Brakes The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

Starting this thread with the hopes of reducing the number of 5-lug or general brake upgrade threads that have been appearing on the forums since most of the major brake conversion sites have gone down.

This thread will be strictly informational, and any off-topic banter or user specific questions will be deleted/edited at discretion of mods. I don't want this to turn into a 21-page thread where someone can't find the info they need.

WHat I need are people who are knowledgeable in specific conversions to write up threads detailing the parts they used and such. FOr example, someone who has done the simple SVO rotor lincoln 5-lug and ranger drum setup may want to list what parts they used for their conversion and any other details on the swap. I realize there is more than 1 way to skin a cat, so we might have a few different ideas on one specific swap.

I'll edit this post into an Index once info starts being written up, but lets keep this thread clean and free of post which may start to clutter it up. Thanks

4-cylinder to V8 brake upgrade.


Basically to upgrade an 87-93 4-banger Mustang to 87+ V8 specs, these are the parts you'll need. Pre-87 V8's will be similar, but may have slight differences.

87+ Brake booster
87+ V8 spindles
11" rotors
87+ 60mm Brake calipers and brake lines.

No need to swap the MC as both the 2.3L and 5.0 share the same 21mm master cylinder. Basically unbolt it from the booster, pull it forward and swap the booster to the V8 unit.

As for the PV, you shouldn't need to change anything since you are adding more power to the front brakes.

In the wheel wells, swap out the spindles, rotors, calipers and bolt the new brake lines to the body hard lines. You may find that with the 4-banger struts, there is a gap when you try to bolt the strut to the spindle. The solution is either to use spacers or washer to close up the gap, or to run 87-93 V8 struts.

Bleed the brakes, and you should have working brakes.

NOTE: A popular upgrade is to swap SVO 73mm calipers onto the stock fox Mustang. While easy to do, this requires a MC upgrade since the calipers require more fluid volume. The next step up for MC to use is the 94-95 Cobra 15/16" MC (24.5MM bore). At this point, for the amount of work involved, there are better alternatives to go with.

5lugs...the cheap easy way.

Late model resto sells a kit for $400 to convert the basic 4-lug Fox into 5-lugs. Basically the kit uses OEM Ford components...in one easy kit with lube and misc items.


Basically, the requirements are as follows

Front (w/11" rotors): For the 87-93 V8 Mustang... 84-86 SVO or 84-92 Mark 7 front 11" rotors (either with or without ABS...doesn't matter)

Front (w/10" rotors): For the 79-86 and 87-93 4cyl cars, use the 83-92 4cyl Ranger front rotors

Optionally you can elect to replace the bearings at this time, or reuse the ones in your 4-lug rotors. Most often, they will directly swap over.

Rear: (All 4-lug drum rears) '83-'92 Ranger/Bronco II Left (driver) side axle (29-5/32") from a 4cyl or 3.0L V-6 with the 7.5" rear end, or '86-'97 Aerostar RIGHT side axles (29-5/32") is what you want. The 9" drums are off the 7.5" equipped ranger or aerostar.


Simple swap the axles and drums, and you are good to go.

Pros: Keeps stock fox offset up front and in the rear. Doesn't change a thing other than add a 5th lug. Cheap, Easy

Cons: Limited wheel selection. Front hub is the issue

List of the OEM Sn95 wheels that fit the front rotors without modification

94-96 16" Pony Wheels
94-95 17" GT wheels
94-97 Cobra 17" Wheels
1995 Cobra R wheels (OEM)
V6 Mustang wheels

Other SN95 wheels will bolt up, but you won't be able to run the center caps.

Booster selection

Just wanted to post some info i've learned as a reference to others to answer the eternal question..."What Booster do I use?" and "Do i need a booster?"

First off, i offer this not as telling you what to use, but info for you to make your own educated decision...so please use at your own risk.

With that said? When should you use a different booster??

Easy answer is to simply look at what Ford did. When they put rear disks on the back of the Cobra, they upgraded the booster. All the vac boosted SN95's use a larger booster as well...so someone at Ford has determined a safe passenger car should use the upgraded booster. If you are running SN95 brakes all around, why not run the SN95 booster as well? Even Turbo Coupe rear disks are basically 1993 cobra brakes, and those got an upgraded booster as well.

