Kevin - Thanks for the info on the Wilwood rotor part numbers as that is one thing I couldn't figure out on my own.

As to my leaning towards the 930 calipers, I really only have a few requirements:

1. I need a little bit more thermal capacity in my brakes. I currently have Carrera brakes with an cool brake kit ducted to the front spoiler, etc., but they are just barely adequate.

2. My track wheels are 8x16s in the front so ideally I need something that fits under 16" wheels

3. I want to "do it right" but I don't want to go overboard.

The 930 front brakes (and keeping my Carrera rears for now) seems to meet my requirements. The Wilwood HD rotors make it even more appealing. Do the 993/S4 (or any other options) fit under 16" wheels?

Mike,

While I will not tell you what to do, I'd strongly advise against using 930 front calipers/rotors with Carrera rear brakes.

Having some experience at these sorts of things, thats a real bad combination for a multitude of reasons that include biasing as well as brake torque.

My best advice to you is to save some $$$, add some 930 rear calipers to the upgradem, and do this properly.

JMHO, but people never have the money to do something right, but they always get the money to do it all over again. I see this happen too many times and frankly, its both tragic & avoidable.

hmm,
hydraulic bias for 911 S or A is 1.596 w/ a very small rear rotor bias

hydraulic bias for 930 is 1.604 w/ a very small rear rotor bias

hydraulic bias for 930/Carrera is 1.637 w/ a very small rear rotor bias w/ a medium front rotor bias

the net bias is going to be proportional to the available brake torque

just for comparison
993tt 2.061 w/ no rotor bias
993 GT2 Evo 1.862 w/ medium front rotor bias
996 1.72 w/ medium front rotor bias
early 996 GT3 & 996tt 1.919 w/ no rotor bias
2003-2004 GT3 Cup 1.931 w/ medium front rotor bias

these all work well

would more rear bias be preferable? sure in all the above cases more rear would be very useful

I used 964 fronts/rear on 930 rotors years ago, they fit under the 16" Fuchs I was using at the time, the 7" front required a small ~5mm spacer for axial clearance 944 7s would have been fine w/o a spacer.

993 are much bigger, radially they probably would fit be awfully close, axially I doubt it, but never tried that.

your 8x16 fronts are going to be fine for 930 or 964 on 930 rotors but probably not 993 on 930 rotors

Shoot, Mike

Now is your opportunity to move your MC up to the trunk like the boosted cars, and install a bias bar adjustable dual master cylinder.

Would make changing the MC a whole lot easier, too. Don't you just hate trying to plug the fluid supply line in?

Would take a bit of extra doing on your early chassis, though.

There are three things you haven't mentioned which might in the short term keep your fluid from boiling without changing your calipers:

1) Are you using a 600 degree F fluid? I suppose you are, but you can now get one with a dry boiling point of 683.

2) Have you swapped out your caliper pistons for ones made of stainless steel? I know those are available for SC piston sizes.

3) Do you use titanium backing plates? Or homemade ones from stainless sheet?

It took all of those (in addition, of course, to ducted cooling) for me to get my SC to hold up to full race conditions. When you are on the cusp, sometimes fairly small improvements by way of reducing heat transfer/fluid boiling can put you back on the right side of the thermal capacity line. Your motor is more potent than an SC, but you have the thicker front rotors to start with.

Of course, if you are sucking 245 hp out of that 3.2, that sounds like about what the early 930s made, doesn't it? Another way of looking at spending more $ than you thought you wanted to spend to get a larger brake pad area is to allow for some future increases in kinetic energy. Pauter rods, independent throttle bodies, EFI, race valve springs, and the right cam and you could be looking at 300 hp.

Mike,
Adding to what Walt said you could consider taking off the ducted brake cooling and adding 964 lower A arm scoops instead. I have been reading threads about this mod and it makes sense that the scoop would direct a lot more air to the center of the rotor than the small 3" duct (sprint cup cars run three to four 3" ducts to each rotor with inline fans). I bought the parts and will be doing this first before upgrading the rotors on my car. Together with the titanium backing plates, and RS683 fluid and I think you may be able to get by with the Carrera brakes. Also, I have been doing a full cool down lap each session without touching the brakes to make sure I have shed enough heat to not boil the fluid in the pits.
Cheers,
Chad

Walt - you are essentially reading my mind. I have done most of the things needed to help with "heat management" with the exception of brake fluid (still using Ate Super Blue), but the thought has crossed my mind to simply go through my existing set up and maximize everything.

