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

Mustang5L5

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So Mike, I started re-reading these to see if I missed anything, and twice you mentioned the use of the 94+ SN95 MC when using the PBR calipers. I know you say the 93 Cobra should work fine but it seems like maybe you used to prefer the 1 1/16" MC for that particular upgrade?

87-93Â Ford Fox Body Mustang Brake Upgrades

87-93Â Ford Fox Body Mustang Brake Upgrades

I'm not the author of that webpage.

I tend to recommend staying away from the 1 1/16" MC unless running the 94-98 GT/V6 setup. With the PBR and cobra setups, it tends to result in a hard pedal.

Basically, look at what the factory did from the start and model that. MC's are "tuned" for the calipers on the car to be a specific ratio in terms of MC bore surface area to caliper piston surface area.
 
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NightFury

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I'm not the author of that webpage.
I apologize, I must have gotten some bad information on that.

Basically, look at what the factory did from the start and model that. MC's are "tuned" for the calipers on the car to be a specific ratio in terms of MC bore surface area to caliper piston surface area.
I'm completely out of ideas. The brakes have no stopping power. I've already purchased a second pair of calipers, new MC, prop valve delete, and bled it 400,000 times. Could the stainless braided hoses I'm using be at fault? That's the only other thing that isn't factory.
 

Mustang5L5

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Hoestly, your car is a sort of enigma. I don't know why it's not braking the way it should. Like I said before, your combo mirrors a factory combo and a setup countless other guys run and have no issues with.

I don't think the SS lines will make a difference. I installed them after converting and it was a negligible difference in feel.

I'd almost suggest rotor/pad compatibility issues there, but I hate suggesting throwing money at the problem when i'm not there myself to inspect the car and see for myself what the issue might be. It could be something simple,
 

NightFury

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The rotors are mid to upper level solid Centric's, and the pads are Hawk HPS. I would think that even with mismatched pads/rotors, the car would lurch to a stop at 15mph if i pressed hard enough on the brake pedal.

What if I tightened a brake line nut too much, would that pinch the opening or is that hard to do?
 

Mustang5L5

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What if I tightened a brake line nut too much, would that pinch the opening or is that hard to do?
Easy way to see if oyu have restricted flow is to bleed the brakes. Does the fluid flow easily with a bleeder cracked wide open? If the pedal presses to the floor easily and you get good flow, safe to say you don't have a brake line restriction.
 

NightFury

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*takes a long deserved sigh of relief*

I finally figured out what it was. After reading through several conversion posts, something struck me when I read that the 94/95 spindles had to be ground down to accept the PBR calipers. Naturally I had done that but I recall the caliper being a little too snug when I tightened it down. So I removed it and sure enough, the caliper was catching on the spindle and wasn't able to float freely. After filing the spindle down some more and ensuring the calipers floated freely, I test drove it and it was light years better.

I feel kinda dumb not having thought of that while I was installing the calipers but looking back on all my issues, it made perfect sense. Thanks to everyone for the help and I guess add this one to the list of things to check in the future!
 

jrichker

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Mustang5L5

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*takes a long deserved sigh of relief*

I finally figured out what it was. After reading through several conversion posts, something struck me when I read that the 94/95 spindles had to be ground down to accept the PBR calipers. Naturally I had done that but I recall the caliper being a little too snug when I tightened it down. So I removed it and sure enough, the caliper was catching on the spindle and wasn't able to float freely. After filing the spindle down some more and ensuring the calipers floated freely, I test drove it and it was light years better.

I feel kinda dumb not having thought of that while I was installing the calipers but looking back on all my issues, it made perfect sense. Thanks to everyone for the help and I guess add this one to the list of things to check in the future!

Always something silly like that huh? Glad you found that out before replacing too many parts. Like I said befor,e your setup is quite common so I was scratching my head as to why it wasn't working for you.
 

