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Dark Horse HP front caliper mount - Radial or Axial?

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66
95
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
Has anyone seen how the Dark Horse HP front calipers are mounted? I googled the crap out of it but couldn’t find any worthy pics or info. Axial like Mach 1 Brembos or radial like GT350 Brembos ? The rotor dia appears to be smack in the middle at 15.3” but with the GT350 style alum hat. Asking for a friend….
 
66
95
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
Yes

I was investigating because this might be a simple bolt on slight upgrade for the Mach 1’s. Mach 1 uses a 15” 380mm rotor with an axial mounted Brembo 6 piston caliper. Very capable but heavy. The new S650 Mustang with performance brakes uses a 390mm rotor with alum hat much like the GT350, and based on what I just learned it also uses an axial mounted Brembo 6 piston caliper. So….this might be a way to get a slightly larger and lighter rotor on the front of a Mach 1 if paired with the corresponding S650 axial mounted caliper.

Still in question is if this is indeed a different rotor than the 394mm GT350, only 4mm difference? Part numbers are not yet on the parts.ford.com sight. Then there is wheel clearance, does this caliper fit the Mach 1 HP wheel better than the GT350 caliper?

I think we are learning that the S650 with performance pack is using the unique Mach 1 knuckle or something very very close.

Fun stuff, more to come.
 
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Keep in mind that moving to a larger rotor limits wheel choices and the larger rotors really are not needed. There is a reason why the GT4 and FP350S use smaller diameter rotors - reduced weight and wheel fitment. They also use a true motorsports quality brake system. The FP350 uses AP brakes front and rear. Knowing people who have installed the APs on their GT350s for track and race use, they might have a smaller diameter rotor, but they outperform the factory brakes.
 

JDee

Ancient Racer
1,817
2,020
Exp. Type
W2W Racing
Exp. Level
20+ Years
5 miles from Mosport
The brakes on the Mach1 are completely capable of track day use without issue. I got zero fade from the completely stock brake system and immeasurable wear as well.
If you're racing, that's a different story simply because of the weight of the stock pieces. Racing demands a proper racing brake system, track days, not so much.
 
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The Mach 1 / S550 Brembo brakes are up to at least sprint racing with proper pads and cooling ducts. Are they as good as an AP or Brembo race kit, no, but the factory brakes cost a lot less.
 
66
95
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
Agree with everything said. I come from the days of playing with fox body’s and part of the fun was figuring out what mixed and matched. Our Mach will be a track day toy only and always on 19” wheels because that’s what we already have, two sets.
 
1,256
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In the V6L
Keep in mind that moving to a larger rotor limits wheel choices and the larger rotors really are not needed. There is a reason why the GT4 and FP350S use smaller diameter rotors - reduced weight and wheel fitment. They also use a true motorsports quality brake system. The FP350 uses AP brakes front and rear. Knowing people who have installed the APs on their GT350s for track and race use, they might have a smaller diameter rotor, but they outperform the factory brakes.
The FP350S weighs 3380 pounds and the brakes are sized accordingly. The OP's question is about swapping in other OEM Ford brakes, and the issue isn't really size, it's the mechanics of getting the parts to actually fit together and bolt up. Everything in the front suspension in an S650 is specific to that car, even if it's borrowed from another version that looks the same. For instance, the DH front caliper looks like axial mount. So, are the mounting holes the same size and distance apart as the ones in an S550 Mach 1 caliper? If they are, do they position the caliper so that the rotor is exactly centered in the caliper pad pocket? Will the pad friction materials match up with the rotor's friction face? If any of those is "no" then you need to swap the knuckle. But then, does an S550 knuckle have exactly the same suspension link and steering mount points and geometry as the S650 part? Having done this dance on some of my cars, it rapidly becomes a mess if you're not very careful.
 
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The FP350S AP brakes are better than either the OEM GT350 or any of the other S550 brakes. We have replaced full weight GT350 and S550 setups with the APs and they do perform better (better modulation and pedal is firmer when hot), weigh less, and fit under an 18" wheel. But, they are expensive.

Short version, if you already have the S550 Brembos, I think this swap is a waist of time and money. You gain weight and need a larger wheel (reduced tire selection). Also, swaps are not that straight forward. Anyone know the Dark Horse caliper piston area? What size master cylinder? While an axial mount, will the DH caliper bolt to an S550 spindle? Will the rotor be centered properly? For example, the S550 caliper will bolt to an S197 spindle and work with an 2014 GT500 rotor, but a lot of people do not like the resulting low / long throw of the pedal do to the mismatch of the SS550 front caliper piston area to the S197 master cylinder. This combination also has the rotor slightly off center in the caliper.

