Disc Brake Challenge Part III: Removing and Replacing the Brake Rotors

Thursday, August 6, 2009 by David Horvath
With the worn out brake pads off and the calipers checked and repaired, it was time for Samuel to move on to the brake rotors.

Step 1: Removing The Old Brake Rotor

This looks simple enough right? There are no stud clips so the brake rotor is just resting on the nose of the axle hub ready to be lifted off. Well, not quite, as Samuel soon discovered...

bare rotor

Normally there will be some corrosion on the hub and the rotor hat. That's to be expected.

A little tap on the back with a hammer or rubber mallet will usually knock the rotor loose but that wasn't to be this time.

The first rotor came right off the nose without any issues. After about 5 minutes of pounding and rotating on the driver's side rotor he found it wouldn't budge. 

He next tried some PB Blaster spray on the rotor. That didn't work either. It was really fused to the hub. It was the time to pull out the heavy artillery. 

I had him put on some safety goggles and I got out the largest 3-jaw puller I had in the tool box. This is not the greatest idea since it's hard on the wheel bearings but we didn't have much choice. It just wouldn't break loose using normal means.

jaw puller

After a few quick turns of the wrench it finally broke loose from the hub with a huge BANG!

The driver's side overheated severely due to the sticking caliper and apparently cooked off the anti-seize compound that was originally between the hub and the rotor.

You can see the extent of the damage to the rotor. This was cooked, warped, and the brake pad compound looked like chocolate icing smeared all over the back of the rotor.

cooked rotor

Step 2: Cleaning The Hub

Now Samuel moved on to prepping the hub for the new brake rotor. This involved cleaning and checking the run-out on the exposed hub.

A wire brush mounted in a drill makes quick work of cleaning the corrosion off the hub. He sprayed some brake cleaner spray on as well.

Any debris or corrosion between the hub and the brake rotor can cause excessive run-out and vibration issues.

Eye protection is a must here!

cleaning the hub

Step 3: Checking The Hub Run-Out

This is a step most folks don't bother with but it's important. As long as everything is torn down this far, you might as well make sure the wheel bearings are not shot. 

Excessive bearing play can cause vibrations. It can also severely damage the brake rotor and brake pads. This can easily be checked using a dial indicator mounted to the strut tube. The run-out specs and instructions for this procedure will be listed in your vehicle's shop manual.

hub run-out

Step 4: Mounting The New Brake Rotor

Having established that the hub and bearings were okay, Samuel then carefully applied a thin film of anti-seize compound on the surface of the hub. He was careful not to get any on the studs themselves. You never want to put anything on the stud threads. He then mounted the new ATE Premium One brake rotors.

Before doing so, he put on a fresh, clean, pair of gloves to make sure he didn't transfer any grease or anti-seize compound onto the new rotors. Any contamination on the rotor surface can transfer to the new brake pads and keep them from bedding in properly!

The ATE Premium One brake rotors have a nice Meta Cote protective coating on them. The unique pattern of the slots minimizes noise, maintains an even, clean surface on the pads, and eliminates fade during heavy braking. The slots also aid in wet braking conditions.

They are nicely packaged and due to the Meta Cote surface, they are ready to install right out of the box.
rotor


Some rotors are not anti-corrosion plated and will come packed with a thin film of protective oil on them that needs to be cleaned off before installing them.

On those rotors, you will need to clean off the packing oil with brake cleaner spray and a lint-free cloth before installing them. You should only clean off the portion of the brake rotor that will make contact with the brake pads. 

The oil can stay on the brake rotor hat and inside the cooling vents (if it's a vented rotor).  As the rotor heats up, that will burn off and the resulting residue will help protect the rotor from corrosion. It's just like curing a cast iron skillet. If you clean it off the entire rotor, any exposed area not in contact with the brake pads will rust and turn an ugly orange/rust color very quickly.



Step 5: Checking The Rotor Run-out

The next step is also very important. You want to check the rotor run-out to make sure it wasn't damaged or bent. Excessive run-out will cause brake vibrations and a pulsing in the brake pedal. Samuel attached the rotors to the hubs using three of washers and nuts per rotor. 

It's critical to do this check before the rotors are driven on to make sure they are true.  Most rotor manufacturer's will not warranty a rotor for warping or run-out issues once they have been driven on.

The typical allowable run-out spec is .004" (.10mm) maximum.

Here Samuel is checking the run-out using the outer edge of the rotor.

rotor run-out

Now that the rotors are checked and ready to go, it's time for him to move on to the next step...

Disc Brake Challenge Part IV: Installing The Hawk HPS Brake Pads And Calipers

Stay tuned...

Comments on Disc Brake Challenge Part III: Removing and Replacing the Brake Rotors

Wednesday, May 5, 2010 by Robot B9:
I could not help but notice that the old brake rotors appear to also be the ATE Premium one and they were quite rusty. Is this what I should expect from the rotors I just bought?
Wednesday, May 12, 2010 by Dave:
The rotor on the driver's side was severely overheated due to the sticking caliper. It pretty much cooked the protective coating off the surface of the rotor. The other side wasn't nearly rusty and the replacement rotors still look good almost a year later.

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