964 calipers over 28mm rotors

[dede911]

Hi,

Still looking for upgrading my brakes.

But since my previous post "930 fronts.." ended in a fight between some people, I started this new topic.

I'm still leaning regarding a 930front set-up, but i'm also thinking about 964 calipers over 28mm discs.This would be a good improvement regarding heat management and looks more stock than the huge 930 stuff...

I know there are solutions to use 944T rotors the VCI way, but because my car should also stay road legal, I can not use adaptors.

My question is: Would it be possible to install the 964 calipers direct to the strut (boge) and install AP or Wilwood discs with custom hats?

The spacing on the 964 bolt holes should be "sorted".

Your input will be appreciated.

André

[GeorgeK]

Hi André,
People have been using 964 front calipers over Carrera 3.2 discs for a while. very functional, although some will be shocked at the idea. One needs to watch the pads for wear, because the 3.2 discs are 24mm thick, vs the 28 discs of the 964. Then there's the fitting of the caliper that requires an adapter (the right way) or an elongated hole on the caliper (the frowned upon way, but one that passes inspection in Europe, since the hole is covered by a large washer).

[KTL]

Let's hope the bickering doesn't migrate over to here.....

You can fill and re-drill the holes on the calipers fairly easily. Three ways of doing it:

1. Tap the holes and insert threaded rod with threadlocker. Then punch/stake the plugs
2. Press in suitably sized rod that has been turned on a lathe to your desired press fit.
3. Weld holes. One caveat here is the caliper seals should be replaced due to weld heat compromising them.

Then drill your holes 3.5 in. on-center and at a height suitable to your disc diameter. Difficulty here is the disc diameter can't be much greater than 299mm (stock 964 size) because as you move the mount holes inward (standard spacing on 964 caliper is 3.75 in. on-center) you can only move them down so much before you risk the material around the hole being too thin.

Wilwood doesn't have a good disc in 28mm thickness. I've looked, believe me. AP Racing and Brembo certainly do have a good sized 28mm disc. A bit spendy but good discs.

Your hat thickness has to be minimal to keep the rotor away from the ball joint. Typical hat thickness i've used is 1/4 in. 6061-T6 aluminum alloy. I'd also recommend you consider the rotors that have floating hardware. I've found my fixed rotors exhibit a considerable amount of "plinking" noise from heat expansion/contraction when parked after a race. My front rotors are Wilwood 309x32mm HD or GT rotors with simple 6061-T6 solid hats.

[winders]

dede911,

There has to be a local shop that has done something like this a million times. Have you checked around?

Scott

[dede911]

Kevin,

Is it correct that a 964 caliper is centered over a stock 24mm disc, when bolting straight to the strut?

If this is the case, the 28 mm disc will add only 2mm on each side. This would make it easy to check that the clearence with the ball joint is OK.

Scott,

Many people here use 964 caliper on 3.2 disc, but for real track use, I think this is not good enough regarding heat management
Others use 993 gear,but cars are track only...
For competition, only 930 is homologated...that makes them expensive...

André

[tadd]

Not to derail, but wouldnt something like a 2xxx alloy be way better for a top hat than 6061?

I mean hats get hot if your working the brakes. Its all about at temperature strength in my mind... and 6061 doesnt have it. Heck, I'd seriously consider steel hats properly lightened to avoid the problem all together.

Color me curious.

t

[winders]

Originally Posted by dede911

For competition, only 930 is homologated...that makes them expensive...

André,

I don't know about there, but here in the USA I was able to buy four brand new 930 calipers from a dealer for less than $2400. Front and rear cost the same. They were out of stock when I ordered and shipped from Germany a few days after the order was placed. You must be able to get them in Belgium.

Scott

[KTL]

I can take a look tonight on my car and see if a 964 caliper is centered over the Carrera disc, since I have 964 calipers on the shelf and my Carrera has been on jackstands for an embarrassingly long time.... not for much longer, thankfully.

If memory serves me right, I recall the caliper not being quite centered. It can be fixed with spacing washers or slight milling of the mounting "ears" depending on the direction of movement needed. Please don't tell me the milling would be disallowed. Some original calipers are milled/cast like this. Just have to avoid too much milling which would weaken the mount ear.

