2011-2015 Kia Optima Brake Rotor Minimum Thickness and When to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2011-2015 Kia Optima, the front rotor is a vented disc that starts at 28 mm thick, and Brembo's catalog for this generation lists a minimum (discard) thickness of 26.4 mm. The rear rotor is a solid disc that starts at 10 mm with a minimum of 8.4 mm. The number that rules your specific rotor is the one stamped on it after "MIN TH": once a micrometer reading at the thinnest point reaches that figure, the rotor gets replaced, not resurfaced.

Optima Rotor Thickness Specs at a Glance

Brembo's replacement catalog for this Optima generation lists the following discs. Front diameter depends on the engine, trim and wheel package, so measure the rotor or check your build before you buy.

Two things stand out. First, the front rotor only has 1.6 mm of total wear allowance, roughly 0.8 mm per face. That is not much, and it is why many Optima front rotors are already near the limit by the second set of pads. Second, the rear rotor is thin to begin with, so a rear disc that has been resurfaced once is often below spec after a single machining pass. Brembo also lists a slightly stricter minimum (26.6 mm front, 8.6 mm rear) for its coated Xtra line, which is a reminder that the stamp on the part actually installed on your car is the figure to trust.

How to Measure an Optima Rotor Correctly

The minimum thickness is stamped in millimeters on the outer edge of the disc or on the hat, usually marked "MIN TH." HELLA's technical guidance calls for a brake disc gauge, and says the disc must be replaced once it reaches or drops below that value. A straight-jaw caliper reads high, because it bridges the raised lip at the outer edge instead of reaching the worn friction face.

1. Loosen the lug nuts, lift the car at its jack points, support it on stands and remove the wheel.
2. Find the "MIN TH" stamp and write the number down. If the rotor is aftermarket and unmarked, use the spec table above as your reference.
3. Clean the friction surface of rust and pad deposits so the gauge sits on bare metal.
4. Measure in the middle of the pad sweep, a short distance in from the outer edge, not on the lip.
5. Rotate the rotor and repeat at several evenly spaced points around the disc. Use the lowest reading, not the average.
6. If readings differ noticeably from point to point, the rotor has thickness variation, which is the real cause of most pedal pulsation complaints.

Do the rears too. Rear rotor wear on this car is easy to overlook because the front brakes do most of the work, but the rear disc has very little margin.

Signs Your Optima Rotors Are Due

Thickness is the hard limit, but most owners notice symptoms first. The common ones on this generation:

• Pulsation in the pedal or steering wheel when slowing from highway speed. That points to thickness variation in the front rotors, and on a disc with so little wear allowance, resurfacing usually takes it under the minimum.
• A deep lip at the outer edge you can catch with a fingernail. The lip itself is not a spec, but a tall lip means the face has worn a lot.
• Grooves or scoring from a pad that ran down to its backing plate. Metal-on-metal contact can take a rotor below the limit quickly.
• Blue or dark heat spots and cracks starting at the vent edges. Any crack means immediate replacement.
• Heavy rust on the rear discs of cars that sit outside, especially on the inner face you cannot see without pulling the wheel.

Not every brake complaint is the rotor. The 2011 Optima is included in NHTSA recall 13V-114 for a stop lamp switch that may work intermittently. A failing switch can keep the brake lights from coming on, keep the brake pedal from canceling cruise control, cause intermittent push-button start, and light the ESC warning. If you see those symptoms, have a dealer check the VIN for open recalls before you replace parts.

Replace or Resurface?

Resurfacing removes metal from both faces, and the machined rotor still has to be above the minimum with some allowance left for future wear. With only 1.6 mm of total allowance on both the front and rear discs, there is rarely enough material on a used Optima rotor to machine it and still get a full pad life out of it.

HELLA's guidance is clear about the order: new pads should only go on if the discs have not been worn below the minimum, and discs are always replaced in pairs. A fresh pad on an undersized rotor overheats the thinner disc, which then warps or cracks sooner.

What to Replace With the Rotors

• Pads. Always fit new pads with new rotors. Old pads have worn to the pattern of the old disc and will not bed evenly. Our ceramic brake pads suit a daily-driven Optima because they run quiet and keep wheels cleaner.
• Hardware. Replace the pad clips and anti-rattle springs, and clean and lubricate the caliper guide pins. A brake hardware kit fixes most of the uneven pad wear that shortens rotor life.
• Calipers if needed. A caliper that drags or a guide pin that sticks wears one rotor faster than the other. If one side measured much thinner than the other, inspect that caliper and replace it if it binds; see our brake calipers.
• Fluid. Check the fluid condition while you are in there and follow the interval in your owner's manual.

If both axles are due, a matched set saves a second job. The 2011-2015 Kia Optima front and rear brake kit includes rotors and pads for both ends. For a single axle, browse our brake rotors.

How Hard Is the Job?

Front rotor replacement on this Optima is a moderate driveway job with basic hand tools: remove the caliper, remove the caliper bracket, take off the rotor (a stuck rotor may need penetrating oil and a few taps with a mallet on the hat), clean the hub face, then reverse the steps. Torque the caliper bracket bolts, caliper bolts and lug nuts to the values in the factory service manual, and tighten the lug nuts in a star pattern so the new rotor seats flat.

The rear is similar, but retract the rear caliper piston the way the service manual describes for your car's parking brake setup, and confirm the parking brake holds before you drive. Pump the pedal several times before the first drive so the pistons come back out against the pads, then bed the new pads in with a series of moderate stops without coming to a full stop, and let the brakes cool.

Frequently Asked Questions

What is the minimum front rotor thickness on a 2011-2015 Kia Optima?

Brembo's catalog lists 26.4 mm for the front vented rotor, which starts at 28 mm new. Use the "MIN TH" figure stamped on your rotor if it differs.

What is the minimum rear rotor thickness?

The solid rear disc starts at 10 mm and Brembo lists a minimum of 8.4 mm. Because it is so thin, a rear rotor that has already been machined is often at or below that limit.

Can I resurface Optima rotors instead of replacing them?

Only if the rotor is still well above the minimum after the cut. With 1.6 mm of total allowance, most used Optima rotors are poor candidates, and replacement is usually the better value.

Do I have to replace rotors in pairs?

Yes. Replace both rotors on the same axle together so braking stays even side to side, and fit new pads at the same time.

Why does my Optima's steering wheel shake when braking?

The usual cause is thickness variation in the front rotors. Measure at several points around each disc; if readings vary or the rotor is near the minimum, replace the rotors and pads together.

Sources

1. Brembo parts catalog, Kia Optima 2010-2015 generation (2.0) - front and rear disc diameter, new thickness and minimum thickness
2. Brembo parts catalog, Kia Optima 2012-2015 generation (1.7 CRDi) - 300 mm and 320 mm front disc specs, Xtra minimum thickness
3. HELLA Tech World: Testing the minimum thickness of a brake disc - MIN TH stamp location, disc gauge, replace at or below the limit, pairs, pads only on discs above minimum
4. NHTSA recall acknowledgment 13V-114 - 2011 Kia Optima stop lamp switch recall and symptoms