LaVidaLoca

Anyone built their own adapter brackets? Got any pics?

I have been working on fabricating a set and have done several mock-ups in aluminum just to check fit and alignment. By my calculations the J55 caliper holes need to be .750 inches further out than the stock calipers. Much less than that the calipers hit the rotor and much more than that, the pads are off the rotor.

I have looked at pictures on Doug Rippie's web site and can't see how that type of adapter can keep the pads completely on the rotors. Anyone used these and checked the pad position??

I am experimenting with a bracket that will rotate the caliper up and towards the front about 1.625 inches. This allows proper height and the bracket clears the knuckle.

CentralCoaster

my C5 adapters measure .75 there also.

The easy measurement is the offset you need to move the caliper bracket outward.

LaVidaLoca

Thanks for the reply. Once I figured out how much offset the puzzle became HOW to get there. The holes would have to be very close together and you have to clear the mounts on the knuckle which are over 1" in diameter and still leave some metal around the bolts to the calipers.

Do you have any pics of your adapters?

chicagotom

I have an 87 and I would like to upgrade my front brakes also. I have a set of calipers and rotors off a 95 are these the same as your zr-1 calipers?

Thanks
Tom

LaVidaLoca

I don't think so. The ZR1 used the J55 brake package with a 13" extra wide rotor. Although I think they both used the same mounting configuration. I am not 100% sure of this, so someone else jump in if I am incorrect.

chicagotom

I have taken measurements of my 95 rotors and they are a little over 13" in diameter, about 2-3/8" overall width with a little over 1" width between the swept areas. I also looked at vette specs by Mike Antonick and according to him the zr-1 brakes were made standard on the 95 vette.

I think we have the same brakes. What year vette is your early C4?

Tom

CentralCoaster

Pay attention to what way your bolt heads need to go, and how much clearance they need.

I had to use allen bolts, since i wouldnt have had room to get a socket on hex bolts.

The offset between mounting points is the thickness of my adapter, which is basically a c5 adapter.

it'll be completely different from your setup, but this will give you an idea of how i bolted mine up. The adapter is just a plate with 4 holes in it.

I'm sure someone already makes the part you need.

Jeffvette

All Corvettes in 95 and 96 got the J55 brakes (13" rotors and caliper)

Jeffvette

Kevin, the shield you have mounted, is that for ducting?

BrianCunningham

I've got the J55's on my base suspension '95

A fellow forumite upgraded his '94 with J55's, here a pic of the 12's vs 13's

CentralCoaster

It's the stock shield, but I'll probably remove it.

My initial plan was to enlarge the center hole and hook up a cooling duct to it... dunno if i'll get around to it (or even need it!)

LaVidaLoca

Thanks for the pic. I can't do it quite that way since there is no real offset between the early C4 and J55 calipers, just a difference in the radius of the hole locations. Your's looks like a very clean conversion.

-js-

I have also been looking into this since I have a set of the calipers . I did have one member email me saying that he was working on an adapter but as of today I have no word if its been completed. During my searches I came across this link http://www.ls1.com/forums/archive/in.../t-124902.html from an F body it has some good part number info. And here is pic of an adapter that was used. http://www.amiraq.com/images/13brakes/bracket.gif I know this isn't made for early C4 Y bodys but it looks similar to other adpaters.
So LaVidaLoca is saying their is no offset in the in/out direction just the up/down due to the 13" vs 12" rotor ?
Thats very interesting. I too was planing on making my own.

CentralCoaster

I see what you mean, without the offset, where to put the bolts, and the adapter material.

I made mine out of cardboard first just to check those sorts of things.

I couldn't use the normal c5 adapters because of interference with the wilwood setup, even though the bolt holes were in the right place.

Is the vertical spacing of the holes different for zr1 vs. c4? If so, you'll get some extra meat there.

Maybe you could come up with an adapter that mounts to the inboard side of your knuckles then goes out to that same surface level for the new brackets to bolt to... although that still leaves a problem with not enough material around the bolt holes....

hmm

-js-

Here is the pic from DRM for the 84-87 twin PBR adapter for reference.

LaVidaLoca

Thanks for the pic. I see the configuration, but still can't get the numbers to come out right. To get the calipers to move out .75 inches makes the holes so close together that there is not room for clearance AND to have enough metal around the new mounting bolts. If I move the calipers out 1.0 inch everything clears, but the pads are about .125 inch off the top of the rotor. This may not be unacceptable, but I am trying to keep the pads completely on the rotor.

-js-

I don't have a rotor to mock up yet but I'm "assuming" that the adapter will move the mounting out 3/4" and the new mounting holes are 3/4" away from the original location. So that part is similar to the pic from the F-body adapater just change the 1.08 measurement to .75 then the offset needs to be set to its original position nothing like the F-body adapter that is set back .13 ".
F-body adapter pic
My math puts the center points of the mounting holes 1 1/8" apart so it gives you a 1/2" radius and 1/8" of clearance if you have the same radius on the original mount.
I have also seen posts from others that used the DRM unit and they did mention having to grind or file a small amount to get it to fit. My guess is the factory bracket is what they worked due to casting variances.
I'm not claiming to be the expert on this its just what I have come up with from the information I have thus far.

LaVidaLoca

The holes are not a "linear" .75" apart. Remember that you are dealing with a bunch of concentric circles. While the brackets are made straight, the holes are actually arranged on a circle. The original factory mounts are about 3 and 3/16ths out from center and are 3.5 inches apart. The new holes are about 3 and 15/16ths out from the center (+3/4 inch RADIUS) and are 5 and 1/8th apart. Draw this out and you will see that you cannot just draw a straight line thru the original holes and then measure up 3/4ths of an inch to another straight line. The radius of the new mount is 3/4ths greater than the radius of the old mount.

I drew this out and the holes ended up 7/8ths of an inch apart, center to center. The original mounts on the knuckle are 1 and 5/16ths wide at their greated diminsion. This puts the new bolts in contact with the edge of the old mounts at 3/4ths of an inch out.

I just fabricated some brackets that should work by rotating the calipers towards the front of the car. I just uploaded a picture of it here:

http://pg.photos.yahoo.com/ph/black8....net/my_photos

See what you think.

-js-

The adapter looks fine. Nothing like DRMs.
How is the bleeder position ?
I'll look at your non linear circle tomorow. Thanks for the info. I'm sure your going to get some request for those.

CentralCoaster

problem solved... the spacing of the holes, and the radius of them both combine to give you enough meat between the holes.


And it looks like those drm adapters fit just like i said.... those long bolts go in backwards, and the adapter mounts on the inner surface of the knuckle, then extends around it to be flush with the outer knuckle surface.