I use them for the front derailleur, not the rear. It's a lot more difficult to get the front tension correct without one.

I have them near my stem for all 4 cables. Very handy in a pinch, but I need to lube them periodically, sweat and sports does not do them well.

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TrainingBible Coaching
http://www.trainingbible.com

I'm with you, I think they cause more problems than they're worth on a bar-end-shifted (tri) bike. I have them on my road bike, and use the rear one occasionally, but could just as easily use the knob on the rear derailleur. I just recabled my P3 and did not use them.

I disagree with the previous poster about the FD needing one. Put it in the little ring, get the cable tight, and that should be it. I've never needed any further adjustments.

I've never used mine. I've got a couple of roadie friends who swear you have to have them, but I've never seen them use them either.
Mark

I have them for the brakes. My training wheels are 25mm and my race wheels are 28mm. They work great, but because I perspire profusely, I need to keep the threads coated in grease.

No bike I've owned had them in the original build. I've never wished for them. I find the time when I'm not riding is sufficient for minor adjustments.

Similarly I have not had them, thought they would be helpful, fitted them, then shortly afterwards removed them.. even when set up meticulously they do add drag to the line and can effect shifting, especially if the line already has a convoluted path... that was on a road bike...
i also removed them from my tt bike.. although it is a lot more tolerant due to DA tt shifters....

They aren't "necessary".. front mech as said just needs to be set up properly, rear mech already has one on the rear mech.. just use it.. and so long as you run in your cables ahead of any important event you ought to have no issues during the event, barring a crash or a knock etc..

Not sure how bad cable access is on the FD of your wife's Trek, but that's the only cable that doesn't have a form of cable tension adjustment already in-line. I installed one on my tri bike's FD and haven't adjusted it since the cable/housing settled in over the first few miles.

I'd be disinclined to tear them out--but I would go through a thorough clean and cable adjustment. There's no reason they're actually harming anything. My bet the problem is elsewhere.

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The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important.

-Albert J. Nock

Yeah of course depends on where they are placed but a word of warning, IF placed on a radius of the cable (as many are between bar and frame entrance), the barrel adjuster will cause edges to be presented to the cable which will add drag to the line.. whether this impacts shifting of course depends on the rest of the set up... think of the cable going around the edges of pentagon..

Removing these ONLY has IME reduced cable friction markedly in what was otherwise a new and clean set up...more on road shifters than TT shifters as it turns out..

No doubt in some instances they may impact the performance less.. but suggest don't rule them out as a possible contributor to reduced shift performance.

Fair point, Shadwell. I guess I had in mind my own routing, which has it on a nearly straight section of housing where it's about as benign as possible.

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The question of who is right and who is wrong has seemed to me always too small to be worth a moment's thought, while the question of what is right and what is wrong has seemed all-important.

-Albert J. Nock

Yeah there OK there.. a bit like to the good old days when the down tube cable stop had them in it.. they never caused an issue there.. ah fuck I'm Old... :(

I have one on my rear derailleur cable only.

I can't stand it when my adjustment isn't perfect all of the time. My rear derailleur may get bumped a little while it's in the car and I can make an adjustment on the fly. When I switch wheelsets I may also need a slight adjustment.

That's just me and I'm really anal about the adjustments. I won't put one on the GF's bike cuz I don't want to complicate things for her.

jaretj

Thank you all for the comments. Didn't know about greasing the barrel adjusters so I will give that a try and make any necessary adjustments. I think by the end of the season I am going to remove them, as one person commented it just over complicates things for some riders.

In my experience, the in-line adjusters just add drag to the cable. This extra drag makes shift performance worse and wears out shifters (road, not so much TT) faster. I prefer the style that are built into the frame. I'm not sure which brands still use them, but those actually work. On a TT bike, I would leave them off. You can just switch to friction and tune in your shifts in a pinch. No need to mess around with inline adjusters.

One a road bike, they can be handy. I was in a 4 day stage race in Arkansas a few years ago. We had something like a 110 mile stage with quite a bit of climbing. About 30 miles in to the stage, my right shifter lever broke off and I was stuck in my 11. By using the barrel adjuster on the frame of my Storck, I was able to get enough cable tension to move the chain to either my 13 or 14, which was enough for me to be able to stay in the race and finish in the pack. On the real steep climbs I had to pull on the cable (and hold it there) that ran down my downtube in order to get into a good climbing gear. On an internal routed frame without barrel adjusters, I don't think I would have finished the race.

inline barrel adjusters on an SC tells me it's probably a 7-series, maybe a 2-series. if it's the former, and it's not the 2014 version, there was an update to the BB cable guide which addressed some chronic shifting issues...see how to tell which one you've got here.

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Carl Matson