RD hanger notch - B screw problem
09-05-17, 10:19 AM
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RD hanger notch - B screw problem
Hi!
I bought Ridley Helium RS (Shimano 105 5800) and used it for a short time. Recently I used 34/28 combination for first time and noticed, that upper jockey and biggest cog are touching each other. I tried to fix it by using B screw, but unfortunately B screw doesn't push the hanger notch. Is this something with hanger? Any ideas?
(sorry for lacking photo - 10 posts)
I bought Ridley Helium RS (Shimano 105 5800) and used it for a short time. Recently I used 34/28 combination for first time and noticed, that upper jockey and biggest cog are touching each other. I tried to fix it by using B screw, but unfortunately B screw doesn't push the hanger notch. Is this something with hanger? Any ideas?
(sorry for lacking photo - 10 posts)
09-05-17, 07:52 PM
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09-05-17, 09:47 PM
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The "b" screw is a common metric screw and you can switch it out for a longer one. I have a 36 tooth gear on my cassette. When I switched from an SRAM RD to a Shimano RD I followed the directions at Harris Cyclery to use a Shimano MD-591 which is designed for a 34 tooth large cassette gear but to use a longer "b" screw. I think it is a 6mm metric machine screw. BTW, the suggestion works.
09-08-17, 10:16 PM
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I don't think a longer screw will help him. I've heard it suggested to flip the screw upside down since the head is larger and will contact the tab longer. But you may need to remove the derailleur for adjustment.
09-08-17, 10:32 PM
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Something's fishy here. Even the short-cage 5800 rear derailleur is rated for a 28T cog, so it should have no trouble clearing the big cog without resorting to shade-tree mechanic tricks like installing longer B screws or turning the B screw around.
Is the chain way too long or something?
Is the chain way too long or something?
09-08-17, 10:38 PM
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Easy fix, and the third case of the same issue here in the last few days.
You want to build the stop tab back to rotate the RD starting position back. The easiest way is to make a pea sized ball (petit pea sized) ball out of aluminum foil, and pulling the RD back, trapping it between the B-screw and stop tab. That's simply a temporary fix, but in actuality can last for months or longer. It will only fail when you pull the RD back to remove the wheel and lose the pea.
The permanent fix depends on the frame (dropout) material. You can weld on some material then file a new stop where you need it. Or, drill a small hole radially, and set a pin there, then fill with metal/epoxy, and file to shape. The pin gives it added strength and helps keep it home. Position it so the B-screw hits it, or at least close, because the resin fill isn't all that strong.
You want to build the stop tab back to rotate the RD starting position back. The easiest way is to make a pea sized ball (petit pea sized) ball out of aluminum foil, and pulling the RD back, trapping it between the B-screw and stop tab. That's simply a temporary fix, but in actuality can last for months or longer. It will only fail when you pull the RD back to remove the wheel and lose the pea.
The permanent fix depends on the frame (dropout) material. You can weld on some material then file a new stop where you need it. Or, drill a small hole radially, and set a pin there, then fill with metal/epoxy, and file to shape. The pin gives it added strength and helps keep it home. Position it so the B-screw hits it, or at least close, because the resin fill isn't all that strong.
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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.
