cable pull disc brakes issue

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berty bassett

Legendary Member
Location
I'boro
hi
i have bought a bike with cable pull disc brakes , very good condition and by the looks of it not used much at all however , i can not get the back brake set up properly . i have watched yt and done the adjusting the whole unit , i have had the pads out and cleaned them ( with petrol -( i know it wrong but all i had )) cleaned the disc also , put it all back together and just the same , i can pull lever hard as possible as far as it goes and i can still just about move the bike backwards even if i set it up so the pads are binding a little before i touch the lever . the pads have about 1.5-2 mm on them and dont look that worn compared to google images of worn brakes
before i take pads out of front and put in back , is there something that i am missing here ?
first time with disc brakes and not too impressed so far but hopefully with a little help there will be a change of heart !
front brakes are sound by the way
if it makes any difference its a cannondale synapse al , the cable is mostly routed internally but when i released the nut at the brake end i made sure it run free and it seemed fine
i definitely put it back together how it came apart but dont know if it was right in the first place ! like i say it grips but just not hard enough
any help much appreciated
 

I like Skol

A Minging Manc...
My money is on the pads being contaminated. It isn't unusual for people that don't know better to spray aerosol lube around the chain and rear mech but also unintentionally get a good amount on the rear brake. This isn't good and is usually irreversible, no matter how hard you try!

I suggest replacing the pads with a new set but making sure you clean the disc up with a suitable solvent first. Petrol probably isn't good as it will have oils and chemical additives that proper brake cleaner solvents don't. Isopropyl alcohol is good.
 

iluvmybike

Über Member
The important bit with cable pulls is to set the inner pad first so it touches the rotor - then back off a little until not quite touching THEN adjust the outside on the cable - if you give the adjuster a few turns out first you can pull the outer pad right in against the rotor then slack it off once you have done up the pinch bolt. If that still doesn't work the n yes bin the pads...
 
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berty bassett

berty bassett

Legendary Member
Location
I'boro
Many thanks for replies
I will take pads out of the front and try them in the back - if this works/is better then I will get some new pads and the cleaner
Cheers
 

si_c

Guru
Location
Wirral
The important bit with cable pulls is to set the inner pad first so it touches the rotor - then back off a little until not quite touching THEN adjust the outside on the cable - if you give the adjuster a few turns out first you can pull the outer pad right in against the rotor then slack it off once you have done up the pinch bolt. If that still doesn't work the n yes bin the pads...

Depends on the brake caliper. Dual sided cable pull calipers can be much easier to setup than single side pull. With the former you can adjust pad clearance to under a mm on both sides before even thinking about touching the barrel adjuster.

Many thanks for replies
I will take pads out of the front and try them in the back - if this works/is better then I will get some new pads and the cleaner
Cheers
Before you do this, make sure you completely clean the rotor on both sides. If you don't then you run the risk of contaminating your front pads too. My suggestion would be if you do need new pads, to put the new ones in the front. Chances are it is contamination though, I've had the same situation where I rode through a puddle that was contaminated with diesel and the rear brake stopped working entirely. I managed to resurrect the pads by cleaning them with isopropyl alcohol after using some rough sandpaper to remove the top surface. I also cleaned the disc rotor - again isopropyl alcohol and a microfibre cloth worked well.
 
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berty bassett

berty bassett

Legendary Member
Location
I'boro
Your right about contamination I guess - will just get some more pads next time I pass lbs and some of that cleaner
As for the moving parts - there is only the one wire , one disc moving and even when I have the pads catching on both sides of the disc before I touch the brake , when I pull the lever in I can still move Bike
 

si_c

Guru
Location
Wirral
Your right about contamination I guess - will just get some more pads next time I pass lbs and some of that cleaner
As for the moving parts - there is only the one wire , one disc moving and even when I have the pads catching on both sides of the disc before I touch the brake , when I pull the lever in I can still move Bike
Do you know which model of disc brake you have, or which bike you have if not? That may help us advise on how to adjust.
 

PpPete

Legendary Member
Location
Chandler's Ford
I've only limited experience of cable pull disc systems, but at least one bike I've worked on, I tried everything, adjusting cables to millimetric clearances, cleaning rims, replacing pads, replacing rotors - and nothing making a significant difference until I replaced cable outers with compressionless.
 

Tangoup51

Well-Known Member
First off, before validating if your brakes are tip top or skip worthy, you need to make sure they're as tight as they can be. - By that, I mean they have the Least brake lever pull at the handlebars and have the least gap between the rotor and the pads. - This means playing around with your cable slack and your barrel adjusters until you've found a harmonious balance between a Firm brake lever feel and passive rubbing. - The less slack you give the cable (tighter) the more it will move the outboard pad in and vice versa.

You should also ensure your caliper is correctly aligned for this, contaminated pads or nowt, you should have your caliper properly adjusted for whatever is to come.

The easiest way to do this, is to visually gauge that the pads are running in a straight line in relation to the rotor. If they're off-canter then you've got a problem and will need to realign your caliper. - A wildly off balance caliper will make it difficult for your pads to bite as they should.
Anything else isn't going to be causing your current issue.

If you can come close to any of this, you should at the very least be able to lock your rear wheel when riding.

... IF you find that's not the case, then take note of the noise your brakes make when you pull them.

Is there alot of metallic, scraping noises when you brake?
Is it very quiet?

If there's alot of metallic noises occurring and not much braking, continue using your brakes and see if there's any improvement.
Such noise usually indicates fresh rotor and pad engagement, meaning they need to "wear in" before they start becoming effective at braking.

