Rotor Options for 930 Front Calipers?
 

I am toying with different options for upgrading the brakes on my car (currently has Carrera brakes on it). One potential option is 930 front brakes. I am not clear on exactly what the options are for rotors, though, and what the pros and cons are for the different options.

Is a '78-'80 930 rotor bolt on? If so, is the only downside the cost? ~ $375 each?

What about the VCI options? Floating or non-floating are still ~ $350-$400 each. I'm assuming the VCI rotors include the hats and the rotor, but at replacement one would only have to buy the rotor? What rotor does VCI use? Do they sell the replacement rotors?

Which Wilwood rotor is correct for this application? These seem to be around $150 each, but hats would be needed and I'm not sure what the options are for the hats.

Are there any other options?

Can't answer all of your questions, but the standard 930 rotor will not fit in the front (the offset is different). Therefore you will need aftermarket hats. I got a set, with rotors, from Steve at Rennsport. Not sure which rotors can then be used as replacement once they are worn out.

The standard 930 rotors will fit the rear though.

/Johan

*****Bill V.*****

Same here. When I got my rotors from Steve I noticed they were shipped in an O.E. Porsche box with 993 turbo p/n's on them. My guess is that they are 993 Turbo rotors with their outer diameter machined down to 930 diameter.
Here's a couple pictures in comparison to stock SC front rotors
http://i183.photobucket.com/albums/x...ginning144.jpg
http://i183.photobucket.com/albums/x...ginning145.jpg
http://i183.photobucket.com/albums/x...ginning143.jpg

Mike,

For your car the Wilwood 48 vane HD rotors in 12.19" x 1.25" (309 x 32mm) will work perfectly. These are part number 160-3870 and 3871

http://www.wilwood.com/Rotors/RotorList1.aspx?mktname=HD 48 Curved Vane Rotor

A simple 1/4 thick flat hat with good hardware (use bolts that are NOT full thread and locking nuts) is all you need to make these work. I've gotten my parts from ProBraking in the past, but any good machinst can make these hats in a snap. Simple transfer of two bolt circles onto the hat. I believe Race Technologies also makes a kit for the Wilwood rotors.

Chris Streit and I have run these on our cars for years with great success. He's run them on his very fast GTS4 '70 3.3L widebody racecar and i've run the same rotors on my DE'd '87 Carrera and recently on my '79 SC/930 racecar this past season. Others have preferred to use the slotted Wilwood GT version of this rotor, but I personally don't think it's worth the added expense. We've gotten plenty of life and performance out of our cheaper HD rotors, so we see no reason to step up to the GT.

As an aside, i'd recommend looking at 993/928S4/951S/968 M030 front calipers. They're cheaper to buy, cheaper to service (seal replacement) and adapters are cheap as well. However if you're sold on the 930 calipers for their piston sizes (38/38) vs. the larger 44/36 of the aforementioned 993 calipers, I understand why- to avoid too much front bias (depending on which rear caliper you select)

Personally, I have OEM 930 floating rotors on the front on my car, but if I was going to do it again, I'd go with the setup that Steve at Rennsport has.
As pointed out above, it's a machined 993TT rotor fitted to some custom hats - way cheaper than OEM 930 floating and apparently great durability.
Give Steve a call - he's a great guy and can discuss the various options.

Regards,
Andrew M

i use floating 1978-80 Zimmermann up front
they fit VCI hats @ $568 which means my front fenders are stock narrow. i paid $350/ea for ft rotors in Dec 2008

930.351.048.00
930.351.047.00





Rear is Zimmermann @ $188/ea in Dec 2008

930.352.046.01
930.352.045.01

Thanks for all of the responses. I am in a position where I need a little bit more heat capacity in my brakes, but I don't want (or need) to go all out with something like Big Reds. My track wheels are 16s in the front, so I have been leaning towards a solution that works with the 16s. My car is light (~ 2400 lbs) but with 245 hp or so, I am still getting a bit of a spongy pedal at the end of a run session. Plus, my front rotors are in need of replacement and, well..."while I'm in there..." ;)

I thought about the C2 front caliper with the '86 944T rotor, but don't love the spacer issues and after buying the calipers used and getting them modified, they would be about as much as 930 front calipers and I like the bolt-on nature of the 930s. The 930s are also a decent match as I am considering sticking with my Carrera M rears for the time being. The bias ratio would be around 1.64 with the 930 fronts/Carrera M rears and that would probably be fine (especially with the massive heat capability of the 32mm rotors).

