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I am renovating a bike, I guess it's 10 years old. It has internal gears with pedal brake. And then it has a hand brake in the front, I think it is called "cantilever direct pull". One arm was moving quite smooth, while the other was very stuck, tough not impossible to move by hand.

In the process of removing the arm from the brake boss, something remained on the boss: some kind of brass-looking bushing with a kind of rubber gasket.

The brass part was almost impossible to remove. I tried different things. And only in the end when I took a 60cm pipe wrench was I able to wiggle it off.

I felt victorious until I realized that the power needed to clamp around the bushing was enough to deform the boss itself. So now I have a slightly oval boss, just enough to notice with the naked eye. The internal threading is now too tight, but it is possible to put in the bolts though. The real problem is putting a new brake arm on the bushing. I cant even get in one millimeter onto the boss.

Bushing stuck on boss Picture above shows: Bushing stuck on boss

The other boss, where the bushing easily slid off together with the arm Picture above shows: The other boss, where the bushing easily slid off together with the arm

After removal of the bushing, the boss is slightly oval Picture above shows: After removal of the bushing, the boss is slightly oval

My question is two-fold:

1) How should I have removed the bushing, without damaging the boss.

2) How can I fix the boss now, so that I can put a new brake arm on it?

  • 1) Hit it with penetrating oil (e.g. liquid wrench) and it make take a few days. I don't have an answer on 2). – paparazzo Jul 24 '14 at 13:35
  • Just buy new bosses - they're like 5 bucks for a set. – Batman Jul 24 '14 at 14:27
  • @Batman: And weld them on? – Mads Skjern Jul 24 '14 at 14:57
  • You can unscrew teh bosses from the frame. then screw new ones in. – Batman Jul 25 '14 at 2:50
  • Depends on the frame. Weld on or braze on bosses are common, e.g. framebuilding.com/Bosses.htm – armb Mar 26 '15 at 13:33
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After some thought, and experimentation, I will suggest my own answer.

How to remove

I see two ways:

Without special tools

Use the pipe wrench just enough to wiggle the bushing a few millimeters out. Then use a screwdriver and a hammer to hammer it out.

With a puller

With a rather small "puller". Possibly together with this plate that can close around the boss behind the bushing. The diameter of the rod on the puller might be greater than the inner diameter of the bussing. In that case, I hope it is possible to insert a threaded metalrod into the inner threading of the boss, and then press the puller-rod against the thinner inserted rod.

enter image description here

The two devices need to be in appropriate sizes, and I was able to find that online in my country.

How to fix the deformed boss

Maybe I was lucky, but it was no problem at all. I just pinched on the "ends" of the oval, with the same pipe wrench. After my first attempt I was able to slide a new brake arm on, without any resistance. If that had not worked I would have used a sanding tool, maybe a Dremel.

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Most of the time bosses thread into the fork arms, although it's possible that they are permanently affixed. A shop should be able to advise you, and if they are replaceable should be able to help you find the correct replacement part.

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