Cobra brakes on a GT. I have a problem-HELP Please.

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prsrizdgt

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Mar 12, 2004

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St. Louis

Feb 17, 2006

#1

• Feb 17, 2006

• #1

All the research I did on this indicated it was a bolt on swap, except for some minor issues on the rear, and there is my issue. Everything I read indicated that the GT caliper (mine is a 98 model) will work fine with the Cobra rotor as long as you use the Cobra caliper bracket to place the caliper in the correct position relative to the rotor. Still no prob cause I bought the FRPP M-2300-M rear brake kit to do this. My worn GT brake pads are actually 1/32 thinner than the new stock Cobra brake pad so still no problem right? Well I can't seem to get the caliper piston to collapse enough to make a wide enough opening for the new Cobra rotor which as you know is wider than the stock GT rotor, to fit. I have the caliper off the car, I have removed the bleeder, drained the fluid, and am using a C-clamp to apply pressure to collapse it. It will collapse until it compresses against the emergency brake internals and then stops which does not give me the room I need for the rotor. SO, is this 98 GT caliper really supposed to work somehow, or when people say the GT caliper works, they mean 99 and up? Is there a differance between the 98 and 99 GT rear caliper? What do you Brake experts know about this?

 

jeffnoel

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Aug 31, 2002

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Clovis, CA

Feb 17, 2006

#2

• Feb 17, 2006

• #2

You need a special tool to compress the piston. You can get it as a loaner free at Autozone and others I'm sure. The tool actually rotates the piston while it compresses it.

 

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prsrizdgt

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Mar 12, 2004

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Feb 17, 2006

#3

• Feb 17, 2006

• #3

jeffnoel said:

You need a special tool to compress the piston. You can get it as a loaner free at Autozone and others I'm sure. The tool actually rotates the piston while it compresses it.

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Oh man, that is great help. Thanks so much. This is the first time anyone has mentioned this in the months of reading I've done on the subject. I guess that is what the two small recesses are for on the end of the piston, a place for the tool to fit in. I wonder if there is a way to do it without the tool? With all the ingenuity of people in this hobby, I would think someone has figured out a way without using the tool.

 

jeffnoel

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Aug 31, 2002

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Feb 17, 2006

#4

• Feb 17, 2006

• #4

There may be a way to do it but I tried it and gave up, went to Autozone and had it done in less time than it took to get the tool. I ended up buying the tool recently from Harbor Freight for like $20 on sale recently.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=40732

 

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prsrizdgt

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Mar 12, 2004

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Feb 17, 2006

#5

• Feb 17, 2006

• #5

jeffnoel said:

There may be a way to do it but I tried it and gave up, went to Autozone and had it done in less time than it took to get the tool. I ended up buying the tool recently from Harbor Freight for like $20 on sale recently.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=40732

Click to expand...

Couple more quick questions. What is the effect, if any, on the rubber piston boot while rotating the piston? It appears that the seal/connection is tight to keep contaminants out and would not rotate.

Also, how did you figure this out? Did you put Cobra brakes on your car or are you just a brake GOD ?

Thanks for all your help.

 

jeffnoel

Founding Member

Aug 31, 2002

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Feb 17, 2006

#6

• Feb 17, 2006

• #6

Piston boot doesn't rotate, no effect as that's the way Ford made it to work. Forcing it by doing it another way may damage something. I did drilled and slotted Cobra fronts and also replaced the stock GT rears with drilled and slotted rotors to match the fronts.

 

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dmenard74

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Feb 15, 2006

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Feb 17, 2006

#7

• Feb 17, 2006

• #7

I used a similar tool for mine. It's shaped like a small cube that fit's the end of a 3/8" ratchet. It has many knobs on it for a universal fit. Cost me about $10 at pepboys. I have also use needle nose pliers to engage the slots and turn the piston in. This works okay too.

By the way, if I remember correctly, it's cross threaded.

