Adjusting cable disc brakes

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Adjusting cable disc brakes

Postby nezumi » Thu Oct 17, 2013 1:03 pm

Does anyone have a recommended resource for how to adjust cable pull disc brakes?

The brakes on my commuter seem to need to be pushed very high before securing the cable in order to have effective braking - the problem is that when I try and secure them that high, they won't secure and they slide back down.

The other posibility is that I have worn down the pads at a ridiculous rate. Is there an easy way to tell this?

Second issue (phew!): When braking, the disc itself is moved sideways. Is this how it should be, or should the pads move to meet the disc?
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by BNA » Thu Oct 17, 2013 2:12 pm

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Re: Adjusting cable disc brakes

Postby Mozzar » Thu Oct 17, 2013 2:12 pm

The pads should move the disc a little bit as cable discs only move one disc pad not both. you can make sure that you have sufficient pad left and make sure that your cable is clamped tight enough at the calliper.
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Re: Adjusting cable disc brakes

Postby eeksll » Thu Oct 17, 2013 2:15 pm

good to start with what brakes you have.

I don't understand what you mean with the first issue. Sounds like yourn ot tightening the cable bolt enough.

The second issue. This is normal I believe.
My avid BB7 disc brakes. There is only 1 piston that moves in and out. So as this piston moves to meet the disc, it pushes the disc into the other pad.

On setup/alignment, you postion the caliper so that the disc is a bit closer to the pad which does not move.
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Re: Adjusting cable disc brakes

Postby MattyK » Thu Oct 17, 2013 3:05 pm

seems to be bugger all info on the web about how to set up / install a Hayes CX Expert (aka CX-5).

Avid BB5 setup should be similar though.
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Re: Adjusting cable disc brakes

Postby nezumi » Thu Oct 17, 2013 3:07 pm

eeksll wrote:good to start with what brakes you have.

I don't understand what you mean with the first issue. Sounds like yourn ot tightening the cable bolt enough.

The second issue. This is normal I believe.
My avid BB7 disc brakes. There is only 1 piston that moves in and out. So as this piston moves to meet the disc, it pushes the disc into the other pad.

On setup/alignment, you postion the caliper so that the disc is a bit closer to the pad which does not move.


The brakes are Hayes CX Expert, the replacement for the CX5, on a Merida Cyclo Cross 4.

With the first issue, no matter how I tighten it slips down a bit. Not as far as when the bolt is totally loose, but more like 1 cm further than I would like it.

Good to know that the movement in the disc is expected.
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Re: Adjusting cable disc brakes

Postby eeksll » Thu Oct 17, 2013 3:34 pm

is it possible you have some cable slack after initially tightening the bolt? You would normally take the cable slack out (after tightening the cable bolt) with the barrel adjuster on your brake levers.
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Re: Adjusting cable disc brakes

Postby nezumi » Thu Oct 17, 2013 3:46 pm

eeksll wrote:is it possible you have some cable slack after initially tightening the bolt? You would normally take the cable slack out (after tightening the cable bolt) with the barrel adjuster on your brake levers.


"Barrel adjuster" loses me. :(

The guide I found was for MTB cable discs, so I was only looking at the caliper end. Up top it's 105 brifters.
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Re: Adjusting cable disc brakes

Postby eeksll » Thu Oct 17, 2013 4:11 pm

105 brifters probably dont have the barrel adjuster, you might havea inline one (not sure if they do them for brakes)

Viewing the image of your caliper

Image

when installing twist that black thing (barrel adjuster) at the top left hand corner of the picture all the way in. install cable, tighten bolt, then twist the black thing until you tension up the cable. e.g just before/after the caliper arm starts moving.
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Re: Adjusting cable disc brakes

Postby drubie » Thu Oct 17, 2013 4:37 pm

Not sure about the Hayes, but the mechanical shimano disks (and clones) have basically one fixed pad attached to the caliper and one floating one that the cable acts on from the lever.

The fixed pad is adjustable (usually with a hex head screw on the wheel side of the caliper). What I generally do is loosen the mounting bolts, let the caliper "float" under pressure from the lever until it finds a centre, then adjust the fixed pad inwards so it is as close to the disk as I can get. Only after all that do you futz around with the cable adjustment stuff. The basic idea is to get minimal travel on the floating one, minimal disk deflection (reduces sponginess at the lever) and that's achieved by limiting the disk flex in the first place by making sure that fixed pad is as close as you can get it to the disk.
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Re: Adjusting cable disc brakes

Postby JBark » Thu Oct 17, 2013 5:45 pm

Best method I've found for my BB5s:
http://www.ecovelo.info/2011/04/15/a-fo ... sc-brakes/

It's mainly geared towards the calipers like the BB5s which only have easy adjustment of one side of the caliper, but I can see it being a helpful starting place for most mechanical disc setups.
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Re: Adjusting cable disc brakes

Postby Duck! » Thu Oct 17, 2013 7:52 pm

drubie wrote:Not sure about the Hayes, but the mechanical shimano disks (and clones) have basically one fixed pad attached to the caliper and one floating one that the cable acts on from the lever.

The fixed pad is adjustable (usually with a hex head screw on the wheel side of the caliper). What I generally do is loosen the mounting bolts, let the caliper "float" under pressure from the lever until it finds a centre, then adjust the fixed pad inwards so it is as close to the disk as I can get. Only after all that do you futz around with the cable adjustment stuff. The basic idea is to get minimal travel on the floating one, minimal disk deflection (reduces sponginess at the lever) and that's achieved by limiting the disk flex in the first place by making sure that fixed pad is as close as you can get it to the disk.

This will work for all mechanical disc brakes. :)

I will add that before you start the alignment step, ensure that the fixed (inboard) pad is adjusted so the rotor will actually contact the pad surface and not the caliper body.
I had a thought, but it got run over as it crossed my mind.
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