Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 06-14-08, 08:57 PM   #1
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Rear Derailleur index shifting trouble

I spent an unsuccessful 4 hours today trying to tune an indexed-shifted rear derailleur.

First I set the H and L limit screws. I verify that the chain goes over all the cogs, but doesn't go over the lowest and highest cogs. But then the chain shifts erratically between gears. So I use the barrel adjuster to adjust the cable tension so the chain shifts on clicks. Usually this is all I have to do.

But now for the strange part: after that barrel tension adjustment the thing won't shift to the smallest cog. Even weirder, if I put it in high gear, reach under the downtube and pull on the bare shift cable, and then snap the cable to let it go, it shifts into the smallest cog. But if I shift out, it usually won't go back.

I'm going nuts.

Could this be caused by a bad or binding shift cable? Or do I need a new derailleur spring? Or could this be something else? The cables haven't been changed in about 10 years (about 6 of those it was unused). The derailleur itself is an old Alivio MTB model.
commute is offline   Reply With Quote
Old 06-14-08, 09:31 PM   #2
DieselDan
Senior Member
 
DieselDan's Avatar
 
Join Date: Mar 2003
Location: Beaufort, South Carolina, USA and surrounding islands.
Bikes: Cannondale R500, Motobecane Messenger
Posts: 8,521
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Need new cables and housings.
DieselDan is offline   Reply With Quote
Old 06-15-08, 09:57 AM   #3
rogerstg
Fred-ish
 
rogerstg's Avatar
 
Join Date: Aug 2007
Location: Rhode Island
Bikes:
Posts: 1,800
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by DieselDan View Post
Need new cables and housings.
+1
You could try lubing the cables to get it to work, but that will just confirm that you need to replace them.
rogerstg is offline   Reply With Quote
Old 06-15-08, 10:16 AM   #4
spoke50
Miles over Matter
 
spoke50's Avatar
 
Join Date: Mar 2008
Location: birmingham al
Bikes: trek
Posts: 390
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I had the same problem and the cable looked fine. Took to the LBS and he confirmed that the cable was just barely hanging on by a thread at the shifter. I'd say definatley new cable.
spoke50 is offline   Reply With Quote
Old 06-15-08, 03:18 PM   #5
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I replaced the cables and housings, but it still doesn't adjust properly.

But I did discover that the barrel adjuster on the derailleur is bent. The thing wobbles when I turn it. That's probably not good. Do they sell those things separately? (The cogs on the derailleur look straight.)

Here's what I tried this time:

- disconnect the cable
- shift into highest gear
- connect the cable with it taut
- adjust the (shifter's) barrel adjuster until I can shift into the second highest gear

but now it won't shift into the highest gear again! The derailleur moves a bit... just not far enough to actually move it. If I give it a gentle tap, it shifts right in.

Do I need a new derailleur? If so, any suggestions?
commute is offline   Reply With Quote
Old 06-15-08, 03:30 PM   #6
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 8,065
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Quote:
Originally Posted by commute View Post
I replaced the cables and housings, but it still doesn't adjust properly.

But I did discover that the barrel adjuster on the derailleur is bent. The thing wobbles when I turn it. That's probably not good. Do they sell those things separately? (The cogs on the derailleur look straight.)

Here's what I tried this time:

- disconnect the cable
- shift into highest gear
- connect the cable with it taut
- adjust the (shifter's) barrel adjuster until I can shift into the second highest gear

but now it won't shift into the highest gear again! The derailleur moves a bit... just not far enough to actually move it. If I give it a gentle tap, it shifts right in.

Do I need a new derailleur? If so, any suggestions?
No need for a new derailleur. When you "connect the cable with it taut", you put too much tension on it. It needs to be just a little bit looser.

Try this:
1: shift the chain so it's on the second smallest cog
2: without pedaling, put the shifter in the high-gear position, i.e. the last click. You don't want the chain to go onto the smallest cog.
3: adjust the cable so all the slack it taken up, but not "twangy" taut
4: check that this adjustment allows for shifting between the #1 and #2 cogs
5: use the barrel adjuster in small increments to make sure that the chain is vertical through the derailleur and cogs in both gears
6: verify that the indexing keeps the chain vertical from cog to derailleur in all gears.

If this doesn't work, your derailleur my be worn out, derailleur hanger bent, or the cable may not be routed correctly. There's a couple photos at http://www.parktool.com/repair/readhowto.asp?id=64 that may help.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline   Reply With Quote
Old 06-15-08, 04:28 PM   #7
mechBgon
Senior Member
 
mechBgon's Avatar
 
Join Date: Jul 2002
Bikes:
Posts: 6,957
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by commute View Post
I replaced the cables and housings, but it still doesn't adjust properly.

