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 06-24-07, 09:30 AM   #1
larrysnatch
Newbie
Thread Starter
 
Join Date: Jun 2007
Bikes:
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Old Rear Derailleur Spring Tension (pic)

Hi,

I'm trying to restore/tune-up an old road bike.
It has the original shimano rear derailleur (see picture) which shifts really well.
However, it has no spring tension. I cannot pedal backwards, the chain becomes loose.

Does anyone know how to adjust the spring tension on this derailleur model?

Thanx

Larry

Old Shimano Derailleur 3.jpg
larrysnatch is offline   Reply With Quote
Old 06-24-07, 10:01 AM   #2
stokessd
Senior Member
 
stokessd's Avatar
 
Join Date: Jun 2007
Location: Fort Wayne, Indiana
Bikes: Stowe(3), Terry(1), Cannondale Tandem (1)
Posts: 200
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
are you sure it's not more of freewheel problem than a deraileur problem?

Sheldon
stokessd is offline   Reply With Quote
Old 06-24-07, 10:21 AM   #3
vpiuva
*
 
vpiuva's Avatar
 
Join Date: Jan 2007
Bikes:
Posts: 3,458
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Have you pulled the bottom pivot bolt out to look? Not sure on this model, but many RD have 2 separate holes to mount the spring, one providing more spring tension.
vpiuva is offline   Reply With Quote
Old 06-24-07, 01:30 PM   #4
larrysnatch
Newbie
Thread Starter
 
Join Date: Jun 2007
Bikes:
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Does anyone have experience with such a derailleur? There are 2 pivots (upper and lower), but I am not sure how to increase the spring tension. I could rotate the pivots with the use of an allen key, but that does not seem to add any spring loading.
larrysnatch is offline   Reply With Quote
Old 06-24-07, 01:37 PM   #5
vpiuva
*
 
vpiuva's Avatar
 
Join Date: Jan 2007
Bikes:
Posts: 3,458
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by larrysnatch
Does anyone have experience with such a derailleur? There are 2 pivots (upper and lower), but I am not sure how to increase the spring tension. I could rotate the pivots with the use of an allen key, but that does not seem to add any spring loading.
You actually have to unscrew & pull the lower pivot bolt all the way out to see that the spring is inside. You're right that just turning it some with an allen wrench does nothing.
vpiuva is offline   Reply With Quote
Old 06-24-07, 05:47 PM   #6
dafydd
JRA...
 
Join Date: Oct 2003
Location: philly
Bikes: trek 520 & 736, DeRosa Professional, Fuji Professional, Raleigh International 3-speed, Saronni (any info people?), Humber 3-speed, Raleigh Sports, Carlton Grand Prix coming soon!
Posts: 839
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
it's a simplex derailleur, actually. what you're describing sounds more like

A) Sluggish freewheel
B) Misaligned derailleur hanger or cage
C) If it happens in the lower gears, the upper pulley may be sitting too close to the freewheel teeth to allow for backpedalling.
dafydd is offline   Reply With Quote
Old 06-24-07, 06:02 PM   #7
vpiuva
*
 
vpiuva's Avatar
 
Join Date: Jan 2007
Bikes:
Posts: 3,458
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by dafydd
it's a simplex derailleur
I didn't look at it that close - is this model worth anything?
vpiuva is offline   Reply With Quote
Old 02-01-09, 08:34 PM   #8
PLyTheMan
Senior Member
 
Join Date: Jul 2008
Bikes:
Posts: 71
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Bumping this for help!!

I have an old 10 speed Puch, Shimano derailleur (not sure the model) that does more or less what OP described. Whenever I backpedal the arm of the derailleur that keeps tension pulls forward and causes the chain to slack up and fall off my chainring. I've given the chain a good cleaning and taken all the gunk off the cogs and it still happens. Could be that the little cogs need some more lube to turn, but i dunno.

The cables shift with friction shifters up on the stem, and I've noticed that the cable stop in the shift lever pops out a bit, IE there's not enough tension in the cable. I've tried turning the barrel adjuster where the cable runs into the derailleur counter and clockwise but I haven't seen any improvement.

Does the lack of tension in my derailluer arm come from my cable not being tight enough, the cogs being gunked up beyond what a chain cleaner can reach, or is the spring in my derailleur just gone?
PLyTheMan is offline   Reply With Quote
Old 02-02-09, 01:20 AM   #9
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)
That's the correct operation of the RD. If you pedal backwards in a gear that's doesn't have a perfectly straight chain-line, the angle of the chain will cause it to shift off the bottom of the chainring. This is actually worse with RD having strong spring-tension.

Why pedal backwards?
DannoXYZ is offline   Reply With Quote
Old 02-02-09, 03:06 AM   #10
dabac
Senior Member
 
Join Date: Mar 2008
Bikes:
Posts: 5,689
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 95 Post(s)
Quote:
Originally Posted by PLyTheMan View Post
...Whenever I backpedal the arm of the derailleur that keeps tension pulls forward and causes the chain to slack up and fall off my chainring.... Could be that the little cogs need some more lube to turn, but i dunno.
Would that be the cogs in the derailer cage you're talking about here? While giving them a clean and a lube probably won't hurt them it's not the most probable cause for your trouble.

