86-95 944/968 Brembo brake info

[MattKab]

I've now covered about 10.000 :D miles in the last 15months with a stock 3/4" bore m/c and 951 Brembos F + R. The bias feels right, the braking is phenominal. Nothing but.

The mathematics may well suggest a too forward bias, my front wheels are 95% of the diameter of the rear. Which helps brake bias no end. (I've had bigger tyres on the rear of 4 out of 5 of my previous Bugs)

What is the diameter of the equally sized pistons in the rear callipers and the diameters of the two bigger, dissimilar sized pistons in the front?

I'm not convinced I need the Kerscher split-bore m/c. And I don't want to pull my callipers for such a trivial task, needless hardline fatigue and all that.

Matt

[Superman]

None of the piston sizes are the same. They are always larger in the front and get smaller going toward the back, repectfully (largest pistons are always toward the front). The below concerns the 944/968 with brembo brakes.

86-95 rear, all
30/28mm pistons
98mm pads
299x24mm discs

86 (only) front, axial
36/34mm pistons
98mm pads
298x28mm discs

87-95 front, axial
40/36mm pistons
98mm pads
298x28mm discs

88-95 front, radial
44/36mm pistons
132mm pads
304x32mm discs*

*this can be replaced with the factory 'drilled' 322x32mm 928GTS discs along with the larger 928 GTS calipers.

NOTES: A rear caliper will not fit the front spindle. The 87-95 calipers will fit the 86 spindle (to upgrade the calipers). The 98mm pads, front and rear, will interchange.

[MattKab]

Thanks Superman, just the info I need.

Matt

[MattKab]

Stock 3/4" bore m/c used with '86 Brembos front and rear has a bias of 1.45:1 towards the front

Stock 3/4" bore m/c used with '87+ Brembos front and rear has a bias of 1.72:1 towards the front

3/4" 15/16" split bore m/c used with '86 Brembos front and rear has a bias of 1.078:1 towards the Rear

3/4" 15/16" split bore m/c used with '87+ Brembos front and rear has a bias of 1.096:1 towards the front.

[kiwivw]

Superman,

Why is there a difference in the 2 front brakes in years 88-95, are the bigger ones the M030 option?

Are these the same as "big reds", in other words how can i mount these to a Cb performance spindle, can i use a big red adapter for a 944 or do i need to machine one myself :(

What about rotors which ones could i use on a non-turbo/86T hub?

Does anyone know?

[Superman]

Yes, they are the Turbo S or M030 option calipers that are radial mounted (these are 928 S4 calipers not 993 "Big Red"). The smaller ones are axial mounted.

In regards to your CB spindle question, I know nothing other than Supers. Direct that question to Sandeep or Alex.

[kiwivw]

Thanks Superman,

Teh 928S4 calipers from most of my readings take 32mm rotors, but the ones i have for the 944Turbo S/ M030 option take 28mm rotors is the right?
If so which rotors are these, according to your techincal doc posted here?

[Superman]

No, the Turbo S & M030 have the same 304x32mm discs (and calipers) as the 928 S4.

[kiwivw]

Hmmm,

The calipers i have measure 31mm between the smallest point of the two sides.
The only numbers i have on them are 20.4xxx.xx
is there any way to work out what these calipers are from?
there is no 928 or 951 number on them.

[Superman]

You won't find any Porsche numbers on these calipers as they were made by Brembo. The description you've given leads me to believe they are the axial mounted early Turbo (not Turbo S nor M030) calipers. Do they look like these (http://www.germanlook.com/Forums/attachment.php?s=&postid=15730) ?

[MattKab]

Brake calipers in general are not specific to a model or manufacturer, but are specific to an application. e.g. stub-axles, hubs and rotors are designed around existing calipers. This goes for most brakes on most cars.


When I got these:
http://www.thesamba.com/vw/gallery/pix/85827.jpg

They were amongst 50+ pairs including Bigreds. I wanted nothing but the '86 like those in Supermans pic.

Mr Porschapart had this type of caliper that had the script in cast letters, with printed (small in white, same as big reds) script and he had a pair in red powdercoat that were blank. One pair was black with a Brembo script. All had the cast Brembo logo on the inside.

All 'original' 951 calipers have the script in cast letters, Mr Porschapart suggested that the others were replacement parts sourced from Brembo and not Porsche as the labelled units are only available from Porsche main dealers. He said the axial mount 4pots and the bigreds retail at.. wait for it... One thoasand and two thoasand pounds respectivley, EACH :eek:

I paid £60 each and was happy :) Second hand cars have second hand brakes I told myself.

Matt

[Superman]

The first few years Brembo embossed the brand name on the caliper, these same calipers came on Ferrari as well, and then eventually smoothed it (caliper side face) and the name was added with a sticker.

[MattKab]

Cool! I haven't seen those before.

The Latest Aston-Martin Vanquish has similar I believe but with Aston..

..and they are red, not pink! ;)

[kiwivw]

Here is a photo of the calipers, note it a radial mount with 44/36mm pistons. The caliper beside it is a 944T 86 rear caliper.
The gap between the pads is 31mm, so a 28mm rotor is required.
Any idea what these are?

[Superman]

Those look like the 928 S4/944 Turbo S calipers. I spent some time and checked several resources to confirm the 32mm thickness (which is actually 31.75mm) of the rotor and it is correct.

I did some research and the only one, of this design and radial mounted, that used a 28mm rotor is the 993 Turbo rear caliper.