On the contrary, if it indeed is dead quiet and yet no braking then you've got contaminated brakes.

The easiest way to remedy this is to clean them. Thoroughly. Isopropyl alcohol is a highly effective brake cleaner here, because it evaporates.
When you use strong solvents to "de-contaminate" your pads & rotor, alot of people fail to clean off the solvent in question, the solvent then becomes the source of the new containment.

However, a somewhat popular (yet, effective IME) way to clean your pads (pads, not rotor) is to burn them. Burning the first layer of braking material usually expels & evaporates the majority of containment, but would still need a good clean up after to clean any residue left behind.

The rotor would love a once over with a high grit sandpaper. Note, a once over. Your aim is to remove the first layer of containment on the rotor, not excessively disturb the braking tracks made by the pads. Twin this action with a solvent to wipe off sand grit, and your rotor is set.


Alternatively, you can use strong solvents on your rotor and pads to clean them. Just be thorough, there's no rocket science here. And be sure to wash off any solvent residue with Hot Soapy water.
While it may not interest you strictly, the best products i've ever gotten for high priority brake cleaning and decontaminating was Isopropyl alcohol and Würth industry cleaner.
Isopropyl being the best for its ease of use, cheap price and lasts for ages.

Finally, if you have been successfully methodical and thorough in your cleaning process Take Note that your brakes might have to wear in again, meaning you may still have no braking for a little while. Don't assume that you've failed in your cleaning process.

-
 
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berty bassett

berty bassett

Legendary Member
Location
I'boro
First off, before validating if your brakes are tip top or skip worthy, you need to make sure they're as tight as they can be. - By that, I mean they have the Least brake lever pull at the handlebars and have the least gap between the rotor and the pads. - This means playing around with your cable slack and your barrel adjusters until you've found a harmonious balance between a Firm brake lever feel and passive rubbing. - The less slack you give the cable (tighter) the more it will move the outboard pad in and vice versa.

You should also ensure your caliper is correctly aligned for this, contaminated pads or nowt, you should have your caliper properly adjusted for whatever is to come.

The easiest way to do this, is to visually gauge that the pads are running in a straight line in relation to the rotor. If they're off-canter then you've got a problem and will need to realign your caliper. - A wildly off balance caliper will make it difficult for your pads to bite as they should.
Anything else isn't going to be causing your current issue.

If you can come close to any of this, you should at the very least be able to lock your rear wheel when riding.

... IF you find that's not the case, then take note of the noise your brakes make when you pull them.

Is there alot of metallic, scraping noises when you brake?
Is it very quiet?

If there's alot of metallic noises occurring and not much braking, continue using your brakes and see if there's any improvement.
Such noise usually indicates fresh rotor and pad engagement, meaning they need to "wear in" before they start becoming effective at braking.

On the contrary, if it indeed is dead quiet and yet no braking then you've got contaminated brakes.

The easiest way to remedy this is to clean them. Thoroughly. Isopropyl alcohol is a highly effective brake cleaner here, because it evaporates.
When you use strong solvents to "de-contaminate" your pads & rotor, alot of people fail to clean off the solvent in question, the solvent then becomes the source of the new containment.

However, a somewhat popular (yet, effective IME) way to clean your pads (pads, not rotor) is to burn them. Burning the first layer of braking material usually expels & evaporates the majority of containment, but would still need a good clean up after to clean any residue left behind.

The rotor would love a once over with a high grit sandpaper. Note, a once over. Your aim is to remove the first layer of containment on the rotor, not excessively disturb the braking tracks made by the pads. Twin this action with a solvent to wipe off sand grit, and your rotor is set.


Alternatively, you can use strong solvents on your rotor and pads to clean them. Just be thorough, there's no rocket science here. And be sure to wash off any solvent residue with Hot Soapy water.
While it may not interest you strictly, the best products i've ever gotten for high priority brake cleaning and decontaminating was Isopropyl alcohol and Würth industry cleaner.
Isopropyl being the best for its ease of use, cheap price and lasts for ages.

Finally, if you have been successfully methodical and thorough in your cleaning process Take Note that your brakes might have to wear in again, meaning you may still have no braking for a little while. Don't assume that you've failed in your cleaning process.

-
wow ! what an answer ! thanks
i watched yt videos about lining the whole lot up with card and pretty sure everything is true - i have set them in the right order almost to the point where they are rubbing . while the cable was undone i pulled it both ways to make sure it was free running , put it back together and i can pull it easy until the pads are firm on disc but still i can reverse the bike when pushing it . i don't really want to change cable an outer as it threads through the frame
dont know what make of brake it is but rest of bike is shimano and its a cannondale synapse aluminium
i got it for touring
when brakes are full on it moves silently so everything points to oil on pads i guess
thanks again for your time and i will let you know how i get on but it wont be till the weekend
 

Tangoup51

Well-Known Member
but still i can reverse the bike when pushing it
thanks again for your time and i will let you know how i get on but it wont be till the weekend

That reminds me, disc brakes are a bit funny when you try to use them in their opposite direction of travel. Try to test the rear brake by putting a heavy hand on the saddle and pushing the bike forward, and apply your rear brake, as opposed to wheeling it backwards.

And no worries, just make sure you take your time and do it when you feel like it. It can be a slow, methodical process, so it's best to have a slow, methodical mindset. Goodluck!
 

mrandmrspoves

Middle aged bald git.
Location
Narfuk
The other possibility is that the rotor and pads were just not bedded in correctly when new.
When this fails to happen the brake will never be as effective as a bedded in unit.
 
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