Mustang5L5

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MJBOBBIT is Matt J. Bobbitt. He and Mike, AKA Mustang5L5 are two different guys. I am sure that Mike remembers Matt well; they had some very interesting discussions a looong time ago...

Yup. 10+ years ago or so? I learned a lot from him
 

STWater

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My 85 currently has 4 lug rear disc which I think is from a T bird. Part number on one of the calipers starts with 2307. After I swap my axles to 5 lug, can I re-use the old calipers and brackets if I use 94/95 rear rotors? Or do I need to swap out brackets, calipers, and rotors?
 

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Mustang5L5

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Not compatible. You will need to buy SN95 rear calipers
 

jrichker

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My 85 currently has 4 lug rear disc which I think is from a T bird. Part number on one of the calipers starts with 2307. After I swap my axles to 5 lug, can I re-use the old calipers and brackets if I use 94/95 rear rotors? Or do I need to swap out brackets, calipers, and rotors?
A close look at the photo shows vented disks which were part of the Turbo Coupe brake package.

I found some info from an older post in this thread. It seems that rotors from a 91-92 Mark 7 Varga setup are 5 lug, and fit the SN94-95 axles. Maybe @Mustang5L5 can confirm this since the original post was his.
 

Mustang5L5

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I found some info from an older post in this thread. It seems that rotors from a 91-92 Mark 7 Varga setup are 5 lug, and fit the SN94-95 axles. Maybe @Mustang5L5 can confirm this since the original post was his.
I can't really confirm that since it's a pretty rare brake setup only seen on the 91-92 Mark 7, LATE 92-93 Saleens and the 1993 Cobra R (despite ford's own literature stating the Cobra R had the 1994 rear setup)


Anyway, the brake setup is similar with axle sticking out 0.75" each side like the SN95. So in theory, if you were to find the correct axle brackets, you could use those 45mm Varga's with it. I don't believe the 45mm Varga will bolt to an Sn95 axle bracket. Or perhaps if you purchased pad support brackets for a Mark 7 and used the caliper they would then bolt onto the Sn95 brackets

Problem is rarity. You have 107 Cobra R's, ~100 92-93 Saleens and 14,500 of the 91-92 Mark 7's made. Chances of finding those axle brackets.....slim to none. Most internet searches have VERY little on this brake setup and even i'm not 100% sure on what is compatible with the Sn95 setup.


here's the setup in question on a Saleen. VERY Sn95ish. In fact, if you look up the dust shield part number, it's the same as the SN95. The real question is are the mouting ears for the calipers the same between this setup and the Sn95.

92rear.jpg

92rear1.jpg


I've been trying to get a set of brackets for years. They rarely pop up on Ebay and most people assume they are the same as the 84-90 rear disk 54mm SVO versions and mislabel the auction as such. .
 
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STWater

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Thank you for the replies. I ordered moser replacement 31 spline 5 lug axles. If I get the 94/95 rear calipers and rotors, will these bolt up to same brackets or should I hunt down the brackets too? Just trying to do this right the first time.
 

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Mustang5L5

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You'll need the brackets too.

The calipers are smaller as well, so a master cylinder swap may be needed as well. What's your front setup going to be? Just stock mustang brakes with 5-lug rotors?
 

STWater

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I'm doing a coyote swap so I'm doing everything new from scratch when I do 5 lug swap. Doing a team z coyote swap kmember. Old spindles, master cylinder, booster, calipers are all off. What's my best route at this point? I'm also gona rip the rear disc setup off too now. If anyone has parts I need for sale let me know.
 

Mustang5L5

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Well with the coyote, you'll need to do hydroboost, or manual brakes. With manual brakes, you'll need the new pedal arm with revised geometry.

What do you want for end results? What front brakes? What rear brakes? Are you OK with the 0.75" offset increase of your T-bird and Sn95 disk brakes, or would you like to pull that back in so you can run fatter rear tires?

You have a bunch of options here. What would you like the final result to be?