Bicycle Mechanics - Problem w/re-installing rear Shimano derailleur
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09-18-06, 01:33 PM
I am a new member to Bike Forums and this is my first new thread, so please excuse me if I don't do this quite right. Saturday (9/16/06) I was replacing the tube on my rear wheel. This was the first time that I had taken off a wheel to a multi-speed bike (well at least one with more than 3 speeds). I loosened both rear nuts to the wheel and the small screw to my Shimano derailleur. My mistake was that I assumed the small screw screwed into the frame of the bike. I later found lying on the ground a small flat threaded back plate (used as a nut), which I figured out goes with the small screw. I replaced the tube and was ready to attach the wheel to my bike frame, but couldn't figure out how the Shimano s/b attached. I looked for evidence of some wear on the frame of where it had been attached before, but found none. I thought maybe the small screw went through the derailleur and then through the small hole on the bike frame, but the screw is not long enough. The small back plate seems to fit best just behind the derailleur maybe to just used as a spacer or to position the derailleur just right. I can see some marks on the derailleur as to where the axle nut s/b, but nothing else. I dug out my Owner's Manual (bought 8 yrs ago), but the pictures aren't much help and the derailleur in the pictures look different from what I have. I've also searched Sears.com for my particular model, but unsuccessful thus far. Does anyone have an idea of the best way to re-attach my derailleur? A picture from a website w/b helpful too, if you know of one. Thanks for any help you can provide . . . Ray 9/18/2006
Go to www.parktool.com (http://www.parktool.com) and look up rear derailleur service. Pay particular attention to the "b screw adjustment" section. I'm trying to picture what you're saying, but I think that's what you're talking about.
For future reference, the derailleur will swing out of the way when removing the wheel- no need to remove it in the first place
Do not remove the derailleur when removing the wheel. Shift the derailleur to the smallest cog before removing the wheel.
Compare your derailleur set-up to other similar bikes to see how to re-attach it.
You have horizontal drop-outs and a drop-out mounted derailler, as opposed to one that has a hanger built into the frame for derailler mounting. The screw will go through the derailler mount and into the threaded back plate. The derailler is mounted so that the long slot lines up with the slot in the drop-out and the threaded plate fits against the end of the drop-out's slot to stop the derailler from rotating around the axle when everything is re-assembled.
09-19-06, 12:59 PM
Steev, thanks for the info. Some of the terminology is throwing me, but I think I understand what you are telling me. I need to line up the slot on my derailler with the slot on my frame where the rear axle goes (I assume this is the drop-out?) The screw and threaded back plate are connected to the small hole on the derailler, which just keeps the derailler from moving around. Taking another look at my bike, I did see a small worn place on the back end of the drop-out slot, which agrees with what you said above. Thanks for your help and will give it a try . . . Ray
Steev pretty well had it nailed, and you got it pretty right back at him. The little flat backplate is shaped with a curve that fits snugly back into the dropout. The screw goes through the derailleur and then into the backplate. Ensure the derailleur baseplate itself lines up along the dropout slot or else you will have a beastly time trying to get the hub axle seated properly.
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