Bicycle Mechanics - Rear derailleur grief
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09-27-12, 05:02 PM
My wife's Nishiki Landau is having some shifting trouble. I've adjusted these sorts of things on my own a few times. The bike has a suntour derailleur. An ARX I believe. Her problem is that the shifting is sticky until you over shift and then if you go to correct it you'll only need a minor adjustment to get it in gear. Does that diagnosis makesense? So if she's in her highest gear (6 speed) sheel down shift very little and drop 2 gears but then a similar or smaller movement back in the other direction puts her where she wanted. It also jumps gears a bit on it's own while she's pedaling.
I think thats the general problem. I may need to get home and ask her for clarification if you all feel that this can't possibly be whats happening. Anyway, Is it just simple adjustments to the limit screws?
Please clarify whether this has index (click-click) shifting, or friction shifting where the rider has to manually trim after every shift.
If it has index shifting, the problem you sort of describe is most likely traceable to friction in the cables and housings. After that, other factors include chain wear, pulley bearing wear, mis-aligned gear hanger (or RD cage), overall age and sloppiness of the shift levers and/or the derailleur. But start with the basics, and check the cables by watching and feeling for signs of friction.
09-27-12, 05:45 PM
Ah, ok. Here are some more notes. The the chain and the rear gears (forgetting the difference of cartridge and freewheel) are only about a month old. The shifters are indexed. They click when tightening but not when loosening. It is downtube shifting and I know she's fairly new to the concept so she used to have a tendency to over or undershift in user error. I however never had that problem on her bike but I do now.
OK, this almost confirms a cable friction problem. When she pulls the lever (downshifts) her strength is enough to overcome any friction and it shifts fine, But when she pushes the lever, the system depends on the RDs return spring to pull the slackened cable down and return the RD to the outside. The spring isn't strong enough and the system hangs.
It's like a spring screen door with a rusty hinge. You have no problem opening it, but when you let go, it only closes part way and hangs there.
Since it's down tube shifting, your job is easy, since the problem is isolated in the rear housing loop. Here's a quick diagnostic; put the lever in high gear and shift by pulling the wire away from the down tube, then ease off the tension and see if the RD spring takes the cable back smoothly as you release it. If you feel the cable slacken it's binding between you and the RD.
Field strip the rear end of the cable, squirt some oil through the loop (or replace it) and re-thread the cable. Make sure the loop has a nice fair lead to both the frame fitting and the RD adjusting barrel, since if it meets either at an angle that can cause cable binding. If you replace the housing loop, cut the length carefully (a bit long is better than a bit short) and be sure to use ferrules made for index housing (they're different than brake cable ferrules).
There may be other issues, but do all you can to get this right or better than right. Otherwise you'll never hear the end of it, and may lose a riding companion. (married 30 years).
09-27-12, 06:38 PM
hmm, not so sure about that. For one thing "The shifters are indexed. They click when tightening but not when loosening." sounds like a one-way ratcheted lever rather than indexed, and the ARX is a friction derailleur. The problem may still be cable friction but also possible the derailleur may have suffered a blow that put it out of alignment.
09-27-12, 06:43 PM
The shifters are indexed. They click when tightening but not when loosening.
I'm with cny, that sounds more like my Shimano friction shifters than anything else.
09-27-12, 08:26 PM
I see. I don't have the bike here at the moment so I can't comment specifically on parts. This hadn't happened when she first got the bike. She had a fair bit of trouble with it (threw a chain, accident, tourists that don't understand crosswalks) so maybe the derailleur took a knock. I know for sure that the shifters only ratchet when tightening. Tomorrow I'll have some time to sit with it and try some stuff so all of this advice is very helpful. Keep'em comin! Thanks everyone
09-27-12, 08:29 PM
It sounds like friction shifters to me as well. Counting the clicks will tell for sure. Five clicks=indexed, more =friction.
Friction or indexed, it should be a simple matter to isolate the problem to cable/housing friction by pulling and releasing the wire as FB suggests or to the shifter by inspection of the wire motion (or lack of it) caused by the shifter; putting a paint mark or piece of tape on the shift wire may help visualize the wire motion. If neither seems to be the problem loosen the wire from the derailleur and carefully (watch your fingers) manipulate the derailleur by hand while turning the crank to judge whether it is free to move and shift the chain properly.
Rereading the description, I too suspect that these may be retro-friction levers, especially if the bike is over 25 years old. That negates much of my prior post, but rear housing loop friction can still make shifting more difficult.
Other than that there may not be a problem at all, short of a learning curve. Before index, the standard way of shifting involved a bit of overshift to initiate the shift, then trimming the RD back to center determined by sound. This takes a little more (very little) time to master than modern index shifting, but is easy enough to use once that hurdle is cleared. I suggest the OP ride the bike himself and get it working as well as possible, then demonstrate the shift sequence with the bike in a stand so that his wife can see what is happening and learn how it's done.
09-29-12, 10:53 AM
After checking it out better and doing a test ride I realized/confirmed the following: Shifters are half ratchet, the derailleur is an AR not ARX, the problem seems to be that down shifting is skipping gears. So I guess that rules out friction in the housing. It crunches and sounds like it wants to get into the next gear but then just skips and hits a middle cog. I think the derailleur is pooched. The plastic adjuster part has a crack in t that I think is affecting the spring response.
10-10-12, 12:30 PM
Sorry for pumping a dead thread. Given all of the info above I'm thinking of swapping our the RD. I have a Suntour Honor I'm not using. Would that work?
10-10-12, 01:13 PM
Since you're not using indexing, there's no need to match the derailleur to the shifter. The only derailleurs that won't work are certain modern SRAM ones, apart from those, you can use pretty much anything.
10-10-12, 03:43 PM
Jumping gears on it's own can happen with only a small misalignment in friction mode, but can also happen from a chain that is "snaking." Having to overshift the lever often indicated a chain with excessive side wear, but could be a derailleur with too much play in pivots (much rarer). I'd say if you already have a derailleur mount it to see if there's any difference. If not my prime suspect would be the chain.
10-10-12, 05:30 PM
Hmm. Ok. I'll put the derailleur on this weekend and see where it leaves us. The chain/freewheel were both replaced at most 2 months ago.
10-11-12, 10:43 AM
i faced this issue last summer. solved it with a different freewheel but it still didnt shift super crisp.
here is a vid of what I was going through. sounds the same as your situation
10-11-12, 11:06 AM
The other thing to check is the derailleur alignment to the freewheel through the travel. This can be off due to bent dropout, RD plate or a bent RD and can be checked without replacing the derailleur.
10-11-12, 11:59 PM
This video will solve all of your problems.
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