can rotors on a mazda millenia be cut or must they be replaced
They should be replaced with rotors that meets or exceeds the Original Manufacturers Specifications.
The reason is, in order to remove any run-out or grooves from the rotors from machining will probably bring them close to the minimum thickness. This leaves the rotors more suseptable to warping. Also, the machining equipment has to be well maintained and calibrated in order that a good cut be made on the rotors. But the other reason they should be replaced is, even if they get a good cut on the rotors, they’ll never be able to leave the proper machining finish on the rotors. And the finish on the rotors dictates if the brake pads properly embed themselves into the rotors. And if that doesn’t happen it can result in brake noise.
Every brake job I do, the vehicle gets new OEM spec’d rotors.
That makes sense, I was trying to save a few in these tight times but thank you very much.
My opinion is that it’s more of an economic issue than a quality control one as the cost of machining a rotor may be near what the cost of a new one is.
As to machining rotors, that is a perfectly legitimate and acceptable method of brake repair that will give no problems if properly done.
Properly done means no going under the minimum thickness, sharp cutting bit in the lathe, rotor chucked into the lathe properly, and no getting ham fisted with the cuts being made on the rotor.
In regards to the latter, this means taking off a little metal at a time and when performing the final cut use a chatterband on the slowest speed. This will provide a surface equivalent to a new rotor. If a rotor has a rough surface after being cut then someone either did not know what they were doing or didn’t care.
And I’ve seen some of those cut for 10 bucks at the gas station rotors. They’re cutting way too much metal at one time and not performing a slow cut at all.)
Done more than I can remember with no problems.
I was trying to save a few in these tight times
There is little if anything to save. The cost of machining is likely to be close to the cost of new and then you would find they had less life than the OEM. Modern designs make for lighter rotors that are really only good for one go around. But they do mean lighter weight on the car which means better comfort.
I keep it simple. If there is no vibration when braking. I just reuse rotors as is and slap pads on them. If the rotors are thin, or is vibration, or other rotor issues, I replace them.
I never cut rotors. The cost to cut them is usually the cost of new rotors (or close to it). Regardless, cut rotors are thinner. Also rotors take a lot of punishment. If you get 30-100k (or more) on a set of rotors, they owe you nothing. You got your moneys worth out of them. Just buck up and replace them if need be. The brakes are the single most important part of the car. This is NOT the system to start being cheap on!
If they are still fairly thick and flat - reuse. If they are worn, not flat, otherwise defective - replace.
Use quality parts. Generally OEM are good. there are good aftermarket parts though
To the excellent advice posted so far, I want to ask about another detail–
Since the Millenia has not been manufactured for at least 6 years, can you tell us if these rotors are the originals?
If they are, indeed, the originals, then there should be no question about replacing them, rather than machining them. And, even if they are not the original rotors, you have to bear in mind that once rotors are machined, since they are thinner than they were originally, they will be much more prone to warping from heat.
In many cases, people have rotors machined and then wind up complaining about brake pedal pulsation a few months later as a result of the rotors having warped. The result is paying for machining the old ones and then also paying for new rotors. Very bad economics, IMHO.
Even if you need to save money, I don’t recommend that you have those rotors machined.