About Machining Rotors

Video Transcript

MARK BLOCKER: Hello. In this segment, we're going to cover removing the rear brake rotors. As any time you do work on the brake system, if you replace the brake pads, you need to have the rotors checked, machined and order to replace, if necessary. And just about any local parts houses can do this. They have machine shop services. If you call in advance and set up a time, you can usually drop them off. They can do them on the spot. They can be done anywhere for 15 to 30 minutes, just depending on the type of equipment they use. It can be done relatively quickly, so it doesn't have to put a major delay on your repair project. But it is something that's necessary to have done, and very few individuals would own their own brake light. Basically, what they're going to do is take a caliper measuring device and they're going to find the grooves on here from the wear, and they're going to go to the narrowest groove or the deepest groove and measure the thickness of that rotor at the deepest the groove. And if the thickness of the rotor is within the operating tolerances of thickness designed for the specifications of the rotor, they'll going to go ahead and machine it down where it's perfectly smooth and they always have to go as far as the deepest groove. So, that's where they measure. They have to determine the rotors serviceability. If it's ground down to the point where it can't be turned down safely and still within its tolerances, then you'll have to replace the rotor. And what happens is you see the thickness of the rotor, as the rotor wears down from the friction being applied to it, it becomes narrower and narrower. And they have to maintain a minimal thickness in order for it to dissipate the heat that's built up from braking correctly and prevent the rotor from warping. Also, the piston and caliper assembly is designed to certain specifications. As the rotor wears out, the pads themselves have to go further and further together and closer together, that makes the piston come out further and further inside the caliper. It can only come out to a certain point before it doesn't have enough surface area to seal anymore or maintain its integrity from twisting. And that's the reason for the minimum thicknesses are, and if it's machine down beyond that or you neglect or don't take it in and have it machine and it wears down beyond that point, it can get to the point of safety where the piston and the caliper push it out so far to keep that contact that it can't stabilize itself in an emergency braking situation or in brake supply, the piston can bind and cause the brake system to lock up or fail or lose pressure. Either way, it's extremely hazardous and bad situation. And it's really important to keep the rotors within their serviceable tolerance levels. And each time you replace them and put your pads on, they're re-machined so they're perfectly smooth again and flat. Rotors and metals are actually a real porous surface, if you look at it magnified several times. The other thing that happen is the friction compounds used in brake pads are being embedded into the surface of the rotor and that causes a glazing action to occur, and it decreases the braking friction that can be applied between the brake pad and the rotor, and causes more heat and it reduces braking. So, that's why it's important for you to keep the rotors serviced when you do the pads. Make sure that they're check in machine as necessary. For the training video, we're just going to go ahead and reassemble at this point so that we don't have no loss in time and a delay in the training process. In this segment, I just explained to you the various reasons that you need to machine your rotors and the procedure for doing that. So, watch our next segment and we'll cover removing the rotors.

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