88 Upgrade to 5 Lug/Disc Brake Conversion Confirmation of Plan

Firehawk335

Member
May 3, 2006
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Hey everybody. I have been doing a ton of reading/search across forums for brake upgrades/5 lug conversion plans and wanted to run my specific plan of parts and see if there are improvements/changes i should make before starting on my 88 GT Foxbody. I would love to do a big brake upgrade, but parts/cost availability seem prohibitive. So I wanted to go with a more late gen GT upgrade.

I have pulled some 94/95 spindles at the junkyard and have those ready to sand blast and paint. I also know that i want to run the 03 Cobra Wheels, which appear to only be offered in 17x9 in a 5 lug. With those two things done, here is what i think i need to continue with everything.

93 Cobra Booster
95 GT MC (i think)
3 to 2 block for line adaptation
ford racing proportioning vale
99-04 Front GT calipers
99-04 Front GT rotors
SS Braided Hose adapters/lines for hard line to caliper (i think)
Dust Shields

For the rear, i am looking at doing a pretty big upgrade as i still have 28 spine, 4 lug drums

Looking at getting an Eaton 31 spline differential and 3.73 rear gears (i have a 5 speed with i believe 2.73 gears currently)
Moser 31 spline fox length 5 lug axles
north race car caliper mounting bracket
99-04 Rear GT calipers
99-04 Rear GT rotors
Dust Shields

I know there is an emergency brake change i need to make (dont full understand it, but will work through it with the help of google/youtube)

(i admit i thought about going 9" ford rear and going big, but think since i am stock pretty much everywhere, i think the 31 spline is a great upgrade/compromise that will last me for all my days)

If anyone can share if/what changes i should make/what i am forgetting i would be most appreciative. Also what tire sizes will work for 17x9 i would be most appreciative. Thinking 245/45/17.

Thanks everyone.
 
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91TwighlightGT

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03 Cobra wheel stock tire size is 275/40-17.

I don't know how well a 245/45/17 will fit (I will let someone else chime in on that one), but I would be worried about rubbing on the front with the 275 tire.
 

DudeStang

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Apr 30, 2017
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Hey everybody. I have been doing a ton of reading/search across forums for brake upgrades/5 lug conversion plans and wanted to run my specific plan of parts and see if there are improvements/changes i should make before starting on my 88 GT Foxbody. I would love to do a big brake upgrade, but parts/cost availability seem prohibitive. So I wanted to go with a more late gen GT upgrade.

I have pulled some 94/95 spindles at the junkyard and have those ready to sand blast and paint. I also know that i want to run the 03 Cobra Wheels, which appear to only be offered in 17x9 in a 5 lug. With those two things done, here is what i think i need to continue with everything.

93 Cobra Booster
95 GT MC (i think)
3 to 2 block for line adaptation
ford racing proportioning vale
99-04 Front GT calipers
99-04 Front GT rotors
SS Braided Hose adapters/lines for hard line to caliper (i think)
Dust Shields

For the rear, i am looking at doing a pretty big upgrade as i still have 28 spine, 4 lug drums

Looking at getting an Eaton 31 spline differential and 3.73 rear gears (i have a 5 speed with i believe 2.73 gears currently)
Moser 31 spline fox length 5 lug axles
north race car caliper mounting bracket
99-04 Rear GT calipers
99-04 Rear GT rotors
Dust Shields

I know there is an emergency brake change i need to make (dont full understand it, but will work through it with the help of google/youtube)

(i admit i thought about going 9" ford rear and going big, but think since i am stock pretty much everywhere, i think the 31 spline is a great upgrade/compromise that will last me for all my days)

If anyone can share if/what changes i should make/what i am forgetting i would be most appreciative. Also what tire sizes will work for 17x9 i would be most appreciative. Thinking 245/45/17.

Thanks everyone.

FYI, 03 Cobra wheels can be bought in a 4 lug setup from LMR.

 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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93 Cobra Booster
95 GT MC (i think)
3 to 2 block for line adaptation
ford racing proportioning vale
99-04 Front GT calipers
99-04 Front GT rotors
SS Braided Hose adapters/lines for hard line to caliper (i think)
Dust Shields

For the rear, i am looking at doing a pretty big upgrade as i still have 28 spine, 4 lug drums

Looking at getting an Eaton 31 spline differential and 3.73 rear gears (i have a 5 speed with i believe 2.73 gears currently)
Moser 31 spline fox length 5 lug axles
north race car caliper mounting bracket
99-04 Rear GT calipers
99-04 Rear GT rotors
Dust Shields

I know there is an emergency brake change i need to make (dont full understand it, but will work through it with the help of google/youtube)

For the MC, you are kinda in-between two ideal MC's.

