Porsche 928 Brakes FAQ

Squealing: What to do about squealing brakes?

In a question dated: 6/12/99

I have an 83 928S with new brakes (about 1K miles on them). They squeal like hell. Any ideas on how to rectify this problem? Many thxs

In a response dated: 6/12/99

Your Porsche dealer can sell and install pad dampers/liners. I just received an inexpensive set from http://www.automotion.com for $6.95 but haven’t installed them yet… I figured for $7 it was worth the try:

Automotion P/N Description Reg Sale
—————————————–
BL-900P Anti-Squeal Liners 12.95 6.95

Others have reported less brake dust and less squealing with aftermarket pads.

– michael

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Squealing II: What to do about Squealing Brakes?

In a message dated: 10/22/00

LouisOtt@cs.com wrote: Hi, there have been a few posts lately regarding brake squeal and what to do to stop it. After the track day at Hallet, OK during the 928 OC convention, I decided I needed new brake pads before driving home. I had Mo put them on at his shop where he graciously worked me into his hectic convention schedule. Mo used Metal Master pads and used a material made by BG Products to prevent squeal. It is a thin low viscosity liquid, and the mechanic just put a few drops over the entire surface of each pad and let it soak in for a while. It went on the friction material side of the pad, not the backing. The brakes were assembled without the usual round anti-squeal disks. Just pad against the piston. No beveling of the pad edge or any other technique. It works fine. I have had the pads on for about 6000 miles now including one-track day at Thunderhill where the brakes got very hot. I have never heard any offensive sound from them hot or cold. The product is “Stop Squeal” by BG Products, Wichita, KS., 67213. I bought a small container (1 fl oz) of the product from Mo. BG Products had a presentation of their products at the convention. Possibly Marc White could obtain more info on contacting the company if anyone is interested.

In a message dated: 10/20/00

Hi, Hard glazed pads will often squeel. Glazing is sometimes the result of too much slow driving, but more often occurs when the pads drag on the rotors all the time.
As some others have mentioned, brake dust sometimes contributes even on cars where the pads retract adequately when the pedal is up .Others also mentioned the anti-squeel goodies that hold the pads to the caliper pistons, and the RTV-style goop that you can buy to glue the pads to the pistons. I’ll add to that, and mention that a very light esurfacing of the rotors may be necessary to break a glaze on them too.
Not yet mentioned is sticking calipers, or calipers where the rubber boot has been damaged. The piston is actually retracted by the resiliency of the piston seals. They roll out a little when the brake is applied and the pistion is pushed out, then roll back when pressure is removed, thus pulling the piston (and the pad) back slightly. If the dust boot is damaged, dirt and brake dust may keep the piston from sliding back completely. It also might allow water to get in the gap between the caliper and the piston, promoting corrosion.
On a lark, I decided to try to reuse the anti-squeel clips that stick to the backs of the pads. I’d purchased a new set, but decided to try the old ones anyway. So the new pads went in (Axxis MetalMasters) with the old parts, with a dab of Hi-Temp orange RTV gasket maker on the face of the clips. New, they have a peel-off pad that exposes some adhesive. I stripped that stuff off the old ones (very easy) and just put a dab of orange RTV there, then dropped the new pads in. So far, at maybe 15k on the ‘new’ brakes, everything is fine. Might be the different non-original pads, might be the glue and the anti-squeel clips. The MetalMasters from 928 Specialists came with a happiness guarantee, by the way, and so far I’m very happy. If I could just perfect the technique of getting those pad wear sensors out without cracking the plastic… Good luck! dr bob ’89 S4

(see also Recommendations)

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Squealing III: Why they Squeal & Re-using Brake Dampers

In a question dated: 6/1/99

I also have some very noisy brakes. In searching through the list, there was a message posted 1/24/99 that I could have written describing some high decibel squealing. The response then and now relates to the vibration dampers, which do work nicely. However, once those things are installed, it is virtually impossible to get them out without destroying them. Not a problem if the OEM pads are being replaced anyway, but I regularly need to change out the street pads on my GTS and replace them temporarily with track pads for DE events. I don’t mind the noise at the track, but when the street pads are put back in, the big front brakes sound like a thousand squealing pigs. The smaller back brakes are not so bad. The liners sold by Automotion and which are installed on each pad are minimally effective.

Any suggestions??

Craig Mahon
craig928@ptd.net
’93 928 GTS

In a response dated: 6/2/99

I GOT MY DAMPERS FROM DAVID ROBERTS. IT WOULD BE NEAT IF SOMEONE COULD COME UP WITH A SOLVENT TO REMOVE THE ADHESIVE FROM THE DAMPERS AND FROM THE BRAKE PAD BACKING PLATES, ALONG WITH A SUPPLY OF NEW DOUBLESIDED ADHESIVE DISKS. DAVID?

In a response dated: 6/2/99

Hi Don,

BTW, your cat has stepped on your “Caps Lock” button 😉

A few of the guys have told me they are reusing the vibration dampers, if I understand it correctly they are cleaning the dampers and pads with brake parts cleaner (the good kind that is bad for the environment) and then using generic vibration damper adhesive that comes in a tube and is available at most auto parts stores. I haven’t tried it myself, but it may be worth a try for those that swap from street to race pads on a regular basis.

