I just replaced my rear derailleur with a new one of the same type (Shimano 105).
The only problem I ran into was trying to put the cable back through the barrel adjuster. The end of the cable started to fray, and I could not thread it through anymore. I trimmed a little off the cable, got it threaded, got it attached under the little clamp, and not I no longer have the big cog or the two smallest cogs when I shift.
I am very hesitant to touch the limit screws, as adjusting them without knowing what I was doing is what broke the last derailleur.
Could the problem be that the cable is frayed or is now too short? As a novice at repair, and because the cables run through the inside of the bike frame, should I just take it to my local bike shop?
A shorter cable will not affect shifting at all - the derailleur does not know how much cable extends beyond the clamp. Further, it cannot be the cable alone, as that would not affect both ends of the range. If too tight you may not reach the small cog, if too loose you may not reach the large one.
The limit screws on a new derailleur are going to need adjustment, period. They don't know at the factory the exact setup you (or anyone else) has. Luckily the limit screw are intentionally set tight so that you don't just slap on the derailleur and shift into the spokes.
So the first step is to adjust the limits, which is best done separately from the cable tension. Check the above tutorial, partktool.com/blog or sheldonbrown.com for adjustment procedure, but if it's not specified adjust the outer adjustment with the cable tension loose, and adjust the inner limit by pulling on the cable like a bowstring instead of using the lever. Then proceed to adjusting tension for the in-between cogs. If you are not confident in doing the above then take it to a shop or co-op for assistance.
I guess my concern is how difficult it was getting the frayed cable into the barrel adjuster. It only seemed to make the fraying worse.
Is there any way to stop this fraying?
Yes indeed changing a cable requires length adjustment, The limit screws may need a tweak too, but first cable length(inner) needs to be set . So it has enough length to go through the entire range.
No one said its the cable alone but that the cable change is the first thing to try.
Put the bike upside down and watch how the derailleur moves. Can you manually push it into full arc.(best with cable disconnected) If so your screws are good if not adjust its very simple. Read the ling I provided.
As per fraying if it goes into the outer sheath that's not good. I just at the very tip beyond the clamping screw its OK, but try to contain it.
Try this and than let us know .
Never Give Up!!!
I am sorry, but when one is installing a new derailleur the limit screws need to be set first, as the cable tension is in relation to the derailleur when it is sitting against the outer limit screw. If the derailleur is not underneath the small cog then the tension adjustment will be incorrect. There is no reason to assume that the cable is causing the problem, and again, cable adjustment cannot cause problems at both ends. If the OP replaces the cable he is just inserting more variables, including cable "stretch," which is primarily the housings setting back into place.
Thank you all for the responses.
I finally gave up this morning and brought it to the shop. The cable inside the housing was also completely frayed so apparently adjusting the derailleur would not have made a difference.
The cable has been replaced, and the shifting is working as expected.
OOps you are right CNY I missed the part about new derailleur and thought only the cable was replaced. ( Should not answer posts at midnight) Yes set limit screws by manually moving derailleur across gears and than connect and set cable length. Looking at the photo that cable is shoot so the shop made a good call.
Never Give Up!!!