...on the other hand, in the future I would like to change cams and exhaust (as a minimum) and could probably get another 20 hp out of the engine. If I'm going to do the brakes, I thought I might as well do it right the first time. The problem (?) is that it seems most of the upgrade options are overkill for my needs. I like the 930 option as it is more "period correct" and would have all of the heat capability I would ever need. It just takes dollar$.

And yes, I hate trying to plug those lines into the top of the master cylinder... SmileWavy

This is me exactly. Too bad someone doesn't mod Carrera A calipers to enable the use of a 28mm rotor. I think this is all I would need...

Thanks for all the responses on this thread. They have given me a lot to think about!

It might be worth looking into using 996 front calipers and rotors, it's not anything i've ever done but I believe that others have. The rotors are 318x 28. 2 piece aftermarket versions are also available where you could uses a normal 911 flat hat too.

Bill's right. Steve Timmons provides this kit and it does exactly that- gets you a fatter front rotor without going big big like the 32mm options we're discussing here. maxhouse97 and peter bull are two people that I know of with this kit

Peter Bull's install http://forums.pelicanparts.com/porsche-911-technical-forum/530918-mother-all-ib-brake-upgrades.html

Maxhouse's install starts on page 3 http://forums.pelicanparts.com/porsche-911-technical-forum/433260-993-brake-conversion-carrera-questions-3.html

You can read more jibber jabber earlier on in the thread about what fits and what doesn't.

Bill's also right that there's 28mm aftermarket rotors to choose from. One that comes to mind is AP Racing and I know Bill's posted catalog dwgs of a suitable Brembo drilled rotor.

VCI also makes a kit for the the front to use a '86 951 299x28 front rotor and basic Brembo calipers. I used this for a number of years and it's a nice setup. Nice thing about it is you can do just the front and leave the Carrera rear calipers & rotors in place. Handed the front setup off to a '87 Carrera friend who was convinced he didn't need anything more to do just that- front swap only. He never had any problems with brake fade (he's an excellent, fast driver) but said he'd give them a try since he was tiring of rebuilding his cooked calipers each offseason. He was sold pretty quickly when the pedal stayed high & hard all the time and pad wear dropped dramatically. What helped even more so was getting his IROC front bumper ports hooked to his brake backing plates via my homemade PVC A-arm tubes

Sorry I didn't respond earlier Mike, as I lost track of the thread somehow. The 993 brakes do indeed fit under 16 in. wheels. They fit under BBS RS 80's 3-piece bling no problem. However regular Fuchs are a no-go. You need to have at least 951 16x7 or 16x8 Fuchs to clear the hefty (but not heavy) 993 caliper. If one has large spacers on the front, the 993 would fit the regular Fuchs.

The problem with the regular Fuchs is the mounting pad/ hub of the wheel is too shallow creating inadequate axial clearance. Radial clearance is also a problem because of the tapered wheel barrel of the Fuchs wheels. You may ask, well then how does the 951 Fuchs fit if it is also 16 in. diameter?. The countersunk lugs/deeper hub of these wheels is what creates the added brake clearance. Which is exactly why they were made- for the '86 951 which introduced the basic 4-piston Brembo brake calipers to the 944.

Happened to be browsing DART's site and saw Dave B offers a 930 rotor option if you care to inquire. He's dbanazek here on Pelican

Race Car Service, Race Car Preparation, Porsche Racing Preparation

While the 930 calipers and rotors are nice, there's more than one way to skin the bigger brake cat. I think the 930 calipers are really cool but they present some unnecessary shortcomings IMO.

-Non-differential sized pistonsin the 930 calipers introduce pad taper. Obviously this is a much more pronounced issue with track use. Yes you can flip the pads around on a regular basis to address this. As an aside, if you run differential-sized Brembos "backwards" you'll also get pad taper........

-The rebuild kits for these scraper-seal type 930 pistons are considerably more expensive than the more modern Brembos

I'm not trying to be cheap and foolish here. I'm all for spending good dollars for good installations. But when you can get the same benefit from cheaper, newer parts AND minimize your consumable costs, it's not a bad idea since it's not a cheap venture to replace pads and rebuild 930 calipers. Although i'll readily admit 993 front pads are WAY more expensive than the 930 pad.

End of rant.....

930 rebuild march 2009


http://forums.pelicanparts.com/uploa...1294341303.jpg

Not bad. Price goes up substantially if you need pistons. I can still beat that.

Replacement Rotors, Pads, Hardware

Au Contraire, Sir. :)

Properly installed, 930 caliper pistons are specifically designed to eliminate pad taper and it never happens unless someone fails to clock the pistons, per the factory shop manuals.

