4 Piston calipers: saving myself from...myself...

[dtw]

Well, I was hoping the sickness wouldn't spread, but indeed it has - and only a few short months into 928 ownership. See, in my 911 world, I am a compulsive buyer of parts cars. It is a good gig - smouch a few tasty parts for my own cars, sell the rest or squirrel them away in the vault - the circle of automotive life continues.

When I bought my shark (in all of it's sharkulence), I determined that this would be different - there would be no 928 parts cars! (Even though I knew they were cheap and plentiful....)

So fast forward a few months, after I realized that the brakes on my shark were woefully mismatched to the rest of the car, I began surfing around, pricing out a set of S4 brakes. eBay was a bust - the brakes are just not to be had there. 928 Motorsport sells a kit, but the price is too high for me.

Only one thing to do .... buy a parts car. Yep, last night I hauled home an '86.5 928 in Meteor Gray metallic with burgundy full leather interior. It is just a few important serial numbers away from my own '86.0 Meteor Gray car. It has the all-important monster Brembos - so now I just have to figure out what all parts need to be transplanted over. The car has been baking in the NC sun for 7 years, so I will rebuild the calipers as a matter of course.

The timing is perfect to have found this parts car (thanks, automated eBay search), as I just got my 928 back on the road today after an extensive round of upgrades and maintenance. It is extremely fast now, and definitely is wanting for big brakes. We'll begin the surgery this coming weekend - stay tuned!

[Johnny V]

lol, good story telling! +1 for finding and anti-gravity 928

[MPDano]

Yes, excellent story.

[Danglerb]

Just so you know, unless you track your 928, and then only on certain tracks, will the stock S brakes start to fade and have issues.

Nothing wrong with buying parts cars, its when you start trying to save them you go off the deep end.

[dtw]

OK, time to update this story. After weighing my options, I came down to two options here:

1. Transplant entire front suspension and braking system from donor car
2. Transplant brakes only, using front caliper adapters

I tried option 2 first, but upon test assembling everything, I quickly realized that preserving the ABS functionality would be impossible. That is, without reinventing the wheel - which I really didn't have time for. At the same time, I really did want to have ABS - which was working fine on the donor car, but dead on my car. So I shipped back the early spindles and adapters and proceeded with option one.

Come, as I take you to the depths of Mister Nerdwrench's Workshop - on to the conversion:



These 4-piston aluminum Brembos are truly bad-ass. Here they are as-pulled - monsters!



And, just for fun, here's a front Brembo caliper next to the front caliper of a Fiat X19. The caliper is longer than the diameter of the rotor, by far!



Here's the workbench on the morning of the big day. For the 'easy' conversion, you'll see that we've prepared early ('81 to '83) spindles to mate with the caliper adapter brackets (left foreground on green plastic). I also splurged on some absolutely gorgeous two-piece 993tt drilled rotors - which, as it turned out, were the wrong size anyway. Didn't matter since I returned the lot of it. In the background you are seeing whatever dreck brake fluid was cheapest at my FLAPS - don't panic.

Not pictured is the ATE Super Blue which was introduced after fully bleeding the system with the garbage fluid. Also new wheel bearings as a "while you're in there" exercise - they are cheap.



I have skipped over the pictures of the 993tt rotors mounted on my car, as they were just too painful. Now that I had committed to the full transplant with factory parts, we started yanking parts. This involved a careful reading of the workshop manuals. Late '86 cars had a different tooth count on the ABS sensor wheels - so the front hubs and rear axles must be carried over. Technically, the front sensor wheels are pressed onto the hub - but there's no way I was going to try to remove them. This meant I had the honor of doing yet another frong wheel bearing job. The last time around was such a pain, I paid the pro shop next door to install the inner and outer races. The rear sensor wheel is cast into the CV joint housing - so this meant trying a job I have actually never done on a 911: removing the rear axle nuts! This went fine on one car, and presented an impossibility on the other.

The photo you see above is the product of multiple technical minds - but before any beer had been drunk. I have video of this that I'll post soon, but as you're on the edge of you're seats now I'll just tell you - it didn't work. We lowered the lift and that red-handled pry bar you see folded effortlessly in half. Later trying an Even More Secure Method, I broke two big half-inch drive wrenches with Excessively Long Leverage. Right tool for the right job - we finally borrowed the Mother of All Impact Guns and they spun right off. Damnit...I'd like to think it was the extra hour soaking in penetrating oil but we all know the truth.



Here's a lovely shot of Sharks in Repose in the main workshop of Mr. Nerdwrench. The donor car in the foreground, my shark in the background. Both Meteor Gray Metallic. Donor in auto and standard diff, mine in 5-speed and LSD. '86.5 donor car also features semi-well-executed S4 body kit.



