Are these pads worn down and should I replace them?
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7And the other side?– NoiseCommented Jan 2, 2022 at 15:20
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3I still think you are showing us the back of the pads, please prove me wrong!– NoiseCommented Jan 3, 2022 at 14:24
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Was this the side that touched the disk? If so, they are either catastrophically worn or have been inserted flipped at 180°.– CarelCommented Jan 3, 2022 at 18:35
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Once again, please add a photo of the opposite face as well. While I think you probably have shown the braking face, we (or at least I) would like to understand what happened and that means seeing the other side. Also, what make and model are the brakes? They should have some text on the mechanism somewhere. There are a few different brakes using pads that look a lot like this– Chris HCommented Jan 4, 2022 at 13:46
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1@JoeK I don't have pictorial proof, but 100% sure this was the side facing the rotor. And yes, even I suspect this wasn't the correct orientation. The backside looked like what should have been the correct side. I re-installed them that way; the brakes work like new– Harsh VardhanCommented Jan 6, 2022 at 9:30
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3 Answers
TL;DR: if the original photo shows the pad side of the holders, they were worn out some time ago.
I stole the image below from the first Google image I found. This isn't a recommendation for this particular brand, it's just to illustrate what the pads should look like.
Basically, disc brake pads have a metal backing plate, and the actual pad material is bonded to the plate. Manufacturers will specify a minimum thickness of the backing plate + remaining pad material, which you would measure by calipers. In contrast, with rim brake pads they can just mold a wear line on the pads. On disc brake pads such a line wouldn't be easily visible.
The pads in the original photo don't look like there is any pad material left at all, rendering the question of minimum thickness moot except for future reference. If the photo was of the pad side, then the pads were completely worn out and the metal pad holders themselves were scraping against the disc rotors. This is bad for the rotors (and for reference, the rotors also have a minimum thickness). If the photo isn't of the pad side, then again, you will need to have the pad thickness checked with a caliper to be sure.
You can ask a bike store to periodically inspect your pads and rotors. Alternatively, many of us learned to read basic vernier calipers in high school. A pair accurate to 0.1mm isn't very expensive and has sufficient precision to check wear. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.
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2The scratch marks on the OP's picture do not correspond to what a "working" surface of a break pad would have after some use. They rather look like a "piston" pad side would look like. Even fully and catastrophically worn pads will have the "linear" scratch marks. I still think that the OP's image does not show us the braking side, meaning that it is impossible to estimate how badly these pads are worn. Commented Jan 4, 2022 at 7:26
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@GrigoryRechistov except for the left edge of the top one I agree, but that reminds me of my own crash-inducing wear, combined with the last of the pad proper coming off the backing once it got too thin to hold its structure.– Chris HCommented Jan 4, 2022 at 13:36
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1@GrigoryRechistov Good observation. I've edited the answer somewhat. I was thinking that the circular dots on the holders may have been where the pads attached to the holders like in the top right pic in your answer. Commented Jan 4, 2022 at 16:16
I wanted to share another picture of how new vs. worn vs. catastrophically worn pads would look like. These ones are from my own collection. All pads are lying with the "working" surface up, and the backing plate down.
The two pads at the bottom of the picture are brand new and never used. Thick layers of braking material have no oriented scratch marks and have a somewhat grainy appearance.
The pad at the top left is worn. The braking material is apparently thinner, although without a measuring tool it is impossible to say how much. There are horizontal, slightly concentric scratch marks on the surface of the pad where the brake rotor touched it. There will be no such marks at the opposite side (on the backing plate), likely some irregular surface wear or even rust instead.
The pad in the top right corner is catastrophically worn out. There is no braking material left on it. The backing plate (with its six holes) is visible. This pad should have been replaced quite some time ago.
answered Jan 4, 2022 at 7:41
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Regarding your first point, the other side (which probably was the braking side) on my pads looked a lot like that...one of them had faint circular marks, but I suspect that was from the piston going in and out. So yeah...the factory must have flip-fitted them. Commented Jan 6, 2022 at 9:43
Get new pads. Get enough for both wheels, possibly with a spare for next time.
Fit them, test them, and then check the brake on the other wheel (I prefer to do unfamiliar or significant brake tasks on one wheel at a time, testing thoroughly before doing the other wheel)
If this is really the braking face, the inside, I'd be surprised if you had any ability to stop using that brake. The brakes I've dealt with don't have enough adjustment, at least on the fixed pad, or without improper use of the adjustments on the moving one to wear the pad material right down to the backing. Combined with the wear pattern not looking like the right sort of scratching, what I suspect has happened is that the pad was worn down very thin and the last of it failed and came off the backing. Thin enough and it will be flexible and prone to tearing.
Some pads that caused me to crash badly show similar edge wear on the moving pad - I'd hazard a guess that your top pad is the outer/moving one and the bottom one is fixed. When the rotor has to flex too much, the edge of the pad nearest the hub will make more contact than the opposite edge. Here are mine:
