993 brake conversion, source for rotor adapter

[jager911]

I'm upgrading to 993 brakes f/r on my '74 track car.
I'm going with the Wilwood rotors in front mentioned here by Jeremy and KTL (and 930s in the rear).

If you guys are reading, what are sources for the front rotor hats and the Wilwood rotors? I tried probraking and he is not returning my emails.

I have a local machinist who will machine the rear calipers, will use 930 rotors.

Thanks for any info!

[TRE Cup]

Have you called VCI , and spoken to Doug? He has options for you

[boxsterman]

The rotor hat is pretty simple - just a 1/4" thick aluminum with 5 holes inside for your hub and 8 holes outside for the Wilwood rotor. The adapter is a bit tricky; you need to find someone to get you the offsets.

I have a set of floating rotor hats and adapters custom made by Pro-System, Inc. (Pro-System, Inc. - Brake System Testing & Development for Racing) that works with the 993 n/a calipers and Wilwood rotors. Completely anodized. It cost almost $600. I can sell them to you for $200 plus shipping. I have used the setup for two DE days. The floating setup was simply too noisy for me. It does require 17" wheels. The design also eliminate the problem of the rotor touching the A-arm.

If interested, PM me and I can send some pictures.

-James

[KTL]

Jager,

Your machinist should be able to cook these up no problem. Wilwood provides their bolt circle dimensions for the rotor on the tech info pages for the rotors, so all you need is a precise spec for the 911 hub bolt circle for the rotors. I have some measurements that I took off my hats, but i'd rather trust the machinst to measure the hub to establish the bolt circle. In terms of material, the hat is simply 6061 alloy that's 1/4 in. thick.

Also I have some nice fasteners thar I found to be ideal for this aaplication- slightly overkill 10.9 flange head bolts with matching serrated flange nuts. Quality fasteners that are much cheaper than the uber overkill expensive NAS stuff that Probraking uses.

For adapters I got them from Road & Race in CA for $100. Check out msroadrace on ebay to see them. You can use either type- they have a simple block adapter made out of bar stock, or a more elegant lightweight machined part. I'd give the block one a try because I got the ltwt fancy one and found I had to use a washer on the adapter to center the caliper around the rotor. Also find that my caliper sits above the rotor a few mm. So the adapter could be milled a bit to get rid of the overhang. Lastly, the caliper bolts for this adapter are threaded for M12 x 1.75 socket head and 80mm long is the perfect length.

[78SCSLANTNOSE]

Jager,I'm doing the same set-up on my car next week.I am doing my own brackets for the front calipers.Hers a pic maybe this would help your machinist friend.I'm going with 993 rotors in front and rear that's the only difference.I believe the hub measures 103mm and the bolt holes15.49 have him double check and get the measurements from wildwood for their measurements.

[78SCSLANTNOSE]

Here's a simpler one.

[jager911]

TRE Cup,
I think Doug uses Coleman rotors which are pricey, I'm going with Wilwood.
Boxsterman,
Thanks for the offer, I'm going with the non-floating set-up.
KTL,
I have adapter block already from a buddy. I will take the Wilwood rotor and hub over to machinist and get him to make hats, he does the work for VCI. Machinist mentioned special nuts (J-nuts?) that don't back out. Is that what you used? Thanks for the tips.
In another thread, you mentioned plugging the rear holes with threaded rod and drilling new holes, do the new holes overlap on the threaded rod? Wouldn't welding be safer? I understand heat is an issue with the seals.

[jager911]

78SCSLANTSNOSE,
Nice plans! I have the front blocks already, I'll get hubs and rotors to machinist so he can measure if I can't find a source.

How are you making 993 rotors fit in rear? Advantages over 930? Cost seems similar. Thanks.

[78SCSLANTNOSE]

Jager,maybe these pics of the front and rear rotor measurements might help your friend.Its from a 930 rear rotor and 911 front rotor.As for the 993 rotors.It's what I have.From my understanding I wont have emergency brakes using 993 rotors,but I wont have to widen the calipers or shave brake pads.The measurements of 103mm and 15.49 are for the rear.

[jager911]

78SCSLANTNOSE,
Good point on not having to widening throats of calipers as I'd hate to waste pads by shaving.
I have spare 993 rotors so that would be ~$300 saved.

Let me know how your install goes as I'm not doing mine for a few weeks yet.

[JeremyD]

Rear Pads are no big deal - I think I had the same set of pads on mine (that were shaved to fit) for over three years -

The 930 rear rotors and bolt on - and you retain the parking brake. If you really dont want to shave your pads - find some 965 rear calipers (that's what I did this time)

[onboost]

Originally Posted by jager911

I'm upgrading to 993 brakes f/r on my '74 track car.
I'm going with the Wilwood rotors in front mentioned here by Jeremy and KTL (and 930s in the rear).

