Early 930 rotor questions

greglepore · 05-09-2005, 03:54 AM

My 914-6 came with 79 930 brakes. While changing out the A/X tires yesterday, I noticed a crack in one rotor, extending from the outermost hole to the edge of the rotor, and downward about halfway to the next hole. Is it critical to replace this rotor immediately for a car that sees mainly street and A/X use, or do I just watch it carefully?

Second, obviously at some point I'm looking at rotors. Is there an alternative to the hideously expensive early 930 rotor (at around 400 bucks a pop). I'd prefer a slotted rather than drilled rotor anyway, to avoid cracking w/ eventural track use in the future.

89911 · 05-09-2005, 04:01 AM

Call Steve at www.rennsportsystems.com. He can get a Brembo that will fit this application. The downside is they are very expensive also. With a 914, you could expect a pretty lengthy life.

jakermc · 05-09-2005, 07:18 AM

I don't think the rotors are that expensive, its the inner hats on the floating rotors that push the bill up. I think you can buy new rotors that fit your existing hats, recycling the expensive part of the set-up.

89911 · 05-09-2005, 08:37 AM

The rotors for these car are VERY expensive (factory list $625/each). Of course, some can find these cheaper in Europe from what I hear. The demand for it is very limited because of the short time used, many aftermarket companies don't even stock them.

jakermc · 05-09-2005, 09:56 AM

Floating rotors appear to be only $150 here:

http://www.vehiclecraft.com/Brakes/930_upgrade.htm

Here is more detail:

http://www.vehiclecraft.com/Brakes/vciweb4.htm

The rotor kit is $800 - $1000, which includes hats and rotors. The expense seems to be in the hats, not the rotors. This is a two piece system, you only have to buy the hats once.

greglepore · 05-09-2005, 10:09 AM

Close, but not quite. I checked VCI after posting. The $150 price is the uprgrade price from non-floating to floating with their kit. The good news is that they have non-drilled rotors available for around $265, but I'm waiting for a confirming email that they'll work with the factory hardware; it appears from the website they will.

don911 · don911's Garage

You may want to find out the brand of rotor that VCI sells. When I was trying to decide on rotors, I remember some threads on some aftermarket rotors warping easily.

Also, I have factory 930 rotors and am using the VCI hats and T-locks so the rotor they sell should work with the factory hats.

jakermc · 05-09-2005, 11:08 AM

Keep us posted. I have 78/79 930 rotors on my car as well and will eventually need to replace my drilled rotors. Like you, I'd like to go slotted on my next set.

greglepore · 05-09-2005, 12:32 PM

Doug at VCI confirms they work with factory hats. $249 for slotted 12's, 269 for slotted 12.75's. I didn't get into specifics as to whose rotor it is.
Still steep, but not as hard a hit as the factory part, an better yet, no holes to crack.

89911 · 05-09-2005, 01:12 PM

If you check the archives, you might see a post or two from me on VCI's rotors. I did 930 upgrades on my car 3 years ago and purchased their rotors up front. These lasted my one weekend DE before they were warped. Prior to this, I used may original carrera brakes and rotors and never had rotor warpage. I turned the rotors, ran them again for a weekend. They warped again and I threw them away. I called Doug and he stated that this was atypical. $500 bucks for 4 track days. Since then, I used brembos from Rennsport and I have had no issues in 2 years. Just one look at the two rotors side by side and you can see the brembo has twice the mass. These weren't cheap but at least they are lasting. If VCI is still selling the type that I had 3 years ago, run away. My goal here is not to "bash" VCI. I've had my calipers adapted by them for a fair price. I'm just trying to save someone the $1100 I spent for front rotors that year. At least you were warned.

Bill Verburg · Bill Verburg's Garage

I would spend a little extra and but a se6t of stock '78 -80 rotors, SSF has 3 sets on their shelf last I talked to them. They are expensive but are also much higher quality than the aftermarkets.

Steve W/ uses 993tts that are machined down, you could probably do the same, but you would need special hats.

For a light relatively lighter, slower car(no offense intended)

the VCIs will probably be ok. It's the heavier faster cars that beat them to death.

