clinchy993

So my 964C2 will be back this week from the bodyshop



The KWs wil be going on ,the powerflex bushes will be going on

but I suspect the rear brakes will be a let down being of the 2 pot kind

So with that in mind, can I move the front calipers to the rear and fit some 993 fronts or other ?

Do need adapters ?

Rocket Rob

If you are doing street driving, why not get the 4 pot calipers that were installed in the C4's and later C2's? That's what I did. Its a straight bolt on.

If not street, how are you using your car? That would help narrow the options available.

Frank 993 C4S

If you're not tracking your car extensively just get the 4 pot rear calipers. They are a straight bolt-on as Rocket Bob states. If you're going to the track more often, get more track oriented pads. The brakes on these cars are great and you definitely would not need to upgrade them for street driving.

If you want to go "all the way" and upgrade to "Big Reds":

Front Calipers (black):
928-351-423-03 (928GTS)
928-351-424-03 (928GTS)

Front Calipers (red):
993.351.425.10 (993TT)
993.351.426.10 (993TT)

Front pad set
993-351-949-00 (standard Porsche)

Front Rotors:
965-351-045-00
965-351-046-00

Caliper Adapters from FVD:
FVD 351 964 499 (x2)

Rear Calipers:
993-352-421-00
993-352-422-00

Rear Rotors:
951-352-041-91 (x2)

Rear pad set:
965.352.939.04

999.073.402.01 Caliper mounting bolts x 4

You can purchase all the parts at Design 911 (design911.com) – Total price will be a little north of BP 2000. The Adapters for the front calipers can be bought at FVD (www.fvd.com) and cost Eu 258 + VAT for both.

clinchy993

She is going to be tracked

GazC2

I don`t think its recommend to put your front ones on the back , the piston sizes are bigger than the rears fitted to the later 964 (I think) and affect the rear bias.

none of the above from experience but from reading other posts of course if I am talking a lot of tosh no doubt someone will clarify

KaiB

I can say without reservation that one can indeed use the front calipers on the back. This is exactly what we did with Claudia, and added RS rotors. Up front are big blacks with AP rotors; the M/C and p/v remain the stock sizes.

Heretical say some online, but this was done by one of the best race shops in the country and I can testify that it works wonderfully.

Claudia has seen 14 hard track days since end June this year and I can testify that her brakes are fantastic - so much for the naysayers - I'll stick with what Gamroth and Weiner toss out, the products work and these boys know that.

Bill Verburg

Just because you can doesn't mean you should

there are several reasons not to move fronts to the back. The most important is bias, stock a 964 has 1.734 front bias, this puts it firmly in the middle of the range of bias used by all rear engine Porsche i.e 1.5 -2.0

move the fronts to the rear and the bias goes to 1.00, way too much rear

the next most important reason not to is slave to master ratio which is directly correlated to pedal feel and control. Stock 964 has an already sloppy 43.17 ratio which as at the far end of acceptable, a performance ratio would want to be down around 30. Move the fronts to the back and the ratio goes the wrong way to an unacceptable 54.6, not only way too sloppy but also doesn't move enough fluid to properly service the calipers

third reason not to move the fronts to the back is the rotor that each caliper is designed for, fronts want a rotor 28mm thick w/ a min 24, rear rotors are 24mm but wear down to 22mm, this leads to possible hyper-extension of the caliper pistons resulting in total loss of brake power

Frank listed most of the parts you need to upgrade 964 brakes, in that configuration there is going to be a lot of front bias so for track use I'd remove the p/v and possibly use higher friction pads in back. Additionally the slave, master ration isn't the best either @ 49.0, installing a 993 master cylinder setup changes this to 37.3

Lastly instead of caliper adapters you can use a steel 964RS or 964t front wheel carrier or a 993 or 993RS aluminum wheel carrier

KaiB

Yessir...it is indeed your advice on brakes which helped guide me through this build and I most assuredly thank you (see avitar). Just relaying real world info here. Kai

Bill Verburg

Methinks that something was lost in the translation,
anything less than ~ 1.4 bias just does not work for rear engine Porsche's, that's some real world information

alexjc4

Just to be clear then what would the bias be if you used big reds on the front and 964 std fronts on the rear?

KaiB

Methinks that something was lost in the translation,
anything less than ~ 1.4 bias just does not work for rear engine Porsche's, that's some real world information

But...why on earth would my car work so well; neither the pv nor mc were altered from stock. I'd love to have you drive it Bill, if we could find a way.

Bill Verburg

My guess is miscommunication or misunderstanding somewhere

It just flat doesn't work much below 1.5

KaiB

Open to everything here, certainly from you, Bill, but...

I have the 928GTS calipers up front over the rotors in my avitar and the stock front calipers were moved to the rear - hung over the 24mm RS rotors.

They work wonderfully, although you are saying they should not. This setup is Gamroth/Weiner approved, tested by them many times over and then re-tested by me in anger...fantastic setup, I wish you could drive it.

Bill Verburg

roughly 1:1 I'd need to do the math factoring in the rotor sizes but stll very close to 1:1

here are some bias ratios to think on
all '69 -83 911 hydraulic ratio 1.596 net ratio 1.491

'84 -89 3.2 Carrera hyd 1.306 net 1.220 by far the lowest ratio ever used on a rear engine Porsche

stock 964 hyd 1.720 net 1.734

964RS hyd 1.572 net 1.713

993 hyd 1.572 net 1.604

993RS hyd 1.472 net 1.426 next lowest after 3.2 Carrera

996 7 997s are up ~2.0

Bill Verburg

My best wishes to anyone that chooses to emulate that setup