Since I've talked about replacing my rotors, I've been doing some reading and the subject of "run out" has come up numerous times...does someone want to explain what it is and how to check it to me?
 
 In simple terms that even I can understand...

Jim, "runout" is the term used for when a rotor, or other rotating object, is not turning perfectly parallel on it's axis. Think of a bent wheel on a car. If you watch it from behind(or from the front, but it's safer from behind...you won't git run over dat way!), you can see it "wobbling". Rotor runout is basically the same thing, only not as visable.

A rotor can have a runout problem for a couple of reasons. The rotor could be warped, or the surface of the rotor that sits on the hub could have dirt, rust, or any other kind of debris that would keep the rotor from seating flat on the hub. Before checking for rotor runout, always make sure the bearings are good, and are tightened to specs. Loose bearings will give you a false reading when checking runout.
Also, if the rivets have been removed, be sure to install at least three of the lug-nuts back on the studs, to hold the rotor tight against the hub. Turn the lug-nuts around backwards, putting the "flat" side against the rotor.
To check for runout on a disc brake, you need a dial indicator, preferably one with a magnetic base. You would set the indicator on the surface of the rotor, about one inch in from the outer edge of the rotor. Then you "zero" the indicator. Once that is done, you turn the rotor by hand, all the way around, watching the indicator for movement(runout). The factory specs for Sharks is .005". That's NOT a very big number!!!
It is important to keep the rotors running square/straight on Sharks, due to the calipers being fixed in position. If there is excessive runout, the pistons in the calipers will pump in & out, sucking air past the seals in the process. This creates air in the system, which means...no brakes!

HERE'S a pic that may help explain...I hope.

When replacing rotors, always be sure the surface of the hub is CLEAN, and the surface of the rotor that sits on the hub is CLEAN! Sometimes, if you have a rotor that has a bit too much runout, you can take it off, and reposition it on the hub, and get a better reading. You have 5 different positions to use on a five-lug rotor. The only time you cannot do this is on the REAR rotors...there is a hole in the rear rotors that you must line up on the hub. This hole is for access to the e-brake adjustment. If you install the rotor off by a hole, you won't be able to adjust the e-brake without removing the brake calipers, and the rotor.

(Long winded, I'm sure. Easily understood? I don't know...ya'll know I'm not very good at 'splainin stuff like this.)