[Jazzbass]

Before the VIR event two weekends ago, I rebuild my calipers. I have 951 4 piston Brembo calipers on my car, which makes the rebuild process a little more interesting.

The first problem is finding rebuild kits. For a 911 guy used to $20 ATE rebuild kits available from every parts supplier, this is a much more difficult task than it sounds like. For rebuilding Brembo calipers, Porsche wants to sell you kits that contains a new seal, piston, and boot. Each kit is good for one piston in a caliper and runs $80. This comes out to be $320 per caliper, or $1280 for the whole car .

When you rebuilt ATE calipers, you just replace the seal and the dust boot. Total cost = $20 per caliper. So I started looking for caliper rebuild kits for Brembos and found one (1) place that sells them - Zeckhausen Racing. They sell seals and boots for Brembo calipers individually. $10 per seal = $40 a caliper = $160 for the whole car. Much better.

The first issue/concern I had was my front calipers. They are the older "scraper ring" design from an 86 951. Brembo changed the design later (not sure when) to use dust boots. Zeckhausen sells the later style rebuild kits, but they assured me that the newer seals would be fine in my older calipers. So I bought them, installed and after a weekend of track use, I feel I can say that they were 100% correct.

Now to the fun part - those who were at VIR know I was having serious brake issues as a result of the rebuilds. It turns out that two of my calipers (FL and RR) were leaking - badly. The funny part? I at first attributed this to the initial "spongeyness" you get from a fresh caliper rebuild and DROVE TO VIR with two leaking calipers Actually, everything went fine until 2 miles from the track when all of the fluid finally leaked out and my pedal went to the floor. That was a fun little surprise. I should have bought a lottery ticket because I had brakes the entire time I was driving at highway speeds - I only lost them on the 25mph back road literally 2 miles from the VIR gate.

So what happened? I'm an idiot, that's what. I've rebuilt many ATE calipers in the past, all successfully. ATE calipers have huge pistons - 46mm fronts and 42mm rears. This typically makes them difficult to push in with a fresh seal, so you take a c-clamp and gently push the piston in. Easy-peasy.

Brembo calipers, with their smaller pistons, don't really require a lot of force to insert. In fact, if it DOES take a lot of force to insert, most likely the piston is cocked in the bore and stuck on the edge of the new seal. You need to straighten it out. What you should NOT do is assume it's just like the big ATE pistons and push it in with a C-clamp. Why? Just a guess, but I think it'll tear the new seals a little:



Whoops. As it turns out, that little bit of missing rubber is important. The seal on the left is the 28mm seal from the rear caliper. It's missing the biggest chunk. The seal on the right is the front 36mm seal, missing a small chunk. The fun part is that I didn't discover how bad the front caliper was until I fixed the rear. Since the rear seal was so bad, it was the path of least resistance for the fluid to leak out. Once I fixed the rear caliper, the front started leaking like a sieve.

Now, getting this resolved at the track was an endeavor made possible by a many people. First, Forklift was the one that convinced me to stay instead of bagging it when I was ready to go home and light the car on fire. Then Bob Mulligan came through big time and lent me his garage space to do the rebuild. I could have done the rebuild in the sand of VIR, but thank God I didn't have to. Bob parked his very nice cup car outside so my POS Carrera could sit in the garage he paid for for almost an entire day while being fixed. To say I was grateful to him for that would be an understatement.

Once I had a place to fix the car, the next big problem was parts. Like I said, only one place in the country sells Brembo seals, and they were in NJ and I was in Danville. I asked around the paddock if anyone had extra seals (or an extra caliper) for me to borrow, with no luck. Apparently rebuilding Brembo calipers is not even remotely as popular as rebuilding ATEs. Fortunately, a phone call to APKhaos helped find me parts. He told me to call Intersport in McClean and talk to Charlie.

I called, and Charlie Murphy lent me a spare 951 caliper to use in rebuilding my own for the weekend. This is impressive for one reason - I have never met or talked to Charlie before this weekend. Intersport has never serviced my car. To him, I was just some random guy who called and asked for help, and he did so without hesitation. So I called him up, told him who referred me and what I needed and his response was "I can have a caliper ready for you in 30 mins". This was Friday about 2:00 pm. Fortunately for me, }{ missed the first day of VIR and was coming down Friday after work. He swung by Intersport on the way, picked up the caliper and brought it to me at VIR. I grabbed the 28mm seal from the donor caliper from Charlie along with a spare 36mm seal I had (actually the old seal from my fronts that I saved) and spent Friday night and Sat morning rebuilding my calipers (with a lot of help from Mat P). I was on track for the 2nd are 3rd sessions Saturday. Once I was running with 16 intact seals, I found the car stopped much, much better.

