Canti Brakes Squealing - suggestions please?

[roubaixtuesday]

The tandem has cantis fitted.

Historically, there's been no problem with these noise-wise, and performance-wise they're pretty good too, albeit a PITA to set up.

But recently they've started squealing, both front and back, and yesterday this reached epic, trumpet on the top register effect.

I have a suspicion that it's related to new rims fitted a year ago, but I'm definitely not going to be trying out different rims to solve it.

The blocks front and back are very different to one another: front ones are brand new, cartridge to accept roadie blocks type, rear are ancient of unknown provenance. So I'm not convinced trying different blocks will really help.

All suggestions welcome.

 

[T4tomo]

Good clean of rims and blocks with hot soapy water.

A little bit of a squeak can be useful to let people know you are breaking / there, an epic trumpet not so good.
I use koolstop blocks salmon or dual compound, on my canti equipped machines

 

[freiston]

Apart from the rims, has anything else changed? If both front and rear were squeal-free and both developed squeals at the same time despite having completely different blocks, it does make the rims a suspect and doesn't show promise that a change of blocks will resolve it. Is it possible that the blocks and/or rims have got contaminated? You could try filing off the surface of the blocks and/or scrubbing the rims. Sometimes my brakes squeal after I've given the rims a good clean but settle down after a few miles - maybe it's a temporary problem caused by new rims that will go away?

Edit - I see that T4tomo mentioned cleaning the rims before me. Toeing in the blocks might help.

 

[roubaixtuesday]

maybe it's a temporary problem caused by new rims that will go away?

We've done well over 1000 miles since the new rims, and it seems to be getting worse - yesterday was a *lot* worse!

So I don't think it's temporary.

Not certain it's directly related to the rim change, just a suspicion.

 

[HarryTheDog]

I cant help you with the squealing but I hate Canti's with a passion.( raced Cx on cantis for years, disc brakes so much better) I have a tandem and its got Magura hydrallic rim brakes . Mine are dead ancient and have a special fitment for them not canti posts but they do a straight swap out system that goes onto canti posts. They are super reliable and will stop you a lot easier. ( only if you have seperate brake and gear levers of course)

 

[fossyant]

Can be wear and the angle of the pad on the rim changing.

 

[presta]

Set the blocks with some toe-in.

 

[freiston]

My front cantis (Tektro Oryx) squealed from when the bike was new and everything I did would not resolve the issue. Eventually I replaced them with Tetro CR720s and the problem was solved. I still have Oryx on the rear wheel but they don't squeal. I suppose that a combination of canti arm, block, rim and frame/fork can sometimes just work together to resonate and scream the house down, and that changing any of the items can resolve it. For information, I use Kool Stop dual compound pads.

Unlike HarryTheDog, I like my cantis

 

[roubaixtuesday]

My front cantis (Tektro Oryx)

Mine are Deore LX.

They didn't squeal for the first 20 years of use. Front pictured:

 

[rogerzilla]

Assuming the (horrible to set up) stud-type pads, it's a compromise between more pad extension for higher mechanical advantage vs squeal.

 

[roubaixtuesday]

Assuming the (horrible to set up) stud-type pads, it's a compromise between more pad extension for higher mechanical advantage vs squeal.

Not sure I understand how MA corresponds to squeal? Can you explain further? Thanks.

 

[Ian H]

I wonder if lubricating the posts with a bit of grease might help.

 

[Punkawallah]

After cleaning with soap & water, I dry and give the rims a rub over with white spirit - seem to get the brake block marks off better.

 

[rogerzilla]

Not sure I understand how MA corresponds to squeal? Can you explain further? Thanks.

More extension gives a wider spread of the canti arms and more MA (also works for centrepulls that use this type of brake). However, too much pad extension causes squeal because there is more to vibrate. They're coincidentally linked.

 

[roubaixtuesday]

More extension gives a wider spread of the canti arms and more MA (also works for centrepulls that use this type of brake). However, too much pad extension causes squeal because there is more to vibrate. They're coincidentally linked.

Ah, ok, that makes sense, thank you.

So...

(1) shortening the yoke reduces the spread and MA but should reduce squeal?

(2) A second question- AIUI the MA is also changed by the height of the fixing point above the pivot (in mine above it's close to, but not at the top of the slot). So if I tried shortening the yoke, I could compensate somewhat by fixing at the top of the slot?