Cursed brakes

aeroart

Hey guys, I am fairly new in this discipline, so I made a mistake, due to the fact that my brakes were making a screeching noise I decided to put some oil on them, and so that happend. I tried everything, baking the pads, cleaning the rotor and the pads with acetone, then I bought Muc OFF disk brake cleaner, still didn't work. So I bought new pads, that didn't work either, so I bought a new rotor, right now with both a new rotor and new pads my brakes still don't work, the disc just slides through.

This is what I currently have:

Brake pads: http://www.halfords.com/webapp/wcs/stor ... yId_165608

Rotor: http://www.amazon.co.uk/PROMAX-ULTRA-ST ... 086&sr=8-2


Thanks anyway

nicklouse

so you tied to use a new rotor with contaminated pads. buy some we pads. while waiting for the pads to arrive. clean the rotors and the callipers with some cycle brake cleaner.


never let oil or brake fluid need the pads.

aeroart

nicklouse wrote:

so you tied to use a new rotor with contaminated pads. buy some we pads. while waiting for the pads to arrive. clean the rotors and the callipers with some cycle brake cleaner.


never let oil or brake fluid need the pads.

No, I changed both the pads and the rotor and It still doesn't work. The pads are brand new.

supersonic

The old rotor contaminated the new pads. The new pads then contaminated the new rotor.

Buy new pads, clean the rotor and start again.

aeroart

supersonic wrote:

The old rotor contaminated the new pads. The new pads then contaminated the new rotor.

Buy new pads, clean the rotor and start again.

Ok, whats the best way to clean the rotor?

cooldad

Isopropyl alchohol (IPA), Have a look on Superstar for the pads. Much cheaper.

Chunkers1980

IPA

cooldad

Chunkers1980 wrote:

IPA

Yeah, brain fade fixed. Ta.

bennett_346

Isopropanol is good but for brakes i've had better success with contact/brake cleaner.

Chunkers1980

I've not used either on mine. They work just fine.

supersonic

Some auto brake cleaner contains oils/anti rust stuff. Be careful.

bennett_346

Chunkers1980 wrote:

I've not used either on mine. They work just fine.

Good for you, doesn't really help the OP though does it, smart arse.

cooldad

Chunkers1980 wrote:

I've not used either on mine. They work just fine.

Presumably you haven't oiled your brakes.

Chunkers1980

No, because that'd be a silly thing to do.

What I was trying to say, badly, is that in most cases just use them and it'll sort most things out.

bennett_346

Not really, ruined pads are ruined pads and it's pointless spending more money on another set just to contaminate them again. For the sake of £5 and 15 minutes don't you think it would be more sensible just to clean them?

It doesn't burn contaminants off for hours anyway.

aeroart

So, I should clean both the brake pads and the rotor with IPA?

Btw thanks guys, I wasn't expecting so many posts .

bennett_346

brake pads bin if theyre contaminated, rotor clean

bikaholic

Remove contaminated pads. Clean rotor and caliper with warm soapy water (I use dilute fairy liquid and scrub with jif, then rinse with water).

Grip a pad by its metal backing inbetween some pliers and hold over the flames of a cooker gas hob (or blowtorch), pad side down and burn off the contaminant.

The pad will catch fire, then give off smoke and then change colour. Remove from the flames when this happens and set it aside for it to cool down.

Then sand the pad using a circular motion to remove a thin layer of the crusted top surface.

When all contaminated pads have been treated, reinstall and re-do the bedding-in procedure.

allthegearnoidea

for the sake of a fiver on superstar for new pads dont bother with trying to burn off the contsminents! it may work, it may not, more likely it'll weaken the bonding between the pad and backing!

as above, New pads, clean the rotor with ipa, rub it down with some sand paper to take the shiny surface off, then wipe over again with ipa, clean any traces of the oil away from the caliper, install New pads, put all back together, you'll need to bed them in a bit so dont expect the first few brakes to be over the bars esque, but one bedded in they should be fine!
Keep the oil away! quite often sintered pads will squeel whn cold, they work best when warmed up, new pads will often howl a little during bedding in, but once done will quieten donw!

bikaholic

allthegearnoidea wrote:

for the sake of a fiver on superstar for new pads dont bother with trying to burn off the contsminents! it may work, it may not, more likely it'll weaken the bonding between the pad and backing!...

Let's rephrase that, "For the sake of a fiver and a 3 day wait...".

It means that you will not get to ride the bike any time soon. The fix I described will cost almost no money and take just 30 minutes max.

Applying some bikaholic logic to why burning off the contaminants work:

Disc brakes work due to friction between the pad material and the rotor.
Friction causes heat and a rise in temperature of both components.
Therefore, the pad material and bonding agent must be designed to still function under these conditions.
Thus, providing the heat via a flame in place of friction should not compromise the pad.

Try it and see.

cooldad

bikaholic wrote:

allthegearnoidea wrote:

for the sake of a fiver on superstar for new pads dont bother with trying to burn off the contsminents! it may work, it may not, more likely it'll weaken the bonding between the pad and backing!...

Let's rephrase that, "For the sake of a fiver and a 3 day wait...".

It means that you will not get to ride the bike any time soon. The fix I described will cost almost no money and take just 30 minutes max.

Applying some bikaholic logic to why burning off the contaminants work:

Disc brakes work due to friction between the pad material and the rotor.
Friction causes heat and a rise in temperature of both components.
Therefore, the pad material and bonding agent must be designed to still function under these conditions.
Thus, providing the heat via a flame in place of friction should not compromise the pad.

Try it and see.

Without wanting to sound condescending, you are advising someone who oiled their brakes to play with fire and possibly comromise the integrity of what's left of the pads. I think you will find that the heat generated by braking and the heat achievable from a gas flame could be different.
Just buy new ones and wait a few days. The old ones are to all intents and purposes fubared.

aeroart

I burnt the brakes, then sanded them down a little, cleaned the rotor. It works fine!

Thanks guys

cooldad

cyd190468 wrote:

If you stay away from organic pads (ie use metal pads they don't absorb contaminants). This means if you do get something on the disc you can just bomb down the nearest big hill and drag your brakes until the disc gets hot enough to burn the crap off. Of course, I live somewhere hot and dry, this method may not work in old Blighty.

They will still get contaminated - they're not solid steel.

YeehaaMcgee

bikaholic wrote:

Disc brakes work due to friction between the pad material and the rotor.
Friction causes heat and a rise in temperature of both components.

Very nearly right. It's almost just semantics.
Disc brakes work by converting movement into heat. Heat is not a by-product, it's the actual goal of their function.

konadawg

YeehaaMcgee wrote:

Very nearly right. It's almost just semantics.
Disc brakes work by converting movement into heat. Heat is not a by-product, it's the actual goal of their function.

I used to think that, but then said to myself, this could not be right i.e. not all the energy is converted into heat, what if, rather than a brake pad rubbing against the disc, one would have a bolt went through it and that immediately stopped the wheel's rotation, and the wheel was a cogwheel on a rack, so the deceleration was just about instantaneous. So no heat.

Energy can't be created nor destroyed - and equal and opposite reaction and all that - I figure that when one accelerates, the entire planet reacts by "relatively" accelerating in the opposite direction, and when one brakes, it accelerates in the same direction... Of course the masses are incomparable, so the planet's reaction is utterly, utterly, unfathomably and unmeasurably infinitesimal...

Should I be doing something better with my time?

YeehaaMcgee

konadawg wrote:

YeehaaMcgee wrote:

Very nearly right. It's almost just semantics.
Disc brakes work by converting movement into heat. Heat is not a by-product, it's the actual goal of their function.

I used to think that, but then said to myself, this could not be right i.e. not all the energy is converted into heat,

Heat and noise.
If you were to immedaitely and suddenly stop the wheel from rotating, then the job of dissipating your kinetic energy is passed on to your tyres, which will invariably fail, causing you to skid.
Skidding is far less efficient than not skidding, so not much heat energy is generated, and so it takes longer to slow down.

supersonic

ne would have a bolt went through it and that immediately stopped the wheel's rotation, and the wheel was a cogwheel on a rack, so the deceleration was just about instantaneous. So no heat.

There is heat (maybe sound too), but not much. A 1kg wheel rotating is not comparable to a 100kg of rider and bike stopping.

The Rookie

Exactly, do the same when your riding and the spokes will abosrb a lot of energy (getting hot in the process) as they destoy themselves, then the front wheel will lock, if your lucky it will slide, if not you make like superman - well for ten feet that is (no I don't want to do it again, the flying is OK, it's the landing that hurts, lots of heat gets generated between your skin and the road!)

Horton

I'm not entirely convinced that a mountainbike disc brake will generate temps of around 1000 degrees Centigrade(gas hob) given that this is the highest temp an F1 brake can handle. Pad Material and bonding agent are designed to work under normal braking conditions. I can assure you that sticking the pad in a flame would not be considered normal conditions. It may, or may not compromise the pad, but for the sake of a fiver and a 2 day wait (all it has ever taken for Superstar to get me stuff in the past), why would you want to find out the painful way that you did compromise the pad? (Going downhill fast, apply brakes, pad disintegrate and either jam up a disc(unlikely) or leave you with no braking at all) Not worth the risk IMO - just clean the disc and get new pads as the others have said

YeehaaMcgee

Horton wrote:

I'm not entirely convinced that a mountainbike disc brake will generate temps of around 1000 degrees Centigrade

Er, did anyone say it will?
I can guarantee you that they will never reach 1000 degrees (celsius) in use on a mountain bike.

Horton

It was a reply to

bikaholic wrote:

Disc brakes work due to friction between the pad material and the rotor.
Friction causes heat and a rise in temperature of both components.
Therefore, the pad material and bonding agent must be designed to still function under these conditions.
Thus, providing the heat via a flame in place of friction should not compromise the pad.

Try it and see.

The suggestion being that Bikaholic considered putting the pad into a flame generates the same heat conditions that braking would. I think it's safe to say we both agree that it won't. What I completely failed to notice was that there was a 2nd page of the thread which I can only attribute to being ever so slightly dickish this morning. Apologies