mpalsal

Is it when there is about 25% left? Translate in to mm?
How thick is the brand new brake pads?

thx.

ygmn

what do you have?
what options as they have different brake packages.

Why does it matter?
what are you trying to figure out?

mpalsal

Hi, 2012 E350 Coupe, base, no 4matic. Just trying to learn about brake wear, when to change the pad, should I wait for the warning light or should I go ahead with visual inspection.

chassis

Wear indicator turns on with approx 2.5mm pad thickness remaining. New pads are in the range of approx 10mm-12mm thick, depends on brand/model.

ChrisHimself

Different pads have different depths for the sensor mounting point as well as OEM/aftermarket pads having different thicknesses and different shims. Some use steel, some use rubberized steel, different thicknesses, etc. It's usually 25-30% in my experience. Porsche/Audi are the same way.

You will notice the noise and brake fade long before the sensor hits, few people with mechanical empathy let it get that bad. My rule of thumb at the shop is when the pad gets to about the thickness of the backing plate, you should consider brake service soon. It's the easiest check. Always replace rotors with the pads, and consider high quality ceramic pad replacements if you want to extend rotor and pad life as well as pedal feel.

Use a high quality high carbon brake rotor, Brembo, Pagid, ATE, MB Genuine is actually pretty cheap on some applications, Zimmerman. Sensors should be Pagid or BOWA. Fluid should be done every 2 years, less if you drive fast. Clean lubricate everything, OEM pads produce a ton of dust. If you can buy new brake hardware, please. It'll prevent the pads shifting around in the caliper, producing annoying clicking noises.

ygmn

change them just before warning light is best.

or when you have brake pulsation or other braking issue.

mpalsal

Thank you for your reply, what is the reason behind the rotor every time you replace the brake pads?

ChrisHimself

brake rotors have gotten thinner so they can cool themselves better internally (they're cast with incredible internal vaning) and weigh much less than they used to. It's why we can't surface grind them the way we used to (never do that) because in the old days when we basically used cheese to stop cars we would have a ton of rotor life and swap pads 2-3 times. These days the pad material uses bonded copper and iron which don't compress (offer great brake feel), hold a ton of heat so you can stop to your hearts content while racing, have great cold braking characteristics, but they cut rather deep grooves into the rotor over time, and you get a pronounced lip. These are Porsche rotors but theyre made of the same material and use the same friction compounds as we do. Second are MB rotors which reinforce that we're all kind of the same.





The physics behind what make German cars so good is pretty fascinating. Your average chinese-made Pagid rotor goes through way more testing (has to be ECE-R90 and TUV approved) and service than your average Toyota part while costing less money, and being installed on much faster cars.

mpalsal

Thank again for such educational explanation. Hope others will benefit from this thread as well.