David Roberts
928 SPECIALISTS
Phone: (770) 928-4777
Fax: (770) 592-4608
Website: http://www.928GT.com
E-Mail: 928@928GT.com

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Re-using Brake Dampers

In a message dated: 6/8/99

928 fans:
Last week there was a thread on changing pads from street to track (and back again) and what to do about the dampers. Since I’m signed up for the DE at Summit Point, I thought I’d break in some new pads (thanks DR) and see if I could reuse the dampers and sensors. I just did the front pads as the rears have plenty left.
1) Remove the caliper from the wheel carrier, 2 bolts (10mm allen socket)
2) Remove pads with sensors and dampers attached
3) Carefully remove the sensors (these things crack too damn easy)
4) Use a putty knife to remove the dampers – they come off easy.
5) Clean the old adhesive off the damper with brake cleaning fluid
6) Put dampers back in pistons and use C-clamp to move pistons back to make room for new pads.
7) Coat dampers with thin layer of adhesive (I used some stuff called
Squeal Silencer from PEP Boys)
8) Slide the pads in – clean up excess adhesive
9) Slide caliper back onto wheel carrier and torque the bolts
10) attach the sensors – carefully

I took it out for a spin, no noise. We’ll see after a couple hundred miles.

Oh, BTW, we lost a guy at Summit Point this past weekend. Brian Redman had just got out of a guy’s Jag (XK120 or some such vintage racer)and handed it back to him. The guy goes into turn 1 and NO BRAKES. The car goes into the gravel, catches a tire and flips over – no roll bar – DOA.
Be careful out there.

Regards,
Joe Rausa

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Recommendations I: Brake Pad & Fluid

In a message dated: 6/21/99

Ed Ruiz and a couple others mentioned the MetalMaster pads on the list.

When the pads started getting thin enough to light the dash indicator, I ordered a set of Hawk Blue pads from DR. I was most interested in the low-dust claim they make. Kinda steep on price for just my casual road driving, but what the heck. David suggested I try the MetalMaster pads first, with a buy-’em-back guarantee if I still wanted the Hawks.

So in they went. In a nutshell, they easily exceed the performance of the original pads that were in the car. After a few hundred miles of careful bedding, they easily outstop the old ones, and make a heck (can’t say h-e-l-l) of a lot less dust in the process. So, mark me down as a very satisfied user. And my hat is off once again to David for making the recommendation, even though it reduced his sale $$ by more than a few Big Macs worth.

David, are these pads available for my Explorer? It’s about due again…

dr bob
’89 S4

In a response dated: 6/21/99

I guess they’re fine for daily driving but… they claim to be Autocross pads… NOT!!! I installed them last Tuesday, drove them to Nevada on Friday and autocrossed them over the weekend… I found the feel a bit spongy which is not a good thing. I’ve got Engine Builders Supply researching Pagid pads for 944 N/A cars.

Miles Smith
’87 944 n/a

Recommendations II: Brake Pad

In a message dated: 9/13/00

Hello all,

I would like to find out from those of you who had taken their cars to the tracks, what brake fluid and pads they are using. And where can I order them.

How often do you change the fluid? Do you have 2 sets of pads – one for everyday use and one for the tracks?

The reasons being that I recently had a few laps of the local circuit and the brake pedal go all the way to the floor (after about 5 laps,= approx.15 miles). Luckily it was on a slower corner. After 30 minutes cooling down it was okay.
Thanks
John
88 S4 Euro 5 speed

In a response dated: 9/12/00

I’ve been using Super Blue brake fluid and Hawk Street Plus pads – 928 Specialists carries the pads. I’ve been very happy with the pads performance-wise.

When I first got them they were extremely loud, toll booth operators used to jump out of their booths when I pulled up. However, it turned out that the squealing (a huge herd of pigs) was due to not having the anti-squeal shims (backing plates?) installed. I still get some squealing but I haven’t installed the rear shims yet.

So far the brakes have been absolutely fantastic.

–C.S.

In a response dated: 9/12/00

I use two sets of pads, Hawk Blues for the track, Hawk Street Pads for the street (duh). I change the Super Blue Racing Fluid every six months (as required for PCA Driver’s Ed).

So far the street pads have been the best I’ve every used. They don’t squeel, hardly dust, and provide excellent stopping power. Of course, I also upgraded to GTS front rotors and calipers, and relatively new 17″ All Season Pilrellis. Together, they may be contribution to the overall improved stopping performance. YMMV.

I have yet to try the Hawk Blues, but I’ve heard really good feedback from others that use them. Now that the T-Belt has been replace, I’ll be getting back to DE and autocross.