Lessons learned:

1. Do not force Brembo pistons into the calipers with anything but hand pressure. If you can't get the piston in with hand pressure, something is wrong.

2. The Brembo seals from Zeckhausen Racing work in both old and new style calipers

3. Order and carry extra seals with you to the track. I almost washed out of a $600 weekend because of $20 worth of piston seals.

3a. If the old seals aren't trashed, save them, too - just for emergencies like this. I would have saved the 28mm seal but mine were garbage.

4. Charlie Murphy is a stand up guy who came through big time to help a guy he didn't know and had never met before.

5. I owe thanks to several people thanks for making VIR happen - Charlie, Bob, }{, Mat and Forklift. Thanks guys.

6. After a rebuild, always check for a leaky caliper after a short test drive! In fact, I think I'll start pressure testing calipers on the bench before I put them back on the car from now on.

[BlackTalon]

Dorkiphus -- it isn't just the cars...

[Lupin..the..3rd]

Jazz, couple Q's:

How did you extract the pistons? Pull them out with pliers? Or compressed air? or?

Did you return the pistons each to their original location? Just wondering if it's acceptable to mix-n-match or if the piston/bore somehow wear together and should remain matched? I'd like to start rebuilding some of the brembos I've acquired - I plan to have the caliper bodies hot-tanked after disassembly; just wondering if I need to number the pistons first...

[Jazzbass]

Originally Posted by Lupin..the..3rd

Jazz, couple Q's:

How did you extract the pistons? Pull them out with pliers? Or compressed air? or?

Did you return the pistons each to their original location? Just wondering if it's acceptable to mix-n-match or if the piston/bore somehow wear together and should remain matched? I'd like to start rebuilding some of the brembos I've acquired - I plan to have the caliper bodies hot-tanked after disassembly; just wondering if I need to number the pistons first...

For extraction I used compressed air for the initial rebuild at home and brake system pressure at the track. Getting them out at the track was, um, "fun". Mat P deserves credit here. First we pulled the pads and hit the brake until the pistons were fully extended. Then we pumped the brake pedal until one of the 4 pistons popped out. Then we put it just slightly back in the bore so the caliper would hold hydraulic pressure and held it in place with 3 zip ties. We would then move to the next piston. Once all 4 were out, we cut the zip ties and pulled them out by hand.

It's important to note that Brembo pistons are aluminum. They are not rugged steel like ATE pistons, so you need to be gentle with them. Be careful. This is esp true for the scraper ring pistons like I have in the front, as they don't have any lip at the top to use to leverage the piston out of the bore. The dust boot pistons do have a lip at the top you can use to pry the piston out of the bore if you're desperate, but I don't recommend it. Besides, these pistons tend to come out pretty easily (in most cases). Other times, ATE pistons are a PITFA to get out because the caliper develops a rust ring around the top of the bore, locking the piston in. Since everything on the Brembo calipers is aluminum, this is much less of an issue.

I did return them all to their original location. I didn't hot tank them, so I just laid them out on my bench in order and put them back in the same order. If I were sending them off, I'd label the the pistons with a sharpie on the back like this: LI (left inner), LO (left outer), RI, RO. Since the pistons on each side are different sizes (unless you have 930 calipers), there's no need to differentiate top or bottom.

[VaSteve]

Nice story....those are really amazing brakes.

[forklift]

Glad you stayed and had a good weekend.

[Trak Ratt]

Guess I need to order a set of parts for mine Good story.

[APKhaos]

Nice writeup. Kinda thing it would have been nice to have the first time I worked on the Brembos after having spent years on Carrera calipers.

The Brembo pistons are really easy to damage. Not only are they aluminum, but they are anodized. Damage the anodising, and its time to throw the piston away! If you try to go cheap on this, a galled and stuck piston is in your very near future.

If the pistons are aligned right and properly lubed, they will slide in with the pressure of two thumbs. If they don't, straighten them out and try again. Force them, and your seals are going to look like Jazz' pics below.

FWIW, the Brembos are reconfigurable for left or right side operation. All it takes is swapping the crossover line from one end to the other. This means you can carry one spare front and one spare rear to cover any single caliper failure.

Charlie Murphy is a stand up guy. Jazz, you need to give him some paying work now in order to get your karmic debt expunged.

[VaSteve]

Originally Posted by APKhaos

FWIW, the Brembos are reconfigurable for left or right side operation. All it takes is swapping the crossover line from one end to the other. This means you can carry one spare front and one spare rear to cover any single caliper failure.

What's the difference between front and rear? I thought they were the same size?

[Trak Ratt]

Originally Posted by VaSteve

What's the difference between front and rear? I thought they were the same size?

Size. See Jazz's first post.