odurandina

_


i'm currently runnng 928 GTS 322mm front brakes on my 968... does anyone know if 928 S4 304mm front rotors/calipers will fit on my rear wheels... or what adaptor would i need that could make it work.... or should i go with 928 S4/GT/GTS 299mm rear rotors... and in either case, what calipers would i use ?


also... how often should i change my brake fluid ?



i also found a nice post at:


http://www.audifans.com/archives/1999/05/msg01067.html


which includes the following:



I have been quietly monitoring all the discussion regarding brake upgrades
and I feel it is time to provide some facts that seem to be lacking.

First, let me clear the confusion regarding sizes of calipers. There is only
one "Big Red" (hereinafter referred to as "BR") caliper. It originally came
on front of the 91 Porsche C2 Turbo and has been/is used on the 993, 993TT
993 GT1 & GT2 and the 93-95 928 GTS. The pad used with this caliper is 5.18"
x 2.95" with a new depth of 18 mm.

The next size smaller caliper hereinafter referred to as "S4 caliper") was
the front caliper on the 88 944TS, 89 944T, 89-91 944S2 w/M030 package,
92-95 968 w/M030 package, 928 S4 and 928 GT. To the best of my knowledge, it
was never available in red. The pad it uses is 5.18" wide x 2.8" tall with a
new pad depth of 17 mm.

Note I am only addressing the calipers sizes first. The rotor sizes will
follow as they play an important part in the brake force and balance
equation.

It should be noted the piston sizes in both of these previously mentioned
calipers are the same. The only difference is the total swept area of the
Big Red caliper. 15.28 sq. inches total swept area for the Big Red vs. 14.5
sq. inches for the smaller caliper is an approximate 5.4% increase in total
swept area.

Also important is the piston combination in the Porsche caliper is
unavailable in any other caliper from Brembo. Literally everything regarding
the Porsche caliper is unique to Porsche and Brembo's contract with Porsche
prohibits them from selling any parts etc. for the Porsche calipers. Steve's
"Ultimate Garage" page states the bolts are larger in the Porsche calipers
however I have been unable to verify this. (And believe me, I have been
trying.)

The rear calipers on all the cars mentioned above are the same size however
the piston size combination differ. As well as Porsche using different
combinations of piston sizes in the rear calipers they use different brake
pressure regulators and master cylinders to achieve the correct front/rear
brake balance.

The rear calipers were, depending on the vehicle, available in red and use a
pad size of 3.48" x 2.58" with a new pad depth of 18 mm. This pad has a
total swept area of 8.98 inches. Note this caliper with a different piston
combination was used as the stock front caliper on the 86-88 944 turbo, 944
S2, 968 and various 928 models.

Another area of confusion is rotor size. The rotor sizes for the cars
referred to above are:

Front Diameter
911 GT1 & GT2 380 mm
993TT 330 mm
993, 964, 928 GTS 322 mm
944TS & M030 upgrade 304 mm
944S2 & 968 298 mm

Rear
GT1 & GT2 I don't know
993tt 322 mm
964, 928 S4, GT, GTS,
944TS, 944 S2 (all)
968 (all) 299 mm

The BR caliper requires 17 inch wheels, the S4 caliper will fit easily under
16" wheels (depending on offset) and the smallest 4 piston caliper should
fit under 15" wheels (have not tried this yet.)

The biggest advantage to larger diameter rotors is by moving the clamping
point of the caliper further away from the center, one gets an increase in
brake leverage. Another advantage is more mass to deal with greater thermal
loads. The downside to this is larger rotating unsprung mass which
ultimately affects both acceleration and turn-in.

I have experience with all three sizes of calipers using them in different
combinations front/rear and with different rear pressure regulators,
different pads, etc. on a 93 968. The car is a daily driver and has been
tracked heavily at tracks around the country. I also race a 125 shifter
kart. I started researching braking systems recently when after speaking
with a number of so-called experts in brake systems including Brembo, Alcon,
CoolTech, and others, I was unable to get reasonable, thought out answers to
what I felt were basic questions. My conclusion is most of the folks out
there, including Brembo, Alcon, CoolTech, etc. do not design these upgrades
as a total system solution. (I know I will get flames on that!) There is
much more to this than bolting on larger calipers and rotors. I haven't
addressed here the additional issues of master cylinder size and booster
size which not only are critical components in regards to pedal feel and
stopping power but have numerous variable related to each of them also.