~ Merry motoring ~

In a response dated: 9/13/00

John,
I use Super Blue fluid from ATE & I use Axxis and NAPA brake pads with lifetime warranties. All of these items are available to me locally. As the pads have life time warrantees, I never have to buy new ones. I did wind up buying for 2 sets for some of my cars, that way I always have a spare set when I need them, and can get the worn set replaced at my leisure. This beats having to run to the store while your car sits with it wheels off. I have not had any problems stopping or slowing down at the track, although the longest I’ve gone is 35 minutes of track time before coming off & cooling down. Up until recently I used plain old DOT 4, never more than a week old, at the track, with out any problems. As has been said before “Your Mileage May Very”
– David Moody Jr
’78 5sp (over 175 track miles in the last 9 days w/no brake problems)
’81 AT (hers) (ditto as above re:track & brakes)

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SECTION 2: Replacement Tools

In a question dated: 7/10/99

Actually, I’m hoping to avoid “Brake Pad Surprise.” I haven’t changed brake pads myself since my ’78 Honda Civic (drum brakes), but figured I’d outfit my 928 with new pads and dampers for our one-month anniversary. Having no disk brake experience, I turned to the service manuals and spied a couple interesting items:

“brake pad extractor tool” and “piston resetting tool”

Obviously I don’t have these and wouldn’t mind hearing from someone who’s been there that these esoteric items really aren’t necessary for the task at hand. Anyone?

(Has anyone else noticed that as they get older they get more and more deliberate about such things? Ten years ago I would have popped off the wheels and had at it first thing this morning, manual or no. Today, I went to the library to check the manuals on microfiche and even bothered to look up torque
specified for the lug nuts. 🙂

-Curt
’87 S4 A/T “Squeals like pig”

In a message dated: 7/10/99

Both of these tools are unnecessary. A large c-clamp used gently with a piece of softening material( small piece of wood) to prevent damage to the piston works fine to set the piston back into the caliper. The pads will come out without the use of any special tool with a little common sense maneuvering. Good luck.

Roy Vernik
’94 928GTS 5 Speed
Polar Silver

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Brake Warning Lights

In a question dated: 10/21/00

David Kropman wrote:
Hi, I have replaced my rear disks and pads. The pads are not Porsche pads and do not have the wear indicator sensors. Now that I have my car back I have a flashing brake sensor that I want to switch off. I have a 82S Euro AT. Any tips?

In a response dated:: 10/21/00

David,
Simply cut the wires at the pads up short on the frame and twist the wires together, solder them and a piece of heat shrink. Heat with a heat gun to shrink, get the open end good and hot and flatten with a pliers to close up.
Mark

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Front Brake Sensors

In a question dated: 4/26/00

I was told by my Porsche repair person that the brake sensors need to be replaced when replacing the brake pads? Is this necessary? I was hoping to do the brake pad replacement myself, are there any tricks that I should know of? Regards, Dennis

In a response message dated: 4/27/00

Brake pad ” sensors ” the automatic brake pad minimum wear thickness warning system is a small cube of plastic with a wire embedded in it . when the pad wear down too far it breaks the wire . If the wire is not broken the ” sensor ” can be used. The warning brain is looking for a complete circuit many times a PO will cut the wires at the plastic, strip the insulation and twist them together . This defeats the system

Jim Bailey
928 International
jim@928intl.com
79 928 5spd
80 928 5spd
68 911 5spd

Brake Line Replacement

In a question dated: 2/27/00

In attempting to replace the Brake Force Regulator (BFR) I am succeeding in rounding off the nut attaching the brake line to the front of the BFR. It is stuck in real good and getting it off looks very bleak at this point. Has anyone replaced the brake line from the BFR at the left front of the car all the way to the rear brakes? The manual shows that brake line splitting at the rear and going to both rear brakes. I am contemplating in cutting off the #@%*! (offending) brake line, replacing the BFR and replacing the line. Any thoughts from the group?

In a response dated: 2/27/00

While this is too late to help you, perhaps we can help prevent someone else from having the same problem.

1) Always use the special flare wrenches to remove/install brake lines.

2) Always counter-hold the fitting.

3) I certainly would not consider replacing the entire brake line to the rear of the car because of a damaged nut. If the car is drivable, a good garage will be able to cut a short section of the steel line off and replace it.

If you want to do it yourself, remember that this is a very safety-critical task. You will need to buy a flaring tool set that is suitable for making the flares on a brake line. This is a “double flare”, and the standard plumbing flaring tool will NOT be satisfactory, and it is NOT safe to use standard single flares on a brake system.

You will also need to buy a short steel brake line with the proper connection on one end to mate with the brake pressure regulator. You must then either cut and flare the other end of the short line and the cut-off end of the rear brake line, and mate them with a suitable connector.
Wally Plumley
928 Specialists

In a message dated: 2/29/00

I suppose that I over-simplified my suggestions on removing brake/clutch lines.

>> 1) Always use the special flare wrenches to remove/install brake lines.

I have them in mind to take off the line to my master clutch cylinder.

>> 2) Always counter-hold the fitting.

Always counterhold the fitting IF IT CAN ROTATE. If you allow the fitting to rotate, the steel line will be twisted and damaged. There is sometimes a separate screw-in fitting in a cylinder or device, sometimes not. You may need to modify a wrench for tight access, grinding the wrench head down. I try to pick up common sized wrenches at yard sales (boot sales to our UK friends) or flea markets to make into special tools – bent, ground down, cut in two, etc.

Wally

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Stainless brake lines

In a message dated: 11/11/00

Folks,
The reason that most stainless lines do not pass DOT testing, is due to the fatigue resistance of the stainless wire used in the braid itself is extremely low. The most common failure point in stainless lines is in the high stress area around the end fittings where there is not sufficient strain relief.

Some companies who offer stainless lines have adapted a “spring” type strain relief at the junction of the fitting and line, and they have passed DOT.

