Gt500, or S550 mustang gt base 4 pot brakes

[J_Train]

hmm. i have no proof now (collision center sanded them down to smooth them out) but mine said FOMOCO Brembo on the inside but they had the stamping on the outside like yours with the DG17..... maybe they didn't have the outer portion?????? they weren't new I know that cause there was a $30 as most reman stuff have.

 

[J_Train]

painted then cleared..... decided I liked it cleared better.

pinted

then cleared

 

[CDW6212R]

Very good, and what clear did you use? I have something from VHT, yet to try, but it has to be high temp for sure.

 

[J_Train]

Axalta's clear coat from my collision center here at work. its just automotive clear but handles temps upwards of 650 or 750* so the Alalta rep said it would work. I would if had to wait 3 weeks for the VHT. I should of had one of the guys spray it but I wanted to try so they're not perfect but good enough for me lol

 

[CDW6212R]

They look great, the trick there is being glossy they would be easier to keep clean.

 

[GLOCKer]

Looks really nice!

 

[MINERALGSVT]

Looks great!

BTW - for your AWD, 4WD owners - I reached out to Chris to see if there's something he can do for us. He replied and said he would do some digging for me. I'd love to have these or some S550 brakes on the front of my XP8..

Todd

 

[J_Train]

well I ran into a road block..... I cannot use the Boss style Brembo the way it is made it will not sit flush to the bracket I should of checked it before paint but was too excited and had them before I had the brackets. Also sorry for the late 5 month reply/update but I was busy trying to find a solution and spend time with family been going to Disney with the kids a lot. Anyways Ill post pictures sometime today to kinda show what I ran into. so now to try and sell these to someone with a 2005-2014 mustang that wants to up grade. Then buy S550 4 piston calipers. I'll post pictures of those as well to show why these should work.

 

[J_Train]

My issue with the Brembo Boss calipers

The modification to the S550 Caliper from fully torqued racing. That I think will be a better route seeing that if I milled down the back of the Brembo it would affect the strength of the caliper and I don't believe there's enough material to machine off of the brackets to clear the bracing on the caliper.

 

[GLOCKer]

Yikes! That's a bummer.

 

[MetricMuscle]

I've read thru this thread but still not sure what the obstacle is to making a bracket to mount a different caliper be it an OE part of Wilwood, etc. Is the rotor offset an issue? Would using a radial mount caliper make things easier? Assume we were to start with the upgraded 2001 - 2002 Sport larger rotor diameter.

 

[CDW6212R]

What most people should be going for is a notably larger rotor(12.5" or bigger), and a caliper with a larger pad, which also matches the OEM caliper piston area. Most common performance calipers in OEM applications, have smaller piston areas, and the brake forces will be reduced from stock. That mean more pedal pressure required to get the same braking.

Most aftermarket kits simply provide larger rotors and more attractive calipers, but with virtually the same braking power. The larger rotor will inherently gain some brake power, but caliper piston size can make big changes, so that needs to be matched well.

I need a much larger brake pad than the stock caliper pads, so I had to hunt through a lot of aftermarket calipers, to find one I liked for my severe duty usage. These below are 7520 brake pads, 6.75x2.97x .80" thick. The pads are not cheap, and this one on Amazon is one of a few they carry. There are a bunch of different compound versions, I like that many of them come already bedded in(machine run in).
https://www.amazon.com/dp/B00TO68AL...olid=32X1ZA2MRI77P&psc=0&ref_=lv_ov_lig_dp_it

 

[MetricMuscle]

I like that calipers with opposed pistons don't use sliding pins and extra bracketry. Some even make changing brake pads super easy, just pull them out of the top of the caliper with it still mounted. That's that racer stuff right there!

Hey Don, can you clarify how you go about determining what size piston to look for? Are you saying the total area of all 4 pistons should be the same as the 2 we currently have or is there some other ratio? I woulda thought that to keep pedal travel the same that the area of the pistons would need to be the same but it doesn't sound like that is the formula you use.

 

[CDW6212R]

The piston area does need to stay about the same, ideally the same or just a hair larger. The calculation is only for one side of a caliper, opposing pistons do not contribute more force. So the stock calipers are near to 1.75" pistons, two on one side. I don't know the official size, I've seen a figure very close to 5.0 sqin. That's why the smaller Mustang calipers of the 90's aren't ideal. The people adapting Cobra rotors that are 13" are gaining from the bigger rotor(stock is about 11"), so the Cobra calipers that are near 43mm or so are close, but a hair small. I don't know what the newer Mustang calipers are in piston areas, I was researching for my brakes in about 2005.

Do note that many race caliper do not have street seals, keep that in mind. Race caliper pistons usually have just simple seals like a square profile o-ring. Street seals are far better for the street, because the seal is large and includes the outer dust boot. The whole seal flexes and protects the piston/caliper joint much better than a race caliper. Race calipers are expected to be serviced often, removed etc, more than once a year for example. Being off so much, tha's when the whole caliper and piston area is cleaned thoroughly, or the seals even replaced. I have the SSBC calipers intended as replacements for 65-82 Corvettes, the race seals I do care for well. I clean them as well as I can each time I replace brake pads.

