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Old 01-17-10, 03:45 PM   #1
sharky nrk
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bent rear derailer

1991 SR600 C'dale Crit 3.0 w/ 105 group - i think the rear derailer might be bent. I recently replaced all the cables and housings and added Sora STIs and I cannot seem to get the rear derailer shifting right no matter what I do. I started to suspect the rear derailer might be bent as when it looks like the guide pulley is directly underneath the sprocket, the chain still clinks and jumps like something is off. When i pull the derailer downward to straighten the pivots it does not make a straight line from the pulley but rather sits at an angle towards the rear wheel.

Is this an indication it is bent and what is the proper way to straighten it, or do I need to buy a new one.
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Old 01-17-10, 04:15 PM   #2
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You may have a non-indexed derailluer on the bike. I would just put a Sora on to match the shifters. Before doing that make sure the derailluer hanger is not bent. Roger
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Old 01-17-10, 04:15 PM   #3
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You need to take it to a shop that has a Park Tool DAG-2, or equivalent, tool designed to check and straighten the derailleur-hanger. Get that sorted first. Then see about the rear-derailleur (RD) - does it shift? Still no? Then think about repair/replacement.

DAG-2:

http://www.parktool.com/products/det...=48&item=DAG-2
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Old 01-17-10, 04:30 PM   #4
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It shifts and it is for sure an indexed rear derailer. I don't think the hanger itself is bent but rather the derailer itself, possibly at the upper pivot. Maybe I can take some pictures, taking the bike to my LBS requires a solid hour drive.
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Old 01-17-10, 04:54 PM   #5
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+1 on what panthers007 said.
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Old 01-17-10, 05:03 PM   #6
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It shifts and it is for sure an indexed rear derailer. I don't think the hanger itself is bent but rather the derailer itself, possibly at the upper pivot. Maybe I can take some pictures, taking the bike to my LBS requires a solid hour drive.
Here are your options in that case, if you're fully confident that it is nothing else.

1) Order a alignment guage
2) Order a rear derailleur

You can pick one, and if it's not it then it must be the other, heh.
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Old 01-17-10, 05:07 PM   #7
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if you had issues before, then i would agree that you have a bent hanger. bent RDs are sort of rare.

however, did you have shifting issues before you you changed your cables and shifters? do you have a shimano RD? if you are using shimano shifters with non-shimano RD, then you are going to have shifting issues.

what happens if you perfectly dial in a gear and ride without shifting? does the chain still jump? if no, then you probably just have a shifting issue.
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Old 01-17-10, 05:41 PM   #8
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Its full 105 minus the STIs. I did have inconsistencies in shifting prior to replacing the downtube 105 shifters (indexed) to the Sora STIs but I am not sure they are the same issues I am having now since it was three months of downtime between last ride on DT shifters and the STIs.

The issue presents itself in certain sections of the cassette, namely the largest sprocket and the fourth sprocket but its there in some form all the time. What seems to happen is that the guide wheel will be directly underneath the sprocket, but the takeup wheel will not be: why i think it could be bent. Again I will try and take pictures.

If i just put in in a single gear and pedal along it will stay in gear - in a few it will be fine - others it might jump and make noise.
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Old 01-17-10, 05:49 PM   #9
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To know (or guess) whether the RD is bent or the hanger, watch the chain running through the idler cage. If it runs smoothly and the two pulleys appear to be in line, then odds are it isn't the RD, but the hanger that's bent. Also if the Idler cage is closer to the wheel at the bottom than the top, indicating that the hanger is bent inward that's another clue. Hangers get bent inward from crashes all the time.

If it does appear to be the hanger, try this poor man's solution. Stick a correct size allen key into the upper pivot bolt, and use it as a lever to gently bend the hanger. Bringing the key up, brings the hanger out. Do this slowly by degrees, checking your work by eyeballing if the idler cage is coming parallel with the wheel, and/or by turning the cranks and seeing how it runs. Note that bending (straightening) the hanger will change both the trim and limit screw positions. so you'll have to re-adjust everything afterward. Techies will frown on this, but race mechanics have been doing this for eons as an emergency field repair, and with good eyes and hands achieving results comparable to those with the tool.
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Old 01-17-10, 07:15 PM   #10
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well i am gonna have to readjust it anyways cause I just took it all the way apart to get a look at it, i am uploading pics now - they are off the phone cause i can't hold my dslr and get the pics of the bike on the stand
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Old 01-17-10, 07:25 PM   #11
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pics







i don't think the hanger is bent, it looked very straight and when compared to a straight edge showed no deviation top to bottom.



















