How To Diagnose Failing Brake Rotors

Like all auto parts, brake rotors wear out and will need to be replaced eventually. It's recommended to check the rotors every time you replace your brake pads, but sometimes rotors will fail between brake pad changes. Driving with worn out or damaged rotors isn't exactly safe, so we always recommend checking your rotors as soon as you recognize the signs of bad rotors.

We put together this guide to assist you through the rotor inspection process. All the information you need is in this guide. If you have any questions, we encourage you to reach out to us.

The Dangers of Driving With Bad Rotors

Worn rotor

When your rotors are worn too thin, they can't absorb as much heat. The effect of this is that the pads and calipers get hotter than they should. You will feel this as brake fade. In other words, you won't be able to stop your Volkswagen that well. With reduced stopping power, your VW can be dangerous to drive on the road. Your brakes might not be reliable, especially in an emergency situation where you have to slam on your brakes. To ensure that your VW's braking power remains reliable, replace your rotors as soon as you determine that they're worn out or damaged.

Signs of a Bad Rotor

The symptoms of a bad rotor don't start cropping up until the rotor is really damaged or worn. So we strongly suggest checking the rotors every time you replace your brake pads. Rotors typically last as long as two or three sets of brake pads. However, if you experience at least one of the symptoms listed below, it's imperative to check your rotors as soon as possible.

  • Noisy brakes (squealing or squeaking noise)
  • Excessive vibration in the brake pedal and/or steering wheel
  • Longer stopping distances

A more surefire sign of worn rotors is obvious grooves or scoring on the surface. When you check the rotors following the tutorial below, you'll be able to easily spot grooves or scoring, as well as other types of rotor damage.

How to Access the Rotors on Your VW

New rotor

To access the rotors on your VW, you would need to take the following steps:

  • Loosen the lug nuts on the wheels by about a quarter of a turn
  • Lift one end of the vehicle (the best way to do this is with a floor jack and jack stands)
  • Remove all the lug nuts and then pull off the wheel

Inspecting the Rotor: What to Look For

When you have the rotor in front of you, it's time to visually inspect it for signs of damage or extreme wear. You want to look for three main things:

1. Normal Wear and Tear

When a rotor is new, there's no wear, of course. Eventually, as the brake pads repeatedly come into contact with the rotor surface, a lip will form along the edge of the rotor. At some point, you'll have to start measuring the rotor thickness to make sure that it still meets the minimum thickness requirements. All car manufacturers, including Volkswagen, stamp the minimum thickness on the outside edge or hub of the rotor. The best way to accurately measure the brake rotor thickness is with a brake rotor micrometer.

2. Physical Damage

Sometimes a rotor will get damaged from being paired with the wrong type of brake pads. Common signs of physical damage include:

  • Bluish burn spots on the friction surface of the rotor
  • Grooves or scoring
  • Cracks

3. Warping

A warped rotor doesn’t have a smooth and even surface. But you won't be able to see warping or disk thickness variation with your eyes. First, use a dial gauge to see if the runout exceeds 0.002 inch. If you find that your rotor is warped, it’s possible that the wheel hub isn’t spinning on a flat plane. It’s worth checking the wheel hub runout, too. Also use a micrometer to check the rotor for variation in it's thickness.

What if Your Rotor Needs to be Replaced?

If you have a bad rotor or two, they will need to be replaced as soon as possible. It's always a good idea to replace your rotors in pairs to ensure even braking performance.

It's pretty easy to replace your rotors at home. Here's a great tutorial to follow. You can also save a lot of money on genuine OEM brake rotors if you order from us because we offer wholesale pricing. Check out our catalog of brake rotors to see how much money you can save!