Brake Pad Change

PLEASE NOTE: The newer and massively improved Boxster brake service information is HERE. What follows below is the old, original stuff I wrote up. Use it only for historical purposes. Please visit the new pages HERE for the latest info!

Well, I was very surprised at how long it took to wear out my brake pads, but at around 20,000 miles my brake wear dash light finally lit up. Knowing that the light didn't mean impending doom, and after contemplating having the dealer put the new pads on, I finally found time to do it myself today. It was surprisingly simple, and thanks to the brief instructions posted on the Boxster Racing Board, I had no problems figuring out how to do it. For your viewing pleasure, here some even more detailed instructions with photos.

Prior brake data on my Boxster:

At around 15,000 miles I bought new brake pads to take with me to track events, just in case the wear indicator would light up while at such an event. The front and rear brake pad sets are separate parts. The "part" comes in a box with 4 pads (2 per wheel). The rears have a 996.xxx part number, which, according to the Porsche part numbering system, means it's a 996 part which in this case is also used on the 986 (obviously not all 996 parts can be fitted to a Boxster!). The fronts have a 986.xxx part number, which means they are unique to the 986. I've checked, and indeed the Boxster S pads are the same as the 996 pads (at least for the initial model years of the 996).

Boxster front pads: 986.351.939.xx
Boxster S front pads: 996.351.939.xx
Boxster and Boxster S rear pads: 996.352.939.xx

List price per set is between $100 and $120 (front pads cost more, for some unexplainable reason). I was given about a 10% PCA member discount.

Some notes on the Porsche part numbers. The last two digits, denoted above as "xx", may vary; they are simply a revision number for the part, with higher numbers meaning a later revision. For the most part, it really doesn't matter what revision number you get, assuming they haven't made any radical improvements during the revisions. I've found that the parts counter at the dealer usually only has the latest revision number in stock, because pads are a consumable that doesn't sit on the shelf for a long time.

Update May 2002: My early sets of front Porsche pads were revision 11 or 12 or 13. My last set of Porsche front pads was revision 16. Chris Brown and I both had very negative experience in pad lifetime and wear characteristics using revision 15 pads on the track; we think that these pads have been tuned more in favor of quiet or dust-free street use, or something like that, which has a negative impact on durability with track use. I highly recommend use of Pagid Orange pads for the track. They are much more durable and long-lasting (2x - 3x), easily offsetting their higher price (less than 2x). They also feel better on the track and exhibit less brake fade. Here are the Pagid Orange (RS 4-4) part numbers:

Boxster front pads: U2407
Boxster S front pads: U2406
Boxster and Boxster S rear pads: U2405

I've found Paragon Products to be a good source for the Pagid Orange pads, priced at under $200. There a couple of theoretical drawbacks to using these pads on the street (more noise, more dust, more heat required for most effective braking), but I actually have not found these to be a problem for daily use, and the benefits have been dramatic for me.
At around 17,000 miles I decided to change the brake fluid before heading up for another two-day driver's ed session at Thunderhill raceway. There were no signs of any trouble, but after all my prior track days, and since the fluid was a good year and a half old, I just knew I would feel better heading into Turn 10 at 100 MPH having fresh fluid and air-free brake lines. The dealer changed the fluid and said that I still had plenty of pad life remaining, no need to change them yet. With regard to rotor lifespan, he said that you simply get new rotors with every other change of worn brake pads.
Between 17,000 and 20,000 miles, I kept a close eye on the thickness of the pads, and kept comparing them to other Boxsters I saw.
Finally, at around 20,000, the wear indicator lit up.

The rear pads seemed to have a lot of life remaining. I'm estimating on all these measurements here, but I would say that new pads are 15mm thick. My rears had 8mm left. My fronts had 4mm left. The wear sensor is a little plug on a wire that sticks into a hole in the edge of the pad. When the pad wears down to about 6mm, the hole becomes exposed. Another millimeter or two of wear and the sensor is triggered. I'm not certain, but now that I've changed the pads the sensor wear indicator is off, so I think the sensor doesn't "break" when it is triggered, although one of the sensors sure looked like it could have been broken. It depends on how worn it is, so the sooner you replace the pads after the sensor is triggered, the more likely you won't have to replace the sensor. In any case, now that I know how the sensors fit in the brake pads and get triggered by wear level, I'm pretty comfortable just keeping an eye on the pad thickness by looking through the spokes, and not assuming that the wear sensors will detect wear. Obviously, if you change them all at once, the rear pads will never be an issue; you would just need to peek at the front pads and see if they're getting to the point where the pad is no thicker than the backing plate (that seems to be an approximate thickness of worn out pads).

Given the number of track and autocross days I've put on these brake pads, and given how well the factory brakes perform over time, I see no reason to experiment with aftermarket pads like the Pagid and Porterfields that others have had bad experiences with. The factory brakes are awesome and last a long time. [ Note: I've since revised my opinion on this and love the Pagid Oranges. If you only do street driving, the factory pads are great. If your car sees the track, then get the Pagids. ]

OK, so here are the steps for changing pads on one wheel.

Tools

You'll need the following:

A floor jack or the emergency jack from your spare tire toolkit.
Your locking lug bolt key.
A lug bolt wrench. (It is best to tighten the bolts with a torque wrench. If you don't have one, have a mechanic tighten the lug bolts to the proper torque when you're done. Boxster factory spec is 94 lbs. torque.)
A hammer.
A nail punch or a bolt, at least 3" long, less than 1/4 inch diameter. (For tapping out the caliper pin.)
A large pliers.
A needlenose pliers.
Optional: tweezers
Optional: a rag.

Remove the Wheel

(Forgive me if this is Basic Tire Changing 101, there may be a trick or two here not everyone knows, or that someone might forget!)

Park on a flat surface where the car won't roll. If there's any doubt, block one of the other tires with a piece of wood.
Put the transmission in gear so that the rear wheels can't roll. (For a Tiptronic, putting it in Park does this.) Set the parking brake.
Jack up the desired corner of the car, far enough so the jack is taking a little weight off the tire, but little enough so that the tire still has good traction on the ground.
Loosen each lug bolt just enough so it is no longer tight. This will make step 6 much easier! Loosen in a diagonal star pattern to evenly distribute the lug bolt torque. This is common procedure for avoiding uneven torque and potential warping problems.
Jack up the car until the tire is clear of the ground by an inch at most. If you jack it up way off the ground, you'll just have to lift the wheel higher, which is harder on your arms and back
Remove the lug bolts. It's easiest if you remove the top bolt last, keeping the bottom of the tire pinned to the axle with your foot or leg. This prevents the wheel from tipping outward as you loosen the last bolt.
Pull the wheel off and put it aside. Here's what you have:

Remove the Old Pads

Using the needlenose pliers (or the big pliers), pull out the cotter pin that holds the big caliper pin in place. In this photo I've colorized it red.
In this photo I've colorized the various pieces. The caliper retaining pin is red. The spring clip is green. The wear sensors are orange. The pad plates are blue.

You may be able to simply slide the big retaining pin out. Or you may need to tap it out using the hammer and a nail punch or a long bolt. While pushing down on the spring clip, push the retaining pin towards the inside of the car. When the pin clears the spring clip, the clip may pop up suddenly, unless you're pushing it down. Don't be startled. Finish tapping or sliding the pin out, and remove it.
Using the tweezers if you have them, needlenose pliers if not, remove the wear sensor clips from the old pads. Squeeze the little expansion tabs inward, while simultaneously pushing the clip upwards out of the notch in the pad. It is colorized red in this photo. (Note that in this photo the retaining pin is still there; you can remove the sensors before or after removing the pin.)
Pull the spring clip out of the way. The wire leading to the outer pad's wear sensor is clipped to the spring clip, and you can un-clip it if necessary. In this photo the spring clip is pulled back and the inner pad's wear sensor is colorized red.
Before you remove the pads, take your large pliers and compress the caliper pistons by squeezing each pad against the caliper.

You should check your brake fluid reservoir level (in the front trunk) before doing this. If the reservoir is full to begin with, compressing the pistons might cause some overspill, so placing an absorbent rag over it may help to catch a bit of overflow and avoid a big mess. (I had no such overflow. Perhaps doing one wheel at a time, checking the brake pedal after each one, helps avoid overflow by limiting the amount of compression to one caliper's worth at a time.)