Options?? Either the 1993 Cobra Booster, or the 1994-1995 Sn95 booster. They are ALL 205mm tandem boosters, the main difference is the 1993 cobra booster uses the fox firewall bolt pattern and thread while the SN95 booster has a lug moved slightly and metric bolts. If you are buying new, get the 1993 Cobra booster. If you look used, you can get 94-95 V6 boosters dirt cheap. Just be aware that you are using 14-year old used parts. If the MC was leaking at any point, there may be a good chance the booster is bad. The differences between SN95 v6, GT, and Cobra are negligible, so don't sweat using a V6 booster at all. For installation techniques, search the forums.

If you decide to retain the stock fox booster for whatever reason, at least make sure you are running the 87-93 Booster. To compensate for the lack of assist, you will want to run a slightly smaller bore MC as well. (more on that later).

Another option is to convert to Hydroboost like the 96+ V8 modular cars. It offers more assist than a vac booster, so you can run a slightly larger bore MC to compensate.

Master Cylinder selection

This one is a little tougher to answer. I strongly suggest you research heavily before deciding on your MC. But more often than not, if you change your calipers to another set of calipers off another car...you need a new MC.


Brake hydraulics work similarly to the principles of leverage. You have the Master Cylinder, and the Slave Cylinders. The ratio between the two determines pedal effort. Easiest way to explain why you need to change your MC is to think of a lever. Say you have a fulcrum, a long lever and 500 pounds. We all learned in 1st grade the closer you move the fulcrum to the weight, the easier it is to lift the weight. This is equivalent to a smaller bore MC. The smaller the MC bore, the easier it is to operate the brakes (softer the pedal). Of course, a side effect is that now your lever is longer. The closer you move the fulcrum to the weight, the longer your stroke is to lift the weight. There will be a point where you simply cannont reach the lever, so you are unable to lift it. This is equivalent to decreasing the bore size of the MC so much that you can't operate the actual brake to MAX braking effort. The key here is to find a bore size that is small enough to reduce the work effort, but big enough that it will allow the brake to work to max potention? Understand? Good...now the details.


What MC's are available? Here's the short and sweet info list

http://1985mustanggt.com/Reference/2009-09-19_Mustang_MC_Info.pdf

You will also need a 3-2 conversion if you are using an 87+ Mustang as a chassis as well as needing to modify the combination valve by removing the proportioning plug. This is covered elsewhere in this thread


87-93 fox - 21mm bore = 346mm^2
79-81 Fox (power brakes) = 7/8in = 22.2mm = 387mm^2
15/16 CObra = 23.8mm = 445mm^2
1" Cobra= 25.4mm = 507mm^2
1 1/16" GT/v6 = 26.98mm = 572mm^2
1 1/8" SVO = 28.5mm = 638mm^2

Final number is the bore area in millimeters squared. SO you have 6 choices...somewhere in there is the MC you want to use.

Now, the list of the calipers and their piston area sizes.

FRONTS

87-93 60mm calipers
-2827mm^2
-5654mm^2 for 2 calipers

SVO calipers: 73mm piston
-4185mm^2 each piston
-8370mm^2 for 2calipers

99-04 GT Front : 44.5mm pistons
-1555mm^2 each piston
-6220mm^2 for 2 calipers

99-04 COBRA 40.5mm pistons
-1288mm^2 each piston
-5152mm^2 for 2 calipers

94-98 COBRA 38mm pistons
-1134mm^2 each piston
-4536mm^2 for 2 calipers

94-98 GT/V6 calipers : 66mm piston
-3421mm^2 each piston
-6842mm^2 for 2 calipers

2000 Cobra R Front 36mm/40mm pistons
-2275mm^2 each caliper
-4550mm^2 for 2 calipers

GM C5/C6 front caliper 40.5mm/40.5mm pistons
-2576.5mm^2 for each caliper
-5153mm^2 for 2 calipers

GM ATS/XTS Brembo caliper 42mm x4 piston
-2771mm^2 for each caliper
-5542mm^2 for both fronts

Baer T4 Front caliper (44.45mm x2 pistons, 34.93mm x2 pistons)
-2511mm^2 for each caliper
-5022mm^2 for both fronts

