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Time for derailleur change?

561 views 5 replies 5 participants last post by  Cyclopod 
#1 ·
My Shimano XTR rear derailleur has been working flawlessly for almost 3 years (faithful, year round, weekend warrior). In the past 3-4 rides the RD has been a bit of a pain. It may be a coincidence, but it started when the RD snagged a branch. I changed the derailleur hanger, but it didn't seem to fix it. At the start of the last two rides I had to play with barrel adjuster and will get it to work for the 6 low gears, but it will ghost shift at the 3 high gears. On a couple of occasions I noticed the chain jumped off the guide pulley (maybe too warn).

Is there any point in trying to fix the derailleur (new pulleys) or is it time for a new derailleur? Anything I should pay attention to?
 
#2 ·
Check whether or not the RD was bent by the branch.

Eye the RD from the back of the bike with the chain on the middle chainring and fifth sprocket. Draw an imaginary line joining the two pulley wheels - this line should then be parallel (if not, very close to it) to the sprockets.

Turn the bike upside down, put the chain onto the small-small combination, look from diirectly above and check to see if the pulley wheels are parallel to the sprockets.

If the two observations show that the pulley wheels (hence the cage as well) are parallel to the sprockets, then I would say that the RD does not need replacement. And, I would double-check the hanger, cable condition/routing and replace the pulley wheels instead.
 
#3 ·
+1 on the above advice, and also thoroughly look it over for cracks. Lastly re-check the gear hanger allignment. If it wasn't bent or cracked by branch, odds are it's OK. One other possibility, when it got snagged the rear housing loop might have gotten kinked causing the cable to bind.

If you don't find the problem have the LBS give it a look see. They might catch something you missed.

AS RDs age they do get sloppier, mainly because of wear at the pivots. There is long term slow degardation of shift response, but you get used to it and usually don't notice. The fact that it's kind of sudden, following an incident leads me to believe it's either cracked, bent or OK, but not sloppy from age.
 
#4 ·
Derailleurs are pretty tough. My guess is that something else is wrong.

Check the derailleur hanger alignment. Your shop should have a tool (Park DAG-1) which checks the alignment and may be used to bend (align) the hanger.

Also check the cable housing; my bet is on the housing. It's possible that the housing was deformed causing more friction between the (inner) cable and the housing. Housing needs to be replaced every so often anyway for good shifting performance.

It's possible too that the inner cable has problems; a frayed cable can result in really crappy shifting. Eventually the cable will break and you won't be able to shift at all!
 
#5 ·
also check the cable and housing it may be time for new ones of those! I commute with my bike and it was wierd that the rd cable just crapped out all at once! put on a new one and is was like a brand new 3 year old Mech!
 
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