Brake rotor wear

[Yellow Saddle]

Thanks for the photies. That disc is still safe but you will find that when you fit the next set of pads, they won't contact properly. Although it will still give exactly the same stopping force in spite of the reduced contact surface, it will be impossible to bed the discs in properly and they will probably be noisy throughout their life. Next time you change the pads, treat yourself to new discs.

 

[winjim]

Thanks for the photies. That disc is still safe but you will find that when you fit the next set of pads, they won't contact properly. Although it will still give exactly the same stopping force in spite of the reduced contact surface, it will be impossible to bed the discs in properly and they will probably be noisy throughout their life. Next time you change the pads, treat yourself to new discs.

I'm guessing several iterations of ever so slightly misaligned pads have caused that concave wear. You say it's safe and I've no reason to doubt that, but for reference, how worn would it need to be for you to declare it unsafe?

 

[Yellow Saddle]

I would guess about 0.6mm remaining would be pushing it.
As for the concave wear, it is not your fault. All discs wear like that.

 

[huggy]

I don't have disks, but why don't the manufacturers put wear indicators on the swept area? You know little drill holes. I have them on my tyres and rims and car disks, on those there's 2 one for nearly worn and the other for worn out.

 

[winjim]

I managed to dig out that micrometer at work so I've measured the rotor. The worn part averages 0.037" or 0.89mm, while the unworn part averages 0.073" or 1.75mm. So my rotor is about 50% worn.

More interesting, vintage tool fans, is the micrometer itself. It's a Tesamaster 0 - 1". Calibrated in inches obviously, due to its age. To read it, there's a screw gauge for the tenths, followed by some digits which flip round like the date reading on a wristwatch for the hundredths and thousandths, and then of course a Vernier scale for the tenths of thousandths. It's a lovely piece of equipment and I really like it. I must remember to return it to the bottom of the unused toolbox whence it came.