95GT will be on the firmer side of things, while 93 Cobra MC will be on the softer side. Which one you pick ultimately depends on your tastes. The good thing is that they both use the same 3-2 conversion kit so they can be interchanged easily. I would personally start with the 93 Cobra MC. The 99-04 V6 came with the same setup you are putting together with vacuum brakes and a 1" bore MC like the 1993 cobra. The only unknown is if the pedal ratio on these cars is the same as the fox body.


As for ebrake cables, it's easy on an '88.
Center cable

Cables to the calipers

Bracket to modify the handle (or you can weld it) THIS USED TO BE UNDER $5
https://rover.ebay.com/rover/1/711-...0001&campid=5335821607&icep_item=113744439967

How to install it
 

Firehawk335

Member
May 3, 2006
28
3
13
03 Cobra wheel stock tire size is 275/40-17.

I don't know how well a 245/45/17 will fit (I will let someone else chime in on that one), but I would be worried about rubbing on the front with the 275 tire.
Thanks. The tire size you put is what I meant just apparently can’t type/think this morning.
 

Firehawk335

Member
May 3, 2006
28
3
13
For the MC, you are kinda in-between two ideal MC's.

95GT will be on the firmer side of things, while 93 Cobra MC will be on the softer side. Which one you pick ultimately depends on your tastes. The good thing is that they both use the same 3-2 conversion kit so they can be interchanged easily. I would personally start with the 93 Cobra MC. The 99-04 V6 came with the same setup you are putting together with vacuum brakes and a 1" bore MC like the 1993 cobra. The only unknown is if the pedal ratio on these cars is the same as the fox body.


As for ebrake cables, it's easy on an '88.
Center cable

Cables to the calipers

Bracket to modify the handle (or you can weld it) THIS USED TO BE UNDER $5
https://rover.ebay.com/rover/1/711-...0001&campid=5335821607&icep_item=113744439967

How to install it
So instead of GT brake components from a 99-04 should I be doing them from a v6 of the same years?
 

Firehawk335

Member
May 3, 2006
28
3
13
Went back to some other posts for the master cylinder booster matchup since I want to get it just right. See where some have used the 95 booster with a 93 cobra mc. Would that be a better option and am I correct then that the 95 booster will require some adaption with the bolt pattern? Or better just start 93 cobra booster and mc and see how it goes?
 

Mustang5L5

i'm familiar with penetration
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Feb 18, 2001
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93 cobra and 94-95 booster is essentially the same thing. Only difference is the bolt stud pattern. They are both the same size booster.

93 cobra will bolt right in. 94/95 requires slotting one stud hole.

if you look around, 93 cobra boosters are a bit tough to find at the moment.
 

Firehawk335

Member
May 3, 2006
28
3
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93 cobra and 94-95 booster is essentially the same thing. Only difference is the bolt stud pattern. They are both the same size booster.

93 cobra will bolt right in. 94/95 requires slotting one stud hole.

if you look around, 93 cobra boosters are a bit tough to find at the moment.

Ok thanks!
 

Firehawk335

Member
May 3, 2006
28
3
13
Running into some hiccups and now thinking I should rethink going to big brake setup. My pricing of parts is for gt/v6 setup mentioned above plus 93 cobra parts is coming out more expensive than I thought honestly. Can anyone confirm a few things for me? First, is the 93 cobra MC and 93 cobra brake booster the recommendation for a big brake kit setup? Or is there a different setup you would recommend? SVO, etc?

Second, will the big brake kit work with the 2003 cobra wheels, 17x9?

Next, is it wrong to try and save money by sourcing reman/new parts from rock auto/advance/autozone/etc? For example, LMR sells the cobra booster for $200. Rockauto sells this unit for $70, https://www.rockauto.com/en/moreinfo.php?pk=12029977&cc=1134076&jsn=507&jsn=507. Is it a difference in quality, or is this just fine? They also have the cobra calipers front and rear plain for reasonable compared pricing to 99-04 gt/v6 calipers. But am I heading down a slippery slope? Just seems like I could do a better budget build, space the purchases out, and not drop $2,800 all at once, or possibly in total like some of the "kits" out there.