If you have a rag, I suggest putting the rag between the pliers and the caliper to avoid marring the caliper surface. This is purely an aesthetic precaution.

Have the pliers grip the pad and the caliper where the caliper pin would go through them if it were still in. Squeeze slowly and strongly until the pad is as far away from the rotor as possible. What you're doing is pushing the caliper pistons back into the caliper so that there's room for your new, full-thickness brake pad to fit between the pistons and the rotor.

I didn't know about this when I did mine, but it has been recommended to use the nipple shown in the photo at the upper right of the caliper as a release valve when compressing the pistons. If you loosen the nipple and connect a short piece of rubber tubing from it to some container, when you compress the pistons, the excess fluid will flow out into the container instead of back towards the reservoir. You'll need to replentish the reservoir with new fluid, but this is said to be better for the ABS system. Don't forget to re-tighten the nipple when you're done, or you'll have a dangerous brake fluid leak!
Now you can actually just pull the pads upward to remove them, as the following photo shows with the pad colorized red.

Install the New Pads

Notice the difference between my worn and new front pads. You can see the hole where the wear sensor sits, and how it has been exposed in the old pad. One strange thing: notice in the photo on the right, that the new pad has what looks like a pin right next to my thumbtip. This pin looks like it will fit in a slot on the caliper housing, but it doesn't quite fit right, and my old pads had no such pin. So I just took my pliers and twisted it until it came off. I don't quite see what its purpose is. If anyone knows, please email me!

Drop the new pads in place. If there doesn't seem to be room for a pad to slip into place, it's probably because you skipped step 5 in the previous section, or it's because you didn't compress the pistons far enough, or because you waited a few minutes and the pistons started to decompress. Whatever the reason, if this happens, just drop your old pad back in place (it will fit because it's worn), and use the pliers again as in step 5 above to compress the pistons back into the caliper so that the new thick pad has room to fit.
Move the spring clip back in place.
Snap the wear sensors into the sensor holes and notches of the new pads.
Pushing the spring clip down with one hand, push the big retaining pin through the proper holes in the caliper and pads, until it's all the way back where it was. To make the following step 5 easier, notice where the cotter pin hole is, and line it up on top. If you have some anti-seize paste, such as Porsche's "Optimoly" paste, it's helpful to wipe just a little bit of it on the parts of the retaining pin that come into contact with the caliper and the brake pad backing plates. This will ensure that next time you have to remove it, it will easily slide out and you won't need to tap it out with the hammer-and-nail-punch method discussed earlier. Fewer tools is better!
Stick the cotter pin back in the retaining pin. It can be hard to see the hole for it if you weren't keeping track of it in step 4.
Carefully -- because your car is jacked up -- get in the driver's seat and press the brake pedal. It will be squishy at first, then it will be nice and firm on the second press. You don't want the squishy feeling to happen later when you really drive the car and come to your first intersection!

Put the Wheel On

(Once again, forgive me if this is obvious and not specific to Boxster brake pads.)

Lift the wheel back into position.
Use your foot or leg to keep the bottom of the wheel from tilting out until you get a couple of lug bolts on.
Hand-tighten the lug bolts. Do the top one first.
Wrench-tighten the lug bolts. Tight but not torqued (you can't really torque them when the wheel is freely spinning). Go in a diagonal star pattern to evenly distribute the increasing tension.
Lower the car back onto the ground. Remove the jack.
Torque the lug nuts to 94 lbs.

Brake Pad Break-In

The Boxster owner's manual suggests that new brake pads be treated gently for about the first 200 miles of city driving, more if you're just doing highway miles. It seems to me that the new pads will work fine when needed (obviously it would be a catch-22 situation if you were required to expect non-working brakes during a 200 mile city driving break-in period), but perhaps for longer life this break-in period helps. I sure wouldn't want to put on brand new pads at the track and hope they are working correctly on Lap 1. It seems much saner to put them on at home, break them in for a day around town, and then drive on them to the track before putting them in an important situation.

[ Note that the Pagid Orange pads have specific "bedding-in" procedures, where you do a series of braking sequences at certain speeds to break them in. Once you bed them in, they're ready to go. See the Pagid instructions for the particulars. ]