Tips for checking breaks

[maxslomoff]

hello,
i've been curious about my brakes lately.

i have a 325is. the back brake disks are smooth and flat and when i run my finger along the disk to the edge there is only a small lip at the edge of the disk. I assume this lip is made when the break pads wear away a strip of metal on the disk but leaving the edge untouched.

my front disks on the otherhand seem slightly wavy and they have lines or indentations that i can feel with my finger and the lip on the edge of the disk is much more pronounced.

does this mean i have bad front disks?
how do you check your break pads?

is there anything else i should do to inspect my breaks?

thanks for your help.
max

[Torque]

The indentations and grooves are not good. You should get new rotors when you have that.

I don't understand what you mean by checking the pads. There are 2 things you can check. You can take them off and check that they are wearing evenly on all sides (if they are, good; if not, you have a problem somewhere). You can also just look at how much of the pad is left, but our cars have wear sensors so you really don't have to worry about that, as the car will tell you.

Hope that helps.

[Dirty Martini]

Agree with Torque, you absolutely need new rotors next brake job if you have a pronounced "lip" at the outboard edge. And if they're "wavey" to the point that you can feel it with your finger, I'd say the sooner the better on that brake job. New pads, new rotors, good to go.

[4evrwyntr]

Yes, the rotors should be all smooth.... unless you have slotted rotors .
I wouldn't bother with the brake pads, as anything that is wrong with the brake pads would probably show up on the rotors... or on the wheels (too much brake dust) and other things, like driving quality (with a frozen caliper) or smell (again, frozen rotor). If you're pads are going low, they will do so in pairs, and your car will warn you.

Unlses you got a bad brake sensor.

Essentially, what they said.

[maxslomoff]

interesting you mention smell 4evrwyntr,
sometimes i get a horrible smell from my car after i drive, but i wasn't sure it's the brakes.

also, i do get a lot of brake dust on my whees that is a pain to clean off, but i thought this was inevitable. is it not?

[4evrwyntr]

I know the m3's make a lot of dust...

You might want to check that smell - make sure it is burning brake pad if you're afraid of the brakes; you can usually trace it to one of the pads. Smells like burning metal, if you've ever smelled that before.

[bob318]

I had to lock up my breaks today due to going way to fast over a hill and commin up behind a pig. I locked them up and whiped it around and took off in the other direction. I went to break for the stop sign to see if i was good to roll it and i barly had breaks it seemd like.The pedal was just really hard to press down and I had maybe half the breaking power. So i got away from him and slowed down to check my breaks and they just didnt seem to have the breaking power i did previously. So i got home and checked one more time and now they seem fine. has anyone experinced this? Is there an explanation for this?

[tomctx]

Got them too hot, they faded. When they time to cool off, they returned to normal.

[bob318]

thanks, thats kinda what i figured.

[4evrwyntr]

Unless you got them too hot and they glazed...

[bob318]

glazed? there kinda fucked up now. I dont know why i would have messed them up by locking them up once in the cold weather.

[4evrwyntr]

They should only glaze if you're racing... but...

[kyle_baker]

definitly need new rotors, how are the pads?

[maxslomoff]

what will happen if i postpon getting the rotors?

[maxslomoff]

also, is it normal for the rotors to rust? i think this is why they've eaten away so much. often i'll see a coat of rust on them, but after you use the braked a bit, the rust wears away