CX 70 /50 | linear spring hack

[Cormac O'Keeffe]

Hi,

Here's a little tip for anyone else running cantilever brakes such as the CX70s that use a linear spring.

I was having trouble with the arms not springing back once the brake lever had been released. After ages of faffing about, the mechanic at the bike shop diagnosed and solved the problem in about 3 minutes.

Apparently, the linear springs can lose their tension over time. The trick is to pop it off the retaining tab, and wedge a screwdriver between the brake arm and the spring and slowly/gently bend it back in the opposite direction. This re-tensions the spring and gets the brakes away from the rim again (cf. photo below). 

Just thought I'd share this tip as I see a bunch of people use these kinds of brakes here and you might have encountered the same problem.

PS Apparently it works for v-brakes too.

[Patrick Moore]

I’ve used this method many times for cheap v brakes, particularly after the tension screws have been torqued down so thoroughly that the Phillips heads have been ground smooth. It’s easy and effective and lasts — well, at least a couple of months, until the tension weakens again. I have to say that I didn’t have any tension problem with good quality straight cantilever springs.

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Patrick Moore

Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum

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[Josiah Anderson]

Yep, that's a useful trick. Do be aware that those springs can break if bent too far though; I've seen that happen on cheap v-brakes. Probably not as much of an issue for CX-70s and other higher-quality brakes, but I'd just use the adjuster screws instead if possible.

Josiah Anderson 

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[KenP]

Nice tip.  Also, take the brake off the frame post and clean and lubricate the arm where the coil spring and the little pin sticks into the frame because the end of the spring needs to swivel inside somewhere.  Somehow it helped by cleaning in there to get the brake arm to swivel back and forth better.  Does anyone else know specifics?

[Cormac O'Keeffe]

I'm a little curious to know two things.
1. Do replacement springs exist?
2. What kinds of cantis do people here tend to favour?
One great thing about cantilever brakes that I've discovered is that they offer so much potential for endless fine-tuning and general messing about

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[Steven Sweedler]

Cormac, I have been using Shimano BR MC 70 cantilevers for several years. They use threadless post brake shoes that last me for years, I am primarily a tourist and  many of my miles are on bikes weighing up to 80 lbs and I am confident in stopping. Easy to find on ebay, prices have ridsen in recent years though are still reasonably priced.

Steven Sweedler
Plymouth, New Hampshire

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[Philip Williamson]

I just got into the spring-bending game. It works pretty well. I had some issues with a very nice v-brake, and some pretty heavy hitters were like, “Yeah just bend the springs.” 

“What? What about these little screws?”

“Bend. The. Springs.” 

It works. That particular brake turned out to be broken in a couple key ways, but instead of faffing around with different screw depths on the replacement, I backed out both sides a couple turns and did all the adjustments with bending the springs. It’s also kinda fun to bend stuff and make it match. 

Philip

Bending springs in Santa Rosa, CA