Quote:
Originally Posted by PLyTheMan View Post
...The cables shift with friction shifters up on the stem, and I've noticed that the cable stop in the shift lever pops out a bit, IE there's not enough tension in the cable.
As long as you can still get the chain onto the biggest sprocket/chainwheel, having the cable go slack when the der is in position for the smallest sprocket/chainwheel has no influence on function.
Usually the shifter can pull a bit more cable than what's actually required, and the der range of motion is controlled by the limit screws.
If you're really picky one could argue that it'll mean that you'll have to tweak the shifter a tad more before the der begins to move, and that a slack cable can slap and rub against the frame. Functionally it's a non issue IRL.
The easiest fix is simply to stop moving the shifter once you're in the right gear, and before the cable go entirely slack. Pushing it all the way against the stop isn't improving anything.

The only thing that would prompt me to do something about that is if the cable end got hung up on the shifter and didn't settle properly when the shifter was engaged again.

Quote:
Originally Posted by PLyTheMan View Post
...Does the lack of tension in my derailluer arm come from my cable not being tight enough, the cogs being gunked up beyond what a chain cleaner can reach, or is the spring in my derailleur just gone?
Forget about the cable. Spring is a possibility, as are guide & jockey pulley, but I'd check the freewheel first.
dabac is offline   Reply With Quote
Old 02-02-09, 04:45 PM   #11
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,789
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 223 Post(s)
Quote:
Originally Posted by stokessd View Post
are you sure it's not more of freewheel problem than a deraileur problem?

Sheldon
+1

That's my guess as well. An old gummed up freewheel will do what the OP describes. A weak derailleur spring would degrade shifting, which the OP describes as working "really well" still.

Remove the freewheel and soak it in solvent, then blow it clean with compressed air. Add a little oil and Bob's your uncle.
JohnDThompson is offline   Reply With Quote
Old 02-02-09, 04:51 PM   #12
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,789
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 223 Post(s)
Quote:
Originally Posted by vpiuva View Post
I didn't look at it that close - is this model worth anything?
It looks like one of the all-metal Super LJs, with a long cage. One of these (in NOS condition) recently sold for $143.50 on eBay.
JohnDThompson is offline   Reply With Quote
Old 02-02-09, 05:48 PM   #13
PLyTheMan
Senior Member
 
Join Date: Jul 2008
Bikes:
Posts: 71
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well, I gave everything a good cleaning and took it out for my commute today and, as long as I don't cross the chain from smallest back to smallest front it is okay. I'm still not sure whey the derailleur pulls up when I'm on that combo as it was never a problem before. Also, could you explain why the freewheel would be the cause of this problem? EDIT: nevermind, I think I understand now... This weekend I'll pull it apart and try to clean the freewheel.

As for my cable issue, the problem is that I push my shift lever all the way up, so that it should be in the lowest gear in back, but the cable doesn't pull back with the lever and I don't shift into my smallest. So now my lever is as far up as it can go and the derailleur has stopped on up from where it should be. Generally if I run over a pot hole or do a little bunny hop it will pop into place. I think that I might just need to run some new cable.

Last edited by PLyTheMan; 02-02-09 at 05:51 PM.
PLyTheMan is offline   Reply With Quote
Old 02-02-09, 09:54 PM   #14
Grand Bois
Senior Member
 
Grand Bois's Avatar
 
Join Date: Mar 2005
Location: Pinole, CA, USA
Bikes:
Posts: 16,836
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 139 Post(s)
Quote:
Originally Posted by JohnDThompson View Post
It looks like one of the all-metal Super LJs, with a long cage. One of these (in NOS condition) recently sold for $143.50 on eBay.
There is some similarity to the SLJ, but that's an SX410. The arms are black plastic covers with thin metal and they have more steel parts. They're about 30 grams heavier than an SLJ. They work well, but don't sell for any thing near what an SLJ goes for unless the buy thinks he's getting an SLJ.
Grand Bois is offline   Reply With Quote
Old 02-02-09, 10:01 PM   #15
Grand Bois
Senior Member
 
Grand Bois's Avatar
 
Join Date: Mar 2005
Location: Pinole, CA, USA
Bikes:
Posts: 16,836
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 139 Post(s)
Simplex derailers have a little tab that has to hook onto the forward edge of the hanger. You can see it in this picture of my Super LJ. If it's not in that position, you won't have any spring tension.

Grand Bois is offline   Reply With Quote
Old 02-03-09, 02:22 AM   #16
dabac
Senior Member
 
Join Date: Mar 2008
Bikes:
Posts: 5,689
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 95 Post(s)
Quote:
Originally Posted by PLyTheMan View Post
..the problem is that I push my shift lever all the way up, ...the cable doesn't pull back with the lever and I don't shift into my smallest. ....I think that I might just need to run some new cable.
Sounds like an excellent suggestion!
dabac is offline   Reply With Quote
Old 02-03-09, 02:45 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)
Quote:
Originally Posted by PLyTheMan View Post
As for my cable issue, the problem is that I push my shift lever all the way up, so that it should be in the lowest gear in back, but the cable doesn't pull back with the lever and I don't shift into my smallest. So now my lever is as far up as it can go and the derailleur has stopped on up from where it should be. Generally if I run over a pot hole or do a little bunny hop it will pop into place. I think that I might just need to run some new cable.
This is a common symptom of too much friction in the cables and the RD's spring can't pull itself into the correct position.
DannoXYZ 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 08:51 PM.