Tadd,

I agree the 6061 is not the highest strength alloy. I myself didn't select the material. The hats came in a rather basic kit. But the hat material has worked for a number of years on various cars. The old MotoDelta 1970 3.3L GTS-4 hotrod in our fleet has been running the same hats for around 4-5 years and I ran them (the same hats, as I donated/swapped them to Chris' car) on my '87 Carrera for a couple of years on the track. The 1970 car used either Dunlop slicks or Hoosier slicks (both non-DOT radials) so the brakes were put to the test with very high levels of grip.

[Bill Verburg]

Originally Posted by dede911

Hi,

Still looking for upgrading my brakes.

But since my previous post "930 fronts.." ended in a fight between some people, I started this new topic.

I'm still leaning regarding a 930front set-up, but i'm also thinking about 964 calipers over 28mm discs.This would be a good improvement regarding heat management and looks more stock than the huge 930 stuff...

I know there are solutions to use 944T rotors the VCI way, but because my car should also stay road legal, I can not use adaptors.

My question is: Would it be possible to install the 964 calipers direct to the strut (boge) and install AP or Wilwood discs with custom hats?

The spacing on the 964 bolt holes should be "sorted".

Your input will be appreciated.

André

964 and 944t calipers are essentially the same(swap bleeds and feeds and they are interchangeable), the fronts are both designed for 28x298mm rotors

the caliper mounts are a few mm off from the 3.5" A/S mount, some people have hogged out the mounting holes a tad for use w/ 24x282.5mm 3.2 Carrera front rotors, this is an unsatisfactory setup as the caliper pistons are subject to hyper-extension in when the pads are worn, additionally using big calipers on small rotors is a fruitless effort. Stock 911 brakes are plenty powerful, they can suffer from heat issues when used on track in heavier cars. I have never checked the radial range for the holes when used in front, it may be possible, similar to what has been done w/ that caliper body for use w/ 309mm rotors in back

If caliper adapters are not allowed then get a set of correct 930 f/r calipers w/ 304x32 front 2 piece rotor/hat assemblies and a 930 rear 28x309mm rotor, the rotor is a bolt on and retains parking brake you will need to discard the backing plates as the mounts need to be trimmed off. The rear calipers can be modified by multiple shops.

Best of all, 930s fit under 15" Fuchs

[lonewolf]

Andre.
Listen to Bill.
Bill knows brakes.

[juanbenae]

Originally Posted by KTL

Let's hope the bickering doesn't migrate over to here....

[tshebib]

I'm also looking to upgrade my brakes for the same reasons (rebuilding calipers twice a year, overheating, excessive pad wear, etc.). It seems through my research here and other internet sources that to do it right your looking at approx. $4000+/_. Does this seem fairly accurate? Also, there seems to be very little discussion about the Brembo upgrade. brake system components Rebel S Racing Products
I already have 17" wheels so is there anything wrong with this setup that I should know about? What is the rear to front bias on this setup?

Thanks, Tom

[wildcat077]

Tom,

Yes 4K seems about right.I installed 996TT brakes on my 89 and with the adaptor kit and the 996TT calipers and rotors,it was pretty close.
The plus side is that your pads will last you two seasons and your rotors even longer and you won't have to flush your brake fluid and rebuild your calipers every two or three events !

The Brembo kit is pretty much spot on as far as proper size and bias goes,it may seem expensive at first but in the long run it will outlast any stock OEM setup !
I was considering that option but i got a good deal on the 996 setup ...

Cheers !
Phil

[KTL]

Originally Posted by tshebib

It seems through my research here and other internet sources that to do it right your looking at approx. $4000+/_. Does this seem fairly accurate?

I say no if you're taking the "easy" route I mentioned in the other thread that went haywire. Even if you have to pay someone like VCI to adapt a set of front calipers for you, no way you're approaching $4K

But, I don't know what car/equipment you have and what you're doing with it (track day? full race?)

My feeling is that a good brake tweak for a mildly modified street/track car is:

>Basic 964/944T small Brembos
>'86 944T rotors with spindle spacers
>Typical SC/Carrera 20.64mm master cylinder
>Original Carrera rear calipers and rotors works
>Some sort of effective brake cooling like the A-arm scoops or AJ-USA or NERP style shop vac nozzles plumbed to rotor backing plates.

It works fantastic for much lest investment that some of the larger brake setups.

