Bicycle Mechanics - Frozen/broken barrel adjuster
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10-18-09, 11:30 AM
I puchased a used CoMo tandem. The right barrel adjuster was frozen. Attempting to free it, I broke it off. Photo of left adjuster attached. It's aluminum in a steel frame, so the right one was corroded in place.
1) What brand are these/where can I get another one? Or another pair with the same threads?
2) How can I get the broken threaded part of the right one out? I broke off a 1/8" easy-out in it already, after soaking with WD-40. I did manage to remove the easy-out chunk, but it wasn't easy.
Looks like someone didn't believe in anti-seize.
10-18-09, 11:44 AM
Most barrel adjuster threads, both shifter and brake, are the very common M5x.8 so any adjuster should work once you dispose of the dead body. Any LBS should have plenty of replacements.
Try a better penetrating oil like Kroil and give it time to work.
10-18-09, 03:03 PM
You could try drilling it out, with a bit just smaller than the thread. Once the aluminum wall of the adjuster is sufficiently thin, it might could be pried out with a sharp tool such as a pick, or maybe a pocket knife. The heat of the drilling might even cause it to release for that matter, and shoot out as the bit passes though. Good luck, I feel your pain for sure. I mostly work on vintage stuff, so I know this kind of situation quite well.,,,,BD
10-18-09, 03:19 PM
Thanks, folks. Suggestion on drill size, if it comes to that? Since these are dissimilar metals, I've heard that heating and cooling with the Kroil in place can help. How hot can I heat it before damaging the paint? I have a Milwaukee heat gun. I've ordered one of those digital infrared thermometers, which I need for other projects anyway.
10-18-09, 06:27 PM
As for drill size, pull the other adjuster out, and get as close you can to that size, without wiping out the threads. In other words, make the bit about the same diameter as the "bottom" of the threads, without going over that. I would be real wary of using a an actual heat gun. Maybe a hair dryer, as the heat gun would quickly discolor or fry the paint, without a lot of warning.,,,,BD
Worst case scenario, if all else fails. Drill it out to 5mm, slip an adjuster in to use as cable stop, and use an inline adjuster. I have them on my Tiagra eqipped Le Tour 12.2, and there's NOTHING like being able to adjust cables on the fly, hehe.
10-18-09, 06:47 PM
They make a device called an easy out for that specific purpose. And as suggested there isn't any better than kroil for lossening up stuff. I once soaked a 4 inch hydralic infeed cylinder for a center type grinder over night at a Cat. plant was able to get it working like knew when 600 lbs of hydralic pressure wouldn't budge it the night before. jagwire sells a selection of any adjuster you should need.
10-18-09, 06:58 PM
He already broke an easy out off in it, and it was quite a chore getting it out?,,,BD
10-18-09, 07:10 PM
Drilling it out and just using one for a guide is a good idea. Always nice to have a fall-back position.
10-18-09, 07:15 PM
A 5x0.8mm thread has a nominal minor diameter of 4.2mm (.165"). Given that, a 5/32" bit should take care of the old barrel adjuster. An 11/64" or an actual 4.2mm bit would be even better. You should have an easy time doing this as you already have a perfectly centered pilot hole. I would suggest drilling in increments rather than going right in with the 5/32" bit though. As you start to hit the minor diameter of the thread, chances are the rest of the adjuster will be screwed out the back of the braze-on.
You have such easy access to this area that I wouldn't bother with heat. You only risk damaging the paint.
Just a thought: I would use a pencil type soldering iron to heat the piece still inside and then try another easy out. Gently.
10-19-09, 10:24 PM
Just a thought: I would use a pencil type soldering iron to heat the piece still inside and then try another easy out. Gently.I'm still staring at it, deciding how to proceed. I have lots of patience. Well trained in patience. I'm trying to figure out the heating thing. I have an aluminum thing inside a steel thing. The coefficient of linear expansion for aluminum is about 70% higher than the same for steel. Meaning if I heat the combination, the aluminum insert gets tighter, not looser. But it I heat the whole thing and then blow a freeze mist down the center of the aluminum, maybe it gets looser. But that won't last, once I get the Easy Out into it. Or maybe if I just do heat and cool cycles on it, that'll cause movement of some type at the interface and that will help the Kroil to get in there. While I'm thinking, I'm waiting for the Kroil to arrive. Don't expect a denouement at any moment.
But keep those cards and letters coming!
10-20-09, 05:41 AM
Just drill it out. It will be a lot easier than you might think. Save the Kroil for your next job.
If it helps identifying the brand, I have them on the Peugeot I rebuilt... they were on the bike when I bought it (2nd hand) and the remainder of the equipment was Tiagra/Sora. Maybe there an old Shimano fitment?
PS. They gave me trouble also - one didn't want to give up the plastic ferrule that was on the cable housing!
10-20-09, 09:46 AM
Just drill it out. It will be a lot easier than you might think. Save the Kroil for your next job.I'd like to finish up with two operable adjusters if I can. I'm a little nervous about drilling to the root diameter because these parts are dissimilar metals corroded together. So I'm afraid I won't be able to get the aluminum threads out of the grooves after drilling. I can reach the ones on the ends with an awl, but not the ones in the center, assuming that I'll have to dig them out in chunks, rather than have the whole thing come out looking like a helicoil. So are you saying that the thread should come out pretty easily after drilling to root diameter?
10-20-09, 10:04 AM
I'm recommending this as the easy route only because you already have a pilot hole.
Once you have drilled to the root diameter, the remains of the threads will likely just fall out of the hole. Any that don't will be easily removed using a tap. I've done this several times on badly corroded fasteners (certainly far worse than can happen on a bike) and the result is always the same. The only problem I ever had was when I did not go all the way through the root diameter and tried to run a tap into the hole. I won't make that mistake again.
10-20-09, 10:40 AM
Heating the stub may seem counterproductive but several heat/ice cycles could break the bond between the two parts.
As joejack mentioned, the tap drill for M5x.8 threads is 4.2 mm so drilling the broken barrel out to that diameter and then rethreading with an M5x.8 tap should clean up the treads nicely. Most likely the tap will follow the original threads if you start it carefully.
Another possibility is to drill it out to 5 mm (13/64" is very close) and use a barrel adjuster with a nut under the barrel and just slip it into the now-clearance hole in the frame fitting. Thread the adjuster into and out of the nut to adjust cable tension. Use double nuts if you are concerned about spontaneous loosening.
03-02-10, 10:39 AM
The Kroil didn't work, probably because the Easy-Out was also getting a piece of the female threads. Drilling to root diameter and tapping worked great, very easy because the aluminum is so soft compared to the steel of the frame. New barrel adjusters. Now I can adjust shifting underway, which is especially nice on a tandem.
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