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Randy67
04-07-2010, 05:07 AM
Car is an 81 Camaro being made into a C-Prepared autocross car. I looking to upgrade the front brakes to a 12" setup, but not the 1LE stuff (even though I have some B-body spindles available). Rear brakes will be 98-up S10 discs.

I have been looking at circle track 12" x 1.25" or 1.38" 2-piece rotors, but trying to figure out what rotor hub to use with the rotors and get the spacing close to right is not a easy at it looks (at least for me). I can make hubs out of the stock rotors or use 3rd gen rotors to move in it a little more if needed. Looking to use a 4-piston calipers as well, unless there are better options. I will have a caliper bracket made unless there is one that will work. Looking to see if anyone here has done this or has some good ideas.

Money is an issue, trying to avoid big dollar setups. This car will only be used in autocross, not street legal at all. TIA Randy

Apogee
04-07-2010, 11:43 AM
Randy, we co-developed an "HD12" kit a couple of years ago primarily for the late-model B-bodies using our GMTS HD hub and a custom 2-piece DBA rotor assembly. It turned out pretty slick IMHO. The DBA rotor is 302mm x 32.5mm [11.9 x 1.28] and can be used in conjunction with a wide-body GM D52 caliper or equivalent...meaning that you can opt to run the aluminum Wilwood D52 replacements if you want to shed even more weight, although interstingly enough, the HD12 kit with the cast iron calipers is still lighter than the factory B/D-body brake setup.

I can think of several 4-piston caliper options, however all are going to require probably more work than going with something that's already been designed, tested and proven in the field. For more information regarding the "HD12" kit, give me a call or email and I'll point you in the right direction or go visit the Impala SS Forum here (http://www.impalassforum.com/vBulletin/showthread.php?t=228173) for a write-up.

We can supply custom hubs for your 5x4.75 wheel pattern assuming that's what you're running.

Tobin
KORE3

Randy67
04-07-2010, 12:38 PM
Sounds like a good idea, pretty straight forward setup. I will read up on it more this evening.

Any issues with having the large piston caliper up front (the Camaro calipers I have are 2-15/16") with the small piston S10 caliper out back? I plan to run dual master cylinders which should help out with this. Just wanted to be sure it wasn't too much of a mismatch.

Apogee
04-08-2010, 02:59 PM
Randy, you should be ahead of the curve with dual master cylinders, so it shouldn't be an issue. The S-trucks had either single 2.5" piston calipers or dual 1.8" piston calipers which equates to roguhtly 5 square inches of piston area in both instances. the larger 2-15/16" calipers have ~6.78 square inches, or about 28% more piston area. While potentially difficult to handle with a single tandem MC, that should be easy to overcome given your setup.

Tobin
KORE3

jake72ss
04-08-2010, 06:33 PM
Tobin, how would you compare the HD12 setup to let's say standard C5 setup, I'm thinking of changing my current b body/1le setup to something better, oh yeah wilwood d52 twin pistons with hawk 9c1 style pads.
Thanks, Jake

Apogee
04-09-2010, 05:15 AM
Tobin, how would you compare the HD12 setup to let's say standard C5 setup, I'm thinking of changing my current b body/1le setup to something better, oh yeah wilwood d52 twin pistons with hawk 9c1 style pads.
Thanks, Jake

Given the rotors, you would be correct to expect the HD12 brake kit to be a solid performer, and it is. What you lack in rotor diameter, you make up for in thickness and caliper piston area. Combine it with the appropriate pads and they can be pushed extremely hard in a track environment with very good results, even if you happen to be flirting with the 4500# mark like most B-body applications. If squeezing performance brakes inside a 15" or 16" wheel is important to you, these would be tough to beat in terms of performance value per dollar IMHO...similar to a C5/C6 kit for 17" wheels.

The C5/C6 kits have larger rotors and less piston area, so they tend to give better driver feedback through the pedal but certainly will require more pressure to do so. Modern twin-piston floating calipers give better pad support than a single piston caliper can. The additional rotor mass can be helpful depending on the car and where it's driven. Part price and availability is tough to beat, both OE and aftermarket. Given the choice between the two, C5/C6 kits will win every time if my wheels allow it. If going with 15's/16's, the HD12 would be a no-brainer for me.

As a side note, you mentioned running 9C1 pads with the Wilwood calipers. I don't know whether it's different with the Wilwood calipers, however the 9C1 pads are thicker than the standard pads and had to be used with 9C1 calipers on the factory thickness rotors. The fat pads can't be used with the wide 32.5mm thick rotor...just not enough room inside the caliper body for that.

Tobin
KORE3

novaderrik
04-09-2010, 07:46 PM
if you don't mind going to the 5X5 wheel pattern, then you could try a rotor and caliper from an early 80's 1/2 ton 2wd pickup with the HD brake setup on the b body spindles.
those rotors are 12X1.25".
another option for rotors that are easier to replace would be turn down a B body rotor to a hub and use a set of early 90's Astro AWD van rotors on it- they are also 12X1.25 and slip on over the hubs once you take the caliper off with no need to mess with the wheel bearings. i don't know if those rotors have the proper offset to fit under the caliper in the stock mounting location.
i played around on various websites looking up rotors, wheel bearings, and calipers one night, and on paper it all fits together. i might grab some parts at a junkyard some day to see if it all fits together in the real world.

DAK
04-10-2010, 07:31 AM
The S-trucks had either single 2.5" piston calipers or dual 1.8" piston calipers which equates to roguhtly 5 square inches of piston area in both instances. the

I believe Randy will be using 98+ s-10 rear discs. I dont recall exactly the piston size but its around 1.75".

Randy67
04-10-2010, 09:38 AM
Derrick, sounds like a couple good ideas. Let us know if you figure anything out. With the HD12 setup as a fallback setup, I am going to play around with different hubs and see if I can come up with a 2-piece rotor setup based on circle track stuff. I need to find how much the rotor parts add to the offset so I can try and figure it out.

Dak, Tobin was comparing the size of the front calipers on S10's vs the front caliper on my Camaro, showing a 28% size difference. With a dual master cylinder setup, this shouldn't be a problem to using with the S10 rear calipers.
Randy

DAK
04-10-2010, 08:03 PM
Rear brakes will be 98-up S10 discs

this shouldn't be a problem to using with the S10 rear calipers

Randy you got me confused. So are you using s-10 rear discs or s-10 front brakes on the rear?

Randy67
04-11-2010, 05:19 PM
I'm using the rear discs from the S10. What we were talking about is the size difference between the S10 rear and the Camaro front caliper and would it cause a problem with front to rear balance.

DAK
04-11-2010, 07:48 PM
Then you're looking at a some what similar setup that I have on my Olds. Imo the large gm caliper is a good match to the rear s-10 caliper.

DAK
04-18-2010, 02:12 PM
I just remebered I mocked up this setup on my 12in b-body spindles a couple yrs ago. C3 corvette front rotors and hubs cut from g-body rotors. It all fit together quite nicely. I never finished the whole setup so I cant comment how well it works.

https://static1.pt-content.com/images/pt/2010/04/011-1.jpg

https://static1.pt-content.com/images/pt/2010/04/0171-1.jpg

Randy67
04-18-2010, 05:14 PM
That's a pretty cool setup. Is that a wide Caliper like mentioned above? D52 Pads? Curious minds want to know.

DAK
04-18-2010, 10:44 PM
Yes those are d52 calipers, pads and the Howes are designed for a 1.25" wide rotor which the C3 rotor is.