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Pelican Technical Article:

Rear Brake Rotor Replacement

Jared Fenton

Time:

2 hours2 hrs

Tab:

$25 to $50

Talent:

***

Tools:

Stout Phillips head screwdriver or socket, penetrant oil,

Applicable Models:

VW Jetta GL (1999-05)
VW Jetta GLS (1999-05)
VW Jetta Wolfsburg (1999)

Parts Required:

Brake rotor

Hot Tip:

Engage the parking brake to clamp the rotor when removing the

Performance Gain:

Better braking

Complementary Modification:

Replace brake pads

Brake rotors (or discs as they are often called) are perhaps the most important part of the braking system. The brake pads rub against the rotor to slow the car down. At the same time, the rotor also dissipates heat from the friction generated. If the rotor becomes too thin, or develops grooves in the surface, their ability to stop the car decreases.

When replacing your brake pads, you should always measure the thickness of your brake rotors. If they fall below the specified value, they should be replaced with new ones. Check for grooves in the rotor, and make sure that you take several measurements of the rotor in several different places. This will guarantee you that you get an accurate reading. If the brake rotor has a groove in it, it should most certainly be resurfaced by a machine shop, or simply replaced with a new one. Rotors with grooves not only brake less efficiently, but they also heat up to higher temperatures, and reduce your overall braking ability. Additionally, the rotors can warp from the excess heat generated.

Use a micrometer to measure the thickness of the brake rotor. From the factory, the rear brake rotors on your Jetta will be 9mm. The wear limit is 7mm. If the thickness is adequate, you can have the rotors turned on a lathe to remove glazing and grooves from the old pads. In practice, I usually just replace the rotors. It is a bit more money, but you get peace of mind.

If you do find that you need to replace your rotors, replacing them is a pretty simple job. The procedure for the front or the rear rotors is very similar. For the sake of this project, we'll look at replacing the rear rotors.

The first step is to jack up the car and remove the road wheels. If you haven't already, remove the caliper and brake pads. Refer to our articles on Jacking up Your Mk4 Jetta and Rear Brake Pad Replacement for more details.

The rotor is secured to the hub by a small Phillips head retaining screw. Over time, these screws can seize up, making them difficult to remove. I recommend spraying it with good penetrant oil beforehand. Letting it soak for a day or two can work wonders.

Speaking of corrosion, the rotor may require some heavy smacks with a dead-blow hammer to get it off the hub. This was the case on our project car, being from the Pacific Northwest. The increased moisture causes the metals to corrode and lock the rotor to the hub. In extreme cases, you may need to spray the holes in the rotor with a good penetrant spray, such as Aerokroil and let it sit for a few hours. This can sometimes free up the rotor.

It's also a good idea to clean the face of the wheel hub once the rotor is removed with some brake cleaner and a soft brush. Once clean, I like to put a light coat of anti-seize compound on there. It helps to prevent corrosion and also keeps the rotor from sticking to the hub.

After the new rotor is installed, reinstall the caliper frame and the mounting bolts. Your new rotors should last a long time, and you should see an improvement in your braking after the wear-in period for your new brake pads.

Shown here is the rear brake assembly on the Mk4 Jetta.
Figure 1

Shown here is the rear brake assembly on the Mk4 Jetta. Removing the brake rotor requires you to first remove the brake caliper and pads. Please see our article on Rear Brake Pad Replacement for more information.

The brake rotor is secured to the hub by a small Phillips head retaining screw (green arrow).
Figure 2

The brake rotor is secured to the hub by a small Phillips head retaining screw (green arrow). I highly recommend spraying this screw with some penetrant oil and let it sit for a few days. It also helps to break it free with the pads and caliper still attached. Then fully remove the screw when you're ready to remove the rotor.

Now maneuver the rotor out from behind the caliper-retaining frame.
Figure 3

Now maneuver the rotor out from behind the caliper-retaining frame. If the rotor is stuck to the hub, whack the backside with a hammer to free it up.

Be sure to coat the mounting surface of the hub (green arrow) with a light coat of anti-seize compound.
Figure 4

Be sure to coat the mounting surface of the hub (green arrow) with a light coat of anti-seize compound. This will prevent the rotor from galling to the hub. Installing the new rotor is the reverse of removal.


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