Heres the story. Rear derailler, wasn't shifting to the lowest cog, I thought the cable tension might have been a bit loose so I tightened the rear adjuster barrel, that didn't seem to make much of a difference, so I took it to the local shop. The next day I go to pick it up, and the mechanic started to explain to me that the rear adjuster barrel wouldn't turn...said it was way too tight and I must have bumped it against something. He told me to just use my indexing on my shifter.
Does that make sense?? Now I'm kind of a rookie at this stuff, but the barrel was turning fine right before I left it at the shop for the night. Is this kind of thing fixable??
Whether you got ripped or not, I don't know. The most common cause for the RD not to shift down, in my experience, is the cable isn't slidding smoothly inside the housing. You can disasemble the cable and wipe it down with steel, or copper wool to remove the oxidation and then spray the inside of the cable-housing with TRI-FLOW or WD-40, or some other non-oily lubricant. Then reassemble every thing. The adjustment nut can be sprayed also, then back it out -use pliers if you have to free it up- about half way to have some threads to tighten or loosen the cable.
Of course, you can always replace the cable and housing with teflon lined housing and teflon coated cable. These run from $12. to $50. a set. Choose your own poison. Good riding to you.
From Sarasota, FL sitting in front of a computer spewing random thoughts!
Intense Uzzi SL, Masi Speciale, Trek 3700 Nashbar Single Speed, Old Cilo Road frame
Just thought I'd add a comment that WD-40 is not a lubricant, it is a solvent. It's good for loosening rusted parts or cleaning. But, I usually stay away from the stuff myself. If you use it you have to be very sure to wipe it completly off or wait till it dries. Any remaining will break down the lube you apply afterwards rendering both useless. I'd use the recommended Tri-Flow or just a silicone lubricant.
Has the limit screw been adjusted properly?
Check by shifting the derailleur with your hand, directly on it. The limit screws are mounted on the parallelagram and keep the pulleys out of the spokes or from dropping the chain off the outside cog, loosen the appropriate screw until it shifts for you.
If your pulleys are not in line with you cogs when sighted from the rear, (slightly "outboard" at the bottom for campy), something is bent- either your dropout on the frame or the derailleur or both, usually fixable.
To adjust your derailleur(rd), undo the cable at the rd, screw the abjusting barrel down to bottom and turn out a bit for slack, at this point it should be resting on the outside cog, re-attatch the cable,tightly-no slack, turn the barrel back down for slack, turn your shifter one click, rotate pedals and turn adjuster until it shifts, then move the sifter up and down the gears and adjust barrel accordingly to get the best shifting through tthe range.
If you can't turn the barrel, you threads may be damaged- try a different barrel and/or "chase"(re-cut) the threads on the rd
I agree with Pat that the limit screws would be the first thing to check. I would guess that your local wrench would have checked that one already.
Your local mechanic could be correct that you buggered your derailure after it left his shop. Bikes and especially derailures do not transport well in automobiles unless you use a good bike rack. Even then, you can bang them up getting them mounted. Bikes are strong in use, but fragile when they are handled.
Try taking off your derailure and rinsing it in Kerosene. Kerosene will work both as a solvent cleaner and as a thin lubricant. Kerosene is not as aggressive as other solvents such as the carrier of WD-40 and will do less damage to your synthetic/plastic/rubber parts.
Naturally, you will have to wipe and dry the kerosene off of the derailure before relubricating the derailure with another lubricant.