[tshebib]

I track my car as often as I can. It has a 3.6 V-ram in it and other goodies including brake ducting. I do drive it on the road but with some of the mods I've done my wife will no longer get in it . it looks like the 964 front only upgrade is still going to cost $2500 so the question would be why not put the new Brembo GT on the front ($2000) and maybe add the rears later. Would this throw the front to rear bias off too much initially? I kind of like the idea of using all new components that bolt right up but can be convinced either way at this point. BTW I live way up here in Nova Scotia so anything I do will be through mail order.

[tshebib]

Oh, and thanks for your replies Kevin and Phil.

Tom

[dede911]

Kevin,

did you already had the opportunity to do the measurement of the 964 caliper bolted to the strut, and the position of the caliper to a 3.2disc?

I'm really interested.

Thanks

André

[jmh61]

Apologize for the semi-hijack, but I am really interested in Andre's original question about 930 fronts and Carrera rears.

At Road Atlanta last month I had significant fade at the end of a session going into 10A. Made the whole 10A 10B experience an adventure I don't want to repeat. I am running stock brakes with the AJ brake cooling ducts with block off plates, but am still getting fade at the end of sessions. I am happy with the brake performance with the exception of the fade.

I would like to use bigger rotors for heat management but run 15" Fuch wheels. It seems my only option is to go with 930 calipers and rotors. I would like to try running the 930 brakes on my fronts using a VCI type setup, but I have a couple questions:

1. Will the stock master cylinder work well for 930 fronts and carrera rears?

2. Do I remove the stock proportioning valve or leave it in?

Any comments are appreciated.

[KTL]

Tom,

That info helps. I suspect the "cheap" setup I describe may be a bit challenged on a 3.6 car. If you're looking for a OE-based system, you can do it pretty well with a collection of parts similar to the Brembo kit and use consumables that are much cheaper than the Brembo pads (you probably need to (or will soon) replace the "stock" pads that come with the kit, for track use) and rotors.

The "993" brakes a lot of us have installed work fantastico as well.

>993 calipers with caliper adapters. Good used calipers are around $500 and adapters are $150

>Wilwood HD or GT front rotors 12.19" x 1.25" with simple 1/4 thick Aluminum hats. Around $400 including hats & fasteners

>23.81mm 930 master cylinder. $200

>993 or 965 (preferred) rear calipers w/resized mounts $400 or more

>930 rear rotors are the easy bolt on and retain parking brake usage perfectly. Or if you ditch the ENTIRE rear parking brake assy and trim some needless chunks of aluminum off the trailing arms you can use 964 FRONT rotors on the rear. $320 for 930 rotors and shop around a bit to find 964 fronts for pennies on the dollar. I got a pair of 964 Ate front rotors recently for $116 shipped.

>Race pads $400

So you're in for around $2500 for a system that requires not a whole lot of customization. Hardest thing is the rear caliper resizing. But it's totally DIY-able. A dufus like me did it with some threaded rod and a drill press. Everything else is bolt on.

It has decent balance for a stock-based system. I previously had 993-Wilwood front and 930 rear calipers & rotors and the bias kinda stunk on my 2400 lbs stiffly sprung racecar. Too front biased. So I got off my procrastinating arse and re-sized the 965 calipers I had on the shelf and what a difference it made. Now I can really work the brakes without locking the fronts too easily.

Andre',

Sorry I did not get out to the garage last night. Fell asleep putting the kids to sleep. Will get you that info tonight.

[KTL]

Originally Posted by jmh61

1. Will the stock master cylinder work well for 930 fronts and carrera rears?

2. Do I remove the stock proportioning valve or leave it in?

Any comments are appreciated.

1. Yes. Pedal travel is a little bit long but still works OK. The "cheap" system I described (964/944T front calipers and stock Carrera rears) has similar piston sizes as the 930 front, Carrera rear setup.

Coincidentally my buddy with the "cheap" system recently posted his Road America video.

RA '12 NASA - YouTube

Point of sharing is not to show how blisteringly fast he is. Because he's not, yet. But pretty good for a stock-ish car on Toyo RA-1 tires. 2:42 is pretty darn good for a first timer at Road America and the point of sharing is that Road America is similar to Road Atlanta in that there are some seriously hard braking zones in several places.

2. You remove the proportioning valve (actually is a pressure limiting valve).