Replace front brake rotors?

[importcar]

140,000 miles on the original rotors. Last resurfaced at 60,000. No weird noises or vibrations when braking. Is it time to replace amyways? I don't have the tool to measure the thickness.

[djb2]

That's a lot of miles on one set of rotors. So yes, they likely need to be replaced.

But the only way to tell for certain is to use a micrometer on the rotor. $10-$20 will buy one with standard (0.0001" on the vernier) accuracy, which is 10x or 100x better than what you need for brake work.

Select a model with squared inside corners, rather than a semi-circular frame. Harbor Freight has a $20 version with a mechanical counter that avoids errors reading the scale. They used to carry a $10 one that was good enough.

Note that most digital calipers or dial calipers won't work for this job -- they have flat measuring jaws. There are ones designed for brake work have pincers to get over the unworn ridge on the rim, but they cost more. If you do get a digital one, make certain that it has a "hold" button because one side always puts the display upside-down.

[DxElite]

Wow, my friend's stock rotors barely even lasted him 90K miles, he just got his last resurfacing done. The guy who did it for him showed him that it was barely thick enough after it was done and that would be the last time. He said that machining it again would make it drop below minimum.

You should ask the guy who machines your rotors what the thickness is. And if it's still above minimum and there isn't any warping, technically you can keep running on them.

Personally, I don't like running on rotors that are close to the minimum.