Cable wonkiness

[Owlie]

I tried the barrel adjusters today to address some of the derailleur problems I've been having. It worked, to a point.

For some reason, I now have a ton of slack in the front shifter cable (and therefore I can't shift into the middle or large chainring). I've tried loosening the bolt that holds the cable in place and manually pulling the cable taut, but there just isn't enough cable there. The same area of the cable (I marked it with a sharpie before I started) ends up at the screw every time. Yet there's still slack in the cable!

Any ideas?

[OakLeaf]

Do you have the shifter at the lowest gear position before you start?

[Owlie]

Do you have the shifter at the lowest gear position before you start?

Yes. I was using the directions in the repair book as a starting point (and proceeded to accomplish little more than getting grease all over the book. Horrifying!)

[OakLeaf]

Holding the cable with a pair of pliers? It can be hard to hold it taut with fingers while tightening the bolt. If you're going by the book, I assume you tightened the barrel adjusters all the way short before you started, also. (Make sure the pieces of the barrel adjuster are engaged - I've screwed them all the way apart before, and it can be a little tricky getting them back together.)

Also, a service manual without grease on the pages is no service manual at all.

[Owlie]

Thanks for the tip on pliers. Not that it did anything in this case, but made it much easier to grip!

The fact that I can keep turning the barrel adjusters clockwise (I assume that's "tight" because that's how everything else is) to no effect is a bit worrying. I don't think there's THAT much extra cable normally.

(Seriously, there's enough slack that I can touch the cable to the frame!)

[DebW]

Is the cable frayed? Look inside the shift lever. Is the housing frayed, wires sticking out of it, or the ferrule worn through? Could the cable anchor bolt on the deraulleur be stripped? Is the cable not running under the bottom bracket correctly?

[Owlie]

Is the cable frayed? Look inside the shift lever. Is the housing frayed, wires sticking out of it, or the ferrule worn through? Could the cable anchor bolt on the deraulleur be stripped? Is the cable not running under the bottom bracket correctly?

Cable bolt's good. (The slack is between the plastic thing under the bottom bracket that holds the cables and the shift lever, somewhere. I imagine a stripped cable anchor bolt would result in slack all the way through. Am I correct?) Cable seems to be running under the bottom bracket correctly. (I even cleaned out a bunch of gunk in that area.)

At risk of sounding thick, how exactly would I go about looking for a frayed cable, and where, within all the stuff up there? (My shift levers have that freaking thumb trigger, being Sora, so that may impact where I have to look. The book is not helping here.)

[lph]

(The slack is between the plastic thing under the bottom bracket that holds the cables and the shift lever, somewhere.

The spring that pulls the cable taut(ish) after you've shifted gears is in the derailleur. If the cable is tight between the derailleur and the bottom bracket, then the der is working and as you said, the slack is elsewhere.

Check one more time that the cable moves freely and smoothly under the bottom bracket. I found out after a ton of trouble that my cable had dug a v-shaped gouge into the plastic bottom bracket thingy, and was sticking there. I fixed it by taking the cable out and reshaping the gouge into a u-shape carefully with a thin drill bit.

Otherwise I'd suspect a fraying cable too. When that happens a cable can grow more and more slack as it gradually unravels. Usually happens inside the shifter lever, but I don't know your type of levers well.

PS. Barrel adjusters work by lengthening the housing, i.e. giving the cable a longer way to travel, ie. tightening the cable, when you screw them out. So start by screwing the barrel adjusters all the way in, clockwise* (you can see them growing longer or shorter after a few turns, you want them as short as possible) before you start tightening the cable by hand. If you've screwed them a bit too far out in advance they de-attach and can be a little fiddly to re-attach. Check by wiggling it sideways.

(*I get the feeling I may be confusing barrel adjusters on brake and gear wires here. Please correct me if I'm remembering wrong, fellow mechanics )

[DebW]

PS. Barrel adjusters work by lengthening the housing, i.e. giving the cable a longer way to travel, ie. tightening the cable, when you screw them out. So start by screwing the barrel adjusters all the way in, clockwise* (you can see them growing longer or shorter after a few turns, you want them as short as possible) before you start tightening the cable by hand. If you've screwed them a bit too far out in advance they de-attach and can be a little fiddly to re-attach. Check by wiggling it sideways.

(*I get the feeling I may be confusing barrel adjusters on brake and gear wires here. Please correct me if I'm remembering wrong, fellow mechanics )

Barrel adjusters work the same on brakes and gears. Your explanation is totally correct, LPH.

If the cable is slack between the bb and the shifter and tight between the bb and derailleur, then it is somehow binding in the BB. Check if the cable slides freely around the BB. If not, you need to fix or replace the cable guide. To check for a fraying cable in the shifter, shift to the inner front ring, pull the brake lever open, and look inside it with a flashlight. If you see any individual strands or sharp wire sticking out, then the cable needs to be replaced. Also look for strands of sharp wire sticking out of either end of the cable housing.

[laura*]

Yet there's still slack in the cable!

A while back at the bike co-op, there was a patron who was installing brand new low-end Shimano brifters. One of them just wasn't shifting right. It turned out that the head of the cable had popped out of it's little pocket in the brifter. This likely happened while the cable was loosened from the derailleur - the slack traveled up the cable, the head disengaged, and the brifter design kept the cable from self reseating. The solution was to take a little cover off of the brifter, reach in and reseat the cable, and then keep some tension on the cable until it was clamped to the derailleur.

[Owlie]

Holding the cable with a pair of pliers? It can be hard to hold it taut with fingers while tightening the bolt. If you're going by the book, I assume you tightened the barrel adjusters all the way short before you started, also. (Make sure the pieces of the barrel adjuster are engaged - I've screwed them all the way apart before, and it can be a little tricky getting them back together.)

Also, a service manual without grease on the pages is no service manual at all.

Uh...there may be a non-zero chance that I've partly unscrewed the barrel adjuster, and it isn't sitting in its threads properly...

[Sky King]

ok Owlie, I want an update on the cable saga!

[spokewench]

I'm with Laura - check your shifter - sometimes the cable will get loose from its route at the shifter area and this will cause strange loose cable issues.

I had this happen once when I was taking my mountain bike out of the car and I was just brain dead and could not figure out what happened until I went to put the bike back in the car and saw the cable de-routed at the shifter end. DUH!

[tzvia]

I replace all cables once a year as part of basic maintenance but sometimes it's not enough. A cable frayed between the bb and front deraileur and it started shifting like s@@t. Thought it was the deraileur till I got home and gave it a good look. Cable was only a few months old...

Back the cable all the way out and away from the bb and check it for damage like broken strands. Check the plastic bb guide for damage (crushed or packed with crap?) Hold the end, and click the shifter, do you feel it pull? Does it stay pulled or does it release what it pulled when you finish the shift?

[Owlie]

I've cleaned out the plastic cable guide on the bottom bracket, and it doesn't appear to be worn. (The bike only has ~1100 miles on it.)

I think the cable has worked its way free of its normal route, since I don't see any fraying or broken strands. It doesn't help that I think I unseated the barrel adjuster and the threads aren't lining up properly. I think this may be beyond my skill to fix. (When it comes to mechanical stuff, I need someone to actually walk me through this, and since my resident 'mechanic' is in Arizona at the moment...)

I guess I needed to get acquainted with the LBS here anyway. And a full-on tuneup is probably best done now rather than in spring...