thuged_out

i have 15% left on my front brakes, can i drive it for another 500 miles? i have to go to morro bay from LA and come back friday and cant replace the brakes before i go.thanx

Lynn

If your car has more than 2833 miles on it, I think we can safely assume that another 500 will be no problem.

What I did was assume that the remaining 15% of the brakes would be completely worn out after 500 miles and used proportions to calculate how many miles it would have taken to wear 85% of the brakes.

x/.85=500/.15

DtS

Lynn's calculations seems to be pretty educated and I think hes assumptions hold true

....Or you can just drive until the brake-warning light goes on.

thuged_out

thanx lynn, its obvious that u know what u r talking about. i have another q. its my first time replacing my brakes and my dealer said that i HAVE to replace the rotors as well with the brake pads. i dont relly know about mechanical stuff, but it seems strange to me that every time i replace my brake pads i have to replace the rotors also. i think he's just trying to make money. he quoted 196 just for the pads and 450 for pads and rotors. i checked the rotors and they look/feel smooth as a mirror. thanx

jl88

The dealer is just trying to make more money off of you.

The general rule is you change out rotors every other time you change brake pads.

So unless you do some heavy-footed braking, there's no way you need to change out the rotors.

Lynn

I agree with jl88. While MB rotors seem to wear more than other brands they shouldn't need to be replace with every pad change. When the time to replace the does come, you might want to look into cryogenically treated (chilled) rotors. They last longer.

peet

Lynn's right. I had cryo rotors on my M3 (notorious for bending them) and they performed better than new (well they were - both).

Mirror smooth isn't necessary a great finish on a rotor too though. So keep that in mind. What you want is something that has a cardboard/back of formica texture. Matt finish.

DO NOT sand with sandpaper... But if you are handy, go with a non-silica based abrasive to remove mirror finish off rotors. Do some research. Brakes happen to be one of the easier DIY projects. They scare the crap out of you the first couple of times - after all this is what stops YOUR car. But now I can almost do brake jobs in my sleep!

Good luck.

P

P.S. This may be a good time for Porterfields!

mleskovar

Rotors have specified wear limits. Measure them, don't rely on any 'formula' to replace them. Although once you have established a wear frequency for your driving style it can hold true.
Surface inspection of rotors for cracks is more important than how 'slick/mirrored' they look. Once I started using Porterfield pads the rotor wear almost stopped...along with the brake dust.
Lynn's calculations are right on and remind me of why I graduated with an English discipline instead of engineering.

afarrar

when the wheels are off, you will be able to see minimum specifications printed on the rotors. measure the thickness of the rotor (be sure not to measure the lip) if either side is below minimum, at the minimum, or .2 mm from the minimum, i would replace them both.