Will they stretch less under high braking force…yes. Are they suitable for racing…yes, if they are checked every race and replaced on schedule. Are they suitable for street use where they are to be installed and never looked at again or never replaced at regular intervals….no.

Jim Murphy is currently testing some stainless, DOT approved lines, they have been on his 928 for almost 2 years now and we will review the condition of the braid in a few months and see how it has held up against daily usage.

Best bet….stick to the factory lines and never worry for 10 years or so of any kind of use!

—
Marc M. Thomas
DEVEK
650-592-5287 phone
650-610-0557 fax
http://www.devek.net

SECTION 3: Brake Drag

In a question dated: 8/8/00

:Hi all! I’ve got a 86 S (Euro spec) whith ABS. Lately I have been encountering some strange things. Several times the braking system would build up the pressure by it self and (while driving at any speed), therefore, the car starts to brake and slow down. The braking-pad get’s totaly stiff and loosens up first after i press it down whit a great force. What could be wrong? What should I check? Please help me.

Mike

Response

Mike, I had a situation in which my brakes would occasionally drag. I thought one of the front caliper pistons may have been sticking, necessitating a rebuild. Dave Roberts suggested I bleed the system first, that I may have boiled the fluid. I fully bled the system about 2 weeks ago and I haven’t had any problems since. By the way 928 Specialists sell “speed bleeders” which make it an easy one man job.

Hope this helps

Gary Tilson
’89 928 S4 Guards Red/Tan
PCA Member – PeachState Region
928 Owners Club

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Brake Drag & Fade

In a question dated: 4/14/2000

The brakes on my 87 5sp seem to be getting worse. I first had a problem last year on the way to Sharks in the Harbor, which is a 3 hour drive. After about 2 1/2 hours of driving, both front calipers began to apply themselves at highway speeds and I found myself looking for a way to cross 6 lanes of traffic with a rapidly decelerating car. By the time I reached the safety lane I was floored in 2nd gear and the brakes were smoking. The brake pedal was completely at the top and would not budge. After sitting about 15 minutes, everything was fine and I completed my trip. On the way back, I kept the speed at 60 or below and the brakes were fine. I replaced the fluid and figured that took care of it. 6 months later on my next 3-hour trip the same thing occured. But this time, after cooling down the pedal is noticeably spongy and must be pumped once after the car stops to keep it from sinking to the floor. I replaced the rotors and pads, bled the brakes and refilled with ATE Super Blue. But, the fading hasn’t gone
away. What should I try next? Master Cylinder?? The problem seems consistent and manageable, so I’ve continued to drive it around town. Is this a bad idea?

Lee,

In a response dated: 4/14/2000

Sounds as if the brake pedal push rod is misadjusted.

In the master cylinder, there is a very small hole in the side wall of the cylinder, called the bleed hole. This hole should be located just in front of the piston cup. When the pistons and cups are in the fully released position, this exposed hole allows fluid to pass freely from the cylinder to the resevoir and vice versa.

If the brake pedal push rod is misadjusted so that the holes are covered up by the piston cups, the fluid is trapped in the system. Heated fluid expands, lightly applying the brakes. This heats the fluid, which applies the brakes more, which heats the fluid more, which …. – You get the picture.

Another possibility is that you have a bad flexible brake line that is acting as a one-way valve, but that usually affects only one wheel on a 928. I think that the pedal rod adjustment is more likely.

Wally Plumley
928 Specialists

Brake Drag II

In a message dated 9/12/2000

I have been having the problem of my brakes dragging for too long myself. I did adjust the rod at the brake pedal, and it did help, but now I am experiencing brake drag after a few miles. Stomping down on the brake releases it for awhile. I think, based on all the input I have received from list members, that I may have to handle the brake master cylinder: either rebuild it, replace it, or just take it apart and thoroughly clean it out. My problem began just after I replaced two of the flexible brake lines. The other thing I am considering is rebuilding the calipers based on the thought that when I changed the lines I got kaka into the system and mucked it up.
—
Dan Shapiro
’82 928 5 speed “S package”
Chiffon/Brown
Borla exhaust, Custom radiator
’77 Scout SUV

Reponse(s)

In a message dated: 9/12/00

Possibilities are crud in the fill/bypass valve orifice in the master cylinder, or possibly some crud from the hoses migrated into a caliper. Have you been able to isolate which wheel or even which end of the car is braking? A quick stop and a five-digit right-handed non-contact pyrometer would be a suitable measuring tool for this test.

A relatively easy optin to try might be a fluid flush and replace. If you want to get together someplace between Glendale and Tustin or near Lakewood, I’ll pass the amazing brake/clutch fluid flush gismo to you to use. You get to buy your own fluid of course. The biggest part of the flush with this thing is getting the car in the air and pulling the wheels to access the bleeder valves. Ince attached and pumped, you can walk from wheel to wheel, letting that nasty old fluid blow out, replaced by clean new happy fluid…

Anyway, let me know off list if that is something you’d like to try before you pull anything serious off. Besides, you’ll want it to bleed/flush after you do any serious parts swapping anyway.

