Balancing canti brakes

[jonthefish]

I'm new to cantis so may be missing something obvious. Am trying to install Shimano DX cantis. Cannot balance spring tension despite trying numerous combinations of brake arm and spring, spring orientation, holes in frame (3 options) and grub screw adjustment.
When I swop springs between brake arms the relative tension appears to move with the spring. This suggest to me that there is much variability in the springs themselves.
New springs?
Or am I being thick (more than possible)?
Ta

 

[rosstheboss]

Silly question - have you got the springs the right way round? I asked a similar question a few years ago and this was the answer! Funnily enough with DX brakes as well

 

[WD Pro]

I find its impossible to do the balancing correctly first time - let them settle / relax, tweak just a little (I mean a little ...) pump the brake a few times and then let them relax, repeat as required.

The time to relax could be a week or so, just tweak when needed

WD

 

[jonthefish]

Silly question - have you got the springs the right way round? I asked a similar question a few years ago and this was the answer! Funnily enough with DX brakes as well

Springs are coiled R and L for respective sides. I think that's right :? .

Are there two options for spring location in brake arm? There is a "hole" that seems the obvious place to locate the end of the spring. But it could also be located against the "ramped" section of the spring seat (but that does not seem right to me).
I've seen springs on evil bay for £1.99 so tempted to try that if only to negate one variable.
Many thanks.

 

[doctor-bond]

What kind of straddle wire are you using? Is it the fixed version with the disc in the middle comme ca:

Or an old fashioned variable straddle, like this chap:

If the former, then that's to blame: the most pointless invention ever, causing countless hours of angst and recrimination. Splash a coupla quid on a nice variable straddle and they become as forgiving as an old shoe.

If you are already straddle-wise then something is bent.

 

[xerxes]

If the former, then that's to blame: the most pointless invention ever, causing countless hours of angst and recrimination. Splash a coupla quid on a nice variable straddle and they become as forgiving as an old shoe.

The former, pointless invention, was actually supposed to be safer, with the separate straddle wire there was a possibility that if the cable snapped the straddle wire could catch on knobbly tyre tread and lock the wheel.

 

[jonthefish]

I have not yet attached any cabling at all. All I've done is mount the brake arms and immediately noticed (and tried to resolve) variation in spring tension.

Given that pad clearance is (I assume - but may be talking bollocks) partly determined by spring tension I was concerned. Presumably the variable tension/pad clearance could be mitigated by asymmetric yolk tension but that seems a very bad plan.

The brakes have fixed straddle wires with disc, but these not yet attached.

Maybe I'm worrying needlessly and should complete installation?

Thanks again
Jon

 

[doctor-bond]

@ Xerxes-

With the early hook type straddles then there was a possibility that the straddle wire could bounce out:

But a snapped cable could happen what ever your set up, with pretty nasty consequences. As with all risk, it's a matter of consequence and likelihood. With any of the setups, the consequences are pretty bad, but the likelihood is low for the average rider. For Shimano, who were effectively responsible for many millions of riders, the likelihood was much greater, hence their 'safer', crapper solution.


@ JTF - get em cabled up: that's when the fun begins (bin the fixed straddle). With the variability of: the pads in the arms; the straddle wire); and grub screw adjustment, there is plenty of room for manoeuver.

 

[minor_LEGEND]

Those brakes have a plastic dust cover that goes over the spring, they have a dimple/teardrop on them which, if the spring is correctly installed, should point down when the cantis are mounted, or atleast be symetrical, this was also to stop the brakes being able to open towards the spokes of the wheel (the teardrop).

The rear canti's tend to have a stronger tension of spring.

 

[frank.youngman]

+1 on fittings the things and then letting them settle.On my Clockwork I was constantly changing spring pressure,one day they worked,the next day one arm stuck.In the end I polished the bosses,used a less sticky grease on the bushes and eventually they sorted themselves.They still don't brake well and I am minded of Bikepro's comment:Whats the least expensive way to guarantee good cantilever performance? Buy V-brakes!

Following that theme next up was my 1991 Cannondale Beast which sports XT M750 V-brake levers and modern 2013 V Brakes and all I can say is that power and modulation are excellent by comparison with the dear old Clockwork.