But I did discover that the barrel adjuster on the derailleur is bent. The thing wobbles when I turn it. That's probably not good. Do they sell those things separately?
They do sell them separately. In fact, the LBS probably has 50 used ones in a bin, so it won't cost much Replace the barrel, unless you're pretty sure the derailleur is shot.

Derailleurs can get loose in the joints, so as a quick test, you can hold the derailleur at the lower pulley and gently push in and out. If you see and feel much slop in the derailleur's upper pivot and parallelogram pivots, then there's a limit to how precisely it's going to locate the pulley cage. In that case, pick up a new derailleur, and if you need help picking an appropriate one, post more info and/or pictures of your bike's current drivetrain.
mechBgon is offline   Reply With Quote
Old 06-15-08, 05:25 PM   #8
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I haven't tried Jeff's steps yet, but here's some photos of the derailleur.

BTW: There is some slop in the derailleur arm, I'm trying to figure out how to measure it.
Attached Images
File Type: jpg IMG_2435_2.jpg (43.7 KB, 30 views)
File Type: jpg IMG_2416_2.jpg (42.9 KB, 32 views)
commute is offline   Reply With Quote
Old 06-15-08, 07:13 PM   #9
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 8,065
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Quote:
Originally Posted by commute View Post
I haven't tried Jeff's steps yet, but here's some photos of the derailleur.

BTW: There is some slop in the derailleur arm, I'm trying to figure out how to measure it.
Hmmm... the second image seems to show that the derailleur hanger is bent inward slightly. However, parallax may be throwing me off. Try taking another picture from directly behind the bike- the middle (4th) cog should line up with the middle (2nd) chainring.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline   Reply With Quote
Old 06-15-08, 07:36 PM   #10
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Photo attached.

I think you're right. It does look a little bent inward.

I put the chain on the second front gear and the fourth rear gear. You might be able to see the handle of a little orange screwdriver handle sticking up above the chain. That's the second chainring.
Attached Images
File Type: jpg mightbebent3.jpg (85.9 KB, 21 views)

Last edited by commute; 06-16-08 at 06:22 AM. Reason: fixing photo rotation
commute is offline   Reply With Quote
Old 06-16-08, 06:35 PM   #11
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I tried the above advice, but it still won't shift into the small gears reliably.

So I pulled off the hanger, cleaned it up, and put it down on the table. The hanger is almost as flat as the table! If it is bent, it's only by a couple degrees.

I'm hoping LBS has them in stock.
commute is offline   Reply With Quote
Old 06-17-08, 08:39 PM   #12
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well, I installed the new hanger and the derailleur looks somewhat straighter, but still it won't shift into the highest gear without coaxing.

I'm starting to think that the old Alivio derailleur is just too worn out to work properly. It seems like it just isn't pulling hard enough on the cable in the high gears. In fact, no matter how far I let out the H screw, I can't get the chain to run off the small gears into the frame (even after disconnecting the cable).

Maybe I just have derailleur envy, but it may be time for a new one. Any suggestions for something that will work on an old IG 7 speed? Can I just pick up any 8/9 speed derailleur?
commute is offline   Reply With Quote
Old 06-17-08, 09:14 PM   #13
DieselDan
Senior Member
 
DieselDan's Avatar
 
Join Date: Mar 2003
Location: Beaufort, South Carolina, USA and surrounding islands.
Bikes: Cannondale R500, Motobecane Messenger
Posts: 8,521
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Do the derailer pivots move other then the intended direction? If so, replace the derailer. A new Alvino would be fine.
DieselDan is offline   Reply With Quote
Old 06-17-08, 09:24 PM   #14
JTGraphics
Senior Member
 
JTGraphics's Avatar
 
Join Date: Dec 2006
Location: So Cal
Bikes:
Posts: 2,673
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I loosen the cable clamp turn in the barrel adjusters all the way make sure your shifter is clicked all the way down with the chain on the small cog replace the cable make sure its in the groove on the RD and straight it looks like it was before. When you have the cable clamped in take up the slack shift to the next gear adjust the barrel adjuster if it didn't move up to the cog adjust while turning the crank till it does, and make it nice and quiet, shift up 2 adjust if needed fine tune small turns shift up and down and check, adjust as needed this works for me.