Anybody else in the Long Beach CA area that needs any of the tools in the collection is welcome to borrow them. Besides the usual hammers and crescent wrenches, I have AC repair tools including an electronic freon leak detector. Free advice is a dollar a minute, help is about double that… Anyway, yell if you need something I might have that you can use. I think I even have those special gauge-wires used to measure ride height 😉

dr bob

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Brake Drag III

In a question dated: 9/12/2000

—
Dan Shapiro
’82 928 5 speed “S package” Chiffon/Brown
Borla exhaust, Custom radiator

In a response dated: 9/12/2000

A relatively easy optin to try might be a fluid flush and replace. If you want to get together someplace between Glendale and Tustin or near Lakewood, I’ll pass the amazing brake/clutch fluid flush gismo to you to
use. You get to buy your own fluid of course. The biggest part of the flush with this thing is getting the car in the air and pulling the wheels to access the bleeder valves. Ince attached and pumped, you can walk from wheel to wheel, letting that nasty old fluid blow out, replaced by clean new happy fluid…

Anyway, let me know off list if that is something you’d like to try before you pull anything serious off. Besides, you’ll want it to bleed/flush after you do any serious parts swapping anyway.

Anybody else in the Long Beach CA area that needs any of the tools in the
collection is welcome to borrow them. Besides the usual hammers and crescent wrenches, I have AC repair tools including an electronic freon leak detector. Free advice is a dollar a minute, help is about double that… Anyway, yell if you need something I might have that you can use. I think I even have those special gauge-wires used to measure ride height 😉

dr bob

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Section 4: Fluids

In a question dated: 6/30/99

I recently had a problem my first time ever out on a race track. I boiled the braked a couple times. And noticed a lot of brake fluid came out of the vent. I dont know if it was from the boiling or from the hard turns and it sloshing around. I notice a racer with a 928 put a rag ovet the cap and secured it with a rubberband to keep the fluid off of the paint. Glenn 86 928s

In a response dated: 7/1/99

Glenn!

When was your brake fluid last changed completely? Sounds to me as though it is waaay overdue. More experienced track users than me advise changing your brake fluid before you take your car onto the track, no matter how long since it was last changed. At the very least, you should bleed the brakes beforehand. I assume that the symptom you experienced was increased pedal travel, with it feeling ‘soft’ underfoot. If you had to apply more force to the pedal than usual, but it still felt firm, you experienced brake fade – overheated brakes. The cure for this is to fit S4 brakes (I wish!). Change your brake fluid to get the best out of your brakes. (I’m surprised Ed didn’t give you this advice when he replied.

Glenn Evans
1980 928 Petrolblaumetallic Certainly not an automatic!

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Brake fluid dot 4 or dot 5

In a question dated: 7/24/00

Hi, could anyone please tell me whats the difference between Dot 4 and = Dot 5 brake fluid. I have a bottle of Dot 5 brake fluid which is not = silicon based can I use this or should I go for the Dot 4?
Tia /Rehan

In a response dated: 7/24/00

DOT 5 is for racing use only. It has a very high boiling point, but it also has a very short shelf life. Considering that most race cars have their brake system fluid replaced just before every race, shelf life is unimportant. However, for street use, very few owners would want to be paying to have the fluid changed once a week. DOT 4 is just fine for 99.99% of the driving that we do. Personally, I use ATE Super Blue Racing Fluid. It’s DOT 4 and has a fairly high boiling point. During some speirited runs, I have been able to boil the fluid, but now that I have the GTS rotors, that
should not occur. YMMV. ~ Merry motoring ~

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Silicone Brake Fluid I

In a quesion dated: 3/9/99

In the last two issues of “911 and Porsche World” two opposite views on silicone (DOT5) brake fluid have been published. The first was very enthusisastic about the DOT5 fluid, mainly because of two properties: (1) it doesn’t attack the hoses/tubes/paint etc.. as the polyglycol fluid does (2) it doesn’t absorb moisture, meaning the the boiling point doesn’t come down in temperature In the recent issue, Bruce Andersson was very sceptical about the DOT5 fluid for two reasons: (a) It is slightly compressible, thus giving a soft feel (b) if you put the silicone fluid into your system, there is always some polyglycol remaining which keeps absorbing moisture (causing gas bubbles when overheated)

So my questions: to (a):did anyone already try DOT5 fluid in his shark? How was the pedal feel afterwards, was there any effect on the ABS performance? to (b) does anyone know how serious this is or if the system can be flushed with anything? Any other opinions / experiences ?

Kurt
90 S4 Auto Euro schwarzmetallic

Response(s)

In a message dated: 3/9/99

One serious drawback to the silicone type brake fluid is that it will gel in lower temperatures… something that will undoubtably give you a strange feel from the stop pedal. Besides that, the owners manual and factory workshop manual both state NOT to use silicone type brake fluid, and considering the price of parts, that is good enough for me. I’ll just be content to have my brakes flushed every spring. (I know the manual states every TWO years, but they are not considering that the old girl spends her winters sitting in the garage.)

Jim Lisankis
1981 928 S 5 Speed

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Silicone Brake Fluid II

In a question dated: 1/25/00

A while back someone mentioned not using DOT type 5 brake fluid in a Porsche… Without saying why. I’ve had very good results using DOT 5 (Silicone based) fluids in motorcycle disk brake systems, and it doesn’t eat paint. (Always a plus with the master cylinder up on the handlebars 🙂 Someone want to comment on the pros and cons of DOT 5 in a 928? I’m asking because stainless lines are in my cars future and a replace/bleed will be required anyway.

