I saw a post today about brakes, and it made me realize how little I know about them. So I googled brake tech, and started reading, and there were some terms I didn't know, and couldn't find anything on. One of them was "Rotor Runout" I found a pic that trys to explain it, but there is no text as to what I'm looking at.



so exactly what am I looking at and what is the rotor run out?

 

http://www.aa1car.com/library/2003/bf110322.htm

Worn bearing could cause rotor runout even though it's not listed.

 

It looks like the sketch above is missing the axle center line about where the word 'Rotor' is. If you put a dial indicator perpendicular to the rotor face at the rim and then turn the rotor the dial indicator would show an in and out movement. Often this is called a warped rotor.

Here is an excellent write up about warped rotors by Carroll Smith http://www.stoptech.com/tech_info/wp...rakedisk.shtml

Here is the URL for all of the tech articles at this site
http://www.stoptech.com/tech_info/te...e_papers.shtml

 

Ok, now that confuses me even more. That first article says that a bench lathe can cause rotor runout, but that turning the rotors on the car prevents that. Please explain, cause it sounds to me, that it is the rotors not being perpendicular to the axle line. Like the are mushrooming out or in, as shown in the pic, it looks like the rotor is mushroomed out away from the car, if the car was on the left side of the pic.