,

dykaar

The key statement is the brake regulator: "they use different brake
pressure regulators". If you want more rear brake, start by swapping the 928 pressure regulator. You can also get a bias adjust valve. Also note that the rear rotors have the drum parking brake inside, so its unlikely to take a front rotor.

When I went to BRs, I bought the VCI kit using Coleman floating rotors.

Change the fluid before every track event.


Regards,

doug
Waterloo, Ontario Canada, eh


86 951 (http://www.pcaucr.org/index.php/visu...egory&catid=61)
01 E320 (W210) 4matic Wagon (http://www.benzworld.org/forums/w210...body-do-2.html)
00 540i-6 (http:// http://www.trillium-bmwclub.ca/forum...sp?postid=1916)
94 855 turbo Wagon (sold in 09)
85 535i-5 (sold in 07)
76 300D (sold in 92)
83 944 (sold in 86)
I apparently only buy cars designated by numbers

odurandina

thanks a lot....

so is anybody running oversize brakes in the rear ?

OakRZB

I'm trying to order the kit from 9Products.Com. It's a lot of work due to the parking brake offset of the later/larger rotors available. I'll update when I receive the kit (from Finland....)

Of course if you delete your parking brake, you just need (custom) adapters and the right caliper. I'm installing 996TT's all around (350mm front, 330mm rear rotors)

Good Luck

odurandina

this might not be necessary....

Robert M. (XSChop and hybrid V8 944/968/driveline upgrades/innovator), is making up a workable setup right here.

https://rennlist.com/forums/944-turb...ne-rotors.html

rlets

FYI, there are a few bits of incorrect info in that text from audifans you posted. But let me ask you this; what makes you think you need bigger rear brakes?

A full flush of the brake fluid is good to do every 2 years. 1 year if you're using something like Motul that picks up water more quickly. A quick bleed right after every track day is a good idea.

Rich

xschop

Yeah Alan, just keep the rears (300mm) with the incorporated E brake mechanism. If you are going Hydroboost, you'll have the same stopping power as your current set-up. To get more stopping power on the cheap, mount up the Cayenne 330x 32 rotors up front. You'll need to trim your adapters axially and shim them out radially.

odurandina

my front rotors are the 928 322 mm. i think that'll suffice for now.

but i wouldn't mind going a little bigger than stock in the rear, eventually.

xschop

It's really unneccessary on these front engined cars. In an *** Heavy 911 bigger rears are a must. The Cayenne rotors are less than half the cost of the GTS rotors and bigger, plus they'll fit your current calipers (i'm assuming you do not have M030 spindles)

odurandina

correct, just the stock spindles and the Big Red/Black adaptor kit from Paragon.

the reason i used the Big Blacks is because the inlets are oriented on the preferred side.


if the Cayenne rotors are interchangable with the 928 GTS rotors and available at Autozone...

that'll be a hoot.




thanks,

i guess i don't need them at all, since there's only a bit of added weight coming to my engine bay.

and the 968 rear rotors are pretty good already.

BoostBuggy

the piece you reference I wrote a long time ago....

Rich L. care to share what the "few bits of incorrect info in that text" are? Other than noticing I listed the 993TT with a 330 mm front rotor (it was 322 mm - Don't recall what I was smokin' that day) I don't see anything incorrect.

dp951

My brakes Big reds , Big Blacks and big reds on the turbo s and stock ones on my other S S4) they all brake well one of the mail improvements was the type of pads ( stiff brake lines )and a good master cylinder as well as correct brake bias, on the rear front can be used but reallt the rears are fine for moderate conditions ...the bigger brakes are great but the right combo on the s4 calipers and the car also stop very well. not mention a suspension on top of the brakes..

Darkstar1

I am looking for a caliper adapters to put 996TT 4 piston calipers on 350 996 turbo offset rotors on a 968 spindle. Any ideas? Xchop do you still machine hubs and could you make one that doesn't need the spacer rings?

Yes I bring this thread back to life!

Thanks

TheBlau

Darkstar,
In doing some brake upgrade research I came across this page - it has a link to some photos of custom adapters made for fitting up 996 GT3 brakes. Could be a good starting point. As of now - I don't think anyone makes an off-the-shelf solution...but it could be a great opportunity for XSChop or Only944!

http://www.jackals-forge.com/lotus/9...keupgrades.htm

mikew968

I raced my 968 for 8 years and never felt under-braked with S4 brakes on the front and stock brakes on the rear. It is possible to have too much rear brake and upset the balance of the car.