One drawback of going to the 86.5+ S4-type front suspension is the upper ball joints. They are not serviceable or replaceable. If your upper ball joints are trashed like mine were, this leaves you 3 options:

1. New upper A-arms from Porsche - $900+ each
2. Rebuild existing A-arms by sending to Der Faterland - $450+ each, and an interminable wait. As a proud American, I demand

instant gratification amd minimal downtime, which brings us to option 3:
3. Aftermarket A-arms in steel, with replaceable ball joint cartridge - less than $300 each. We have a winner!

Here they are being fitted in the picture above. It was the 2nd part to go back on my car, after the tie rods with fresh boots (as pointed out in the WSM, late '86 tie rods are of a different length than the early '86, and must be transplanted along with the rest of the suspension).

If you have never removed the front upper A-arms on a Porsche 928 but would like to get a feel for the experience, that's no problem. If you have a five pound sledge and a stout bench-mounted vice, you can play along at home. Head out to the garage.

Drop your pants and chuck your sack up securely in the vice (be sure your 5lb sledge is within arm's reach). With a clean shop towel, wipe away any beads of nervous perspiration from the prepared work area, and proceed to beat bloody hell out of your nuts with the sledge.

When you regain consciousness, repeat this process 3 more times (there are four retaining nuts in total) and you will have an accurate portrayal of this job.

A bit of exaggeration perhaps - and truth be told, with a 21mm GearWrench, even the driver-front nut is not that bad. Be sure to install the large washers under the rear nuts - they are important for the secure installation of the front subframe.

The new A-arms are a nice bit of kit and include solid bushings versus the big rubber donuts originally provided by Porsche.

This noticeably improved handling response/feel!



Fully assembled front suspension,ready for brake parts and hub.



Finished front corner! These are beautiful, but I wish those 993tt rotors were still there...



Driving around a day or two soon provided an unbearable squealing sound. Rear brake shields grinding on the rotors. Uggh. I had to endure this for a solid week. The noise was hideous. Part of the problem is that the big caliper need more room on the 'ear' of the hub, and the two forward nuts/bolts can't be installed on the dust shield - they interfere with the caliper.

Rather than ditch the shields - as we are striving for OEM-quality installation - I worked out a solution. The holes for the original bolts have just enough meat to be tapped for an M8 Helicoil. The ears are aluminum and the tap will rip through them

like butter - so get it right the first try. I installed the Helicoils with some blue Loctite and then zipped off the excess 'coil poking out the back with a die grinder.



The other issue is inadequate clearance between the rotor and the shield. You can see here where the rotor ground down the shield. I fired up the die grinder and cut down the shields a few millimeters more.

[dtw]

I cut down the original bolts to the proper lenth to ensure proper clearance, and we left with a nice, stock-appearing installation.

This completes Stage 1 of the brake conversion. The ABS and pad sensors are currently not wired, which means I have two more idiot lights on my dash. Meh, who's counting. Braking feel is utterly transformed. This car now has the proper "Hand of God" braking feel that Ferry (or Ernst) intended.

Stay tuned for Stage 2, when I will transplant the late '86 ABS pump and computer, and figure out some sort of wiring solution - probably with some automotive-grade aftermarket connectors. We noticed that Porsche felt quite strongly about grounding the bejeezus out of the ABS sensor wiring - there are grounds bloody everywhere - so we'll pay careful attention to that in the solution that is ultimately fabricated. We'll probably skip the larger vacuum servo and master cylinder of the late '86, as pedal feel/modulation is excellent with the existing parts. The later servo/MC provide a somewhat firmer feel, but with less feedback.

[garylewa]

Excellent write up man; I would love to do this conversion on mine but your story brings up too many "war wounds" when I was trying to get my car up to snuff. Your "balls in the vise" comment had/has me in tears. When I'm ready for more self imposed abuse I will reconsider this upgrade, but right now my car stops fine. But ohhhhhhh, do I wish.........
I removed the wheels when I first thought of doing this, scoped out what needed to be done (& purchased........) and said forget it. I changed the pads and sensors, refinished the rotors and rebuilt all four calipers (painted them all black also). Now your thread has me considering "what if...............". My wife would kill me. Again, great story.

[MPDano]

Please post this in the Common Fixes Thread. This is a great write up.

http://forums.pelicanparts.com/porsche-928-technical-forum/607208-most-common-928-issues-fixes.html

[milkman383]

Excellent writeup for sure. Makes me glad I held out for a 86.5+ and X 1/9? You have (at least one of) those as well? Cool!!!

We'll have to meet up at VIR, I'm there 20-30 days a year.
-jeff