May I ask is this a setup that was working before or is this something your setting up fo the first time? I ask because you could also have a compatabality issue "pull ratio" with that old MB derailleur and your shifter your using, just what is this combo?
__________________
It may not be fancy but it gets me were I need to go.
http://www.jtgraphics.net/cyclist_bicycles.htm

Last edited by JTGraphics; 06-17-08 at 09:34 PM.
JTGraphics is offline   Reply With Quote
Old 06-18-08, 06:14 AM   #15
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
JTGraphics - I can do all the steps you mentioned, but here:

Quote:
shift to the next gear adjust the barrel adjuster
if it didn't move up to the cog adjust while turning the crank till it does
When I adjust the barrel adjuster enough so it goes to the next highest cog, then it won't go back down to the highest gear. It shifts reasonably well though the remaining gears, albeit off by one.

(I can trick it into going down by either pushing gently outward on the cage or by pulling on and snapping the cable under the down tube.)

Quote:
May I ask is this a setup that was working before or is this something your setting up fo the first time? I ask because you could also have a compatabality issue "pull ratio" with that old MB derailleur and your shifter your using, just what is this combo?
This has been getting worse for the last 500 miles or so. Except the cable, all the "transmission" equipment is original though, so it's probably not an incompatibility.

DieselDan
Quote:
Do the derailer pivots move other then the intended direction?
The top pivot wobbles in and out a small amount. I the wobbling top pivot to two other derailleurs. One is a year old SRAM, it doesn't wobble at all. The other is a low end Shimano, as old as mine but ridden less. It wobbles but a smaller amount.

I'm surprised how cheap the Alivio shifters are (at least at nashbar). The hanger from LBS cost just a bit less. I wonder if it would be worth a couple extra bucks to spring for the next model up.

Last edited by commute; 06-18-08 at 06:42 AM.
commute is offline   Reply With Quote
Old 06-18-08, 04:00 PM   #16
JTGraphics
Senior Member
 
JTGraphics's Avatar
 
Join Date: Dec 2006
Location: So Cal
Bikes:
Posts: 2,673
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well at this point is sounds like you have done everything, so if you take the cable off and the chain with your fingers push the RD over how is the return strong or weak? possible return spring problem weak or broken. Check the shift lever and cable ends. Check cable for sticking for some reason did you replace outer casing? make sure the hole is round and not squashed. Don't take it for granted do a physical check I just say this because many times people will say yayaya because they were sure because they did the job but ends up being a problem.
Hay good luck hope you find the trouble.
__________________
It may not be fancy but it gets me were I need to go.
http://www.jtgraphics.net/cyclist_bicycles.htm
JTGraphics is offline   Reply With Quote
Old 06-19-08, 06:25 PM   #17
DannoXYZ 
Senior Member
 
DannoXYZ's Avatar
 
Join Date: Jul 2005
Location: Saratoga, CA
Bikes:
Posts: 11,606
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Are the cable-pulls of the shifter compatible with the lateral-throws of the derailleur? Take a picture without chain of the RD in the smallest cog position and one in the biggest cog position. Rotate the cage so that the two pulleys are vertical and take a picture from directly behind the cogs so that the camera is centered on the cog that has the RD on it. With the older 6/7spd stuff, there's only a 0,25mm difference in spacing, but it adds up to large spacing differences between the two ends of the cluster.

Quote:
I tried the above advice, but it still won't shift into the small gears reliably.
By this do you mean going from smallest to bigger cogs isn't reliable, or only from big cogs down to smaller cogs? If it's the 2nd scenario only, it's a sign of insufficient return-spring tension in the RD or too much cable-friction. Did you oil/grease the new RD cables where they go into the housing? I find that the ferrule-ends without the o-ring seals work better, but require more frequent maintenance. Did you also clean-up or replace the plastic cable-guide under the BB?
DannoXYZ is offline   Reply With Quote
Old 06-19-08, 07:36 PM   #18
commute
Member
Thread Starter
 
commute's Avatar
 
Join Date: Jun 2008
Bikes:
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
At work I compared how wobbly the RDs on other bikes were (people probably thought I was crazy). None wobbled in and out from the top pivot as much as mine.

So I went to LBS and picked up a Alivio m410. It took about 2 minutes to tune the derailleur after the install!

Thanks for all the help guys!
commute is offline   Reply With Quote
Old 06-19-08, 09:02 PM   #19
JTGraphics
Senior Member
 
JTGraphics's Avatar
 
Join Date: Dec 2006
Location: So Cal
Bikes:
Posts: 2,673
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
__________________
It may not be fancy but it gets me were I need to go.
http://www.jtgraphics.net/cyclist_bicycles.htm
JTGraphics is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 08:12 PM.