Steve@Rennsport · 03:16 PM

I'd second Bill's advice.

I do use custom Brembo rotors (http://www.rennsportsystems.com/2-f.html) with our billet hats for these applications as they are FAR more rugged than Factory Zimmermans, much less the Coleman rotors that others sell. You get what you pay for.

As we used to use a lot of them (before doing the Brembo ones), I've not found a Coleman rotor in these sizes that wouldn't warp, sooner or later so Caveat Emptor on those things.

greglepore · 05-09-2005, 03:53 PM

Thanks for all the advice. It is a light car, and is more or less an A/X mule currently; it'll see some D/E's in the future, but not his season. For the intended use the brakes are stupid big, I'm sure Carrera brakes would be more than adequate, but they're on the car, so they stay. What I'm looking for is a rotor that will be acceptable for those conditions and not cost a fortune for now. I do agree that you get what you pay for, and when the car sees some track hours, well, time to invest.

Steve, do your rotors work with the factory hats also, or is your system specific to the custom hat?

Bill, no offense taken, its really lighter and much slower (due mostly to the gearing) but between 40-110 I'd run you for pinks

Bill Verburg · Bill Verburg's Garage

If you don't need them, *(you don't for A/X) the bigger rotors are slower than stockers

derickc · 05-09-2005, 04:25 PM

Greg,
I think it's actually fairly easy to swap the hubs for the later (86 to 89) style non-floating rotor hub and use those rotors (more like $150 each).
I've seen this done on several cars, but don't recall exactly what is involved with the conversion.

-dc

Bill Verburg · Bill Verburg's Garage

The late 1 piece 930 rotor has the wrong o/s and will not fit correctly as a replacement for the zero o/s early rotor/hat combo.

It works fine on late 930 because of hub and fender mods

Jim2 · Jim2's Garage

OK, so after reading this thread I sit here with my new uninstalled aftermarket rotors from V__ intending to install them on my 79 930 which sees intense track duty from aggressive solo I competition and lapping days.

89911 says they warp and are junk. Do I bother installing these things or just get the originals? I can always sell the V__ rotors to someone with a street application.

I live in Canada so I had to endure some cross boarder brokerage and duty on the V__ rotors which in the end were only 25% cheaper than the originals.

My factory rotors had lots of street miles yet they still performed well for the last two track seasons, but the cracks simply looked too big, hence my desire for the V__ slotted rotors.

What to do? 89911 what do you suggest?

Jim

Steve@Rennsport · 05-09-2005, 10:02 PM

Quote:

Originally posted by greglepore
Steve, do your rotors work with the factory hats also, or is your system specific to the custom hat?
[/B]

Hi Greg:

Our rotors do not mate to the Porsche full floating hats; you must use the OEM rotors, only. Ours are specific unto themselves.

I'd agree (again) with Bill. For AutoX work, dragging around those big brakes is just a big liability. Get some Carrera brakes and tuck those Turbo ones away for the day you need those things; open track use.

89911 · 05-10-2005, 04:45 AM

Quote:

Originally posted by Jim2
OK, so after reading this thread I sit here with my new uninstalled aftermarket rotors from V__ intending to install them on my 79 930 which sees intense track duty from aggressive solo I competition and lapping days.

89911 says they warp and are junk. Do I bother installing these things or just get the originals? I can always sell the V__ rotors to someone with a street application.

I live in Canada so I had to endure some cross boarder brokerage and duty on the V__ rotors which in the end were only 25% cheaper than the originals.

My factory rotors had lots of street miles yet they still performed well for the last two track seasons, but the cracks simply looked too big, hence my desire for the V__ slotted rotors.

What to do? 89911 what do you suggest?

Jim

If your going to run a 930 intensly on the track, I don't think VCI's rotors will hold up, if they are using the same manufacturer. I found my old pictures of comparing the 2 different rotors. I isn't hard to see the difference. I ended up throwing away the rotors (ouch) and selling the custom hats to recoup some of the money. Just trying to help someone from money I wasted.