So, I'm going to begin the process of changing out my brakepads, and there was a little note in OctaneGuys great brake pad write up there that if my rotors were lipped, I should replace them as well. After reading that, I went out to my car to see what it was like, and low and behold, they are lipped, both front and rear! My question is, how much lipping is too much? Just from feeling it, it seems around a millimeter or so. Should it be more drastic? Should I worry, and replace the rotors as well? This is a purely street car, with occasional canyon runs. I walked around the neighborhood, and started feeling the rotors of cars (I'm sure i looked strange, touching everyones disc brakes). They all have it to an extent, but the newer cars didn't have as much..

My car has around 50000miles, with about a millimeter of lip on the front rotors, and less on the back. Should I be worried when I put new pads in?

 

While it does make getting calipers off a pain, the lip at the edge of a roter isn't a problem per se. Each rotor has a minimum thickness. If the rotor is thicker than this, you can leave it on the car. If it's very close to this number, and you have aggressive pads, you may want to replace rotors as well. If the rotor is scored or wavy, or you just like a perfect surface to bed pads onto, you can have the rotors machined before putting everything back together. There's a place near me that does it for $15 a rotor.

This is caused by pads that have an outer edge that is inside the outer edge of the rotor. All brakes with this geometry will do it. Different pad compounds are more or less aggressive on the rotor material.

Don't worry about it, measure the rotor thickness, and check it against the minimum spec. Sorry, I don't know that for the Mini off the top of my head....

Matt

 

minimum specs for the mini according to the bentley manual is 19mm in the front, and 7 mm in the back

 

Be careful,

Mini rotors should not be machined, if they are below specs or warped they should be replaced.
Turning the rotors is just not a good option as it makes the rotors weaker.

Victor

 

Sounds good, I'll have to check in the morning. Thanks all!

 

So if the rotors are scored but well over minimum thickness, what's the deal? I've never, ever heard that machining to flat was a bad thing if the rotor surface wasn't all it should be. I'm willing to learn more, but why is machining a rotor (as long as the final thickness is above the minimum) a bad thing? I'm all ears.....

Matt

 

I can think of a few reasons NOT to machine rotors:
1) machining off of the hub can create new/different runout, and influence pad wear
2) machining can also bring a rotor close, but not past min thickness, but a few miles can push it past the min thk, and then all sorts of issues can occur
3) machining removes thermal mass, thus making the entire braking system less efficient, and prone to fade
4) machining can exaggerate existing coning issues
these are just the ones off the top of my head, some shops machine rotors on the hub. this is a better practice. rotors are becomming more of a toss-out item, as engineers push them and remove mass already.