mrblue

I am very much a novice when it comes to derailleurs. As a matter of fact that is why I just bought a used road off craigslist--so that I can learn how to maintain/adjust derailleurs.

Anyway...

I am dealing with my rear derailleur at the moment. I understand cable tension is very important for smooth shifting, and said cable can be finely adjusted by turning the barrel adjuster on the rear derailleur, itself. Cool. However, I noticed I also have two barrel adjuster on the frame, on the upper portion of the down tube--one for the front derailleur and one for the rear derailleur. Why do I have two barrel adjusters for the rear derailleur (one on the frame and one on the derailleur) and which one do I use to make adjustments? Or do I use them in tandem somehow?

Please advise.

Thanks in advance.

Bill Kapaun

My trigger shifters both have a barrel adjuster + the RDER has one.
Some days it seems that a 1/2 turn one way or the other is useful for some reason. Maybe my aluminum frame bike has a different coefficient of expansion than the steel cable? and I can give it a tweak while riding.

You didn't say WHAT bike you have.

BTW, when setting up the rear, I have both adjusters about 1 turn out and then attach the cable.

FBinNY 

Either is fine, depending on your preference. I tend to adjust from the RD and leave the frame adjusters most of the way down but with room in either direction for on the bike fine tuning.

There are adjusters on the frame because some RDs and most FDs don't have adjusters. Consider yourself better off than those whose frame lacks the adjusters (as many do these days), so you have no barrel adjuster for the FD. Two may not better than one, but it's far better than none.

jyl

Also it is hard to reach the derailleur-mounted adjuster while riding . . .

I see that newer bikes with internal cable routing sometimes have barrel adjusters inline with the cable housing.

fietsbob

the one on the RD itself comes with the RD, the shifter may have one of its own ..

On the repair stand. I prefer the one on the RD itself
so I am right there to watch the effect turning the adjuster has on locating the pulley under the cogs .

Now some RD have None , then to synch Indexing, you need one somewhere else.

with Friction shifting you really dont need any.

Andrew R Stewart 

Pity the rider who has indexed front shifting and NO adjuster...

Don't forget to lube the adjuster's threading. I've seen WAY to many that are frozen in their stops. Andy.

WrightVanCleve

I have 3 for the rear and 2 for the front.

I don't like the adjuster on the down tube so I put in a inline barrel adjuster on the cable right next to the shifter. I can easily adjust those and it is smooth adjustment, where the one on the down tube adjusts just like the rear mech with that little bump to hold it's spot, which I really don't like having to always turn one "click", sometimes I just need it to be a little in the middle of that.

The one on the frame is for you to easily adjust while riding and should be able to fine tune(as much as those allow anyway.)

FBinNY 

Figures that a van Cleve would have 3 of something that most of us have only one of (or none or two).