valleyrider

Maybe this happens more than I think it does, but I have never heard about it before.

I was riding home from work yesterday and my shifting was all over the place. I'd shift up and it would shift down, I'd shift down and it would shift down 3. So when I got home I went to take my panniers off and index my gears and saw this:




That stretched my cables out in a hurry. So now I need new cables. This happen to anyone else?

RubeRad

It didn't go back to normal when you took the panniers off?

If the cable actually got stretched, you should have no problem taking out that slack either with the barrel adjuster, or if too extreme, by loosening the fixing bolt and pulling the cable taut.

valleyrider

It didn't go back. I tried indexing with barrel adjust and fixing bolt for a while, and I got it greatly indexed going to easier gears, but coming back to harder gears it really struggles, and according to my source (GCN), this is a common symptom of cable stretch. They are really old cables, anyway. I bought the bike used about 9 months ago and never changed anything on it, so I'm not too shocked.

I have a cyclocross race this weekend, and I'm a little worried about my shifting ability for that. Any tips in the meantime, or should I fiddle with the barrel adjuster and fixing bolt some more?

Darth Lefty 

Oopie oopie!

"Cable stretch" sounds hinky to me. The loop of housing or the cable within it might be kinked. Shifting down to easier cogs works better than shifting up since it is dragging the cable positively into the shifter and the other direction is just letting go of the cable and hoping the RD's spring pulls it back. But the fix is the same. Good opportunity to switch to color coordinated housing! :-D

RubeRad

The cable might have stretched when it was being pulled, but once it stops being pulled, it will not continue to elongate. It is common for new bikes to experience a little cable stretch over the first month or two of use, then it is usually done.

For a cable that is a fixed length (for you maybe now a little bit longer fixed length than before), slack/tension should be able to be adjusted to recover good shifting.

A bunch of related things to check for:

Did the housing get pulled partly out of its housing stops? Or are there ferrules that are not all the way on? (Or did there used to be loose ferrules but they closed up now?)

In an extreme case (probably not here), the derailleur or hanger could have gotten bent, and that misalignment would cause poor shifting that could not be tuned out by any amount of barrel-shifter twiddling.

If the only problem left is slower changes in one direction, it's probably just cable friction. New cable/housing would solve that, and it can never hurt, especially when you're unsure how old your cables are.

But in the meantime try dropping chain lube or other light oil into all entry points of your housing.

Shift to a big cog, then put slack in the cable by shifting the other way (with the bike stationary so the chain remains on the big cog). Then pull each segment of housing out of its stops, and drop 5-10 drops of oil in each end. Slide the housing back and forth on the cable to distribute. You might feel the housing start to slide easier as the oil works around, which would indicate that cable friction was indeed your problem.

If you can't get smooth enough cable/housing that way, it might be the cable is so old that there is some fraying somewhere (inside the housing?), in which case you definitely need to replace.

AlTheKiller

yes. "cable stretch" is rarely, if ever *actual* stretching of the cable. Most commonly there are a variety of other things. First I'd check the condition of your housing. was it kinked down low? Second, I'd loosen the cable fixing bolt on the derailleur to loosen up everything and check the ferrules(ends of the housing) for damage, check the cable for kinks/fraying/corrosion too. If everything looks good I'd turn the barrel adjuster all the way down, then back it out one revolution. Reattach the cable and adjust as necessary.

chefisaac

No issues with it at all. I use Ortlieb panniers and the connectors make it pretty much impossible to impede shifting or breaking.

valleyrider

I tried to replicate this happening, because it seemed pretty ridiculous, and I can't believe that it ever happened at all. The only way the derailleur would be in a position to allow the hook to catch it like it did was if I was in little ring up front and my 11t cog, which I hardly ever am. And even then it requires me to grab the cable and pull it towards the hook to get it to catch like this. I did a gravel climb on my way home, and at the top it requires me to haul my bike through some thorns and vines to get to another path, and maybe I was in that gear up there, and a vine caught the cable and pulled it up onto the hook? I dunno, it's confusing me.



I'll play with the fixing bolt some, and drop some oil in the housing. Thanks for the tips on that, I tried to lube the cables before, but with internal cable routing I couldn't find any place to put the lube in! Of course it never crossed my mind to loosen the cables and open it up a bit. Hopefully that will help me out for my race.

bigbenaugust 

It looks to me like that cable could be a little shorter?

valleyrider

Pictures are with the RD in the slackest of most slack positions, so it's actually pretty good in the other gears.

bigbenaugust 

Actually, I remembered I brought my 18sp into the office today and not my SS and looking at it in 34x26 (as low as she goes) and the cable falls in about that neighborhood (where the pannier hook would go). I do not use hooked panniers, however.

Can you tighten up the hook a little with pliers so it doesn't catch the cable?

valleyrider

Well, I could, but I put them on and take them off so often, and it is already a pain to get that hook off, I feel like it would be much worse if I would tighten it more. Of course, now I am always going to check when I hook them up to not catch it.

hyhuu

I don't get. The cable didn't even touch the hook so what's the problem?

valleyrider

If you look at the pictures, you can see that the hook is hooked through the rack, and the cable is caught on the hook. You can also see that I am in my smallest cog, so as I shift to the larger cogs, that cable will become tighter, but since it is hooked on the hook, problems will happen.

hyhuu

Sorry I still don't get it. The cable is non-compressible. When you shift to the larger cog, the only thing that would move is the cage plate.

valleyrider

Hmmm, you're right, I guess you don't get it...

FWIW, the whole RD moves on the spring mechanism because the cable gets more or less taught.

hyhuu

Gotcha. Now I get it.

valleyrider

Update:

Y'all are cool. I pulled out the cables a bit and did a bunch of lubing in the housing, got my shifting impeccable for the CX race on Sunday. My bike shifted better for the race than it has since I bought it. It's amazing what kind of difference a little lube makes.

Thanks again.

BobbyG

Well, last week I had my rear shifter act up. It wouldn't reach the highest or lowest gears and felt slack. Over the years I've had shift and brake cables fray, but this was a new bike with a 9-month old rear shifter cable. I tried adjusting it, but to no avail. I usually replace these myself, but this is my first "brifter" equipped bike, so I took it to the shop. The tech confirmed the cable was frayed and then asked, "have you fallen recently?" As a matter of fact, my bike rolled out from under me while while I stood waiting for a light to change a day before trouble set in. The bike has shifter cables running across the top bar. He explained to me that he has had experience where a rider falls and a leg or shoe or something snags a cable and stretches it out resulting in slack, fraying or an all out break. I'm not sure if that was the cause, but it seems plausable to me.

RubeRad

That's great news! Glad we could help. At some point, of course, housing lining is worn, and cables start to fray, then you definitely want to just change it out. A lot of people change it out on a schedule (annual), just to be safe.

That's what she said