Does the OP's friend's Mach 1 have brake cooling ducts installed? Are they using an actual race pad (and not one that gets away with dual street / track use)?
 
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66
95
Exp. Type
HPDE
Exp. Level
20+ Years
Michigan
“Asking for a friend“ was tongue in cheek. I knew this would stir up discussion in the why waste your time arena.

Already researching piston area, swept area, etc., wasn’t going to waste my time if they were radial mount as it would be a bridge to far for the minimal gain if it required a knuckle swap as well. But yes, need to understand the weight difference as well as the mounting dimensions. From what I understand of the DH it uses the Mach1 knuckle and hub/bearing. So….its very reasonably to think the caliper ears were simply extended to accommodate the 10mm larger rotor ?? Doubtful they tooled up a new knuckle but possible if the ears got too long to be stable.

Would it be a worthwhile swap if it was all bolt on…eh maybe, probably not but I enjoy do the research.

I guess what got my attention more than the slight dia increase was the GT350 style alum rotor hat as a way to reduce unsprung weight.
 
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[...]Anyone know the Dark Horse caliper piston area? [...]
That information is easily available on the Ford website:


The 2023 specs are here:


Both DH and Mach 1 have six 36mm pistons in the fixed front caliper. The DH rear has a four 30mm pistons in a fixed caliper, while the Mach 1 had a single 45mm piston floating caliper. Because a single floating caliper piston applies pressure to both pads, it produces as much braking effort as a two 45mm pistons in a fixed caliper. The DH rear caliper has less effective piston area than the Mach 1, suggesting a shift forward in brake bias.

There's no way to know if that matters, though - the DH has an "Electronic Brake Booster" so it's a reasonable bet that both pedal feel and brake line pressures are managed by an algorithm that adjusts f/r and l/r bias based on conditions. This system sounds like the one used on the C8 Corvette. It's described here:


If pedal feel is controlled by the Electronic Brake Booster, presumably the market for stainless lines will evaporate.
 
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Based on the above information, the rear caliper piston area for the DH is 1413 mm square. The S550 read caliper area is 1590 mm square. So a difference of about 10% in piston area. I am not going to take the time to try to figure out if there is any actual difference in bias - that would require a series of computations based on pedal ratio, master cylinder boar size, piston area, swept area,... you get the idea.

Just so people understand the piston area calculation, for a fixed, multi-piston caliper, you only calculate for half the number of pistons (i.e. just for one side of the caliper). So, if it is a four piston with 30mm pistons, you calculate the area for a 30mm piston then double it.
 
1,256
1,253
In the V6L
Based on the above information, the rear caliper piston area for the DH is 1413 mm square. The S550 read caliper area is 1590 mm square. So a difference of about 10% in piston area. I am not going to take the time to try to figure out if there is any actual difference in bias - that would require a series of computations based on pedal ratio, master cylinder boar size, piston area, swept area,... you get the idea.

Just so people understand the piston area calculation, for a fixed, multi-piston caliper, you only calculate for half the number of pistons (i.e. just for one side of the caliper). So, if it is a four piston with 30mm pistons, you calculate the area for a 30mm piston then double it.
Your explanation is correct, but there are a couple of points to keep in mind for someone making these kinds of changes. First, the pedal ratio and the master cylinder bore size don't change if you only change calipers so you can ignore them. If you're doing a compatibility assessment, focus on the piston sizes, although, within a reasonable range of change - say up or down 15% - they don't change braking much - you can get a bigger difference by changing pads.

Second, where a difference can arise, even with a small change in piston size, is in brake pedal feel and travel. Caliper pistons don't move very far when you put the brakes on (unless you've got knockback) but they do have to move a bit to close the small gap between the pad and the rotor. If you install front calipers with larger pistons, the increase in total piston area (all six pistons in the right caliper, six more in the left) means you have to move a larger volume of brake fluid out of the master cylinder to generate the pressure you need to slow the car. The fluid volume increase isn't much, but it's amplified in reverse by the master cylinder bore and the pedal ratio, and it can be a surprising effect. There are lots of threads in forums talking about mushy brake pedal after putting Mustang GT PP brakes on a non-PP car.

One thing you haven't mentioned in your praises of AP brakes is the graduated piston sizes. Putting the smallest piston at the leading position and the biggest in the trailing position prevents pad taper under heavy braking loads. The GT350 had graduated 34-36-38 piston sizes on the front and 30-32 in the back. All the front brake pistons on the GTPP/Bullitt/Mach1/DH are the same at 36mm and the rears are either single piston floaters or they're the 30-30 setup on the DH. To me, that's a hint of how Ford actually expects the cars to be used.
 

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