I don't have a percentage, but seems to be pretty consistent for all the
Benz' I've worked on... the light always comes on right after you pass the
point that those little brake wear sensors will come out without breaking.
I could usually get at least 2 of them out on each brake job, but always
ordered 4... Most people 'brake on through' the sensors before they do
anything about it. Unless the style has changed in the last couple years,
the wearing part of the sensor is *maybe* the diameter of a wire
coat-hanger. So, that's the thickness of the brake pad stopping material
when the light comes on. You still have a good thick bit of metal once
you're past the pad lining... and then the piston of the caliper after
that... not to worry.
I would say you are at the last 10% of your brake pad. I wouldn't dare
continue driving for extended time because sometime the brake rotor wears
unevenly... and that 10% margin is just near the end if the rotor is worn
So, then answer is... if the light comes on... better get it changed very
I have a 1997 E320 and my experience, although a different car, is that
you don't want to wait. Have the pads replaced within a few hundred
miles, if that. You are less than 1/4-inch of pad when the light comes
on. If you wait you not only have to replace the pads, a simple job, but
the rotors as well.
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