-Larry Ware
82 auto (Moss Green Metallic)
Florida Plate: “V8 SHARK” lrware@pipeline.com

In a response dated: 1/25/00

Most of the auto manufacturers specifically warn against using silicone fluid in their brake systems. There are several reasons, but one important one is that it is very, very difficult to properly bleed the brakes with silicone fluid. It entrains air very readily, and the entrained air is almost impossible to get out of the system. While it doesn’t eat paint, it destroys paint adhesion if you ever need to repaint. BTDT – big time! I threw away almost a full gallon of silicone fluid – $$$! I don’t want it anywhere near any of my vehicles – including the bike.

Wally Plumley
928 Specialists

In a response dated: 1/25/00

In addition to what Wally P. wrote, before silicon based fluid can be used in a system that had non-silicon based fluid, the brake lines, MC and calipers must be completely purged of all non-silicon based fluids. The two fluids are NOT compatible. Even if you could get a 100% purge, the silicon based fluid will still feel “spongy” underfoot. DOT 4 ATE Super Blue Racing Fluid (or the Gold version) have a fairly high wet boiling point and are not very costly. Since I do track events, I replace the brake fluid every 6 months. It takes about an hour including the time to take off and replace all four wheels. YMMV. Merry motoring. ~Ed~

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Castrol LMA Brake fluid

In a question dated: 12/17/99

Along with my new suspension, I’m installing new brakes all the way around. I’ve seen Super ATE(?) mentioned a lot as the brake fluid of choice on this list. This product is not readily available in my neck of the woods. The 12/98 issue of Excellence had a tech article on the Brembo 4 piston caliper. The author mentioned Ford Heavy Duty, and Castrol LMA as two products that are popular among Porsche users. The Castrol LMA is available everywhere, even at the corner Fred Meyer. Is there any reason not to used this product?
-Adam Birnbaum
-88 S4 Auto

In a response dated: 12/17/99

Adam,

The Castrol LMA is fine for the street. ATE Super Blue has a higher boiling point which makes it more suitable for track use. One big advantage to using Super Blue and it’s gold equivalent (ATE 2000?) shows up when you change your brake fluid. You can tell when all the old fluid is flushed from the system because the new fluid is a different color when it is bled from the lines. Jim

— Jim Stadter
’83 928 S 5-speed
(U.S. spec) ’88 928 S4 5-speed
Lone Star Region PCA (Austin)
928 Owners Club (http://www.928oc.com)

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Section 5: Upgrades

In a message dated: 7/8/99

I recently upgraded my 78 928 to S4 brakes all around. The following is a list of parts you WILL require…

-4 S4 calipers

-4 S4 or equivalent brake rotors (W pads)

On the front end…

-2 S4 lower ball joints (If you are using the early aluminum ball joints you will also require an aditional excentic adjuster)

-L.H. + R.H. spindle and brake caliper mount (Steering knuckle

-2 Brake lines from the S4 calipers to the inner fender

On the rear end…

You have two ways to go..

1st way (cheapest, but perhaps not as good)

-2 brake lines from the caliper to the inner body

-4 5mm spacers (to space the caliper into the car more to line up properly with the disc.) -(recomend) 2 30mm+ studed “Hub centric” wheel spacers (The rims sit noticably further in when compaired to the front, NOTICABLY!)

2nd way (More expensive but probably better)

-2 Brake lines

-2 rear S4 hubs

-2 complete rear axels (I don’t know how far out the rims will sit in the rear since I did not go this route)

From an application point of view..

-If you are going to be club racing then you should NOT use the Phone Dial rims because of a clearence issue between the face of the caliper and the outer facing face of the rim, not a diameter issue I had orriginally thought of. Of course if you are going racing you probably will have a different set of rims!

-If you are using the car as either a daily driver or only plan on autoXing the car they should be excellent! There is enough room between the caliper and the rim for the everyday type guy, about 3.8mm near the center of the rim at the closest point. You might say that 3mm isn’t enough, but it is right at the hub of the rim where flex is at a minimum, however I wouldn’t want to test that on any club racing events! But for autoX and the street it’s fine.

-Options to upgrade to (if you can afford it)

-Most important upgrade would probably be the S4 master cylinder. (However I am using my stock 78 one and contrary to popular belief my 78 one works perfectly. No spongy pedal or lack of braking feed back on the pedal. The only thing to watch out for is NOT to fill the resivoir to MAX, but rather about 3/4 to MAX. I think from heat expanding the fluid under race situations it will over flow and spray on your hood Have You upgraded the Rear Brake Bias?

In a message dated: 3/12/00

Dear fellow sharksters: Here’s a topic that hasn’t been brought up in a while; Rear brake bias. As some of you know, early 928 models came with a 33 Bar rear brake bias regulator. When the S4 brakes were installed in the 86.5 my the rear brake bias regulator was changed to 18 Bar. Kim Crumb recimmended that folks that want to extend the life of their front track pads should consider replacing the rear brake 18 Bar regulator with a 33 Bar, or even a 55 Bar (a 930 part) regulator. I have the latter and I do not feel any harmful effects during regular street driving, including an occasional drive in slippery stuff.

