jwillman

I remember reading some posts about putting 928S brakes on an OB as an effective way to upgrade. Are the rotors and calipers different or only the calipers. What is the difference and how much better are the S brakes than stock OB?

Thanks

VT928

The "S" brakes are a significant upgrade from the 78 thru 81 brakes on the front US cars. The rotor is 282mm in diameter and 32 mm thick and directionally slotted. The caliper is much larger and the pad area has almost twice the surface area. To do the change over to "S" brakes is somewhat complicated, you have to replace the front spindles with the spindles from a 82 to 86 US car. The bolt spacing on the "S" caliper does not match up to the spacing on the 78 thru 81 US brakes. Due to work and cost involved in replacing the spindles most people upgrade to the 4 piston S4 calipers that can be mounted to thier current spindles with adaptors. Several 928 vendors have all the parts needed for the upgrade. The 304 mm rotor and the brembo caliper is a better brake combo, is easier to do and costs about the same a an "S" upgrade. When I upgraded my 80 Euro S from the factory "S" brakes to S4 brakes the "S" stuff (spindles, rotors, calipers, pads and lines sat in the garage for years and I finally ended up giving them away.

Paul 1980 Euro S Red/Blk Lea

karl ruiter

As stated above it is calipers, rotors and front spindles. I got my last set from here or ebay or something for a very low price ($150 or something). Note that I was very unhappy with the brakes on my '79 when I got it. Upgrading to the S brakes did not fix it. Putting in a new early booster did not fix it. Finally, I put in a later booster and new master and now I am very happy with them. Not sure if it was the new master or the bigger booster or the combo of that plus the S setup that did it.

pcar928fan

My vote is the booster was the key... MC certainly didn't hurt though!

Landseer

I've got the S brakes and they are very good for street.

Used S spindles should to be scrutinized a little bit.

The inner bearing has a tendency to spin, leaving tracks and discoloration.
Just something to watch for if you grab some salvaged ones.

I'm stocking a spare set just as a precaution.

Mrmerlin

the wear will be evident on the inner bearing seat on the bottom of the spindle

karl ruiter

I agree it might have been the booster. I was comparing the performance to that of my '82 and I had a late booster in that as well. Seat of pants: I don't feel a big difference in the braking of my S4 vs my S braked cars with the late booster, but did not like the way my '79 felt with pre s brakes and the small booster.

Landseer

Thanks for the insight regarding booster.

IcemanG17

the early cars have large rotors, with fairly small calipers-pads...& a 9" booster.... the "upgrade" to S brakes is slightly bigger rotors, with MUCH larger calipers-pads and a 10" booster.... They only got better from there...

My experience.... S brakes work VERY well....I endurance race them, with ZERO issues....the key to effective braking is proper pad selection with good fluid and brake lines.....on a street car....just about any 928 brakes are fine....unless you drive REALLY fast...and honestly if you do...its time to jump to the track...since any street driving that pushes a 928 to the limit is WAY to fast for the street!!!!!

hacker-pschorr

My 79 has S4 brakes with the stock booster and is a dedicated track car. I keep being told my car has awesome brakes, but I don't know how to use them

When you put in the later booster, did the later bias valve come with it?

My 81 was upgraded to S brakes, still the stock booster and no complaints with those brakes either.

IcemanG17

This is a VERY good ???

My "Estate" has excellent brakes....far better than any other 928 I have driven, including the Widow...which I thought had good brakes at the time....

The Widow had massive tires and GTS brakes with a 33? bias bar....

The Estate has S brakes (race spec) all around and has a 55 bias bar..I think this is the key...since most S4+ have only a 17? bias bar..so the rear brakes to almost nothing...

When I come off track and touch my wheels....the fronts are hotter..but there IS heat in the rears....so the brakes are working!!!

karl ruiter

I did not change the bias valve. Before this last step my brakes felt just like 914 brakes: nice firm pedal, but the car just keeps going. Could well have been the master, as almost every thing was wrong with the car and that was pretty much the last major part I had not changed.

hacker-pschorr

I tracked the 81 once with the stock brakes at Road America. Granted it was my first time out on the track "at speed" (versus parade laps) with fresh fluid and pads.
After 3-4 laps the brakes were gone.
I went back later that year with S brakes, same pad compound and never once experienced brake fade.

During the first track event temps were in the 50's, the second event upper 70's.


For my 79 I pan to upgrade to a dual master setup like Mike Simard has on his race car:
http://www.simardracing.com/Brakes.html

If anything this will give easier access to the clutch master

karl ruiter

Jim, if you decided you wanted to go this way, I think I have some extra S brakes parts sitting under my house in L.A. (just remembered) I think that there are at least front calipers and rotors, maybe rears also. Not sure about the condition, but I think I had two sets and I put the nicer set on my car. Anyway these could be yours for the shipping. Let me know and I will have a look next time I am there (about a month from now).

jwillman

I just purchased new rotors front and back for $100 and was hoping it was as simple as slapping different calipers on her. Not sure I want to go to all the trouble to change out all three. As i did nopt buy her for speed I am probably fine with stock. I will throw on the new rotors and pads and see how she brakes.

Thanks All.