Bicycle Mechanics - Adjust rd at down tube stop?

I have always adjusted the rear der using the adjuster located on the rd. I just noticed that there is another adjuster at the down tube cable stop, with a spring and knurling, but no threads that I could see. It turns with a pliers, but not by hand, even after I lubed it. When is the downtube adjuster used instead of the one on the rd? And should it turn by hand?

Thanks.

Bill

Yes it should turn by hand and it serves the exact same function as the one on the rd but it allows the rider to trim the shifting without getting off the bike. They can be hard to turn if the cable tension is high.

It should turn by hand. You can use either the downtube or the on-the-derailler knob to adjust the derailler but, for me, the downtube one is easier to use while riding so it gets more use.

With some disassembly and cleaning, possibly including a retapping of the threads, you can probably get that downtube adjuster working again. If it's a bolt-on stop and not built into the frame, just replace it. I've seen pairs for $10.

The down tube adjuster is useful for fine-tuning the rd shifting while you're riding, as sometimes the drivetrain will shift slightly differently under load compared to on a workstand.

Sometimes cable tension can make the adjuster hard to turn. Also, if the shift housing end cap (aka ferrule) fits tightly in the adjuster (especially if it's plastic), it can make it harder to turn as well. One way to alleviate this is to pull on the housing slightly so that the ferrule comes out of the adjuster. Then make your adjustment and slip the ferrule back in (don't do this while riding though!).

Also, some adjusters are just junk. The Shimano ones are pretty decent, in my experience. One of my bikes came with some no name barrel adjusters which were impossible to turn. I replaced them with Campagnolos which are better, though IMHO I still prefer the Shimanos.

Pull up (toward the head tube) on the adjuster knob. They often have little teeth to keep from accidental tweaking.

Also, they have limits beyond which you can't turn them. It may be at a limit.

Got it working a little, thanks for all the replies!

Which way do you turn to tighten while riding position?

Which way do you turn to tighten while riding position?

Seriously??

Tightening the adjuster or tightening the cable tension??

Well ... with right hand threads, loosening the adjuster (screwing it out of the stop ... any stop) will tighten the cable tension.

I appologize if this sounds a little blunt but ... you couldn't figure this out on your own??

I mean while riding and the RD needs tweeked a little ... sometimes it's hard to tell which way it needs tweeked. So I end tweeking it a little in one direction. If it get's better, OK. If it gets worse ... I turn it back and then a little more. Invariably, I always turn it the wrong way the first time ... so ... remembering which way is "tightening" becomes moot anyway.

I guess I asked because it didn't seem to do anything turning either way, maybe defective or maybe I was defective the time I was trying, will try again at a better state of mind, seriously.

Carefully watch the dérailleur as you turn the adjuster. You should be able to see it move.

I find that it takes a few shifts up and down for the change to take affect. It also seems to me that because of the detents, I have to turn the downtube adjuster a lot more to affect a change at the RD. I know this is not logical and is probably just perception.

A little oil between the housing cap and the adjuster will help loosen things up as well.