Canti brake setup problems

hookooekoo

Retro Guru
I had a look at my own bikes. I set my cantilevers up so that the posts on the pads are horizontal. To put it another way, the pads are at the same height as the bolt that clamps the brake pad post to the cantilever body.

It seems to me that if the brake pad post is angled upwards, as it is in your setup, the pad will swing upwards towards the tyre wall when the brake is released. In any case, the brake pad posts should be horizontal, or close to horizontal, so that the pads meet the rim squarely.

Some years ago when I had a frame resprayed I also had a bent cantilever boss replaced. The frame builder asked me what cantilevers I was using. I believe he asked because the cantilever boss position can vary slightly, depending on the exact design of cantilever. Obviously there is some adjustment available on most if not all cantilevers, but for some unusual cantilever designs the boss may have to be re-positioned.

If it helps, the dimension on my Shimano cantilevers from the centre of the cantilever mounting bolt, to the centre of the pad post clamp bolt, is about 30mm. That's with the adjustment near the top of the slot (upwards almost as far as it can go). The maximum adjustment available is about 10mm (mostly downwards in my case, because I have the pad post clamp near the top of the adjustment slot).
 

grey-beard

Orange 🍊 Fan
I had a look at my own bikes. I set my cantilevers up so that the posts on the pads are horizontal. To put it another way, the pads are at the same height as the bolt that clamps the brake pad post to the cantilever body.

It seems to me that if the brake pad post is angled upwards, as it is in your setup, the pad will swing upwards towards the tyre wall when the brake is released. In any case, the brake pad posts should be horizontal, or close to horizontal, so that the pads meet the rim squarely.

Some years ago when I had a frame resprayed I also had a bent cantilever boss replaced. The frame builder asked me what cantilevers I was using. I believe he asked because the cantilever boss position can vary slightly, depending on the exact design of cantilever. Obviously there is some adjustment available on most if not all cantilevers, but for some unusual cantilever designs the boss may have to be re-positioned.

If it helps, the dimension on my Shimano cantilevers from the centre of the cantilever mounting bolt, to the centre of the pad post clamp bolt, is about 30mm. That's with the adjustment near the top of the slot (upwards almost as far as it can go). The maximum adjustment available is about 10mm (mostly downwards in my case, because I have the pad post clamp near the top of the adjustment slot).
Thanks for the info, food for thought.
I understand what you're saying about the posts needing to be square to the rim, but that is when the brake is applied surely? and when released it will naturally arc upwards following the path of the pivot, this will vary from brake to brake depending on the design. These are a copy of quite an early design and as such are a bit crap, I don't understand how it took so long to come up with the V-brake?
 

novocaine

Dirt Disciple
Lower the straddle by 10-15mm then realign the pads. at the moment your arms are in the closed position when they are open.

This will move the pad to rim contact to the top of the arc rather than the 1 o'clock, your return to open will be on the downward swing of the arc not the upwards and tyre clash will be minimised.

I only joined the forum to say this. :) granted I've been reading as a none member for quite a while, but this time I thought I'd say hello and offer a suggestion. :)
 

novocaine

Dirt Disciple
Yes, that, but to get to that position will need a longer straddle cable too (which would be the correct set up IMHO).

Thank you for the picture, I'd have to go digging in the parts bin storage unit to find a set to picture. :)

 

grey-beard

Orange 🍊 Fan
Lower the straddle by 10-15mm then realign the pads. at the moment your arms are in the closed position when they are open.

This will move the pad to rim contact to the top of the arc rather than the 1 o'clock, your return to open will be on the downward swing of the arc not the upwards and tyre clash will be minimised.

I only joined the forum to say this. :) granted I've been reading as a none member for quite a while, but this time I thought I'd say hello and offer a suggestion. :)
Thanks for the input, I like the terminology, top of the arc makes perfect sense, of course, you have to take into account that it is the arc of the pad contact area we're interested in, and as such that will change depending on how far the pad post is clamped into the calliper. I shall hopefully get a chance to tinker this week.
 

grey-beard

Orange 🍊 Fan
Bad picture, the light was going.
I've kind of got the brakes working, not perfect, but not catching the tyre, but the front does squeal alot!
I came up with a bizarre technique of clamping the lever to the bars and clamping the pads to the rim, then tightening the pads, it sort of worked. I've got some new pads on the way, so I'll try it again and put a spacer in to set the toe in.
Thanks for all the advise guys.
IMG_20210722_210719.jpg
 
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