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TL;DR: 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. Here, the pad holders themselves could have been scraping against the disc rotors, which is bad for the rotors (and for reference, the rotors also have a minimum thickness).

You can ask a bike store to perform periodic inspections. Alternatively, many of us learned to read basic vernier calipers in high school, and a pair accurate to 0.1mm isn't very expensive. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.

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.

TL;DR: 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 for illustration.

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, but 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. Here, the pad holders themselves could have been scraping against the disc rotors, which is bad for the rotors (and for reference, the rotors also have a minimum thickness).

You can ask a bike store to perform periodic inspections. Alternatively, many of us learned to read basic vernier calipers in high school, and a pair accurate to 0.1mm isn't very expensive. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.

TL;DR: 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. Here, the pad holders themselves could have been scraping against the disc rotors, which is bad for the rotors (and for reference, the rotors also have a minimum thickness).

You can ask a bike store to perform periodic inspections. Alternatively, many of us learned to read basic vernier calipers in high school, and a pair accurate to 0.1mm isn't very expensive. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.

I stole the image below from the first Google image I found. This isn't a recommendation for this particular brand, it's just for illustration.

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, but 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. Here, the pad holders themselves could have been scraping against the disc rotors, which is bad for the rotors (and for reference, the rotors also have a minimum thickness). TL;DR: they were worn out some time ago.

You can ask a bike store to perform periodic inspections. Alternatively, many of us learned to read basic vernier calipers in high school, and a pair accurate to 0.1mm isn't very expensive. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.

TL;DR: 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 for illustration.

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, but 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. Here, the pad holders themselves could have been scraping against the disc rotors, which is bad for the rotors (and for reference, the rotors also have a minimum thickness).

You can ask a bike store to perform periodic inspections. Alternatively, many of us learned to read basic vernier calipers in high school, and a pair accurate to 0.1mm isn't very expensive. A small step up would be cheap digital calipers that produce automatic readings and can measure to 0.01mm.