Brake pads, what's the paint?

[Andy Doughty]

As the title says

I am determined to improve the pedal feel on my standard brakes and have always suspected that the rears have never been quite right.

Iv'e just fitted new rear discs and am in the process of fitting new Caterham supplied pads.

On the metal face of the pads, that are in contact with the caliper, there is a paint coating that has been applied with a yard brush and has lumps of paint giving it an uneven surface.

What is it for? I guess it may be an any squeal finish?

My theory is that this creates an uneven surface that makes the pads wobble about and make a little bit of slack in the pedal.

Looking at my old pads they were the same and there are marks where the caliper and piston have partly dug into the lumps of paint.

So, any other ideas?

 

Andy D

I haven't tried the brakes yet

[thinfourth]

Its more like a very high temp grease to stop squeal as you guessed

 

 

Out of interest what pads and how much were they from caterham direct as i have always gone elsewhere for pads

 

The happy handle made me do it

here

[Andy Doughty]

TF

They charged 31.26 inc vat and post.

It is more of a thick paint than grease, in fact I have had to file it off to get a smooth finish to allow the pads to seat correctly.

 

 

[Sheds Moderator]

I suspect this is an antisqueal device. I have seen pads with sticky back antisqueal plates. Cleaning it off *may* make your braking that much more solid, though I suspect that in reality the forces involved are so huge that the stuff will be flattened down very quickly. Certainlyt when I've taken any pads off a car the antisqueal material is always right down to the metal where the piston sits.

 

Don't forget to wire brush/emery paper the sliders and smear them with coppergrease, this will help them retract as planned.

[Mark Durrant]

Andy

 

When was the last time you bled the brakes 🤔 I change the fluid in mine annually as I use it on track/sprints and would recommend that you change it every two years if just normal road use. When bleeding the rears it also helps if you operate the handbrake at the same time as this helps to get the last of the air out of the system

 

Mark D

Comp Sec

 

[Andy Doughty]

BOS

Quite a bit of it has come off the old pads but not all.

On of the calipers has a lump stuck on it which the pad was "rocking on"

 

Mark

I bleed them once a year to try to keep all the seals fresh so don't think that's the problem.

 

I will be trying to get it back to in once piece this weekend so hopefully report back

 

Andy D

[susser]

It's an anti squeal compound;

Some pads come with a PTFE shim that does the same job. Once the piston wears/presses through the material then the brakes will squeal again. This will be cured by a (very thin ) coating of Coppaslip or similar (between the pad and piston).

The squeal is a sound produced by the brake pad as it makes microscopically small movements whilst in contact with the disc.

As these movements are very small, they may be taken up by the "elasticity" of the piston, friction material etc. As the movement builds up and the elastic energy stored in the components builds up, then it will eventually reach the point that it overcomes the friction between the pad and the piston. This causes a very small movement between the two until the forces return to the point where static friction takes over and they stop again.

Thia all happens very quickly, in fact at the speed of the frequency of the squeal, although the disc may ring at a harmonic of the frequency.

It's exactly the same thing that happens during the buildup and eventing of you common or garden earthquake. only a bit quicker. oright, a lot quicker.

kind of stuff.

 

PS

Jags used to have a steel ring in a groove around the periphery of the disc. I'm guessing that this was to have the effect of damping out the vibrations as the disc "rang"; it would do the same thing as putting your finger on a bell, for instance.

IMHO