Greggles

More then a few have upgraded to S4 brakes and everyone who has reported doing it has raved about the improvement. At $3k+ for 4 corners it becomes almost as much as adding a SC. Those big calipers do look very nice!

Does anyone have the advertised 60-0 braking distances for an '86 versus '86.5 (braking dist. is not in the '85 owners manual)? I know brake fading is reduced w/ the 4 pistons, but I would like to know the raw numbers.

Paul D

Greg - I was able to dig up the following from some pages of the 'Porsche 928 Performance Portfolio 1977-1994' book. They didn't list 86 vs 86.5 comparisons but here's as close as I could get.

1983 'S 60-0 = 156', 80-0 = 280'
1988 S4 60-0 = 137', 80-0 = 234'

I'm almost done with this upgrade and I'll be heading to a DE at Watkins Glen the end of May. I can't wait to feel the difference.

mark kibort

stopping distance will not be effected. what they do provide is a better feel during high braking activities, and much better heat disappation during racing applications. i had the old single piston calipers on my first 928 racer, and stopping was not different. IN fact, racing with JP at Road america, he had my old style brakes and wasnt that slower at all in braking. my times at laguna seca are only about a second to two seconds faster, much of which is due to lighter weight and more hp (ie 20-30hp or so). most of braking performance is due to the tires and the driver. However, where the S4 brakes will shine (or larger) is i high stopping demand applications.

hacker-pschorr

The S4 was also heavier, but has ABS and larger tires.

Scott M.

Greggles;

Not the numbers you need, but...

I put S4 calipers on my 79 Cab front/rear and stopping distance was dramatically reduced, but the best attribute is the ability to modulate the pedal. I then went GTS fronts and again the distance to stop the car was also reduced. So much so that I am at the limits of tire adhesion (w/o ABS) at will.

Scott

Ed MD

Mark, as always I appreciate your comments, because I know your opinion is borne from track experience. I sometimes fell inadequate with my 85 brakes when I read the post, but I don't notice anything when I'm driving, even compared to the S4. I assumed that it was that I wasn't taking it to the limit. In reality the limiting factor in my cars is not the brakes but the unit behind the steering wheel-me! Ed M

hacker-pschorr

78-82 calipers / rotors are far inferior to the 83-85 setup. I upgraded the brake's on my 81 to 84 S brake's, there was a huge improvement. S brake's are an excellent setup. Jean-Louis is a perfect example of this.

Two laps with my stock brake's at RA were gone, faded away. With stock S brake's I can run 20+ minute sessions with zero fade.

GlenL

Don't overlook a few factors:

Do the tires support the increased braking? Better feels is nice, but if you can brake to the limit of the tires, then bigger brakes won't stop the car more quickly.

What pads are you running? I switched to Hawk Blues for the first time recently. (DE) I've run a bunch of pads and the difference between good semi-metallic street pads, the Hawk HP+ dual use pads and real race pads is amazing. Moved my braking points in 10 to 30 feet at every corner.

The car does great with the "S" brakes. Not a hint of fade (ATE gold fluid). Not getting out braked by lighter 911s or 944s.

And as to the braking comparison, there's a lot more going on than just calipers. Anitlock tuning? 8" rears?

mark kibort

ABS sure doenst help us, in fact, if it engages (barring a rain stop) you will be amazed on how far the distance will become!! actually, the ABS is a saftey net, nice to have when you do bite off too much,and then you dont flat spot tires! racing ABS like on a cup car is entirely different

MK

mark kibort

yes, while this is true, look at the calipers and pads of the 79 vintage 928. they are like hockey pucks . I ran a race at thunderhill with them on a 79, there was a lot of spongie pedal, some fade, and it took a lot of push to get it to stop! (and at 7 seconds a lap slower pace!)
However, its night and day compared to the 84 system. the difference between the 79 vs 84 is HUGE, where as the 84 to the S4 is much less, but still an improvement. Keep in mind, their are MANY BMWs with 275ish rear wheel hp, and 2900lbs, running between 2:28 and 2:30 at Road america with the 84-85 calipers. the BMW ive been running against at laguna for years now has these calipers. though he weighs only 2500lbs, i do have a slight hp edge. we go at it like cats and dogs, and he has no fade. as glen says, with the right pads and fluids (as well as techniques) stopping power is very close, but in high demand applications, or a longer race, OF course, the S4 brake is superior. PLUS, i remember changiing pads every race, vs every other race with the S4 and on the same track and simular times.

bottomline, the S4 brakes are better, sure, but for the street, its not as important, and better on the track as far as feel and pad, rotor wear goes.
stopping capability is more on the tires/driver/track surface/setup, than anything else

MK

Greggles

So I would be safe to say, unless being used for racing there is minimal difference between the S & S4 brakes?

mark kibort

no need to duck!

hey, the S4 brakes are GREAT . the best in the buisness! However the real difference is in pedal feel, less effort to do the stops we are talking about, but the sheer numbers dont support much actual performance difference as far as stopping distances. Pedal feel, pad wear, system weight, etc are some of the differences.

as you go faster, you need more brakes, just as if i had 420 to 490 rear wheel hp, id want brakes like anderson (F50 rotors, big calipers!)

Mk

Scott M.

Greg;

Do yourself a favor. Come swing by the shop here in south-central Pa. We'll drive each version of the 928 brake system. Early OB, early OB with GTS, S, S with performance pads, S4 and GTS...
I'll take you on my 'special' test track. You'll see the difference isn't minimal.


Scott

mark kibort

can you get both cars to lock up 60-0 or 100-0. then your limitation is not the brakes, its the tires. been doing this too long to not know the difference. Ive raced 79s, 84s s4s and big brakes. feel is better going up, especially from 79 to 84, but from that point forward, its feel. put it this way, if you CANT stop as fast with S brakes vs S4 on the same car, its not the car...........

MK

Scott M.

Well then I'm sorry to say that your not using your brakes to their full potential. You may have some 'race' experience, but there is a whole 'nother world out there. The one we like to call reality. The one I drive a 928 in at least 5 days a week.

Scott