How often do brake pads wear unevenly?

[JimPghPA]

How often have you seen or have you ever seen disc brake pads where a the inner pad by the piston(s) was worn out, but the outer pad still look good enough that it would pass inspection?

What I'm getting at here is if you look only at the outer pad thickness that is left, how decent of an indicator is that whether or not the inner pad would probably also be good enough to pass inspection without actually looking at the inner pad?

And one other question, if the slide pins don't slide very well isn't it usually the inner pad that ends up getting worn out quicker?

 

[Timmastertech]

Quite often which is why the calipers come off and the pads come out on every PA inspection I perform.

 

[vavavroom]

Well, with a floating caliper the inner pad contacts the rotor first and then pulls the outer pad against the rotor. So the inner pad necessarily wears a bit faster. That's why the wear sensor is usually on the inside pad.

 

[mrbreezeet1]

Quite often which is why the calipers come off and the pads come out on every PA inspection I perform.

That's the best way to do it. Actually a million years ago in PA the state inspection instructor told us we had to do it that way.

 

[JTK]

I would say every time for me. Its not what I would call severe uneven wear, but enough to see by eye.

 

[930.engineering]

.

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[Donald]

I think in the rust belt it probably happens a lot.

My guess is many shops don't take the time to properly clean under the SS clips (sandblast or file) and may wire brush the pin if it's a little rusty rather than order (and wait) for a new pin.

Also some shops using poorly machined pads may file the ears a bit to get them to slide properly in the SS clips. But that filed area may now rust.

I am not a pro and don't have a sand blaster. But it takes be awhile to clean all the rust from the caliper brackets and then the pin & boot.

 

[Aichiguy]

I'll take caliper pins for $400. Equal braking pressure can only be accomplished when your calipers slide freely so check, clean, and lubricate your caliper pins at every pad replacement. Also replace the hardware every time and make sure the ears of the pads slide freely in the hardware.

 

[930.engineering]

I think in the rust belt it probably happens a lot.
My guess is many shops don't take the time to properly clean under the SS clips (sandblast or file) and may wire brush the pin if it's a little rusty rather than order (and wait) for a new pin.

True, it happens. But, many (iron) calipers are partially zink coated (eg most BMW calipers), in particular on their sliding areas and they must not sandblasted, not even treated with a steel brush or even with a file. Use a nylon brush (and some thin layer of antiseize) only or they will inevitably rust even more than before. If you don't have an appropriate nylon brush on hand, just use a toothbrush.
.

 

[Donald]

True, it happens. But, many (iron) calipers are partially zink coated (eg most BMW calipers), in particular on their sliding areas and they must not sandblasted, not even treated with a steel brush or even with a file. Use a nylon brush (and some thin layer of antiseize) only or they will inevitably rust even more than before. If you don't have an appropriate nylon brush on hand, just use a toothbrush.
.

I was specifically talking about the area on the caliper bracket where the SS clips fits. The area either needs to be sandblasted or filed if rust is present. If you brush it with a wire brush or nylon brush you will only polish the rust.

 

[64bawagon]

Up here its usually rust jacking under the stainless clips in the caliper bracket. The 2000's GM pickups were notorious for this since there was little or no corrosion resistance on the original parts.

 

[mrbreezeet1]

I was specifically talking about the area on the caliper bracket where the SS clips fits. The area either needs to be sandblasted or filed if rust is present. If you brush it with a wire brush or nylon brush you will only polish the rust.

I understand what you're saying you need to clean it up and lubricate it underneath the clips to avoid rust jacking but I believe what he is saying (the fellow you responded to that is) is that on those specific calibers that are coated, you don't want to use anything abrasive or you will remove the coating thus promoting rust.
Hope I'm making sense I've been up all night.

 

[KrisZ]

I would say every time for me. Its not what I would call severe uneven wear, but enough to see by eye.

On floating calipers that would be my experience as well. The inner pad being slightly thinner then the outer. It’s totally normal IMO.

 

[Donald]

I understand what you're saying you need to clean it up and lubricate it underneath the clips to avoid rust jacking but I believe what he is saying (the fellow you responded to that is) is that on those specific calibers that are coated, you don't want to use anything abrasive or you will remove the coating thus promoting rust.
Hope I'm making sense I've been up all night.

Well if there is rust under the SS clip it needs to be removed. No matter if the caliper is coated or not. If a nylon brush can do it (doubtful) then fine, otherwise a file or sandblasting.

 

[mrbreezeet1]

Well if there is rust under the SS clip it needs to be removed. No matter if the caliper is coated or not. If a nylon brush can do it (doubtful) then fine, otherwise a file or sandblasting.

I got ya! Both valid points. BUT if there is NO rust then do not abrade those areas, thus you will remove the coating.
Agree?
I don't think too too many are coated though.

 

[mrbreezeet1]

Probably goes without saying, but there should not be a taper either.

 

[Jetronic]

How often have you seen or have you ever seen disc brake pads where a the inner pad by the piston(s) was worn out, but the outer pad still look good enough that it would pass inspection?

What I'm getting at here is if you look only at the outer pad thickness that is left, how decent of an indicator is that whether or not the inner pad would probably also be good enough to pass inspection without actually looking at the inner pad?

And one other question, if the slide pins don't slide very well isn't it usually the inner pad that ends up getting worn out quicker?

On cars in my region: 50% chance of that if the brakes haven't been touched. Which pad wears first depends: usually you end up braking on just the inner pad, especially on rear brakes.

 

[Nick1994]

Here in the desert you can go 20 years and the calipers still have plenty of factory lube and the pads wear evenly.

 

[JeffKeryk]

A brake clean and lube service goes a long way... And quality parts! I am leaning towards factory pads nowadays...

 

[The Critic]

+/- 2mm is totally normal.