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Author
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Topic: 5 lug swap questions
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LXjames
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Member # 10791
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posted
 
 
So I know all the necessary parts and mods to go 4-5 lug but does anybody have any personal experience running cobra brakes up front and drum in the rear?
I've seen it on multiple cars but maximum motorsports seems to think its not a good idea saying I NEED to run cobra brakes in the back for some reason.
The only reason I don't want to is because I would have to buy a new cobra mc and a larger booster most likely and if I do that I need to get a crap load of fittings and lines and that's not in the pocket right now.
What I'm thinking is just get a 87-93 mc and booster and do the full swap.
Any answers would be much appreciated!! Thanks cafords
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On Point Motorsport prez.
King Lx
Posts: 4761 | From: Pittsburg CA | Registered: Mar 2011
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coupedup
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Member # 9987
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posted
I think there a memember that did this type 5 lug with drums in the rear, think it was ed650.. not sure tho.
Posts: 4406 | From: Ca | Registered: May 2010
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turbo50
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Member # 6700
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posted
For performance and safety reasons, the larger volume of the suggested master cylinders is desired. Also there are differences between of master cylinders for disc and drum both front and rear on vehicles that you arent aware of other than just bore, piston etc etc. Once you work on these and swap shit around, on any vehicle really, you will understand that there are some that have residual pressure valves in them etc etc.
That being said, if you want it to perform to its full potential then wait until you can do it right and do it once.
If you want it just for the wow factor or have no other choice or want to swap out a bad (existing fronts for example) then do it twice and pay more in the long run.
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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Wht86drop
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Member # 12104
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posted
Im running full 96 cobra brakes with the original 86 master and booster and the p-valve too. Stops great and no issues. I also did my boys hatch with 04 brakes and irs with agai. The same master booster and valve. Noo issues
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Jalapeña Red 86 GT Vert
Yellow 72 Chevelle
Rio Red 97 Cobra
High-Output Generations CC
Posts: 1669 | From: East Palo Alto, Fiji Islands | Registered: Jun 2012
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LXjames
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Member # 10791
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posted
Thanks guys and Dan I get what your saying so I'm gonna shop around see what info I can find but cobra rear ends ain't cheap!
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On Point Motorsport prez.
King Lx
Posts: 4761 | From: Pittsburg CA | Registered: Mar 2011
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turbo50
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Member # 6700
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posted
Regardless, the fact is that there is a required volume differenc from a say 68mm caliper versus a 73mm caliper and from say a wheel cylinder (drum) versus a 73mm caliper.
A residual pressure valve keeps line pressure at say 2 pounds etc
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.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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LXjames
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Member # 10791
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posted
Dan I think I'm just going to have I buy cobra rear brakes an piece together the rest of the shit
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On Point Motorsport prez.
King Lx
Posts: 4761 | From: Pittsburg CA | Registered: Mar 2011
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NEIGHT
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Member # 8741
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posted
Why do you think I'm not 5-lug yet? I still have to find the rear setup for a deal not crazy prices like I've been seeing.
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-Savage Habits-
1992 Summer Edition
1986 Hatch- catfish killer
1964 Impala hard top
Posts: 18548 | From: EA$T $IDE REDWOOD CITY | Registered: Nov 2008
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LXjames
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Member # 10791
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posted
quote:
Originally posted by NEIGHT:
Why do you think I'm not 5-lug yet? I still have to find the rear setup for a deal not crazy prices like I've been seeing.
I'm getting a geared drum 5 lug rear end cobra rear brakes from my boy then I will just have to buy NRC brackets
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On Point Motorsport prez.
King Lx
Posts: 4761 | From: Pittsburg CA | Registered: Mar 2011
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NEIGHT
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Member # 8741
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posted
quote:
Originally posted by LXjames:
quote:
Originally posted by NEIGHT:
Why do you think I'm not 5-lug yet? I still have to find the rear setup for a deal not crazy prices like I've been seeing.
I'm getting a geared drum 5 lug rear end cobra rear brakes from my boy then I will just have to buy NRC brackets
Yeah that's what imma do Cobra brakes all around. I'm tired of drum they suck N lock up too often.
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-Savage Habits-
1992 Summer Edition
1986 Hatch- catfish killer
1964 Impala hard top
Posts: 18548 | From: EA$T $IDE REDWOOD CITY | Registered: Nov 2008
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5.0 LsX
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Member # 10017
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posted
im running cobra fronts and ranger drums, stock 5.0 m/c and booster and its been great for a few years now...
Posts: 1260 | Registered: May 2010
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ed650
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Member # 9897
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posted
I have cobra brakes up front and drums in the back, if you stay drum than the average deep dish wheel will line up with your fender if you do deep dish on a disc rear end your wheels will stick out alot
Posts: 1744 | From: menlo park | Registered: Apr 2010
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turbo50
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Member # 6700
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posted
May work great and you may happen to have the right 1 1/8 bore (more volume booster) Im not here to argue whether folks work or not. I am here to tell you to take it into consideration JAMES.
Here is a cut and paste of a pretty good write up with regards to master cylinders:
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 x 2 calipers
SVO calipers: 73mm piston
-4185mm^2 each piston
-8370mm^2 x2 calipers
99-04 GT Front : 44.5mm pistons
-1555mm^2 each piston
-6220mm^2 x2 calipers
99-04 COBRA 40.5mm pistons
-1288mm^2 each piston
-5152mm^2 x2 calipers
94-98 COBRA 38mm pistons
-1134mm^2 each piston
-4536mm^2 x2 calipers
94-98 GT/V6 calipers : 66mm piston
-3421mm^2 each piston
-6842mm^2 x2 calipers
2000 Cobra R Front 36mm/40mm pistons
-2275mm^2 each caliper
-4550mm^2 x 2 calipers
REAR
SVO REAR calipers: 54mm piston
-2290mm^2 each piston
-4580mm^2 x2 calipers
94-04 rear calipers all : 38mm pistons
-1134mm^2
-2268mm^2 x2 calipers
Grand Marquis Rear Calipers: 46mm piston
-1662mm^2
-3324mm^2
1993 Cobra/Mark7/T-bird 45mm rear calipers
-1590mm^2
-3180mm^2 x2 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.
--------------------
.........when was the last time YOU built something with YOUR own hands?
I offer quality sidework at reasonable prices. PM ME
Posts: 7606 | From: Discovery Bay, California | Registered: Apr 2006
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