rear derailleur bolt stuck

[lph]

Hi mechies

I've been having trouble with the rear derailleur on my commuter mtb, but I'm not sure what's wrong. It skips and gets stuck and does a lot of weird stuff, and there is quite a bit of sideways play compared to the frame. I took it off today to look closer at it, and the jockey wheels are worn but not exceedingly so, but are pretty wobbly side-to-side. So I'll probably be changing those, which should help shifting precision. The derailleur itself seemed good, tight spring and smooth action, but the mounting bolt was a major hassle to get off and on. It was so stuck that I had to really yank on the allen key to budge it. Is this bolt usually this tight? The sideways play was less once I got it yanked into place again, but it seems to me the derailleur is supposed to be able to pivot around the mounting bolt, apart from the separated plate actually facing the frame. At the moment I don't think anything can pivot around the bolt without a lot of force.

Should I take it off again and disassemble it, so that I can grease up whatever is stuck? Or isn't this really a pivot point in normal action? I'm a little leery of disassembling it since I know there are springs and stuff inside. This is a Shimano Deore der, by the way.

[OakLeaf]

If the spindle won't turn independently of the derailleur body, how did you get it on/off? I must not be understanding your issue.

Shimano specs torque at 8-10 Nm, so it shouldn't have been that tight unless maybe the threads are a little corroded? How does your derailleur hanger look? Maybe put a little anti-seize on the threads when you reinstall it ...

I've never tried to disassemble that part of a derailleur. I just put a drop of oil in there (and all the other pivot points on derailleurs and brakes) after I wash my bikes. Exploded diagrams are here - you didn't say which series your derailleur is. There are no springs on the spindle, but you'd need a cerclip tool.

[lph]

I'm not sure what the spindle is. The mounting bolt holding the derailleur to the frame will turn independently of the derailleur body, but only with a lot of force. To put it this way, I would have stopped yanking on the allen key if I hadn't been absolutely sure that that was the only way to remove the derailleur. And I know it's not the threads, they're fine.

I'm not certain if the derailleur is supposed to be able to pivot smoothly around the bolt during normal use, but it looks like it. At the moment it can only pivot around it if a lot of leverage is used, which doesn't happen during normal use.

Thanks for the link! The Park Tool guide to overhauling rear derailleurs shows a spring if you remove the plate which is directly between the derailleur body and the frame, which is why I'd rather not take it apart if I don't have to...

http://www.parktool.com/blog/repair-...lleur-overhaul
(about 3rd page down)

[dianne_1234]

Oakleaf has a good suggestion with the antiseize.

Most SRAM derailleurs I know are not designed to pivot in use.

Most Shimano derailleurs I know are designed to pivot in use, and you'll get better shifting if you can figure out what's keeping yours from doing so. I've taken this pivot apart in the past, it's a little tricky to wind up the spring on reassembly but after a few tries I got it. Might help to have the Shimano TechDoc exploded view for your derailleur as a guide.

Trivia: The lower pivot is the "A" pivot. For nearly the last half a century it's been a sprung pivot in 99.9% of derailleurs. When Shimano added a spring to the upper pivot (in the 1970s?) it became the "B" pivot. That's why, to this day, the screw that adjust the angle of the derailleur body at this pivot is called the "B-tension screw"! (Some Campy derailleurs adjust at the "A" pivot but I don't think Campy calls it that.)

[OakLeaf]

When Shimano added a spring to the upper pivot (in the 1970s?) it became the "B" pivot. That's why, to this day, the screw that adjust the angle of the derailleur body at this pivot is called the "B-tension screw"!

What a cool piece of trivia. I always wondered - thanks for that!

[lph]

Thank you ladies. You are briliant, as always