On the track, the rear pads contribute more towards the overall braking effort. As a result, my front pads tend to last longer and run cooler. During braking in a corner, the inside rear brake wants to lock up, but the ABS keeps it from actually doing so. YMMV.

I have recently heard that Kim Crumb has resorted to using NO rear brake bias regulator, which in effect means the rear pads get just as much braking force as the fronts. I’ll let you know if that’s in fact the case, and what (if any) ill effects result. In the mean time, let’s start the brake debate.

~Merry motoring~

Response(s)

In a message dated: 3/13/00

I don’t believe that my 1980 “S” has a brake pressure regulator. (It has a diagonal split system, so it would need two?) Q. If you have ABS, why would you need or want one? Ed said “I have recently heard that Kim Crumb has resorted to using NO rear brake bias regulator, which in effect means the rear pads get just as much braking force as the fronts.” Well that depends on the force, friction co-efficient and moment, of the rear brakes compared to the front. Usually rear brakes use smaller cylinders (so the same pressure will generate less force), sometimes use different pads with a lower coefficient of friction, and usually have different diameter discs (causing the braking force to translate to a different braking torque). The ideal situation is where the brake bias (determined by the above) matches the weight distribution under heavy braking. It is also considered “safer” for the fronts to lock up before the backs. Smiffy

In a message dated: 3/13/00

Kim Crumb recimmended that folks that want to extend the life of their front track pads should consider replacing the rear brake 18 Bar regulator with a 33 Bar, or even a 55 Bar (a 930 part) regulator. I replaced the 18 Bar regulator in my 93 GTS with a 33 Bar in the fall of last year and ran the car at Mid Ohio and Lime Rock before putting the car away for its winter hibernation. On the track, the benefits were evident- I could brake deeper before a turn (I only trail brake conservatively on certain turns on certain tracks, so I can’t evaluate impending lockup in the rears) but by getting more use out of the rear brakes, I didn’t have to push the front brakes to the point the ABS engages in to get the same stopping power. This is a big benefit since in the past when I mashed the brakes to the point the ABS kicked in, the Hawk pads did quite a number (severe grooving) on the big front rotors. I had just installed some new front rotors and the amount of grooving was reduced (maybe in part due to cryo treatment, but that’s another debate). After a few more DE events I’ll be able to evaluate if the fronts pads are lasting longer. For pure street driving, the improvement is not that noticable and IMO not worth doing (unless you routinely engage in “spirited” driving). I have corresponded with another GTS owner who initially upgraded from the 18 to 33 Bar, then later to the 55 Bar. He’s run a few DE events with all 3 regulators, and is pleased with the improvement of the 55 over the 33 Bar. If I decide to keep running the GTS at the track, I’ll probably opt to install the 55 Bar as well.

Craig Mahon
93 928 GTS 5 spd.
oil sucking monster

In a message dated: 3/14/00
Yesterday I said “I don’t believe that my 1980 “S” has a brake pressure regulator. (It has a diagonal split system, so it would need two?) Well I got it wrong, it has got TWO. Apologies to anyone I have misled. Reading more of the workshop manual, I also found that later models have a dual diameter master cylinder. Never even heard of one of these before. Could it be something to do with getting the ABS working satisfactorily?

One day I expect to own an S4, can anyone tell me how well the ABS works, particularly if any improvements were made that cause particular model years to be better. Smiffy

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Section 6: Rotors

In a question dated: 9/13/00

Ed,

Will you be using a separate set a rotors for the Hawk Blues when you go to the track? My concern with running two sets of pads on one set of rotors is that when one set of pads causes wear to the rotor, then the other pads will no longer be bedded properly because the rotor surface has changed.

I’d be curious to hear from you and other racers on this because my brother
and I recently faced the same situation. He wanted to get a set of track pads for his Golf GTi and then just swap pads based on whether he would be driving at the track or on the street. I recommended that he buy another set of rotors for the track pads because of the bedding issue.

What’s the concensus?

Jim
—
Jim Stadter
’83 928 S 5-speed (U.S. spec)
’88 928 S4 5-speed
Lone Star Region PCA (Austin)
928 Owners Club (http://www.928oc.org)

Response(s)

In a message dated 9/13/00

I do not plan to change rotors every time I change pads. Track pads wear faster than street pads, and will likely mold themselves to the rotor surfaces within a few hot laps. Typically, I drive the first (warm-up) lap with my left foot pressing lightly on the brakes. This helps to get the pads up to optimum operating temps before I start my “hot” laps. YMMV.

Response(s)

In a message dated 9/13/00

Although track pads will cause some wear on the rotors, the street pads will have plenty of time to mold themselves to any changes on the rotors.
Again, YMMV.