I don't know if you can see exactly what I think I see in the picture, but the takeup pulley looks like it sits a tweaked and out of line from the guide pulley. I took the two pulleys off the rear derailer to see if they were buggered but they are just plastic with a sleeve bearing so I can't see what could be messed up there.
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Old 01-17-10, 08:14 PM   #12
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Again, your options are

1) $10 derailler hanger alignment - or procure the tool to do it
2) Assume the derailleur is bent and order a new one

Your pictures don't really show much except for the fact that neither is bent enough to be *extremely* and conclusively bent.
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Old 01-17-10, 08:35 PM   #13
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You don't have an old RD sitting around you could put on to just check? That'd be an easy way to narrow down the problem.
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Old 01-17-10, 08:49 PM   #14
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unfortunately no - new to this cycling thing - bought my first road bike (this one) last year. i had nice trek mtbs in college but none stayed in my hand (were stolen) long enough to replace parts anyways
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Old 01-17-10, 08:54 PM   #15
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when shopping round for a replacement rear derailer - supposing the hanger is not bent - will any of the modern shimano units work. seen 9sp and 10sp ultegra ss units on ebay for less than $50, or better yet is it worth putting a dura-ace or ultegra unit on or should i just be looking for another 105
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Old 01-17-10, 10:18 PM   #16
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A sanity check, and I don't know the answer. Is your 105 derailleur supposed to work with Sora? In other words, do you have an 8s rear derailleur with the right geometry?

Another thing: I'd unscrew the B-screw a lot. That's the little screw that bites into the dropout from behind. The more you unscrew it, the closer the upper pulley gets to the cogs. Put it in the small ring, big cog, and unscrew it until the upper pulley just grazes the cog. Then tighten it just a touch. When you backpedal the upper pulley shouldn't rub the cog. The closer the upper pulley is to the cassette cogs, the more firmly it shifts.

Yet another thing. The adjuster barrel seems like it's unscrewed all the way (where the housing is anchored in the rear derailleur). The silver inner barrel threads into the der, the outer grey thing is your "handle" so you can turn it. Loosen the cable so there is no tension on the housing at all and carefully, carefully thread the barrel back in place. Carefully because the silver barrel is steel and the derailleur is aluminum. Get it all the way in there before you pull the cable through. You should also "max out" the adjusters on the downtube or cable housings by the brifters the same way. It's very hard to pull a cable through too much - usually you pull on the cable end firmly with pliers (careful not to squish/damage the cable), tighten bolt, unscrew one barrel adjuster a turn or so, and you're done. Front derailleurs are more difficult.

I'm writing this at a certain level so forgive me if you know some of it already. The fact that you haven't mentioned b-screw, adjuster barrels, etc, suggested to me that I should explain them.

Finally, short instructions on how to adjust rear der:
1. Adjust H limit screw so der is under small cog.
2. Pull cable through, tighten clamp.
3. Shift one gear lower. Pedal 1/2 rev.
- If it doesn't shift up to the next cog, unscrew adjuster barrel until it does. If it takes a lot of unscrewing, shift into small cog, screw adj barrel all the way down and pull cable through more.
- If it shifts too far, screw in adjuster barrel. If barrel is all the way in, put into small cog, loosen cable a bit.
- Once you can shift one gear at a time, pre-shifting, check each gear. If the shifting gets worse and worse, you may have a bent something somewhere. A drivetrain in good condition will allow you to preshift one shift, pedal 1/2 rev, and shift into that gear quickly and precisely.
4. Carefully shift until you're in the big cog. Tighten L limit screw so derailleur cannot go into spokes, and chain doesn't derail into spokes either.
5. In Small/Large (chainring/cog), unscrew B screw until the upper pulley is as close as possible to the cog without rubbing it.
6. Test gears - use Big/Big, Small/Small, check clearances with crank/front der, spokes/rear der.

Hope this helps.
cdr
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Old 01-18-10, 04:19 AM   #17
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You have the correct approach. The one's delineated with a ....

