Solving Brake Problems
If you find that you have warped rotors or drums, there is a low-cost alternative to replacement. Machining your drums or rotors can bring back a warped part and extend its service life. To do this, you need a piece of equipment called a brake lathe.
You can mount your warped rotors or drums to this machine and it will actually cut a new surface into the drum or rotor. These machines aren’t normally available to the DIYer, but your local auto parts store might have one. If they do, you can remove the rotors or drums from your vehicle and take it to them in to have them machined. They usually charge a flat fee for this. Once your rotors or drums have been machined, you can reinstall them on your vehicle with new friction material and be on your way, vibration-free.
It might not be possible to machine your rotors or drums, however. Sometimes there’s not enough metal remaining in the part to perform a machining. To make this determination, the person doing the machining needs to measure the thickness of the metal remaining on your drum or brake disc. If it falls below or close to the minimum, they cannot machine the part. These measurements are often stamped on the outside of the part and are considered the minimum thickness allowable by the manufacturer. Here’s a video that explains this in a little more detail.
One last note on machining. It’s a little known fact that you should machine new rotors or drums before installing them on your vehicle. Check with any rotor or drum manufacture and they recommend this practice. So don’t think that installing new rotors or drums will solve a vibration problem, sometimes it doesn’t. Manufacturers cover their collective butts by stating that you should machine rotors or drums before installation for best results.
There is a machine that is capable of machining brake rotors on your vehicle. This is the best way to machine rotors, as it eliminates any imperfections in the brake rotors or any runout in the bearing/hub assembly. The smoothest brake jobs I’ve done have been with one of these tools.
Another reason to employ this tool is when you have what is referred to as a captive rotor. A captive rotor is a rotor held on by the hub assembly. These rotors cannot simply be removed after the wheel and brake caliper have been removed; you also need to remove the hub assembly to remove the brake rotor.
This is often a labor-intensive process. If you or your shop has access to an on-the-car brake lathe, you could machine the rotors right on the vehicle without removing them if there was enough metal left. Early 90s Honda Accords are a good example of a vehicle with captive rotors. Here’s a video demonstrating the process of replacing those rotors just so you get an idea of what’s involved in their replacement.
As you can see, it’s pretty involved. If you have captive rotors on your vehicle, I strongly urge you to find a shop with an on-the-car brake lathe to handle your warped rotors should you run into that issue. It might save you a ton of time and money.
When doing your brake job, you might not give a second thought to torqueing the wheels. This might be a mistake. If you over-tighten your wheels, you can actually create a brake pulsation. So if you’ve just installed your wheels and now you have a brake pulsation, you might consider loosening everything back up and checking the torque. Here’s a video on this topic.