DOS

Until fairly recently, none of my bikes had barrel adjusters on the downtube. One has levers and the other two just had stops with inline adijusted in the housing near the shifters. Now I have a bike with dt barrel adjusters, but rather than right side being standard barrel, its wing type lever.

I didn't give it much thought when I got them since I ususally just use the adjuster on the rear derailleur to make any adjutsments; I am not even sure where I got them (maybe the came with the frame) since they generally cost more, and I don't recall paying extra for them as compared to regular adjusters. Since I have had the bike, the wing has been set all the open (so I would have only be able to increase cable tension if need be)

So as I was fine tuning my RD after a recent install (see franken derailleur thread), it occurred to me that perhaps there is a "right way" to set the wing-- either "right" in the sense that it should be set 1/2 way to allow either increasing or decreasing tension or "right" in the sense that "its just the way it done"; sort of like how one's rim labels are supposed to face in the same direction (see very long thread on that issue not long ago).

So, since these adjusters aren't strictly necessary for RD adjustment, how do folks set them?

Al1943

I have set mine so that they could only tighten the cable. But later decided that was a bad idea and have since set them in the middle.
What it comes down to is how much tension you have on the cable at the time you tighten the cable pinch bolt at the derailleur.

FBinNY 

There's no right way. They're there to provide the ability to adjust the trim on the fly while riding. I don't know how I'd set the right side, probably near center, but the left I'd set to the tight end, for normal use, allowing me to move it down to trim the FD when tiding outer ring with the chain coming from the inside end of the cassette.

Right is what works for you and how you prefer it. Feel free to see what suits you best.

AEO

I remember one guy in the TDF... or maybe it was one of the giros... He was reaching back to his RD barrel adjuster while riding.

the wing adjuster is much nicer in comparison.

FBinNY 

that's serious trick riding.

DOS

My thinking as well. Probably my aero obsessed Tri/TT friends would want to get them in a wind tunnel to figure out what way is most aero and then set em that way.

Retro Grouch 

Do cables ever shrink? Once set, why would you ever need to lengthen the cable?

I fiddled with those once, (on a 9-speed bike), I discovered that the wing allowed me to adjust the cable tension exactly 1 cog's worth. I'm thinking that's the max you should ever have to do on the fly.

DOS

Good point. Other than having to make minor adjustment during 1st ride after installing new cable (first ride, woops overtightened cable at the RD...), probably I would never need to. Then again, I don't know that I ever touched the inline adjuster I used to have one way or the other so this whole discussion is probably academic.

shelbyfv

I have found that the downtube or headtube mounted barrel adjusters tend to migrate on their own toward the screwed in position. Since the adjuster for the rear is superfluous I just tighten it down all the way and use the adjuster on the RD. For the front, I mark the barrel so I can spot any movement before the shifting gets funky.

bradtx

DOS, I've had barrel adjusters with the little levers (RHS only) since the mid '90s and have never once adjusted a cable with them that I can remember as the adjustment is rather coarse. I just set them in the middle.

Brad

HillRider

+1. I've got them on a couple of bikes and never moved the right side lever. BTW, these were the style of adjusters that came with Shimano's upper level groups like Ultegra. The cheaper groups (RSX, Sora) came with regular barrel adjusters on both sides.

Zef

The idea of the inline adjusters on the downtube is so the rider can make adjustments on the fly while riding. These adjusters are not a substitute for proper setup or proper maintenance but to correct a problem that develops while riding.

An initially properly adjusted cable will not tighten on its own, especially so while riding. If the derailleur, shifter, and cable are all setup properly and working well at the beginning of a ride then and problem with the cable that would cause a need for adjustment would fall into the following categories:

1. Cable fails completely due to it breaking - this results in cable slack.
2. Cable anchor comes undone or anchor bolt breaks - this results in cable slack.
3. Cable is new and settles/stretches - this results in cable slack.
4. Housing not seated properly and settles into frame/derailleur housing stops - this results in cable slack.
5. derailleur catastrophically fails or derailleur hanger snaps- this results in cable slack
6. brifter not torqued down adequately and slips on bar (this would most likely cause the brifter to slide downward not upward) - this results in cable slack.

I cannot fathom a scenario other than one that results from failure of the shift lever function of the brifter that would cause a need to loosen a properly set up rear shift cable while riding, and if this was the case then the adjustment barrel, winged or not, is not going to be much help in addressing the problem.

Shimano and Campagnolo road rear derailleurs (i am not familiar with entire SRAM line) all have adjusting barrels on the derailleur, if for some reason there is a serious need to loosen the cable while on the road it will most likely be the result of something that would require the rider to dismount to troubleshoot. Therefore the wing in-line adjuster should logically be set so that it allows the cable to be tightened. Setting it in the middle of its range will only limit ones ability to affect adjustment throughout the range of movement allowed by this type of adjuster.

If anyone has a realistic example of where loosening the cable on the fly of a properly tuned rear derailleur is a realistic proposition please enlighten me, the list I drafter above, while not complete, is fairly comprehensive.

-j