Jockey Wheel rubbing Big cog
Still trying to get the old tandem running smoothly. For as long as I can remember, the upper jockey wheel has rubbed the big rear cog (when I’m on the small chainring).
It’s raining, so I decided to try to do something about it. The B screw was put in backwards, which leads me to believe I must have had a shop try to fix the problem in the last 15 years. I pulled it out slightly, which briefly fixed it, but after cleaning up the chain and adjusting cable tension, it has returned. Here’s what I’ve tried so far, mostly in order. Pulled B screw out, and put in from correct side. B screw appeared too short, so I went to Ace hardware and bought a longer screw. Put that screw in from correct side, but at a certain point, the angle becomes wrong and it stops doing anything useful. Tried reversing new longer screw. The head doesn’t stat where I want it to go. Checked chain length, which for 53/34 and what I measure as 17.5 inch chain stay is correct at 57 links. Park Tool says my chain does not need replacing. I was thinking of giving up and taking it to a bike shop, but as there are almost no tandems on the island, I’m not expecting much for my $80. Any thoughts on what I should try next? I was thinking of getting a B screw with a much larger head and then screwing it in backwards. Was wondering if I’d have any more luck with the derailer off the bike. |
Originally Posted by 72andsunny
(Post 21281231)
Tried reversing new longer screw. The head doesn’t stat where I want it to go.
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What size is your rear cassette. You might want to get a road liink or goat link from wolf tooth components to move the derailleur down and back. Very common with the new large cassettes. An inexpensive solution to the problem
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Was your gearing customized?
It sounds like your chain is a bit(1 link or maybe 2) long. The derailleurs you use have limits of chain wrap and customizing this might not have addressed this issue. If your tandem had an eccentric bottom bracket to allow the connecting chain to be adjusted, you may want to look into this area. If the eccentric has been re oriented, it would allow the chain to, in effect, become longer. Photos would be a great help in diagnosis. |
Originally Posted by 100bikes
(Post 21282008)
Was your gearing customized?
It sounds like your chain is a bit(1 link or maybe 2) long. The derailleurs you use have limits of chain wrap and customizing this might not have addressed this issue. If your tandem had an eccentric bottom bracket to allow the connecting chain to be adjusted, you may want to look into this area. If the eccentric has been re oriented, it would allow the chain to, in effect, become longer. Photos would be a great help in diagnosis. |
Originally Posted by akexpress
(Post 21281953)
You might want to get a road liink or goat link from wolf tooth components to move the derailleur down and back.
https://www.wolftoothcomponents.com/...ducts/roadlink It says 10/11 sp but works fine on our 9sp. |
Originally Posted by unikid
(Post 21281630)
Can you clarify what you mean by "the head doesn't stay where I want it to go"? Is the screw turning after you set the length? If so, then maybe try some Blue Loc-tite on the threads?
https://cimg6.ibsrv.net/gimg/bikefor...ccf78bbfcc.jpg |
Originally Posted by 100bikes
(Post 21282008)
Was your gearing customized?
It sounds like your chain is a bit(1 link or maybe 2) long. The derailleurs you use have limits of chain wrap and customizing this might not have addressed this issue. If your tandem had an eccentric bottom bracket to allow the connecting chain to be adjusted, you may want to look into this area. If the eccentric has been re oriented, it would allow the chain to, in effect, become longer. Photos would be a great help in diagnosis. |
Originally Posted by akexpress
(Post 21282216)
most Tamdems have the eccentric in captains bottom bracket so it does not affect chain length to the derailluers
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Originally Posted by akexpress
(Post 21281953)
What size is your rear cassette. You might want to get a road liink or goat link from wolf tooth components to move the derailleur down and back. Very common with the new large cassettes. An inexpensive solution to the problem
Road link looks like what I need, except there website says it won't work with long cage derailers (which I have) and triple chain rings (which I also have). |
Originally Posted by sapporoguy
(Post 21282483)
+1 this solution. I had that problem with a 12-36 cassette. Long B-screw turned in was at wrong angle where it hit dropout. A Wolf Tooth Road Link solved it:
https://www.wolftoothcomponents.com/...ducts/roadlink It says 10/11 sp but works fine on our 9sp. |
Originally Posted by 72andsunny
(Post 21282615)
11/34...this was probably a big cassette in 2003.
