Author Topic: Which puller for Cantilever brakes?  (Read 370 times)

Dave_C

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Which puller for Cantilever brakes?
« on: May 23, 2020, 02:40:11 pm »
I'm stripping my circa 2007 Dawes Galaxy for a new paint job, put can't get the Tektro CRxxx canti brakes off. I'm looking for a bearing puller which is the right size. Screwfix appear to have withdrawn them from sale, at least locally.

Can anyone suggest a bearing puller I could use? Something for extracting bearing off a car might be too large

Any suggestions please? I'd like to reuse the brakes if possible so non destructive removal is preferred.

Cheers, Dave C

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Re: Which puller for Cantilever brakes?
« Reply #1 on: May 23, 2020, 06:12:04 pm »
method varies with brake model; which do you have?

cheers

Dave_C

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Re: Which puller for Cantilever brakes?
« Reply #2 on: May 23, 2020, 07:03:39 pm »
CR720.

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Re: Which puller for Cantilever brakes?
« Reply #3 on: May 23, 2020, 10:42:05 pm »
Can't you fettle summat? I'm thinking of  steel angle with a slot to go behind the brake and two bits of studding to a similar bit of angle sitting on a  long M6 bolt set into  the brake fixing?

Pingu

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Re: Which puller for Cantilever brakes?
« Reply #4 on: May 23, 2020, 10:46:38 pm »
Hammer, wood, curtain pole.

Maybe not.

Dave_C

  • Trying to get rid of my belly... and failing!
Re: Which puller for Cantilever brakes?
« Reply #5 on: May 23, 2020, 10:52:01 pm »
I don't have any angle iron. I have lots of bits of wood but very little steel. The only metal is Ali tube. I suppose I could pop the two fingers of a claw hammer behind and tap from behind.
I was hoping someone might know what size puller to buy. The all appear to be in imperial, 4", 5", 6" etc..

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Re: Which puller for Cantilever brakes?
« Reply #6 on: May 23, 2020, 11:12:28 pm »
this brake uses a traditional brass bush which turns directly on the boss



there are only two main ways this brake  model can get  stuck;

1) that it is seized solid and doesn't even rotate on the boss any more
or
2) that the brake arm still rotates OK but  there is a burr on the end of the boss which is preventing the brake from simply sliding off.

The latter can arise if the bolt has been overtightened, for example.

 [FWIW the nominal wall thickness of the boss above the screw threads is only 0.5mm; you cannot expect to tighten this M6 bolt like other M6 bolts; if  a canti brake has a dummy (integral) boss it is possible to tear the boss apart because the boss sees the tensile load generated by the bolt. With brakes like yours you just weaken the boss and raise a burr on the end of it, if the bolt is overtightened.   This bolt is best tightened to a modest torque with threadlock on it to prevent loosening.]

In most cases if you add oil and keep on working the brake arm on the boss, it will eventually take the burr off (by abrasion) and the arm will come free.  If you try and use a puller the boss may just fail in tension (as per comment above), so for goodness sake don't use brute force unless you have some means of replacing the boss up your sleeve.

cheers

Dave_C

  • Trying to get rid of my belly... and failing!
Re: Which puller for Cantilever brakes?
« Reply #7 on: May 23, 2020, 11:32:01 pm »
Thanks Brucey,

The plan was to pull on the cantilever brake, whilst pushing against the bolt, which I would unscrew a turn or two. Thus not pulling the boss against the frame, but pushing against the threads of the inside of the boss.

The brakes still work, and swivel. Your second reason is correct, I think the bolts were over tightened, mushrooming the top of the boss.

There is very little overhang of the boss so filing the end off is not really possible.

Thanks again, I'll have a look at using the brake to wear the mushroomed end down, to allow it to be released.

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Re: Which puller for Cantilever brakes?
« Reply #8 on: May 24, 2020, 07:24:58 am »
Quote
I don't have any angle iron. I have lots of bits of wood but very little steel. The only metal is Ali tube. I suppose I could pop the two fingers of a claw hammer behind and tap from behind.
I was hoping someone might know what size puller to buy. The all appear to be in imperial, 4", 5", 6" etc..
Brucey's picture and explaination above has given me an idea. Put a piece  of hard wood with two 8 mm holes on boss centres horizontaly across both brakes. Lash the brake arms to it you may be able to get a bolts and penny washers in to the triangle's of the canti arms Insert long bolts into bosses and use a flat bar across your bolts and 3 G clamps  in the middle and ends. Make sure you pack you arm lashing so the whole arm is against the wood to get a straight pull and not twist the brake

Dave_C

  • Trying to get rid of my belly... and failing!
Re: Which puller for Cantilever brakes?
« Reply #9 on: May 24, 2020, 10:18:35 am »
Thanks Aidan, I'll try this!

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Dave_C

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Re: Which puller for Cantilever brakes?
« Reply #10 on: May 24, 2020, 03:02:13 pm »
I got them off by working back and forth. Thanks for the help those who posted and to Brucey for the tip.

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Re: Which puller for Cantilever brakes?
« Reply #11 on: May 24, 2020, 06:59:34 pm »
good work fella!

cheers