was their service tech this was something that made me look good. Every September of October depending on geography and weather I could instantly diagnose shifting problems caused by the grease thickening with the cold.

Greasing cables is fine for the summer and maybe year round in the south, but is a problem during northern cold weather months.

Kimmo 01-13-14 12:25 AM

Plain SS cables in fresh lined housings run pretty smooth without any lube; IMO the lube just extends the life of the liner. Also, (at least some) Shimano housing is supplied pre-greased too.

cny-bikeman 01-13-14 06:14 AM

Quote:

Originally Posted by Al1943 (Post 16405906)
FWIW both Shimano and Camagnolo recommend greasing cables on installation.

There are many, many examples of tech documents that do not get updated with changing technology or design. I just installed a kitchen pullout with incorrect instructions that were based on a design that was changed about 5 years ago.

There was good justification for greasing some cables where they passed through housing into the 90's. Neither cables nor housing were predominately stainless, and housing still was not all lined. There was a significant difference in diameter between cable and unlined housing, especially for shift cables, because the same housing was often used for both. That was particularly true for department store bikes. The result of metal-to-metal contact, combined with friction and water, was that it was very easy for corrosion to occur inside the housing. Housing that pointed up at the ends, such as that for the front derailleur and the rear brake on a women's (open) frame was particularly vulnerable, but the micro environment inside any housing section inevitably included some moisture.

Our shop standard was originally to grease all cables where they passed through housing, and we even added an additional "plug" of grease at the cable stop if the housing pointed upward, as a barrier toward entry of water and contaminates. I did the same for bikes I assembled in a contract I had with Sears - their maintenance contract claims went down precipitously as a result, because cables had not been lubricated at all previously.

With the advent of lined housing some lubrication was (and is now) still needed for non-stainless cables, though the tighter tolerances call for oil rather than grease. That is especially true with the sometimes lighter springing of more recent rear derailleurs and indexed shifting, which depends on free movement of the derailleur by spring action alone.

one_beatnik 01-13-14 07:12 AM

No one seems to have mentioned this, but what about checking the derailleur stop screw?? Those change while riding at times and we just don't notice since we're using it and the change is so gradual. Make sure your derailleur CAN move to that last chain ring and that the stop screw isn't doing it's job!


All times are GMT -6. The time now is 07:39 PM.