So, the '78-'80 stock 930s fit? Are they all floating or are some non-floating?

Yes, they fit in 15 " wheels too. The '78-80 hats bolt to the 911 hub and the 930 caliper bolts to the strut.

You can use either floating(ala '78-80 930 or aftermarket) or non floating hats(aftermarket). floating are better for track use.. You can nnot use the '81 up 930 front rotors unless you have 930 fender and hubs or use custom hubs

It would also be better to use a non drilled rotor annulus, though w/ a lighter car you will have better durability than w/ a heavier. The drilled rotors do crack more easily.

i fixed above post

i flared wheel wells to run 951 7x16 Fuchs all around and all is perfect without spacers


also
Boxster complete Kit 65-89 911, 76-77 Turbo

Yeah nice idea, but I need "more rotor" in the front, though.

Next question - will a 19mm master cylinder be adequate with 930 front calipers and Carrera M rears? I'm tempted to try it and see...

not hard info besides my act

i hated my stock original brake pedal feel so i installed 23mm cylinder looking for all the help i could find. It helped a harder feel but brakes sucked anyway

so personally i'd install 23mm now for $300 and 930 rears when i got more coin

Pretty much what I had in mind... ;)

930 front/3.2Carrera rear w/ a 19mm puts the slave/master ratio above 50, the pedeal will be mushy, the brakes will stop the car in a normal forward stop, less so in reverse and will cause rear lock on a panic stop.

you want a slave/master ratio much lower
stock manual thru '76 was ~41
the boosted '77-89 are ~35.2
930 is 33

the lower the ratio the higher and harder the pedal all of the factory race cars are very low 30s and high 20s, when not boosted these real low ratios do require a lot of leg

I have had the 930 set up on my 911 for about 7 years now. I had them originally done by VCI. The machining and the tubing changes were all first rate, but the front rotors they had from Wilwood were poor to say the least. They warped the first DE out. Had them machined and the again warped a few DE's later. I had Steve at Rennsport send me out his set which do look like machined down rotors and have been running this since WITHOUT replacing. We are talking a few dozen DE days along with everyday driving. I am looking at a new set now since I am getting some cracking around the drilled outs and see no reason but to go with the same ones. I would avoid Wilwoods at all cost since these are a much better option.

Well, it seems that this thread was indeed valuable as I didn't even know of the Steve Weiner option for the rotors. That sounds like the way to go.

It also sounds like I ought to budget for the 23mm master cylinder. I had heard an anecdotal story of someone actually running Big Reds and using a 19mm master cylinder, so even though the math pointed to a 19mm being iffy in my case, I thought I'd try it and see. Man, I hate replacing a master cylinder on my car...

Does anyone think that my idea of 930 fronts and Carrera M rears is inherently a bad idea? On paper, it seems to be technically OK - if not flashy and exciting.

That will work ok

When I converted my '73RS-look car to 930 brakes, I left the 19mm MC in for quite a few events just to see how it worked, having read the debates about it here over the years. It did work OK, but it made for a long, touchy pedal action that was difficult to modulate well. I finally went with the 23mm MC, and it was almost too high and hard a pedal. I ended up wishing for something in the middle for a non-boosted application, but there was nothing readily available at the time, and I sold the car before experimenting further. Since then, I have seen Sherwood Lee mention a 22mm MC from a VW Corrado that may work nicely. One guy in the UK said it fit:

http://forums.pelicanparts.com/porsche-911-technical-forum/369088-bigger-master-cylinder-problems.html

TT

You are absolutely correct in your description of what a m/c that is too small or too large will feel like.

I'm sure that Sherwood's recommendation of the 22mm Corrado m/c is also a good one.

for 930 brakes w/ a 23.8 the slave/master ratio is 33.077 which w/o boost will require more pedal effort than many may wish to supply. For reference an unboosted stock '73 is 41.311 and a boosted '83 w/ a 20.6 is 35.192

the Corrado m/c w/ 930 calipers will be 37.172, well w/i the acceptable range, the guys w/ boosted SCs can even leave the stock 20.6 though it is close to the max of the acceptable range, they would probably be much better off w/ a 23.8