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Old 07-16-11, 11:30 AM   #1
izpmuddy
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rear derail has problems shifting to smaller cog

I am trying to figure out what is wrong with my bike, i dont know if its the derailleur or if its the shifter. I assume its the spring in the rear derail. Ok here is the deal, my rear derailleur will shift from the small cogs up to the biggest ones just fine, now if i want to go back down into the smaller cogs on the cassettte it will just stay on the biggest one as i try to click down, but i dont hear a clicking noise. I can get it to shift down if I pull really hard on my shifter cable and then shift, but otherwise its a no go. Also if I release the pinch bolt for the cable the rear derailleur does return to the smallest cog just fine. I'm lost at to what to do and what to replace, If it is the spring in my derailleur are those easy to replace? and where do i get the parts for a shimano xtr rear derailleur?

Your help is appreciated

Thanks!
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Old 07-16-11, 11:37 AM   #2
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If releasing the cable from the pinch bolt lets the derailleur shift to the smallest cog spontaneously, the derailleur itself is probably ok. So, it's either a defective shifter or badly cruded up shift cables and housing.
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Old 07-16-11, 11:43 AM   #3
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If the spring returns the RD to the outside when the cable's detached it's fine. They don't weaken with age, so you can rule that out. Odds are you have a cable friction problem, but before you go there check one detail.

Shift to low and look at where the upper RD pulley and sprocket are closest. You need about 1" of free chain between the two, otherwise the sprocket can hold the derailleur through the chain. You correct that with the "B" screw (top back) tightening it slightly to push the RD lower.

Now, back to the basics. Attach the cable and test. Shift to low, and if the RD doesn't move out, pull the cable away from the downtube like a bow string and let go. If that solves it, you have excess cable friction between the shifter and frame stop. If it doesn't, and now there's slack in that section, the cable is binding between there and the RD.

Usually friction is from worn or dirty housings, but it can also be bad ferrules which let the housing try to squeeze through pinching the ends, or sometimes the wire binds in a clamp or dirt packed where it passes under the bottom bracket.

Start by checking the RD clearance, then do the bow string diagnostic, and follow it from there.
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Old 07-16-11, 02:54 PM   #4
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Try hosing out the insides of your shifters with WD 40. You probably also need to replace the shift cables and cable housings. The short housing found just before the rear dérailleur often collects dirt and other crud causing excess friction on the cable.

Last edited by Al1943; 07-19-11 at 01:29 PM.
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Old 07-16-11, 06:28 PM   #5
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.....your ****ters with WD 40..
A bit off topic but did you by any chance make a typo and spell "shifters" without the "f"? The forum language police are certainly on their toes.
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Old 07-16-11, 07:52 PM   #6
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In other words, you have some type of indexed brake/shifter and shifting to bigger cogs works, but shifting to smaller cogs won't work even when from the biggest cog? And it works if you manually apply a LOT of tension on the cable?

If that's the case, you have classic gummed up brifters. Depending on the make, you can try to clean with some solvent, relube and retry. Some Campy brifters have replacement mini-cogs for brifters if they get worn. Shimano spec an entire assembly, so it's likely the cost isn't worth it unless you can get some wholesale or commercial business price on the part. Basically, the release is likely wedged with some gunk that must be cleaned out. I have 2 colleagues who both ride Shimano. Both I think use lower cost 2200 units. And both have suffered failures of the reverse shifting like you describe in the last year. One was able to do a self repair with solvent. The other replaced with new shifters, new HB tape, and paid a shop a couple hundred, maybe 250 for the service. Not cheap.
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Old 07-18-11, 06:45 AM   #7
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I have this same problem also but its shifting to the larger cogs that doesn't function. I just order a new deore shifter (in broke) but I will try the solvent flush today. will WD40 suffice?
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Old 07-18-11, 08:44 AM   #8
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Can also be a sign that your shift cable is starting to fray around the take-up inside the shifter.
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Old 07-18-11, 08:56 AM   #9
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Come to think of it I just bought a new cable and housing set. I'll replace everything when I pickup my new chain today.
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Old 07-18-11, 09:26 AM   #10
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I have this same problem also but its shifting to the larger cogs that doesn't function. I just order a new deore shifter (in broke) but I will try the solvent flush today. will WD40 suffice?
WD40 has worked for me, but follow with TriFlow or LPS2 to lubricate. Should you decide to open up the shifter, do so inside a clear plastic bag... I still haven't run across that spring!

Brad
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Old 07-18-11, 08:37 PM   #11
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I bought a brand new Microshift MTB RD and the parallelogram doesn't fully retract. The spring appears to be fine and tight but I suspect there's too much tension on the hinge pins. Even removed from the bike it won't retract all the way. Lubrication didn't help so I'm going to return it.

Last edited by Clem von Jones; 07-18-11 at 08:41 PM.
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Old 07-19-11, 01:35 PM   #12
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Quote:
Originally Posted by HillRider View Post
A bit off topic but did you by any chance make a typo and spell "shifters" without the "f"? The forum language police are certainly on their toes.
Yeah, not sure what happened, I was probably working from my iphone.
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