How to Install Zimmermann Cross-Drilled Rotors, and Porterfield Brake Pads

Audi TT Roadster

Porterfield Pads

Audi TT Roadster

Zimmermann Cross-Drilled Rotors -Front and Rear
Contact Jose Rotger for TT pricing

I had been using EBC brake pads since day four of ownership. At 20K miles, in September of 2001, I had been noticing that I was getting a vibration while braking. I believe the EBC pads had greatly contributed to the warpage of my OEM rotors. I had been watching the TT forum regarding the various alternatives to the stock pads and rotors. Some went for the complete swap-out to StopTech Brakes, or even a Porsche model.
I chose to go with the Zimmermann Cross-Drilled rotors, and Porterfield Pads as my alternative.

I started by setting up for this by assembling these Toolstools;
7 mm Allen Wrench
A 18 mm box end wrench (To Remove the Caliper brackets.)
A decent large Phillips Screwdriver (No rounded edges.)
A lug wrench, or 17mm deep draw socket and breaker bar (To remove the lug nuts.
A large water pump pliers, a regular pair of pliers.
A decent set of jack stands and a floor jack. These are invaluable to assist you when doing this job.
A can of spray brake cleaner or equivalent.
A can of 'Liquid Wrench' or penetrating oil.

I loosened the lug nuts, jacked up the car, and set the jack stands in place.
I removed the left front wheel and pad set first. It looked then like this.

Start by removing the retaining clip wire from the front. Use a pliers or needle nose to do this. (It will require a bit of a push on the wire to get this back into place when you are done.)

Remove the two plastic caps that protect the bolts. Using a 7 mm Allen head wrench, remove the two sliding bolts that hold the caliper to the wheel assembly. Set them aside, in a tray or box where you won't kick them all over the floor.
You can then remove the whole caliper assembly from the mounting bracket. Have a piece of wire, (an old wire coat-hanger works great) with you when you remove this assembly. Bend the wire around a part of the caliper assembly, then somplace on the wheel area, to hold this heavy caliper in place. Don't let it hang by the hose. Don't be afraid if it slips, or if you do stress it. You may knock it loose. It's OK that this may happpen once or twice, just don't make a habit of it, and don't leave it that way! You can see here how the wire supports the whole assembly.
You will need to release the pad wear sensor plug from where is it being held, before you can remove the pads.

Look at the picture and press on the tab where the arrow shows. Pull this connector from the mating piece. You can then remove the old pads. You may need to rap or tap the pads from the caliper, depending on what type of glue may have been used to keep the pads in place.
Once the pads are removed from the caliper, reposition the caliper up on top of the rotor, and out of the way. You may find it's easy to hang the caliper, using the wire, from one of the coils of the spring, just above where you are working.

You are going to have to get in close, with the 18 mm wrench to loosen the caliper bracket bolts , top and bottom. (Sorry, this is the best picture I have of this, you will see them easily.) This is going to require some amount of strength and stress, to break these bolts loose. Use a good box-end wrench, so to avoid rounding over the bolt faces.

Once you have the bracket off, set it aside, clean it, and get ready to remove the old rotor.

Use a good, sharp-edged large (1/4") Phillips Screwdriver for this next procedure.
Also, you may need to add a few drops of penetrating oil to this screw before you start. It's set in place very secure, and don't forget, this area gets a lot of heat and cold cycles.
Push in hard with the driver on the screw, while turning the screw counter-clockwise. If you have a good grip on the inside of the cross pattern in the screw, the driver will not slip, and it will turn out. It's HARD TO DO. It requires a strong grip on the driver, and a strong turn, at the same time!
Remove the screw, put it in the pan with the rest of the hardware. You can now remove the rotor. You may find that it's rusted in place a bit. A sharp rap with your fist on an edge, or from the back will dislodge it easily. Get ready, it's heavy! It will come right off!

Your front wheel area should now look like this.

You will need to prep the new rotors by removing the shipping oil, or any machining oil that was left on them. Use a Brake Cleaner, or what I used, was a spray can of Carb Cleaner. I used this, because I had it around. Mineral Spirits will work, a de-greaser, anything to remove the oil. The carb cleaner will evaporate very quickly. Wipe off any excess with a towel, not a paper towel-they leave residue, but I suppose its not that big a deal.

Now you can install the new rotor. Locate the rotor screw, and keep it nearby. Place the rotor over the spindle. It doesn't stay in place, does it? you will have to hold it in place with one hand, and start the screw with another. If someone is nearby, they can help with this. Practice dropping with the *old* rotor, not your new one! It may chip the concrete, or land on your foot or something, but don't drop it anyway!
It should look like this.
Tighten the screw, don't slip the driver now!
Great job so far, but don't reach for that beer just yet!

Now you can replace the caliper bracket. Here it shows it's in place, and a shot of the 18 mm 'shorty' box end wrench.
Tighten both bolts.

Now go have that beer, and fish out the old OEM pad with the wear sensor on it, this one.
Yea, I know, look at the rust. That's from inside the piston, in the caliper. Water gets trapped in there. Not much you can do about it. this is the old EBC pad that I cut and spliced the OEM connector to. It should look just like your OEM pad, if you use them.
Cut the wire in about the middle of the cable. Strip off the insulation of the two wires inside, back about a 1/4" like this.

Twist the two wires together, tape them together, then tape the sleeve that goes around the two wires. It should look something like this.

Then go ahead and replace this connector back into the jack on the strut assembly. I used a nylon cable-tie to hold it in place. If you don't want to do this, you can simply cut off the connector on the strut, and splice the two wire together there. By shorting these wires, the 'brake pad' warning light on the dash will not be lit. I think this way is a more clean solution, and it will allow the user of sensor pads, if you ever wanted to switch to them.

