mpeters951

I've read the Pano 964 brake upgrade articles, but, I'm still left with the question that is not answered by their table of popular upgrades:

Can I do 928 GTS fronts (obviously w/ appropriate rotors and adaptors) in concert with 964 standard 4 pot rears ? I've got the standard 964 4 pot rears in hand to go on my early mfg. date '90 C2, but am left wondering about going a next step on the front - ala 928 GTS. If the 928 GTS fronts can work w/ the new rears, what is the appropriate prop. valve to use ?

Counsel sought.

Bill Verburg

all the 928 front Brembos are trailing mount, to use in a 964 leading mount position the bleeds and feeds need to be swapped. Once that is done the 928S4 front caliper is the same as the 993 front caliper and the 928 GTS front caliper is the same(except for paint) as the 993RS/tt front caliper.

The 928S4 caliper wants a 304x32mm rotor the 928GTS caliper wants a 322x32mm rotor, The S4 caliper can be used w/ a 322 ala 964t & 964RS by using a taller caliper adaptor, but the GTS caliper cannot be used w/ the smaller rotor. 928 front rotors have the same o/s as 964 calipers so you can use the appropriate rotor for your calipers. Be warned 993 rotors use a different o/s and so will need a caliper adapter that o/s's the caliper to match the rotor.

W/ either setup you will want the 30/34 rears used on a 993 or 964RS, not the stock 28/30 rears. p/v is idiosyncratic in that some will want more or less rear bias than others. I'd use your stock p/v at first and adjust from there. There are many that prefer those brakes w/o any p/v at all.

mpeters951

Bill,

Thanks. My read from your reply is that if I want to upgrade to GTS Big Black front, I MUST upgrade rears. Is that the categorical answer ? Is there any upgrade path for front whilst using the 964 4 pot rears ? 928 GTS claws are such a phenomonal deal, but less so if they "drag thru" 993/964RS rears for my application. Hence the Q of what is both an upgrade to front whilst being compatible with the 964 C4 rears.

MP

mpeters951

Bill,

Re-reading; a 928 S4 caliper in front w/ 304x32 rotor & adapter plate will work with the current rear OE rotor and 964 C4 caliper ? Obviously with front feeds/bleeds swapped.

Advise,

MP

Wachuko

I called Sunset Porsche to check in the parts cost.

If going with 928 caliper:

Calipers:
928-351-423-03 Current price (this is their discounted price for customers outside of Oregon): 301.71
928-351-424-03 Current price(this is their discounted price for customers outside of Oregon): 301.71

Rotors:
965-351-045-00 Current price(this is their discounted price for customers outside of Oregon): 161.70
965-351-046-00 Current price(this is their discounted price for customers outside of Oregon): 161.70

Caliper Adapters from FVD:
FVD 351 964 499 (x2) - $118.00 a piece


Rear Calipers:
993-352-421-00 ; 286.07
993-352-422-00 ; 286.07

Rear Rotors:
951-352-041-91 (x2) ; 191.74 a piece

928 calipers are the same as the big reds... but you have to swap bleeds/line and paint them if you want them red... This is what I plan to do with mine. I already have the adapters from FVD and saving for the calipers and rotors.

Found it to be the most cost effective route to get big brakes in my car.

The information I got from the different threads is that you need to upgrade rear calipers if going with Big Red (or Big Blacks ).

I was not planning on changing the bias valve... can't answer that question and can't remember what the final recommendation was.

DAVISRILEY

No, you should go with the 30/34 993 or 964rs rears, not the stock 28/30 rears, for balance. But it will use the stock rear disc. That is the set up that I have currently. Good luck. Take a look at these threads, lot of info in them
https://rennlist.com/forums/964-foru...ke-update.html
https://rennlist.com/forums/964-foru...-c4-again.html
https://rennlist.com/forums/964-foru...ade-ideas.html

Also, is yours a c2? If so, I am pretty sure you want to upgrade the mc, but not sure, as I didn't have to with the c4.

mpeters951

I have read and understand the Pano article and the threads as indicated here. The Q remains however; is the 928 S4/993 (medium caliper) compatible with a 964 C4 rear caliper. I'm not questioning the known upgrade "packages" from the Pano article. But a I am wondering if there is a viable mid-point between the first 2 upgrade paths from the article; #1 upgrade being what I have on the workbench now, 4 pot (small caliper) 964 C4 rears and #2 the Big Blacks w rotors/adapters in front and 993/964RS calipers over stock dimension rotors out back.

The mid point option, if it is a viable one, is the open question, not the well documented known upgrades as in the Pano guide.

DAVISRILEY

Sorry, thought we talking about the 993 turbo caliper. I will have leave that one for bill.

cobalt

Good question although I would guess not. Bill would know best. Although considering the medium S4's/993n/a fronts and big reds all use the same pistons although slightly different pads you will still have the same clamping force of the big reds just less surface area to dissipate heat. the question is how much does the dia differences of the rotors impact the ability to stop the car? I am not sure although I would guess the smaller rear pistons would not work well with the added clamping force of the bigger fronts.

I used the big reds up front and 993 rears without changing the proportioning valve. I find it a good balance and can play with braking by using different compound pads front/rear. I only found the need to upgrade the brakes because my car is dual driver at DE's and I would warp the stock rotors. With the big red upgrade I find on my C2 that I have much more braking than I need. I hit the ABS most of the time and it still does not fade or crack my rotors much. I have even had instances where the brakes even with ABS overpower the R888's I am using.

mpeters951

Cobalt - good response. Thanks; I wonder, as stated, if the 993 fronts over 304's coupled with 964 4 pot rears over 299's could be bought into "balance" thru the use of the right bias valve from the various bias valve options.

That would be the question. The other 2 Pano stated option "kits" I understand.

Wachuko

I know of one 964 running with the big brakes in front and 964 in the back. I have driven that car and everything seems fine for road use. Owner uses the car as a daily driver.

Initially I was thinking of doing just that. Upgrade fronts and use it like that for awhile... so I would also like to know the answer as to how safe is it to do this.

SeanR

Go all the way and put the 993tt big ones on the rear also. We've fitted them on 2 GTS's with a little machine work. Talk about huge.

Bill Verburg

993RS/tt rears don't work on the back of a 964 unless you give up the parking brake as Geofrey did on his 3.8RSR, you need to use Alcon(or other) 2 piece rotor/hat setup like on the 993 tt front.

Bill Verburg

Yes, if you go to any of the 993 front calipers you must use the 993n/a rears calipers which are the same as the 964RS rear calipers. Additionally you may want to increase rear bias further by using a less aggressive p/v or even eliminating the p/v. The bigger the front rotor the more rear brake you will want.

Bill Verburg

At the very least you will want to remove the p/v. You can get more from the rear by using the 993 rear calipers w/ a less aggressive or even no p/v.

All by themselves the change from 964 to 993 n/a caliper increases front braking by 12%, the larger rotor further increases that by a few %.