So be wary of race seals on calipers, it's recommended that the whole caliper is cleaned very well, regularly. You don't want any dirt etc, causing any corrosion down in the piston/caliper/seal area, creating a leak of any kind. I'm mindful of that and actively keep an eye on the brakes of all vehicles, but those more so.

 

[MetricMuscle]

If I did my math correctly, 2 - 1.75" pistons have roughly the same area as 4 - 1.25" pistons. 4.8 sqin vs. 4.9 sqin. 1.25" pistons are roughly 32mm in diameter.

43mm pistons have about 2.25 sqin of area each so 4 would have 9.0 sqin. YIKES! That's allot more area with lots more power.

 

[CDW6212R]

If I did my math correctly, 2 - 1.75" pistons have roughly the same area as 4 - 1.25" pistons. 4.8 sqin vs. 4.9 sqin. 1.25" pistons are roughly 32mm in diameter.

43mm pistons have about 2.25 sqin of area each so 4 would have 9.0 sqin. YIKES! That's allot more area with lots more power.

No, stop, do not count opposing piston areas. Ignore opposing pistons. A four piston caliper with the same sized pistons as a two piston caliper, create the same forces. I don't know how else to explain that, but just ignore any outboard caliper pistons.

The fixed calipers don't have the frictional losses of sliding caliper, so they are a hair more efficient.

The first calipers I used were rebuilt OEM 65-82 Corvette units, those have four 1.875" pistons. That worked but had a little too much power, it would trigger the ABS at 80mph if you hit the pedal hard. Figure out that piston area, and try keep it under that.

 

[J_Train]

The area circled is the issue I'm having with the GT500/Boss Caliper the way the body is made it will not let the caliper bracket sit flush. If I machine the caliper it will more then likely hurt the structural integrity of the caliper, if I machine the bracket it may do the same to it. But I should be able to use the S550 GT caliper. Also Don is right about the pistons. Do not include the other pistons. if its 4 pot only use 2 for measuring, if its a 6 pot the use only 3

 

[CDW6212R]

The area circled is the issue I'm having with the GT500/Boss Caliper the way the body is made it will not let the caliper bracket sit flush. If I machine the caliper it will more then likely hurt the structural integrity of the caliper, if I machine the bracket it may do the same to it. But I should be able to use the S550 GT caliper. Also Don is right about the pistons. Do not include the other pistons. if its 4 pot only use 2 for measuring, if its a 6 pot the use only 3

Is that bracket aluminum? If it is then that likely shouldn't be whittled on at all. If it's steel then depending on how much needs to go, I'd cut that down.

Were those brackets from a kit, thus made of AL? If so, then I'd see about finding a shop that can produce them in steel, fitting the calipers easily, but also maybe bigger to fit closer to the spindles.
I had mine made from a 1/2" steel plate, and a couple more small pieces welded to it. I took a machine shop and extra spindle and caliper, so they would be able to test fit everything. What I had was fairly simple to design and for them to make. My next brackets will be a little harder, because the bigger caliper is tougher to locate with a fabricated bracket(more odd of a shape). I have only held a caliper up next to a spindle with a rotor in hand, nothing bolted up etc. It may be no big deal, I'll get to it in a couple of months.

Below is first my fitting using a Cobra caliper with it's very shallow(.350") offset. The bracket went on the outside and I didn't like that offset, the caliper was outboard a lot(few wheels would have fit).

The next picture is with my final bracket, mounted to the outside and made for a custom rotor closer to the stock offset(these are 1.45").

 

[J_Train]

Is that bracket aluminum? If it is then that likely shouldn't be whittled on at all. If it's steel then depending on how much needs to go, I'd cut that down.

Were those brackets from a kit, thus made of AL? If so, then I'd see about finding a shop that can produce them in steel, fitting the calipers easily, but also maybe bigger to fit closer to the spindles.
I had mine made from a 1/2" steel plate, and a couple more small pieces welded to it. I took a machine shop and extra spindle and caliper, so they would be able to test fit everything. What I had was fairly simple to design and for them to make. My next brackets will be a little harder, because the bigger caliper is tougher to locate with a fabricated bracket(more odd of a shape). I have only held a caliper up next to a spindle with a rotor in hand, nothing bolted up etc. It may be no big deal, I'll get to it in a couple of months.

Below is first my fitting using a Cobra caliper with it's very shallow(.350") offset. The bracket went on the outside and I didn't like that offset, the caliper was outboard a lot(few wheels would have fit).

The next picture is with my final bracket, mounted to the outside and made for a custom rotor closer to the stock offset(these are 1.45").

View attachment 163993

View attachment 163994

It looks like they would have to be machined about half way. they are a 2 piece steel bracket tig welded together.

 

[CDW6212R]

I gotcha, that is very tight. Are those brackets mounting to the outside of the spindle, like my first picture above? Is there any chance the bolts in your brackets are far enough apart, that mounting it to the inside of the spindle, would allow the bolts to clear the spindle" That's how my brackets are, as my 2nd picture shows.

I might have a similar issue with the calipers I'm wanting to use. The bolt pattern spacing can place the calipers really close to the spindles. Changing the rotor size can affect that, but we have a rotor in mind that we want to use. It's a balancing act to fit it all there properly.