Cantilever brakes, stopped rotating, what went bad?

[WooGoogle]

I have a set of Dia Compe 987 and Avid Tri Align II's that rotate fine
when the mounting bolt is not tightened, but will not rotate at all
when the bolt is tightened. Both of these brakes worked fine until
one day for each of them it seemed like it was impossible to adjust
the right and left sides equidistant from the rim and it turns out
that one brake arm was almost locked in place. Is this enough
information for someone to diagnose? Are these fixable?

 

[daveornee]

I have a set of Dia Compe 987 and Avid Tri Align II's that rotate fine
when the mounting bolt is not tightened, but will not rotate at all
when the bolt is tightened. Both of these brakes worked fine until
one day for each of them it seemed like it was impossible to adjust
the right and left sides equidistant from the rim and it turns out
that one brake arm was almost locked in place. Is this enough
information for someone to diagnose? Are these fixable?

Probably dirt, and/or corrosion.
If you can do a good cleaning and lubrication, including taking the arms off the cantilever bosses to clean and lube them, you will likely have good function again.
See Park Tools site:

<http://www.parktool.com/repair_help/howfix_cant.shtml>

 

[Jeff Wills]

[email protected] (WooGoogle) wrote in message news:<[email protected]>...
> I have a set of Dia Compe 987 and Avid Tri Align II's that rotate fine
> when the mounting bolt is not tightened, but will not rotate at all
> when the bolt is tightened. Both of these brakes worked fine until
> one day for each of them it seemed like it was impossible to adjust
> the right and left sides equidistant from the rim and it turns out
> that one brake arm was almost locked in place. Is this enough
> information for someone to diagnose? Are these fixable?

The Dia Compes have a captured bushing that the rest of the arm
rotates around. On my 986's, this bushing corroded and the arm froze.
If it was loose, the arm would rotate, but the spring would not
retract the arm (the inner bushing also holds the spring in place).

Remove, completely dissassemble, and be prepared to hammer out the
inner bushing. Clean everything, paying special attention to the
contact surfaces of the bushing. Reassemble with plenty of grease.
They should be OK.

Jeff

 

[WooGoogle]

[email protected] (Jeff Wills) wrote in message news:<[email protected]>...
> [email protected] (WooGoogle) wrote in message news:<[email protected]>...
> > I have a set of Dia Compe 987 and Avid Tri Align II's that rotate fine
> > when the mounting bolt is not tightened, but will not rotate at all
> > when the bolt is tightened. Both of these brakes worked fine until
> > one day for each of them it seemed like it was impossible to adjust
> > the right and left sides equidistant from the rim and it turns out
> > that one brake arm was almost locked in place. Is this enough
> > information for someone to diagnose? Are these fixable?
>
> The Dia Compes have a captured bushing that the rest of the arm
> rotates around. On my 986's, this bushing corroded and the arm froze.
> If it was loose, the arm would rotate, but the spring would not
> retract the arm (the inner bushing also holds the spring in place).
>
> Remove, completely dissassemble, and be prepared to hammer out the
> inner bushing. Clean everything, paying special attention to the
> contact surfaces of the bushing. Reassemble with plenty of grease.
> They should be OK.
>
> Jeff


Thanks to everyone for the tips. Will try.