 

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prsrizdgt

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Mar 12, 2004

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Feb 17, 2006

#8

• Feb 17, 2006

• #8

dmenard74 said:

I used a similar tool for mine. It's shaped like a small cube that fit's the end of a 3/8" ratchet. It has many knobs on it for a universal fit. Cost me about $10 at pepboys. I have also use needle nose pliers to engage the slots and turn the piston in. This works okay too.

By the way, if I remember correctly, it's cross threaded.

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Cross-threaded? Do you mean it is Left-Hand thread so you have to turn it counterclock-wise for it to go inward?

Do any of you guys have access to a caliper or the tool to give me the diameter of the piston, or the distance apart the pin holes in the piston are? I thought the piston was 1.5 inches.

I am going to make a shade tree tool with a threaded bolt, a plate, and a disc to engage the piston, but it would help to know dims on the piston to locate the little pins that will engage the piston. I don't happen to have my calipers here at work. Can you help?

 

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cooper

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Dec 9, 2005

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Feb 17, 2006

#9

• Feb 17, 2006

• #9

im pretty sure you need to keep the slots in a vertical possition when finshed compresing

 

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prsrizdgt

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Feb 18, 2006

#10

• Feb 18, 2006

• #10

Update for future info searchers.....piston is right hand thread and you turn it clockwise to compress the piston. I made a tool similiar to pics of other tools. Once you know how it works, I guess its really pretty simple. Thanks for everyones input.

 

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markwsoil

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May 26, 2003

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Chicago

Feb 18, 2006

#11

• Feb 18, 2006

• #11

I've never done rear discs, but I suspect you could use the tip of a pair of needle nose pliers spread out as the tool if you were in a pinch and the piston wasn't bound too badly.

One other thing to note is that they get adjusted out by regular use of the parking brake. It screws the piston out until it reaches a certain point at which it acts sort of like a sprague clutch. If what I said doesn't make sense, just make it a point to occasionally put the car in park and work the parking brake a few times. You'll be surprised how much it improves the braking if the rears have worn any.

If you've got your foot on the brake, the rear pistons won't adjust. This is all of course contingent upon whether you got the goofy poorly designed parking brake cable adjusted properly on each side.

 

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bdcardinal

tree hugger

Jun 10, 2003

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santa barbara, CA

Feb 18, 2006

#12

• Feb 18, 2006

• #12

i jsut got cobra calipers. mine had over 100k on them and looked like hell. the rubber was all trashed.

when i took them off i gave them to a friend who made a full kit to adapt mustang brakes onto his 63 Studebaker Avanti.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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Feb 18, 2006

#13

• Feb 18, 2006

• #13

prsrizdgt said:

Also, how did you figure this out? Did you put Cobra brakes on your car or are you just a brake GOD ?

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It's actually pretty common. If you do a brake job on any car with rear disks that has the e-brake as part of the caliper then you have to spin the piston clockwise on all of them to collapse it. It will take some time to screw it in though so be patient

A pair of needlernose pliers can be used as an alternative, but i would go to autozone and rent the tool. They also sell a cube that you put on the end of a rachet and rachet the piston in with.

Make sure when you are done the slots are in the 12 and 6 o'clock position so the pad will seat against it fully

 

stangman16

Active Member

Nov 16, 2004

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San Antonio, TX

Feb 18, 2006

#14

• Feb 18, 2006

• #14

jeffnoel said:

There may be a way to do it but I tried it and gave up, went to Autozone and had it done in less time than it took to get the tool. I ended up buying the tool recently from Harbor Freight for like $20 on sale recently.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=40732

Click to expand...

Yeah - I tried and gave up, ended up buying the one from autozone. I figured anyone else in my family could use it, wasn't expensive and it saves a LOAD of time.

 

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bdcardinal

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Jun 10, 2003

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Feb 18, 2006

#15

• Feb 18, 2006

• #15

the cube is a pile. i know they are cheap, but having the right tool makes the job a lot easier. this is the correct tool http://www.matcotools.com/ProductImages/db25.jpg.