PAOLOP

993 rear calipers is also used to balance front 964RS/965 3.3 (By Bob Gagnon and Bill Gregory)

Ciao
Paolo

Bill Gregory

Here's the online version of the brake article Bob Gagnon and I wrote for Panorama. The 2.4mb article, in Word .doc format, is located here. Note there are two embedded tables towards the end of the article. If you're scanning through the document and you come to a blank space, wait a few seconds and the tables will catch up.

Mezger

To bring that old threat back up again, I was wondering how 996 Turbo calipers work on a 964?
My brakes are pretty much gone and I would like to upgrade them.

Bill Verburg

While it can be done there are issues

one is that the 996tt wants 330x34mm rotors, the usual BB upgrade @ 322x32 is more than adequate for most purposes

Mezger

Thanks Bill!
What else is there besides the standard big red/ black setup?

espanolie

the stock carrera brakes are good enough for most people unless you're gonna track - then just get better pads, which is likely sufficient. save your money

perelet

Besides brakes, it matters how do you mount them and other suspension components. Mounting big brakes on 964 cast iron uprights will add significant unsprung weight and will not help with thermal dissipation. Aluminum uprights will reduce thermal build up about 3x, so using 993 or 993rs uprights is extremly efficient. I find that using 993 brakes on 993RS uprights is probably best thermo/weight tradeoff for 964,

Here's description of all bit's and nuts involved:

http://forums.pelicanparts.com/porsc...pension-3.html

Ideally floating aluminum hat/302mm rotor setup will be the best for 964.

Rear is less complicated - 993 calipers and rotos of your choice.

Hydraulic brake booster from c4/RS/turbo is another good upgrade.

Oleg

cobalt

So what are you suggesting? Sticking with stock brakes and converting to aluminum carriers? It may make a difference however from my experience using stock brakes on a dual driver car is not adequate and they will overheat using cast iron carriers. Single drive will be OK. I guess we would need some data showing temp differences using the aluminum carriers vs cast iron but there are downsides as well. If you rely on the casting to dissipate heat you also risk destroying the temper. Prolonged temps above 500 degrees F for more than an hour will anneal the aluminum softening it. This could be catastrophic for stock 993 carriers. I would suggest adding brake cooling is a must if you switch just to aluminum carriers Rs will probably hold up better but almost as pricey as the big reds..

From what I gather the aluminum uprights will transfer shock 3X more through the suspension, are harder on the car overall and ruin your bearings quicker. (although bearings are cheap enough to replace and should be changed on an interval depending on how often you track the car.)

I admit the stock brakes are decent but when I used them on my C2 with my wife driving as well, we would go through a set of pads in a 3 day event and rotors did not last all that long. The caliper seals would burn up in half a season. The car stopped but it cost more to replace parts constantly.

I upgraded to big reds and yes it does add unsprung weight offset by much lighter track wheels worked perfectly. Driving back to back sessions was not a problem and now we were getting the equivalent of 40 track days out of set of pads. Rotors would be toast at the end of the season both worn and cracked so I switched to aluminum hats and slotted rotors added ducting for cooling and I saw a significant improvement in brake life.

Is it overkill...yes but I found the pedal feel is significantly improved by the upgrade and need to romp on them far less. They have saved my butt a few times when someone pulled out of the pits at VIR while i was moving and then braked early and hard with a Z06 vette or GT3 up my butt. I doubt the stock brakes would have saved me.

I am building a new car less weight and retaining the big reds. I am entertaining using the 993 carriers, unfortunately the RS uprights are not in the budget currently. Ducting for cooling is the first thing I am adding and I am using the Electro-hydraulic booster since it started life as a C4 however I find the vacuum boosted brakes communicate much better and is more than adequate.

jimonycricket

would http://www.rockauto.com/ be a good source to start buying calipers, prices seem pretty good compared to other options.

cobalt

I would be interested to see what they offer if anyone buys from them.

$281.79 for a refurbished big red? Looks like they need paint though but if properly done that is a bargain.

Bill Verburg

I seriously doubt that the aluminum vs steel has more than min effect on heat transfer or shock loads, the aluminum versions are certainly lighter and reduce unsprung weight

there are 4 versions of 964/993 wheel carrier
2 are iron and were used on 964, the base 964 has axial mount calipers that bolt to the wheel carrier

The shiny holes next to each other in the center are the 964 axial caliper mounts


the 964 and 964 turbo used radial mount calipers(also iron)
These are 964t w/ the radial mount ears to the far left and right.


Both of these wheel carriers use the long steering arm designed for ride height close to stock RoW, they can be lowere but the more they are lowered the more bump steer is introduced.

The 2 aluminum wheel carrier versions were used on 993, both have axial mount calipers the base verson used on 993 and 993t have long steering arms equivalent to the 964 long arms

the 993RS, RSR, Cup, GT2 all use a short arm version designed for a much lower ride height, these also come w/ their own different outer tie rods
on left RS short arm w/ straighter outer tie rod, on the right normal long arm w/ kinked outer tie rod


The whole point of these wheel carriers is to nit need caliper adapters which introduce flex and weight and cost,

for the 964 carriers use 964 calipers, for the 964RS/t carriers use either 964RS/t calipers or 993 calipers w/ adapters, also use 964 rotors, the 298x28 versions for the small 964 calipers or 322x32 for the 964RS/t calipers( an alternative is to use 993 calipers w/ an adapter and 928S4 304x32 rotors or 993tt calipers w/ an adaptor and 322x32 928GTS rotors)

for the 993 carriers use 993 rotors, 304x32 for the base 993 caliper or 322x32 for the 993RS/tt caliper

You can fit all sorts of caliper w/ adapters but you need matching rotors which are much harder to come by.

cobalt

The difference in thermal conductivity depending on alloy used is considerable at least 3x as mentioned. I just caution using a carrier as a heat sink, aluminum will become very soft if annealed and can fail prematurely. At 700 degrees aluminum might absorb 140 cast iron maybe 40-50. I believe you would need to heat your brakes up to about 2100 degrees to have issues unless the aluminum has no way to cool itself.

I believe as far as shock absorption goes you will find a difference as well. The aluminum will transmit more through the suspension it might be a good thing commuting more back to the driver or jar the wheel that much more. Would be interesting to do a study I guess.

I cast a prototype for one of the first mountain bike shocks many years ago. They toyed with aluminum vs steel and ended up with magnesium because of impact absorption. I believe it was called the Judy.

Mondrian

Aluminium will fatigue and therefore have a limited lifespan.