If you guys are reading, what are sources for the front rotor hats and the Wilwood rotors? I tried probraking and he is not returning my emails.

I have a local machinist who will machine the rear calipers, will use 930 rotors.

Thanks for any info!

Hmmm, I thought the 930 front rotors could be used in front also with the 993 front caliper... is tihis not true? Who else besides VCI would have the proper adapater for this ?

[KTL]

Originally Posted by 78SCSLANTNOSE

Did you steal that cad dwg from VCI, because that looks exactly like the caliper adapter I have on my shelf for a Big Red setup (made by VCI) that was on the front of my racecar! And yes, Doug uses Coleman front rotors that are $280+ a piece if you go with the floaters....

Some have had so-so results with the Colemans, and I was willing to forego the added benefit & cost of floaters by using the lesser, cheaper Wilwood HD rotors. The Wilwood setup has proven effective on my street car at track days, friend's 3.4L 1970 911S racecar (cstreit), and JeremyD's former 3.4L cabrio used at the track. So the Wilwood stuff appears good enough for me.

I'm not trying to be stupid and suffer from false economy by going with cheap rotors that wear out too fast or warp. The Wilwoods are up to the task IMO and when the Wilwood HD at $80 retail perform suitably for me, I see no reason to spend $280 ea. on the Colemans + their need for eventual replacement of floating hardware. One other reason I switched out the Big Reds on the racecar to a 993 setup is race pads are substantially cheaper than Big Red pads, (neither of which I consider cheap).

RE rotor fasteners, I use nuts that are flanged with serrated locking surface.



J-nuts or jet nuts are deformed nuts that grip on account of the thread interference. I think either j-nuts or serrated ones will work fine. I like mine because I buy them in bulk from McMaster Carr at much less cost than the NAS stuff. I can afford to throw them away time after time I take off my rotors (How often do we do that, every year or two when it's time to replace rotors?) and still not approach the cost of the NAS stuff. These are good quality fasteners made in Germany. Not some cheap crap.

RE the new holes in the 993 rear caliper, yes the new holes overlap the plugs when you redrill. There's no way they're backing out- Loctited (red) in place, staked with a pin punch, and the caliper mounting bolt head is pressing against the plug when the caliper is installed on the trailing arm. Welding is of course an option but the calipers are very good at heat transfer so you'll likely cook the seals. Maybe the other option is to have your machinist press in a piece of alloy rod. In other discussions here some people liked that idea better than tapping and plugging the hole.

I thought the 993 rear rotors have too much hub depth/offset? Bill Verburg shared this when I was doing my rear caliper re-sizing

993 Caliper Mods- Grinding and Drilling

In lieu of the stock Carrera rotor (too little diameter) or the 930 rotor (good diameter but its 28mm thickness requires brake pad shaving if you don't have 930 or 965 rear calipers, also expensive rotor cost) a 996 rear rotor or a '86-'89 928 S4/'86 944 Turbo looks like it can work. I have both of these rotors on my shelf and I believe they'll work by adjusting the offset of the caliper mounts. Fitting mount adapters on the rear calipers is expensive (VCI charges $600 nowadays for mounts and machining the calipers) so I think I can plug and redrill and mill the mount a bit thinner to move the caliper outward.

The 996 and 928/951 rotor has a little less offset than the stock SC/Carrera rotor, but not as much as the 993, so you have to move the caliper outward a just a bit to center around the rotor. But the next challenge is you lose some hub-centricity of the rotor because the centerbore of the rotor is bigger and the indexing screws don't line up......... So i'm still working on seeing if this can truly work. Won't have time to work on that just yet. Kinda busy right now getting the racecar sorted for 1st race in a few weeks and the Webers are a little finicky right now......

[KTL]

Originally Posted by onboost

Hmmm, I thought the 930 front rotors could be used in front also with the 993 front caliper... is tihis not true? Who else besides VCI would have the proper adapater for this ?

Steve Weiner at Rennsport Systems makes a LOVELY set of Brembo 930 rotors and hats to fit the 993 calipers. Ask Jeremy about them.

[78SCSLANTNOSE]

KTL Here's my source 993 front brake caliper adapter As for the rear, If I have to modify the calipers to use adapters for the 993rotors.Its less than the $300 for 930.Jager has a local machinist maybe cheaper for him if it's a friend.

[JeremyD]

Steve Weiner's rotor hat combo.




My 930/965 combo

[boxsterman]

Here is a picture of the hats and adapters custom made by Pro-System. The elongated outer holes enable the rotor disc expand independently as it heats up. $200 for the the hats and adapters.

-James