Turn, Turn, Turn that Rotor
by Pat Goss
Brake pads are consumable parts - they wear out. And they should be checked whenever you have any change in the way the brakes sound, the way the brakes feel, or the way the brakes perform. And they should also be checked once a year or every 12,000 miles. That inspection should include more than just looking through the little hole in the brake caliper to see how much brake pad material is left.
If we look through the hole in the caliper on this brake pad, we’d see what looks like a really healthy pad. But if we inspect it properly, we see that we have this great big ridge, which is what we’re seeing through the caliper and in reality the brake pad is worn out. So you always have to physically inspect them.
The rotors themselves should be machined to make the new pads seat in properly. Or you may have damage to the rotors. But when can they or can’t they be machined? Well to figure that out, you need a brake micrometer. Now this is a very simple tool that gets positioned over the rotor. It takes a measurement in thousandths of an inch as far as the thickness is concerned that’s compared to the allowable minimum thickness of the brake rotor and it’s either good or it’s bad. It’s real simple.
But suppose it’s good and you’re going to machine it? Now there are a couple of things that you need to be aware of. Most manufacturers have stated that you no longer machine a brake rotor off the car. It has to be done on the car such as what we are doing here. Now there are different types of machines to do this.
This one is by Hunter and it has a very unique feature. As you’re machining a rotor, the cutters move from the inside to the outside. And they form a line, even though you can’t see it, that line is much like grooves in a record. And it can produce noise just like a record produces noise. So those lines have to be done away with.
Well, the Hunter unit does away with them as it’s machining the rotor because it gets this gentle rocking motion to it that completely eliminates it. Now if you don’t have your rotors machined on a Hunter lathe, then it will be necessary to use a brake grinder. Now the rotor is still turning, the brake grinder is held up against the surface of the rotor and that grinds away that record type of groove that’s in there and makes the pads seat in, keeps them quiet.
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