Bicycle Mechanics - high/low screws

can anyone give me some insight on how to use these? my gears seem to have a hard time switching to smaller chainrings in the back (sometimes require me to switch 2 times for 1 move). I am just wondering how to use these to fix this problem and not completely mess up my gears

The High/low set screws won't effect
the shifting, or ease of shifting.
The only thing these do is limit the amount of
travel the derailleur makes inward (low,torwards spokes)
or outward (high,towards derailleur).
At least thats my understanding.
I'm thinking your problem may be better
corrected with barrel adjuster.

You can get more information about it at
Park Tools (http://www.parktool.com/repair_help/FAQrindx.shtml)

Marty

The screws are called limit screws, they are so the derailleur dosent overshift the bottom and top gears. The bottom screw is the limit for the top gear, and the top is for the bottom. Tighten and loosen the bottom screw while shifting the bike from 1 to 2 until it dosent voershift the top gear, same for the top screw. That might help your shifting, but there is also a barrel adjustor on the derailleur that adjusts the cable tension...mess with that until you get it all right.

Difficulty shifting into high gear in back can indicate either an overly tight travel adjustment screw or an overly taut cable. On most indexed systems and all friction systems, there should be a minute amount of cable slack in top gear.

I think your problem is caused by the gearshift cable sticking in the housing. Undo the cable at the derailler and take it out from the housings. Clean it and the inside of the housings with something like WD40, lubricate with silicon lubricant, then reinstall.

As already mentioned by the others the screws primarily stop the chain from dropping off the cassette so barrel adjuster cable tension makes the most difference to shifting thna the screws alone. You can fine tweak the screws to minimise running noise but if the screws are adjusted initially to the right position you are more or less set up ok.

Have you checked the state of the cable itself? You might have some alien goo in the housing that impedes the smooth push-me-pull-you of the cable.

Agreed, sounds like that cable needs replacing! How often do you replace your shifter/brake cables and housings? If you do a lot of riding 4,000+ miles/yr. I'd change them out about once a year.

Have you checked your chain for stretch (don't actually stretch, but pins wear and chain gets longer), could also be your cassette is worn!

L8R