(note, opposing piston, fixed calipers only get one side of the caliper factored in for surface area)




REAR

SVO REAR calipers: 54mm piston
-2290mm^2 each piston
-4580mm^2 for 2 calipers

94-04 rear calipers all : 38mm pistons
-1134mm^2
-2268mm^2 for 2 calipers

93-97 Taurus rear caliper (Must use SN95 abutments): 43mm piston
1452mm^2
2904mm^2 for 2 calipers

Grand Marquis Rear Calipers: 46mm piston
-1662mm^2
-3324mm^2 for 2 calipers

1993 Cobra/Mark7/T-bird 45mm rear calipers
-1590mm^2
-3180mm^2 for 2 calipers


If you want me to add any calipers..PM me


Top number is the area of each individual piston. Bottom number is all the pistons added up x 2 calipers. So simply add the bottom number from a set of front calipers, to the bottom number to a set of rear calipers and that is your total slave piston area in MM. Now divide that by the area of the master cylinder in MM^2 and you get your ratio.

The higher the ratio (17:1, 18:1, etc), the softer your pedal will be. The lower the ratio (11:1, 12:1) the harder the pedal will be. Now, if you elect to retain the stock Fox booster, you'll want a higher ratio number to compensate for the lact of assist. If you are lucky enough to run hydroboost, you can find that the extra assist allows you to use a ratio in the lower end of the range. Typically most of the factory setups fall in the 13:1 - 17:1 range (4-wheel disk). Again, i stress to research what other people are using and use this formula simply as a guide.


A lot of guys choose to simply upgrade the front brakes only, and run 5-lug drums. Which MC should they use? Well, compare the piston area sizes of the calipers you choose with those of the stock 60mm calipers, which offers a total area of 5654mm^2. If you increase the caliper size, you increase the piston area which in turn lowers the ratio since the MC has not changed. As a result, your pedal will be softer.

99-04 GT Front : 44.5mm pistons
-6220mm^2 x2 calipers

87-93 60mm calipers
-5654mm^2 x 2 calipers

99-04 COBRA 40.5mm pistons
-5152mm^2 x2 calipers

Depending on which direction you go, your pedal will be slightly harder or softer. In the above example, going with the 99=04 GT front calipers will make your pedal slightly softer due to the increase in piston area. While going with the 99-04 Cobra calipers will result in a slightly harder pedal due to the decrease in piston area. In this example, one may consider to compensate for the slightly harder pedal, by upgrading to a 1993 Cobra/94-95 SN95 booster.

Another common modification is to add 73mm calipers to a stock brake setup. Here you can see why this is bad.

87-93 60mm calipers
-5654mm^2 x 2 calipers

SVO calipers: 73mm piston
-8370mm^2 x2 calipers

As you can see, the caliper piston area is dramatically increased and will result in a solfter brake pedal. The danger here goes back to the lever example. Make the lever longer, and it will soon reach a point where you can't reach it because the stroke is so long. Same here. Since the caliper area increased, it makes the MC bore appear mathematically smaller when you calculate out the ratio. As a result, you run the risk of running out of brake travel to properly operate the pedal. In this situation, you may want to consider upsizing to one of the MC's listed above.

Hopefully this eductated you a bit on MC's and allows you to select the right one for your application


ALso, the brake pedal ration in the Fox cars is 3.5:1 in vacuum boosted operations. I beleive this to be true of 1987+ Mustangs. If converting to manual brakes, one needs to take into account the pedal ratio. Some kits out there modify the brake pedal ratio to compensate for the lack of assist. I suggest you research this as well as I beleive most of the manual brake kits out there make use of the 7/8" MC listed above as well as a different brake pedal ratio....just a heads up.


DISCLAIMER: The info provided is to the best of my knowlegde factual and accurate, but i make no garantees. Any info posted here is simply a guide for you to make an educated decision on your own. I claim no responsibility if you don't research properly and take your car up to 100MPH before testing the brakes out. Use at your own risk.

EDIT: Resource

To indirectly answer his question. The only OEM way to retain rear disk brakes is with the 87-88 Turbo Coupe/1993 Cobra rear 4-lug brake setup.

There are a few options with this, and it can be modified for 5-lug setup with a few changes.

Anyone with experience care to write up a TC rear brake upgrade?