~ Merry mtoring ~

Rotors: Turn vs. Replace

In a question dated: 5/9/00

Should rotors on our ’85 AT 928S be turned or replaced? We found a ridge and are not sure what that means. The brakes do squeal..but what else is new? Your suggestions are truly appreciated.
Steve & Debbie

In a response dated: 5/9/00

The pads normally do not come quite to the outside of the disc on a 928, which does result in a wear ridge at the outer edge of the disc. You will need to measure the thickness of the discs to determine if they are worn too badly to use, assuming that they are reasonably smooth and the brakes do not “pulse” or shake upon application. On the ’85, new front discs are 32 mm thick, and the minimum thickness after maching should be 31.2 mm. Rear discs start at 20 mm, and the minimum after machining should be 19.2 mm. In actual practice, the discs will need replacing when they warp, causing pulsing upon brake application, or when they get scarred and scored because you ran out of friction material on the pads. If the discs get too thin, they will usually warp. Racing or very hard street usage will be a little more critical, and the thickness and smoothness must be checked more carefully.

Wally Plumley
928 Specialists

Rear Rotor Replacement

In a question dated: 11/5/00

Does anyone know where can I find a good description of the procedure to pull out the back rotors? I need to check my parking brakes. It looks that the parking brake set up of one of the wheels is quite rusted since
it gets stuck once the lever is down and brake is only released when the car moves forward with a “clunk” noise. Of course, before pulling out rotors I must know to take the out the brake calipers so any advise will be appreciated. The manuals are not clear enough to me (sorry for my primitive non technical mind!).

Juan
’93 GTS

In a response dated: 11/6/00

Juan, steps as I remember them:

1. Jack up the rear of the car
2. Remove wheels (rear)
2.5 Release the parking brake (Do not forget this step!)
3. Remove calipers – 2 17 or 19MM bolts at least on my ’87
4. Either hang the calipers on twine or wire above rotors – keep from disturbing the sensor wires
5. Remove the two Phillips head screws on face of the rotors (between wheels studs)- Sometimes these are not reinstalled by prior owners or mechanics. I had to use and impact driver on mine. If you don’t have one you might pick one up they are usually under $15.
6. Try pulling and hammering (with a rubber mallet or a wood block and a regular hammer) don’t get carried away with the hammering. If the rotor doesn’t break loose the rotors have two holes where you can screw in two metric #10 (I’m not sure of the thread type) (The 9 volume set describes this) bolts screw in the bolts which presses the rotor off.
7. This will allow you to acces the parking break shoes.
8. The books have the spec on minimum thickness or as a Scott rule of thumb about a 1/4 of an inch. Or if they are wearing unevenly (where one side in down to the metal.
9. Order new shoes if you need them and if things are rusted plan on ordering a parking brake hardware kit (any of the big three will be able to get them). Also check the rotors for minimum thickness which is stamped on the center “hub” of the rotor. If they have a lip on them they are probably under sized. If you can’t determine the minimum thickness a local machine shop will check them for you. (you will need to bring the rotors to them)
10. To reinstall the rotors, do the reverse of the above but before you install the calipers you may have to use a C-clamp to press out the pads
slightly.
11. Also check your pad thickness for wear. If they are touching the brake pad warning sensors they need to be changed too.

E-mail me personally if you have other questions

Good luck
SWS
’87 5sp

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Section 6: Other

In a question dated: 6/19/99

928 fans: This morning I began painting my calipers with the Automotion caliper paint kit. The kit consists of brake cleaner, lacquer and hardner. At $55 & UPS it’s a little salty for a 1/2 pint of paint. I would suggest anyone else just go to an automotive paint supplier, tell them what you need the lacquer for, and they’ll fix you up. Following are some thoughts:

1) Don’t try and change caliper color unless you completlety remove calipers and pads and all brake lines.

2) If you are using the same color, leave the calipers on the wheel carrier, release the pad retention spring.

3) As with most paint projects, preparation is the key. The brake cleaner will remove most of the grime, dust and undercoating. I followed the brake cleaner with a wire brush then synthetic sand paper to rough up the surface. Then cleaner again.

4) Two coats of paint (the second one is supposed to go on only 15 minutes after the first)

5) Use a 1/2″ china bristle brush. Also, get a small brush for working around the “PORSCHE” raised lettering.

6) There was plenty of paint left over, so I figured I’d dress up the lug nuts which had long since lost their paint finish. For these I added a little lacquer thinner to the paint. I don’t know how they will turn out, but I can’t be any worse than they were.

7) Wait 24 hrs. and mount those new Technology Twist wheels (now you know my motivation for dressing up the calipers).

Look out momma, baby got new shoes!!!

Regards, Joe Rausa ’89S4
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“Whats the best technique to launch?”

In a question dated: 7/22/00

“””Whats the best technique to launch?””” I have a question along these lines as well. Is it acceptable to “load” up the torque coverter for about 2 secs by holding the brake and slightly reving the engine up? Im not talking to redline here,,,just enough to get the engine over that intial point that it has to accelerate itself. I get a much quicker off the line start this way and I can easily get the tires to ” light up”…i can never get the tires to let lose from a stand still by just stomping on (yes i know tire spin is waisted energy..but it sounds kewl ) I just hold the brake with one foot..rev slightly with the other and release the brake and then floor it… Tony

In a response dated: 7/22/00

Stalling the Torque Converter or “brake-torqueing” it shouldn’t hurt anything at all. It heats the oil, of course, but not in a couple of seconds. Up to full throttle is okay, but of course, there is an optimum that doesn’t spin the wheels too much. I am assuming you mean IN GEAR, not reving the engine in neutral and the dropping it in gear. Nobody would do that, would they? Have at it.

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