I see this all the time and in every case, severe pad taper has occurred when this happens. :) :)

I hope this prevents anyone else from having this problem as 930 brakes are really good.

I stand corrected, as I forgot the 930 pistons are stepped. My old style 38/36 pistons in the 951 calipers are not stepped (as they shouldn't be since they're different sizes) and that's how I know the taper still happens when the calipers are installed "backwards" ! :D Previous owner didn't bother to flip the calipers over and swap bleeder & crossover tube locations.

This was the exact plan that I had to begin with - VCI C2 calipers/'86 944T rotor and stock Carrera rears. What derailed me somewhat was the use of the spacer to enable the rotor to clear the a-arm and the fact that by the time I bought some used C2 calipers (seem to run $400-$500 a pair on ebay) and then had them modified by VCI ($550, I believe) I could buy new 930 front calipers for about the same cost...

This is great nugget of info. My street wheels are 17s, but I'm using some HRE Fuchs replicas that I've had for years as track wheels and the fronts are 8x16s. Most likely they would clear due to the offsets I'm running, etc. I am going to look into this option for sure.

Thanks for all of the info and help. I will look into all of this for sure.

The basic Brembos can be had pretty cheap, just have to be patient. Honestly, I have a set if you'd like them were you to settle on the VCI approach. I got the calipers somewhere for $250 and you can have them for that. I've got some seal kits you could have too. They are well used and the paint is peeling off. But these are easily beautified by powdercoating them. My loaner set on said '87 Carrera friend's car have been home powdercoated and they're still holding up fine after 3 years of nothing but track use.

VCI needs to update their site with new pricing. Earlier this year another Pelicanite asked me about the brake upgrade routine and he inquired with Doug Arnao at VCI about this small Brembo kit. Caliper mods and adapters are now $650 I think. That said, they are nicely done. Fronts have big sturdy caliper adapters and quality hardware.

I agree the VCI front setup is a bit unorthodox with the spindle spacer and its rotor clearance. Really not a big deal though and it works well. You just heat up the spindle collar with a heat gun or torch and it easily pulls off the spindle with local auto parts store two jaw puller. Warm up the spacer and it also slides right on, same thing when you reinstall the collar.

The fitment is quite good overall, despite having to shave the A-arm a bit to ensure sufficient clearance. I had similar clearance issues around the ball joint area with my 993/Wilwood setup. Point being is these brake changes that use bigger rotors with their shallow offsets make it a tight fit of properly centering the caliper over the rotor while maintaining decent rotor clearance from the ball joint.

Lastly, I like the one-piece '86 951 rotor which reduces hassles with sourcing the rotor hats and fasteners. Although it does make me wonder how much longer will Porsche continue to make a one-model-year-only front rotor? Maybe the Timmons setup using the front only is the way to go. Caliper adaptation is simple and rotors are plentiful 996 stock. Bias is only a bit more front (due to slightly larger dia. 996 rotor) than small VCI setup.

Another thing to note is the small Brembo VCI setup clears regular 16x7 Fuchs in the front no problem. This is not a concern since your 16x8 HRE Fuchs are 3 pc. They should have the same clearance as the aforementioned BBS, since they have "flat" inner rim halves, no?

I'll be honest that I do like the fitment of the 993 Wilwood setup a bit better than the VCI. However the bigger Wilwood rotors and 44/36 pistons will make hyd bias a bit front-biased at 1.83 with the Carrera rears, vs. the 1.64 bias of the smaller 40/36 basic front Brembos and Carrera rears. I'm currently running the 993 Wilwoods with 930 rear calipers and 930 rear rotors, which is a hyd bias of 1.79, because the car came with the 930 rears- I didn't specifically choose them. I don't find it overly front biased but still a bit more rear brake bias wouldn't be bad. My racecar actually was even a bit more front biased with bigger Coleman 12.75" floating front rotors and 993TT calipers, which I decided to change to 993 Wilwood stuff for cheaper & better rotors and cheaper pads.

Kevin

that was me. I finally went with the full monty 930 set up from Steve Weiner and boy they look gorgeous. I am looking forward to test the brakes in spring when the DE season starts.

Hakan

hmmm, if I were you I would go with the Steve Weiner setup.

Good parts + reasonable prices + expert advise = great value

JMHO...

I also just ordered the whole set up from Steve. Cant wait until it gets here. He did say the new MC will require a bit more clearance with my old steel crossmember. Not looking forward to that part but it will be worth it.