Bicycle Mechanics - What else can I do?

My rear Derailleur doesn't seem to have a sweet spot. When I turn the barrel adjuster, it's either too loose or too tight. I can make upshifts smooth and snappy with slow/nonexistent downshifts or vice-versa but not both. Is there something else I can do, or am I out of luck with my low end derailleur (Tourney)?

Figure out a way to increase the tension on its return spring.

I had the same problem; solved it beautifully.

...I'm assuming you've already cleaned and lubed the cable, and made sure the housings are the right length to minimise bends.

If it's a fresh cable, it often helps to put a slight pre-bend in it where it goes under the BB.

Admit defeat. Take it to a mechanic.

Check the "B" Adjustment, closer to the cassette (without touching/rubbing) will make the shift more accurate.

Most likely excess friction in the shift cable housings. Replace the cables and housings. The short housing just before the rear derailleur may be the main culprit.

I reckon there's a good case for making it more tolerant of cable friction...

Crank up that return spring! Bugger buying new cables every six months.

Well, no Kimmo, I didn't check the cables, and that's probably the trouble right there. I had a brake issue due to a rusty/dirty cable until I sprayed WD40 into each end of the housing. I haven't changed the cables since then (or ever) so that's gotta be the problem. I also like your idea of increasing the spring tension. Thanks to all for the advice.

If lubing the cable does not seem to help, then you may have a stretched chain which can cause sloppy shifting. Also make sure the derailleur is securely attached and not a little loose.

If your RD is old with lots of miles on it, the pivots will be sloppy and it'll be hard to get any decent performance from it. Cable friction is also a factor as is hanger alignment, and the condition of your chain.

Try this first, on a stand shift the bike by pulling the cable away from the frame so there's only friction in the last chainstay/RD housing loop. See if it moves smoothly in and crisply out on the spring. If not, remove and replace the housing section and/or buy a stronger return spring if one exists.

Also consider the age of your chain. As they wear they not only stretch, but the amount of side play increases making them more flexible. Unless the jockey pulley is very close to the sprockets, a more flexible chain is sluggish to respond to shifts and requires more overshifting to move over.

As shifting on my bikes degrades over time, I compensate by setting the RD to shift out cleanly on the spring and overshift to make the downshifts work. It's easier to train my fingers than to go nuts trying to get more out of old components than they have to give.

or buy a stronger return spring if one exists.
AFAIK, you can't replace that spring on any common derailleurs, even Campag.

The trick is to jam something under the end of an axial spring... for linear springs, I'm thinking binding some coils together with fine wire might do it.

But it's a last resort... take your cable off, and if the inner isn't stainless, turf it for a proper one. Use the tube on your WD40 can to squirt into your housings and flush em good.

I took the cable and housing off today [checks clock], yesterday, cleaned with WD40, relubed with TriFlow, and reassembled. While still not perfect, it's definitely much better now than before.

Don't laugh - turns out I needed to adjust the b-tension. I should have gone to Sheldon Brown's website and read up more on derailleur adjustment, but in my defense, I'd had it tuned up at the LBS, so I assumed it was the cable/housing and/or the index adjustment. Seems to work perfectly "in the lab". I'll see how well it shifts on my way home from work.

Lubing the cable will only be a temporary fix. With older setups the cable has worn a groove into the inner plastic liner of the housing. Once it does that the friction goes up and lubing it will only give you some borrowed time before it gets gritty and grotty and acts up again. If you enjoy riding the bike invest in a complete set of new housings and good quality ground smooth exterior cables. The difference in feel will make it seem like you've got a new bike.

I know you've sort of fixed it for now with the final B screw adjustment but from the sounds of it the cable and housing was also a contributing cause of your troubles. So replacing the whole cable and housing path will just spruce things up that much more and assure you of many more years of trouble free riding than just lubing up the existing cables.

Originally Posted by FBinNY
or buy a stronger return spring if one exists.

AFAIK, you can't replace that spring on any common derailleurs, even Campag.
Alas, how the mighty have fallen... :50: