[Rendel Harris]

A mate asked me to replace the rather unsatisfactory cantilever brakes on his Tricross (they’re not great, I know as I have one too and they’re the only thing I don’t like about it) with Tektro mini Vs. Removing the cantis today I found that the left rear post has been bent slightly inwards, probably in a crash (he commutes through central London and has been hit twice in the last 18 months). This makes it impossible to get the pad aligned parallel to the rim and so renders the brake all but useless. The options are bend it back myself or take it to a shop, but I have a feeling most shops would refuse to do anything involving bending metal for liability reasons. Has anyone done anything like this? Any information on likelihood of success and the best technique to use would be very welcome, thank you!

Topic

[Sredlums]

Good to hear!

Good to hear!
Another bike saved from the scrap heap! ?

[Rendel Harris]

Got it out now and turns out

Got it out now and turns out both were bent, the post only a millimetre or so but enough to send the pads askew, especially when combined with a small twist in the mount. A bit of judicious twisting (brake not frame!) and bodging and it’s good.

[Sredlums]

Yes, cantilever posts are

Yes, cantilever posts are always steel. But I can not imagine that it’s the post itself that’s bent, I’ve never ever seen that happen. Very probably it’s the mount where the post is screwed in that’s bent, and that mount is part of the frame.

[Rendel Harris]

Many thanks for all the

Many thanks for all the advice on here, much appreciated and it put me on the right track: looking at the bike again this morning I realised that the posts are removable but some previous owner (not my mate) had, perhaps in trying to patch up some crash damage, soldered the post into place. I’ve managed to melt the solder and extract the bent post now so off to the LBS when it opens to get a replacement and hopefully have it all fixed. Thanks again for the help!

[levestane]

I would guess the posts are

I would guess the posts are steel and screw into alloy mounts welded to the seat stays. If the post is bent then a new post should fix it. If the mount is bent, or the stay twisted, I’d be tempted to try and nudge is back into shape especially if the caliper approach is not an option and the frame is disposable.

Another option is cheap v-brakes and twist one of the arms to compensate for the post.

[Rendel Harris]

Thanks I’ll have a look at

Thanks I’ll have a look at that tomorrow, would be great if they are screw ins.

[ChasP]

Watch out there are different
Watch out there are different threads

[ChasP]

Example https://www.ebay.co
Example https://www.ebay.co.uk/itm/382445765436?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=NLINYaUoQ7G&sssrc=4429486&ssuid=vFoBGAplToe&var=&widget_ver=artemis&media=COPY

[Dnnnnnn]

If it were me, and assuming

If it were me, and assuming it’s only bent a little, and because it’s a rear, I’d gently bend it back, winding in a bolt as I went to try to keep the threads OK. If you had a longer bolt which reached beyond the bend point, that might also provide some reinforcement in service.
I suspect the frame clearances might be too great but a deep drop dual pivot brake might also be an option?

[Rendel Harris]

Thanks never heard of them –

Thanks never heard of them – never had a V-brake bike myself – will look into that.

[Dnnnnnn]

Rendel Harris wrote:

Rendel Harris wrote:

It’s aluminium

The frame is alu – but the actual post… I’d have thought that was steel?

[ChasP]

They can’t be welded in if it
They can’t be welded in if it’s an alloy frame, I assume you mean that the boss which the post screws into is welded to the frame? You should be able to unscrew the post and replace it?

[ktache]

Good idea on the brake
Good idea on the brake booster.

[Sredlums]

In tht case I would try to

In tht case I would try to carefully bend it back myself, check for visible damage (cracks etc.), and if there aren’t any, mount the brakes but also use a brake booster as a reinforcement.

[Rendel Harris]

Backladder wrote:

If the seat stay bridge has a brake hole drilled then remove the canti and fit a caliper for the back.

Good shout, it does, looking into it.

[Author]

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