Open to any and all recommendations.

Thanks again for everyones input. So far I ordered the emergency brake hardware for the conversion. Just want to make sure I have my plan straight on the very off chance I buy a bunch of individual parts, and then somehow land on a kit that includes duplicate parts.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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The MC is sizes to the calipers you are using. It’s a specific ratio of caliper piston area to master cylinder bore area and pedal ratio. So the MC you use all depends on what calipers you run.

A 94-95 SN95 booster can be used instead of the 93 cobra MC if youare in a bind. Some mods, but it will work. 93 cobra boosters are getting harder to find. I’d grab the $70 booster and not lose any sleep over it
 

Firehawk335

Member
May 3, 2006
28
3
13
The MC is sizes to the calipers you are using. It’s a specific ratio of caliper piston area to master cylinder bore area and pedal ratio. So the MC you use all depends on what calipers you run.

A 94-95 SN95 booster can be used instead of the 93 cobra MC if youare in a bind. Some mods, but it will work. 93 cobra boosters are getting harder to find. I’d grab the $70 booster and not lose any sleep over it

thanks for the info. Did you ever go the hydroboost setup and if so would you recommend that route? Found where You went the route I’m proposing now and then asked about going hydro boost later. Assuming I’m following the posts correctly.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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I am going hydroboost but for other reasons. My brake setup worked fine with the vacuum booster. Hydroboost conversion is expensive. The adapter kit alone plus lines is $300 then you need to buy an actual hydroboost unit and MC ($200) and then make the hoses.


My brakes worked perfectly fine with the 93 cobra MC and 94-95 booster. Was a great setup that stopped impressively well.
 
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Firehawk335

Member
May 3, 2006
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So definitely get that the 93 cobra booster is the preferred. If going gt or big brake is a 94-94 mc better for the slightly larger bore? I apologize as not having much luck getter a caliper piston to bore size pedal feel understanding. Larger bore means more fluid which means bigger pistons in calipers with normal pedal feel? Or completely wrong and stick to my day job?
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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An MC bore that is snaller will have a longer pedal stroke, but require less force to apply the brakes. An MC bore that is too big will have a shorter stroke, but require much more leg effort.

It’s all about finding the sweet spot.

Pick your calipers first, then the MC to match
 

KRUISR

Well-Known Member
Apr 16, 2015
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I did a full set up sourced at the junk yard.

- Booster from a 94/95 V6
- MC and prop valve from a 94-04 from a non-ABS car (I used one from a '01) - don't need the 3 to 2 adapter. Make sure you get a bit of brake line from the prop valve as the fittings are a different thread than a fox. Simply rework the brake lines with the new fittings. Non-ABS cars use a single brake line to the rear of the car just like a fox. This choice is especially good because if you use 99-04 dual piston front calipers and rear calipers, the front/rear ratio balance mentioned above is already there. No need for an aftermarket proportioning valve either. Booster, MC and prop valve shown on my car.
IMG_0631.JPG
- e-brake cables are standard 94-04 cables - I bought new ones on rockauto.
- e-brake handle from 94-04 (I used one from a '01) - already has correct spring for the cables. Only mod needed is rear mount tab needs to be cut off and moved 1" forward. Everything else fits perfect.
IMG_0551.JPG
- I fabricated the front e-brake cable bracket to support cables at the "T-bar" from the e-brake handle cable. Either fab one or get a bracket from a 94-04 - factory bracket shown. Riveted clip on the right not required.
IMG_0443.JPG


For calipers, pads and rotors (all used from junkyard) I when with a complete Lincoln LS set up and re-drilled from 5x108 to 4x108 bolt pattern. Rotors are vented front and rear sized 11.8" front and 11.33" rear. Both larger than stock 94-04 GT set up. So currently I am still 4 lug.

When I go to 5 lug I will use the Lincoln calipers and pads with 13.22" front and 11.8" or 12.44" rears (I haven't decided which yet). Will just need to fab some new adapter brackets to mount factory caliper brackets.

My current 4 lug set up and fabricated adapter bracket.

IMG_1008.JPG IMG_1010.JPG