A brake rotor is basically a machined disk of a specific kind of cast iron. The rotor is sandwiched between the wheel and the hub and spins with the wheel.
A brake caliper clamps two pads of brake material against it which creates friction and therefore, stopping the force.
Cost of Brake Rotor Resurfacing
The operation of turning brake rotors is fairly close to the operation of doing a brake job – the brake calipers and pads are removed. Then, the brake caliper bracket, followed by the rotor which is then resurfaced.
The labor time for rotor resurfacing is also the same as for a brake job; usually a flat 2 hours. So, at a shop with an $80/hour labor rate, the cost would be $160. At a shop with a $120/hour labor rate, the resurfacing rotors cost would be $240.
In other cases, the job might not be based on book time as there is often a great deal of difference in the case of brake work between book time and what a job actually takes. Some shops use a flat charge for resurfacing rotors; ranging from about $120 to $180.
Shops that do this are also more likely to have a lower flat cost for replacing rotors as an option to resurfacing.
Another case is when a rotor has already been removed from the vehicle for other work or whatever reason. Most auto repair shops, parts stores (if equipped), and machine shops will turn a loose rotor. The cost to turn rotors in this instance is about $12 to $25, as long as it has enough machinable material.
Why Do You Need to Turn a Brake Rotor?
There are two reasons to turn a brake rotor. The first is to provide a smooth and fresh surface for brake pads to bed into and operate upon.
Brake rotors are typically resurfaced any time a new set of brake pads is installed; after which, there is a short process of “bedding in”. This sometimes involves heat cycling that gives an operational cure to the pads themselves.
In the case of ceramic pads, it transfers a certain amount of friction material into the rotor. In the event that this doesn’t go well (for whatever reason), sometimes, noise arises. A cure for that is sometimes to resurface the rotors and repeat the bedding in the process.
The second purpose of rotor turning is to provide two ideally flat, true, and parallel surfaces. If the surfaces of the rotor that the brake pads bear against aren’t perfectly true and parallel to each other, the brake pads will apply stopping force unevenly as the disk rotates – resulting in a feeling of brake pulsation.
Resurfacing Rotors Versus Replacing
The only time resurfacing rotors is a good idea is when machining leaves enough thickness in the rotors such that they will still be above their minimum wear limit when the pads are worn out.
On many modern vehicles, there isn’t a lot of leeways, though it varies from vehicle to vehicle. If the rotors can safely be resurfaced, then, the next question is cost.
It takes more time to turn rotors than it does to simply replace them, so there are cases where it is cheaper to replace rotors than to resurface them. On a 2012 Dodge Grand Caravan, for instance, even mid-range rotors can cost about $25 each, which can make the job about the same in cost to replace rather than resurface.
And one advantage is that a new rotor typically comes with at least a 12-month warranty against problems. It’s best to inquire and to get an estimate of both of the ways to solve a rotor problem in advance.
What Else Can Go Wrong
If bedding in the problem requires rotor resurfacing, that typically comes up after a brake job and is handled one way or another by the shop typically at no cost. Usually, the symptom of that is noisy brakes. In some cases, the problem may be a poor choice of friction material rather than anything to do with the rotors.
If the problem is brake pulsation, sometimes, there are also underlying issues. Brake pulsation is caused by a parallelism problem between the two braking surfaces of the rotor; essentially the thick and thin spots in a rotor.
This usually begins with run-out which is a deviation from true or more simply, a wobble away from the vertical plane. There is a small air gap between the rotor and the brake pads when the brakes aren’t applied. With enough run-out, however, the rotor can brush the pads slightly on every rotation, which over time wears a thin spot in the rotor.
A number of things can cause rotor run-out. One is a poorly maintained brake lathe; if the rotor isn’t set up perfectly true on the lathe, a wobble is machined into the rotor. Usually, then, it takes a couple of thousand miles of driving before a thin spot is worn in the rotor and the brake pulsation appears.
Another possibility is that the hub the rotor bears against isn’t true or has rust or dirt that prevents the rotor from sitting flush. In this case, when the wheel is torqued down, the rotor conforms to the imperfection; essentially causing it to rotate with a wobble and again, eventually wearing a thin spot that causes a brake pulsation.