I have a Surly Long haul trucker w/ a Shimano Tiagra (triple 9 sp.) fr. derailleur. After 3k miles it's acting up;needed soaking, screw is missing,I can't get smallest ring ) Surly now uses Shimano Sora 3403. Would you please hold my hand and tell me whitch way to go; kept on adjuusting or replace?
That derailleur should last you 50,000 miles. Bring your bike down to the local bike shop and show them where the missing screw should go. They'll have something in the loose parts bin to get it working again.
I'd recommend adjusting and maintaining, especially with a front derailleur. If it isn't bent way out of shape, it'll go on forever. Keep it clean and lubricated every time you clean the bike.
I agree. Whatever you replace it with will also need a careful setup and adjustment, and if you get it wrong it will work no better than what you have now.
There are four things that need to be precisely adjusted - the derailleur angle on the frame (outer edge of the cage must be perfectly paralell to the chairings), the height (outer edge of the cage should come within 1-3mm of the top of the teeth ont he big ring - no more and no less), the limit screws (must be set so the derailleur can reach the big and small rings without throwing the chain off), and the cable tension. IIRC, LHTs come with a friction shifter for the front, so there is a wide margin of allowable error in cable tension and you only need worry about the first three. Adjust them carefully in the order I listed them and the derailluer should work.