11.65" rear disc upgrade in 4 lug "Baer on a budget"

[Goodson]

Just like the title says. I did an 11.65" rear disc upgrade on my 88 that had a turbo coupe rear and OEM 93 cobra wheels. I did that modification to it 6 years ago before anyone thought of replicas. I love the 93 cobra wheels and I wanted to put 94-04 cobra brakes on it. The necessity of doing the rear disc upgrade on the 93 cobra is merely for looks. It's just the "Cool" factor, that's all. There isn't any reason to upgrade from the 10.5" rear disc brakes for performance reasons unless the car is an autocross or SCCA car and at that point someone would go to 5 lug first. The front brakes will be a Baer kit because I can't do the custom spindles. I couldn't spend 2 grand on a complete kit for my car so I did this on a budget. I purchased the following items.

-2 rear 94-04 GT/V6 calipers $50 at junkyard
-2 rear 94-04 Cobra caliper cages $70.12 new from dealer
-M-2300-M kit from Ford $168.25 new from dealer
-rotors re drilled to 4 lug at machine shop $43.70
-Baer brakes rotor spacer to center rotor on hub $20.00 shipped

-Total $352.07

That's all that is needed to do this upgrade. It's a very straight forward install. Even the banjo connections can be used from the existing 93 cobra calipers. I took a few pictures of the process and parts.

Caliper mock up. Notice the blue ring. That is the Baer spacer used to center the rotor over the hub.

Caliper mounting differences. This slide pin design changed sometime in the 94-04 run. It affected the caliper fitting between the slide pins. I had to shave off a few thousandths of each slide pin on the new cobra caliper bracket

The cobra caliper bracket. It's different from the GT caliper bracket because it has the cross brace on the front side of the bracket as well as being wider to fit around the vented cobra rotor.

The caliper loaded into the cobra bracket mocked up. Notice the brace as compared to the first picture.

The rotor redrilled to 4 lug.

Everything mocked up.

Backside with wheel bolted on

Front with wheel bolted on

Finally done!

Just figured I'd share with the rest of you guys. My car isn't a 93 cobra, but it has 93 cobra suspension, wheels and brakes.

 

[BADBOYSPACK]

Thanks for sharing, good job man.

Those rotors have me a little afraid, but your not road racing so it should be ok.

 

[LEE93COBRA]

good job and research Goodson.

If it is ok, I would like to quote your post here and put it on my forums in the brakes and suspension room

 

[Goodson]

Lee, go ahead and post up if you want to. That's totally cool with me. I still have those subframes we chatted about over a year ago on the "to purchase" list from you.

Badboys, It really doesn't worry me at all. The rotor would most likely shear a stud off before giving way. The OEM rotors actually move a little when the wheel is off because the stud holes are larger than the stud. When the wheel is put on with 80 ft/lb of force on each stud the rotor is more in compression than in shear force when the caliper is grabbing it. With that in mind notice that the rotors on your car don't clunk from movement when you stop. They are held tightly in place because of the compression load from the pressure of the wheel and hub. And the redrilled rotor won't shear off anything because the tire will just lose traction and the brakes lock up before the breaking point force of the stud. It'd take a hell of a force to mess up the lug holes on that rotor. Many, if not all, aftermarket brake manufacturers use 5 bolt rotors that are drilled to 4 lug in their 4 lug upgrade kits and to my knowledge no one has had a failure with those systems because the rotor was redrilled to 4 lug. Some even open track with them.

 

[LEE93COBRA]

I put it here Goodson.. http://forums.qwiksnake.com/showthread.php?p=92207#post92207

 

[93Cobra#2771]

Excellent write up, Bob. Don't think I won't be doing that sometime or another in the future...

 

[93Cobra#2771]

Bob, is that the abs exciter ring from the TC on your axle?

 

[JimJr]

Great info Goodson. Just for clarification, you said you have a Turbo Coupe rear end. What length axles are in that rear? (ie. 93 Cobra, GT/LX, SN95 length)

 

[SCT93COBRA]

I can re-drill the rotors for anyone who wants to do the swap. I have my own machine shop!

 

[Goodson]

Bob, is that the abs exciter ring from the TC on your axle?

Yes, your correct Richard. That is the exciter ring on the axle. I plan to remove those when I rebuild the traction loc. Hopefully I'll get Scott to do it because I had to slightly hammer in the C clips. Getting the axles out will be a chore.

Great info Goodson. Just for clarification, you said you have a Turbo Coupe rear end. What length axles are in that rear? (ie. 93 Cobra, GT/LX, SN95 length)

Jim, the 87-88 Thunderbird Turbo coupe axles are the same length as the 93 cobra axles. As a matter of fact the whole housing from rotor to rotor is the same as the 93 cobra's except that the TC quad/horizontal shock mount is a little taller and it has provisions for ABS and the appropriate sensors.

 

[racerbox77]

Goodson, Great info. Two questions. what is the part # for the hub spacers? What exactly did you have to shave on the bracket to make it fit?
OK 3 questions. Whats the diff. between cobra calipers and gt calipers?

 

[Goodson]

Woops! The part number for that Baer spacer might be helpful wouldn't it? :uh oh: 6260132 is the number. They were $12 retail when I bought them about 2 years ago and $20 shipped to me. There was an $8 minimum shipping charge.

#2 I had to shave a few thousandths off of the slide pins for the ears of the caliper to fit into it. I grabbed one caliper off of a 99-04 and one from a 94-98 axle laying in the yard. The one from the 94-98 wouldn't fit between the slide pins. Well, that's not totally true. It would fit, but the slide pins wouldn't slide. So I just took my dremel and filed off a thousandth or two on the inside flat part of both the slide pins. The side noted in this pic.

It would have been possible to move the slide pins from the GT/V6 bracket, but I chose not to because I wanted to use the new stuff. So that's why I had to shave off a little of the slide pin. The 99-04 GT/V6 caliper fit just fine with no problems. There must have been a running change sometime in the 94-04 run on the slide pin design and that affected the caliper where more material needed to be machined off of the "ears" of the caliper so it would fit.

#3 There isn't any notable difference between the two calipers at all. They both used the same calipers. The caliper "cage" is what is different between the two.

I hope that was as clear as mud. ;-) I'm not too good explaining the small details over the net sometimes.

Bob

 

[racerbox77]

thank you very much. :thumbsup:

Now what are our options for upgrading the front brakes? I want to keep the 4 lug.

 

[Goodson]

The only options at the present time that I'm aware of are the custom kits from Baer, Stainless Steel Brakes...etc.

I've actually looked at trying to modify 94-04 hubs to 4 lug and using 96-04 spindles because the geometry is much better for steering and alignment on lowered Fox Chassis cars using those specific spindles. But, I'm not so sure that's a great idea because the hubs have to be welded to fill the stud holes and then redrilled to 4 lug. I think the hubs are heat treated like the spindles. But, I'm not sure. If that is true, then the hub has to be treated again by a similar, if not the same, process so that it is safe to use and not brittle from the welding. Now, If I had a cad program I'd take a 94-04 hub and redesign it for a machine shop to take and cut out of steel. Baer uses aluminum for their custom hubs and welds new mounting points on the fox chassis spindle so that the 94-04 Cobra style calipers will fit.

I'm personally trying to find a cheaper and SAFE solution than the Baer kit. They want ~$1100 just for the front kit to transform a 1993 cobra to 13" brakes.