Now you can put the Porterfield pads in place.
Before I will do this, I will prep the pads and calipers, using this stuff, Disc Brake Quiet.
This is the spray version, it also comes in a glue tube. I sprayed the back side of both the inner and outter pads, and the corresponding points on the calipers. Let it dry about 10 minutes. The inner pad has 3 clips that fits inside the brake cylinder. Mount this one first. This is tricky to get into the cylinder. It requires some pressure to bend the clips in, while pushing the pad into the cylinder. You can simply slip the other pad into it;s slot on the caliper bracket.
You will probably need to compress the piston in the cylinder. I do this with a large 'water pump' pliers, that I can easily control the force with. Pushing the piston all the way back is necessary to get the pad assembly back over the rotor, with the one pad in place in the caliper. You will see what I mean when you actually do this. Once the new pads in the caliper assembly are in place, put the sliding 7 mm bolts back in, tighten them, and put the small plastic caps back over the Allen heads. Replace the spring clip. This requires some force. Put the clip into both holes, and use a pliers to bend the looped clip back over the rotor assembly.

Front Completed


That's it. Re-mount the wheel, tighten the lug bolts, and go to the next wheel!

How to do the Rear Brakes, Using Porterfield Pads

Note: some of these pictures look suspiciously like the ones I did for the EBC Pads. They are. The concept is exactly the same.

Loosen the lug nuts with the car still on the ground.

Make sure the car is in gear, and/or you have a block of wood, or something in front of at least one wheel. You will need to release the parking brake to remove the rear calipers.

Jack up the car, by using a floor jack, placing it on the rubber pads under the rear of the car. Remove the lug nuts, and remove the wheel.

Use the 15 mm and the 13 mm wrench to remove the bolt from the top and bottom of the caliper assembly.
You can simply lay the caliper assembly back, as its held in place by the parking brake cable, or use the wire from the front install, to secure it as well.

Remove both old pads from the caliper bracket.

Now, use the 'Water Pump "pliers to grab the piston in cylinder, to rotate it clockwise. You will need to rotate it a few times. You need to do this, in order to collapse the piston back into the cylinder, in order to get the caliper assembly back onto the new set of pads. The new pads will invariably be thicker than the OEM set you are replacing, and in order to get the caliper back over these new pads, you will need to collapse the piston.
Now get the edging clamp and place it on the caliper as shown. You will not need the two screw clamps on the left and right. The edge of the red edging clamp sits nicely on the finger part of the caliper, and the screw part will snug right up to the piston. Tighten it. Then you can get the water pump pliers, and rotate the piston, while also turning the screw on the clamp. You will probably need to rotate the piston, and turn the screw a few times before the piston is compressed. This should be your result. Notice how the piston is now nicely compressed.

Now it's easy to put the pads back onto the disk assembly, and slip the caliper assembly, back on over the new pads. If the piston has been compressed, you should have a lot of play in the caliper assembly, to get it over the pads. Replace the two bolts, use the 13mm and 15 mm wrenches to tighten the bolts. You will notice also that the parking brake seems a lot looser. Step on the main brake a few times, to tighten up the rear pistons, and the fronts.

OK, you did it! Looking back, it wasn't so hard, was it?
Remember to bed in those pads. These instructions help.

How to Avoid Squealing Brakes

Porterfield R-4S brake pads are designed not to squeal. However, the condition of the other brake components can cause squealing or shuttering.

Brake Shutter: Sometimes, after switching brake pad material type, brake shutter occurs. Shuttering happens when the surface of the brake pads and the grooves in the rotor are not making smooth contact. In most cases simply continuing to drive normally is the cure for this as the surfaces of the pads and rotor wear in.

Squealing: Vibration causes high pitch squealing. Vibration originates where the pad meets the rotor, then transfers through the pad to the backing plate. The high pitch squealing noise usually comes from the area where the piston is pushing against the metal backing plate.

Suggested steps to avoid or solve brake squeal and shutter:

  1. Champfer (bevel) the leading and trailing edges of the brake pads using an emery cloth type of abrasive belt approximately * " from the edges at a 45 degree angle. A grinder can also be used for this purpose.
  2. Add anti-squeal compound to the backing plate. CRC is a commonly used brand, available at any auto supply store. In most situations, this will prevent squealing.
  3. Bedding in. After installing new brake pads, drive your car to a speed of 20 mph, then brake GENTLY to 5 mph. Repeat this process, GENTLY braking, 5 more times, then stop and let the brakes cool down for an hour. Try to avoid high speed “panic” stops for the next 50 miles of driving.
  4. Remove glaze If after doing steps 1-3 squealing exists, remove glaze from the surface of the pads with an emery cloth belt. Do not use sand paper as sand paper may leave unwanted grit residue. Glazing is usually caused from contaminants such as metal, silicone and binding agents left behind by previously installed pads.
  5. Clean the caliper “piston to brake pad” contact surfaces. Also remove brake dust build-up from around piston boots and seals. Lube sliding surfaces of calipers.
  6. Scuffing or Turning: If after doing steps 1-5 squeal or shutter persists, have a professional remove the rotors to either “scuff” them (80 grit wheel) or “turn” them on a lathe. “Scuffing” removes contaminants left behind by previously installed pads, and turning removes contaminants and grooves. A new or turned rotor, with a perfectly flat surface, combined with new Porterfield R4-S brake pads, properly installed and broken in, WILL NOT SQUEAL OR SHUTTER.

By Jeff Bipes