1) $10 derailleur hanger alignment - or procure the tool to do it

2) Assume the derailleur is bent and order a new one
_____________________________________________________________________

Anything further is superfluous hyperbole aka "jumping the gun." 1) then 2).
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Old 01-18-10, 05:33 AM   #18
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i appreciate all the responses - I am almost certain the rear derailer unit is fully capable of being shifted but the Sora STIs. I mean minus the issue I am having, while on the stand it shifts itself from bottom sprocket to top, its just that it doesn't do it cleanly, especially in a few places. Prior to posting my query, I readjusted everything exactly per the tech docs from shimano after installing the cables and housings. I started with both barrel adjusters all the way threaded into the units, both at the derailer and the downtube cabel stop. I adjusted the B-screw all the way in and all the way out trying to pay attention to what it did to the angle of the derailer with no real success. I pulled it all apart to take the pics and sanity check myself on the hanger, so when I put it back together I will try it without the chain and check the alignment of the guide and take up pulleys with no chain tension on each sprocket prior to re-chaining.

the front derailer adjusted in like it wanted to be right on, the rear is giving me all the issues - cause something is borked or I don't know. After I am confident I have exhausted looking at what I have now I guess its moving on the the spending money parts - half a tank of gas and $10 or a new rear derailer. Anyone care to comment on the value of purchaing an "upgraded" unit.
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Old 01-18-10, 02:31 PM   #19
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is your chain worn? also make sure there are no stuck links.
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Old 01-19-10, 08:36 AM   #20
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took the chain off and cleaned it with a nylon brush and contact cleaner - got it all put back together and looking at it again I think something for sure has to be bent - but it looks like if it was the hanger it would have to be bent to the outside away from the wheel. I will be on the look out for a new take off rear derailer as well. Cannondale makes a replacement hanger - how to find one I don't know
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Old 01-19-10, 01:50 PM   #21
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Go to bike-shop. Get the hanger bent back into the correct plane. Reinstall derailleur.

Any impact that would bend the body of the rear-derailleur would also have bent the hanger - first. The hanger is made of soft alloy to allow this - rather than bending the stays of the frame. Ask the shop to look at your RD to check for any damage.

This is what you need to do. Buying a new hanger/RD will leave you staring at parts you have no idea how they go together - or work.
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Old 01-19-10, 02:16 PM   #22
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Cannondale makes a replacement hanger - how to find one I don't know
Even if you buy a new hanger you are still going to have to have it alligned.
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Old 01-19-10, 03:41 PM   #23
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This has been a waste of 22 posts so far if you have not gotten your hanger alignment checked at a shop. This is by far the most likely cause - it is virtually impossible to bend your derailleur and not bend the hanger. In fact, the hanger is designed to bend with less force than would bend the frame or derailleur, as it is the simplest and cheapest part, and the easiest part to change. If the bend is minor the shop can probably straighten it out whit the alignment tool when they check it... then you order a new hanger from http://derailleurhanger.com/ amd you can install the new one next time you are tuning up your bike.

Also, if you buy a new derailleur and the problem is a bent hanger then you just wasted the price of a new derailleur.

Further, any modern (made in last 10 years) Shimano rear derailleur will work fine - 105, Deore, Dura Ace, Alivio, SIS, Ultegra, Acera X, etc.

edit: Sora shifters are available in 7 and 8 speed, and an 8 speed shifter might almost work with a 7 speed drivetrain (or vice versa) but will not work perfectly. Are you sure you have the 7 speed model?
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Old 01-19-10, 03:56 PM   #24
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+100 Bent hanger. Doesn't take much of a bend to cause your problems. Hangers are easy to bent, derailleurs are harder to bend. When in doubt, I question the derailleur last. Most of the time, its adjustment, bent hanger, cables.

+10 Unless you have the tools, I would take it to a shop and have them address it. Cost should be minor.

I bought one of the tools off ebay, cost me under $22 delivered to my home. But I work on a lot of bikes, so I have gotten good use out of it. I also bought headset tools from this seller.

http://cgi.ebay.com/Mountain-Bike-Bi...item3c9a61f6d1
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Old 01-19-10, 04:09 PM   #25
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take to shop to check with DAG-2. if they say the need to true your wheel to use it, tell them to use one of their new wheels for the alignment.
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