Author Topic: Rear derailleur sticking and wont shift to smaller sprockets  (Read 1410 times)

CptCool

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Rear derailleur sticking and wont shift to smaller sprockets
« on: February 01, 2017, 11:55:04 AM »
I live in MN so am biking in wet/snowy/salty conditions on my 5mi commute to work & am relatively new to bike maintenance.

2 weekends ago I washed my chain & drive train with the park tool chain cleaning device and a stiff bristled brush for the cogs & sprockets. I then re-lubed the chain.

Afterwards, I've been having trouble with the rear derailleur getting stuck when shifting down to the higher sprockets. I can shift down just fine, but can't shift back up. Sometimes I'll get stuck at the largest sprocket, but other times it'll shift to the 2nd or 3rd largest sprocket before getting stuck. The derailleur in question is an older shimano deore.

Last weekend I took apart the derailleur completely and wiped it clean as the pulleys were full of gunk. I then re-installed it (didn't reapply any sort of lube as I wasn't sure if it used/needed any) & tightened/adjusted the cable so it indexed properly. Everything appeared to work fine on my commute to work the next day and it shifted up/down appropriately. However, on the commute back home it began doing the same thing again where it'd get stuck on the larger sprockets and wouldn't spring back out. If I shift it by hand it still works, but I can't get it to shift using the shifter.

Any ideas of how to get this fixed?

mies

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #1 on: February 01, 2017, 12:11:54 PM »
If you are riding in wet salty conditions, there might be some corrosion in the derailleur linkage. You night be able to limp it along by relubricating it daily. If it's corroded enough, you might need to replace the derailleur.

Multi speed bikes aren't as forgiving about rough conditions. That is why a lot of bike messengers use single speed and fixed gear bikes. Less stuff to break.
Less is more.

Blatant

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #2 on: February 02, 2017, 06:37:13 AM »
Hard to say without seeing it, but when a mech. will shift down/up the cassette but not the other way, I tend to think cable tension.

GuitarStv

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #3 on: February 02, 2017, 07:43:43 AM »
Stuff to check:

- Play with the barrel adjuster to see if your indexing has just gone off a bit.  (http://www.parktool.com/blog/repair-help/rear-derailleur-adjustment)

- You didn't lubricate the derailleur after you cleaned it off.  If you used any kind of degreaser while doing this it's important that you pull apart your derailleur and service the whole thing properly - if you didn't degrease, it's still a good idea to do this somewhat regularly.  (http://www.parktool.com/blog/repair-help/rear-derailleur-overhaul#article-section-3)

- How long has it been since you replaced your cables/cable housing?  Cables and housings take a real beating in the winter, particularly the section of housing near the rear wheel that goes into your rear derailleur.  When the cable gets gummy, shifting will suffer and cause all sorts of problems.  As a quick fix you can unbolt the derailleur, slide the housing up the cable a bit, and apply some light oil.  If this makes things better, then you know that in the spring it's time to replace the cables/housing.

If you want your bike and components to last any length of time you need to get into a habit of rinsing off salt every time you come in from a wet winter ride.  Just use a rag and a bucket of hot soapy water.  If you don't do this, the salt will eat everything (spoke nipples will become corroded and frozen in place, derailleurs will corrode and not function as well, cables will corrode and not move smoothly, etc.).  Just a five minute wash will save you a lot of mechanical headache in the long run.

Clean Shaven

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #4 on: February 02, 2017, 08:02:55 AM »
If possible on this bike, I'd recommend running full length housing for the cables. It'll keep them working a lot better in the kind of conditions you're describing.

CptCool

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #5 on: February 02, 2017, 12:49:31 PM »
Lots of replies - thanks everyone. I'll have to test a few of these ideas this weekend.

I haven't replaced the cables & housing since the fall of 2015, so I'm hoping that's the issue & that I'll be able to limp along until Spring when I can do a full-on overhaul and tuneup of the bike.

For lubrication of the derailleur - I didn't use a degreaser when I cleaned it, but what type of lubrication would you recommend and which parts actually need to be lubricated? Sorry if it's a silly question, but it seems like the chain would lubricate the derailleurs whenever the chain itself is lubricated, correct?

bortman

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #6 on: February 02, 2017, 06:37:17 PM »
I'd use dry chain lube on the derailleur pivots. After you lube it, work the derailleur through it's full range to get the lube all up in there. Don't use grease on the pivots .. it would be hard to get it in there anyway. Grease will only attract grit and in cold temps the grease will slow everything down.

If you have the chance to take the derailleur off of the bike then you could do an overhaul.

http://www.parktool.com/blog/repair-help/rear-derailleur-overhaul

Since you mentioned that that the derailleur is "older", consider that it may be the spring (in the parallelogram, not the one that tensions the cage) that has fatigued and this is why the derailleur won't climb back up to the larger cogs. If this is the case then no amount of lube will help. AFAIK the parallelogram spring can't be replaced so a new derailleur would be necessary.


CptCool

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #7 on: February 17, 2017, 08:22:01 AM »
If anybody is following this or comes across it later, I had to get a new derailleur. The body spring just wasn't strong enough anymore to spring it back to the normal resting place on the smallest ring. I followed the park tool overhaul directions, but in the end it just needed to be replaced. I certainly learned a lot taking everything apart, cleaning, and building it back up though!

cincystache

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #8 on: February 20, 2017, 06:15:45 PM »
Not a direct answer to your questions but you sound like you might benefit from switching to a single speed drivetrain. You get rid of both front and rear shifters. 

Highly recommended if you're looking for a low maintenance solution.


bortman

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #9 on: March 01, 2017, 07:51:34 AM »
I'm not a fan of single-speeds, especially in winter when it becomes easier to break traction when starting or at low speeds. That said, singles make winter maintenance super easy.

I've gotten creative in the past to limit the "work" that the derailleurs have to do while still having a few gears to use through variable conditions. For one setup I took a Hyperglide cassette apart and used spacers so I was left with only 3 (of original 7, 8, or 9) cogs. That way the rear derailleur spring does less work. I got long limit screws from the hardware store to keep the chain on the 3 remaining cogs. I've also used spacers to allow me to keep only one cog on the rear. In this setup I depended on my front derailleur for a two-speed setup. The rear derailleur stayed on, but acted only as a chain tensioner.

GuitarStv

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Re: Rear derailleur sticking and wont shift to smaller sprockets
« Reply #10 on: March 01, 2017, 07:54:06 AM »
If you want to limit the work that your derailleurs are doing, always remember to cross chain when you put your bike away for the night.

Shift to the smallest front chainring and the smallest rear cog.  This puts much less tension on the derailleur spring during the long period that you're not riding it.