Road link looks like what I need, except there website says it won't work with long cage derailers (which I have) and triple chain rings (which I also have). |
Originally Posted by sapporoguy
(Post 21282630)
I have triple chain rings, and pretty sure I have a long-cage derailleur, and the link works fine on an 11/36 or 12/36.
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Originally Posted by sapporoguy
(Post 21282630)
I have triple chain rings, and pretty sure I have a long-cage derailleur, and the link works fine on an 11/36 or 12/36.
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Originally Posted by akexpress
(Post 21282642)
it will work fine on a triple It is more of a factor of the large cassette
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I doubt you will need to add chain links
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Has the tandem fallen over? The photo makes is look like the alignment of the B adjustment screw is off
center to the stop. This could be the problem, as the jockey pulleys could be closer to the cog after a fall and the alignment similar to what is in the photo. |
I think it's completely normal for the jockey wheel to be directly under a 34T cog, using a normal MTB RD. The B screw won't do anything about that. It's fine. I don't see the issue. The spring in the RD determines the pressure of the jockey wheel against the chain, no matter where it is.
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Agreed that derailleur spring determines the float of the derailleur with both pulleys in the same vertical plane as the (largest, in this case) cog.
I still contend that the dropout alignment matters. With the large gear range tandems sometimes have, this would be an important factor. The small chainring and large rear cog combination is in the middle of the range of tensions that rear derailleur needs to handle(small front chainring/ small rear cog being the the most difficult for the derailleur to handle - carrying a lot of the chain wrap/weight as well). The shifting may not be affected through the ability of jockey pulleys to float around a bit. The photo shows that there is a clearly a misalignment. A tandem with a forged dropout such as this should/would definitely have the hanger in alignment to accept the B screw to hit dead center from the factory/builder. Check the most outward edge of the derailleur for any indication of damage; and Check the hanger for paint buckle From the posted photo, it is difficult to determine any /all issues. Two photos that would help the group diagnose the issue: One from behind the bicycle , showing the rear derailleur with the chain on largest cog in rear and smallest ring in front, to show alignment; Photo showing the face of the derailleur from the side having stated that it is all original, except the cassette. |
Originally Posted by Carbonfiberboy
(Post 21283782)
I think it's completely normal for the jockey wheel to be directly under a 34T cog, using a normal MTB RD. The B screw won't do anything about that. It's fine. I don't see the issue. The spring in the RD determines the pressure of the jockey wheel against the chain, no matter where it is.
|
Originally Posted by 100bikes
(Post 21282804)
Has the tandem fallen over? The photo makes is look like the alignment of the B adjustment screw is off
center to the stop. This could be the problem, as the jockey pulleys could be closer to the cog after a fall and the alignment similar to what is in the photo. |
Originally Posted by Carbonfiberboy
(Post 21283782)
I think it's completely normal for the jockey wheel to be directly under a 34T cog, using a normal MTB RD. The B screw won't do anything about that.
From Sheldon Brown: "If your derailer has a B screw, then you install the new cassette, shift to the large cog, and adjust the "B" screw so that the jockey pulley doesn't hit the teeth on the large cog. See picture below for a fully screwed in B screw. Check Sheldon's page about derialer adjustment for more B screw info." https://www.sheldonbrown.com/deakins/lowgears.html |
Originally Posted by 72andsunny
(Post 21284072)
I guess the issue is it makes the gear combination pretty close to unusable.
https://www.jensonusa.com/globalasse...s/rd208z00.jpg |
Originally Posted by 72andsunny
(Post 21284072)
I guess the issue is it makes the gear combination pretty close to unusable.
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Originally Posted by sapporoguy
(Post 21284097)
Just to make sure there's no confusion (which I'm sure you didn't intend!): The B screw may not affect whether it's directly under, but it *does* determine the gap between the big cog and the jockey wheel. So if the jockey is rubbing the big cog, it's the B screw's job to adjust the gap between them.
From Sheldon Brown: "If your derailer has a B screw, then you install the new cassette, shift to the large cog, and adjust the "B" screw so that the jockey pulley doesn't hit the teeth on the large cog. See picture below for a fully screwed in B screw. Check Sheldon's page about derialer adjustment for more B screw info." https://www.sheldonbrown.com/deakins/lowgears.html |
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