Fatigued Rear Derailleur
#1
Senior Member
Thread Starter
Join Date: Aug 2010
Posts: 182
Likes: 0
Liked 0 Times
in
0 Posts
Fatigued Rear Derailleur
I have an early 80's dura-ace derailleur that I have on a road-bike I built up the past summer.
It shifts really well, however I noticed when I shift down to a lower gear on the rear cassette, the top jockey wheel start to ride the cog. However this doesn't happen when I shift up to the same cog from a lower gear.
This derailleur doesn't have a b-screw to adjust to give me more clearance either. Is this a case of a fatigued mechanism? Can this possibly be remedied by shortening the chain by one link?
It shifts really well, however I noticed when I shift down to a lower gear on the rear cassette, the top jockey wheel start to ride the cog. However this doesn't happen when I shift up to the same cog from a lower gear.
This derailleur doesn't have a b-screw to adjust to give me more clearance either. Is this a case of a fatigued mechanism? Can this possibly be remedied by shortening the chain by one link?
#2
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,639
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Liked 3,480 Times
in
1,911 Posts
This derailleur may set the angle based using an upper and lower spring. The balance between the springs is what's key. There should be an adjustment for one of the springs so you can set the balance needed. These derailleurs are sensitive to dirt or dried grease at the upper or lower pivots because friction can affect the balance or the derailleur's freedom to move to the balance point.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#4
Senior Member
Thread Starter
Join Date: Aug 2010
Posts: 182
Likes: 0
Liked 0 Times
in
0 Posts
This derailleur may set the angle based using an upper and lower spring. The balance between the springs is what's key. There should be an adjustment for one of the springs so you can set the balance needed. These derailleurs are sensitive to dirt or dried grease at the upper or lower pivots because friction can affect the balance or the derailleur's freedom to move to the balance point.
I should also note i am using friction shifters as well, if that matters. What is the best/easiest way would I go about cleaning the derailleur springs? Does this require disassembling the mech?
#6
Senior Member
Thread Starter
Join Date: Aug 2010
Posts: 182
Likes: 0
Liked 0 Times
in
0 Posts
Thanks electrik, I think I may try this first. The max teeth for this RD is 26 and I'm pretty sure my biggest cog is smaller than that.
Disassembling the RD for cleaning seems a bit tedious and if shortening the chain doesn't work, that would definitely have to be a rainy saturday afternoon activity...
Disassembling the RD for cleaning seems a bit tedious and if shortening the chain doesn't work, that would definitely have to be a rainy saturday afternoon activity...
#7
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,639
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Liked 3,480 Times
in
1,911 Posts
I know there isn't the classic B-screw adjustment or a fixed stop position for the upper pivot. Look near the lower pivot and see if there's a spring adjustment there. Possibly it uses multiple holes in the cage and you adjust the lower spring that way (common in RDs decades ago).
However the fact that it finds a different balance point, depending on which direction you come to a sprocket from, suggests that it's a friction (dirt, dried grease) issue, more than a spring tension problem.
The balance point is also determined by chain length, but that's trickier because you have 2 chainrings up front, and so are dealing with 2 effective lengths.
However the fact that it finds a different balance point, depending on which direction you come to a sprocket from, suggests that it's a friction (dirt, dried grease) issue, more than a spring tension problem.
The balance point is also determined by chain length, but that's trickier because you have 2 chainrings up front, and so are dealing with 2 effective lengths.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#8
Senior Member
Join Date: Sep 2010
Location: Roswell, GA
Posts: 8,326
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Liked 1,101 Times
in
729 Posts
Behaving differently shifting up or down leads me to believe that friction is the culprit here. If you don't want to dismantle the derailleur to clean and lubricate it properly you might try flushing it out with brake cleaner and after it is dry giving is a thorough lubrication with some light oil. Work the mechanism around while you spray the cleaner to try and work out any grit.
Shortening the chain may help if it is too long to begin with, but be cautious not to shorten it beyond where it will not reach around the big-big cog-chainring combination. Shifting into that combo with a too-short chain is inviting disaster.
A cleaning and lubrication is the most conservative course of action and will certainly do no harm.
Shortening the chain may help if it is too long to begin with, but be cautious not to shorten it beyond where it will not reach around the big-big cog-chainring combination. Shifting into that combo with a too-short chain is inviting disaster.
A cleaning and lubrication is the most conservative course of action and will certainly do no harm.
#9
Senior Member
Join Date: Jun 2011
Location: Sunnyvale, California
Posts: 1,180
Bikes: Bridgestone RB-1, 600, T700, MB-6 w/ Dirt Drops, MB-Zip, Bianchi Limited, Nashbar Hounder
Likes: 0
Liked 0 Times
in
0 Posts
+1 on the cleaning. I can't recall if the old Dura Ace had two holes for the lower pulley assembly pivot spring. But if it does, and someone tried to service the RD in the past, then it may be in the wrong hole and that can throw off tension or cause the pivot spring to sometimes bind inside. You may need to remove that assembly and disassemble to see if there's a washer that's also not correctly in place on that pulley arm assembly. That can also cause binding and unequal behaviour on the up vs. down shifts.
#10
Senior Member
Join Date: Oct 2011
Location: SF Bay Area
Posts: 428
Bikes: 2003 Lemond Zurich; 1987 Schwinn Tempo; 1968 PX10; 1978 PX10LE, Peugeot Course; A-D Vent Noir
Likes: 0
Liked 1 Time
in
1 Post
I have an early 80's dura-ace derailleur that I have on a road-bike I built up the past summer.
It shifts really well, however I noticed when I shift down to a lower gear on the rear cassette, the top jockey wheel start to ride the cog. However this doesn't happen when I shift up to the same cog from a lower gear.
This derailleur doesn't have a b-screw to adjust to give me more clearance either. Is this a case of a fatigued mechanism? Can this possibly be remedied by shortening the chain by one link?
It shifts really well, however I noticed when I shift down to a lower gear on the rear cassette, the top jockey wheel start to ride the cog. However this doesn't happen when I shift up to the same cog from a lower gear.
This derailleur doesn't have a b-screw to adjust to give me more clearance either. Is this a case of a fatigued mechanism? Can this possibly be remedied by shortening the chain by one link?