Shuffling some additional thoughts over from GMF. I will go back through an edit later...
There is a difference between full lock up friction and when it is not. The stopping distance between the two will not be the same. The idea is to balance front to rear so your not fully locking up or as fast.
There are probably numerous additional things to consider, but these are a few of the things I have been bouncing around:
1. front clamping force, rear clamping force; balance of clamping force. This would include static and dynamic weight. Even by changing the height of the car the stock number will change slightly toward less mass moving forward.
2. pad surface area.
3. rotor diameter. Increased surface area. Increase in heat transfer. Increase in heat soak. Decreasing heat fade. Rotor diameter vs.brake torque.
4. pad materials. pad coefficient.
Overall 125 feet from 60 to 0 is okay, but that is not the full range of braking and there are areas of deficiency in the braking system. For example try locking the brakes up at anything over 100 mph.
One of the main things I'm trying to stress here is keep as much of the engineering set up in the first place: Clamping force ratio, disc diameter ratio, brake pad surface area ratio. Throwing the surface area ratio off will create unknown complications. I included another link to an article with some of the math involved, and while I understand the steps and how to do the math, in actuality it is even more complex. I read another article on heat exchange with even more complex math. What I wanted is an overview and come up with numbers related to the 89 to 94 GT(i) to help but together a better educated guess.
I'm leaning in the direction of the Billet Dynapro for several reasons.
1. Ease of pad installation.
2. Thickness of pad.
3. Price of pad.
4. Radial verse lug mount is easier for caliper centering and is more rigid.
5. Overall rotor increase.
6. Clamping force balances out better.
7. Rotors balance out better.
8. Dust boots
Additional side note:
16" wheels would open up four more calipers: Forged Superlite gR Radial Mount Caliper, Forged Superlite 4 Radial MT-Quick Silver, Forged Superlite Internal Caliper, and Forged Dynapro 6A lug mount Caliper. All of these should fit over a 11.75" disc. All of these except the Forged Dynapro 6a lug mount Caliper have a pad surface area of 8.2 inches squared.
I went back a did a stencil on paper of the stock brake pad. My measurements on the original ones were really not precise. I measured everything down to a 32nd of an inch this time and broke that pad down to 1 large rectangle with 15 smaller right angle triangles and rounded up to the nearest thousandth after calculating up A= 1/2(bxh) & A=lxw. I was way off with the original Area = 6.9 inches squared. The new number that I came up with was area= 5.787 inches squared. This is cool and makes me a lot happier.
I called Wilwood Brakes today. The final verdict on the listing for the Narrow Dynapro Radial Mount caliper was that they don't recommend it for under 11.75". The tech support mentioned that they needed to clean-up those additional fitment on the schematic drawings. He did not say it was an intercept issue, but possibly a brake pad overhang issue. I mentioned that the other Dynapro Radial Mount caliper use the same brake pad layout and is listed down to 10.75" rotors. He said that ultimately if you can make it work great. He want to sell me the Dynapro Radials with a proportioning valve. While that will decrease the pressure and reduce the clamping force that is not the way I want to design the system. It does bring up concern for the clamping force numbers that I originally worked out. I knew that the stock proportioning valve and having an interlinked front and rear system would in the finer aspect of the clamping force ratio produce inaccurate numbers. However, everything else being the same the comparison ratio between front to back would still be correct as a percentage of difference. Technically, I believe the clamping force ratio would be altered by the proportion bias between front to rear. I never did work out the exact figure for static and dynamic balance. There a number of factors that will change the balance like vehicle height, struts, and springs. My guess is that instead of making the exact right caliper brand new they used the proportioning valve. Even if it was exactly right it would be good to have the valve.
I don't think I want to take my chance with the Narrow Dynapro Radial Mount caliper. This brings me back to the Dynapro Lug Mount Low Profile calipers. While I cannot make a bracket to work I think I can replace the whole brake mount. A member on Redlinegti showed me a picture of a replacement mount. There are only four bolts holding the whole thing on. I will have to design one that matches the mount height for this caliper and I will have to move it inward by roughly 1/2". I even think there will be no need to lathe the hat either, and it will lighten the whole rear end by as much as 3lbs.
There were some issues with this first set of brackets. Part of the problem was the quick conversion from metric to standard. It did throw some of the measurements off. I ran into two clearance issues: one was the center of the hub, and the other was the bottom relief is not quite deep enough. The first clearance issue was solved by a couple quick passes on grind wheel, the second one however is not as easy. I need an additional 5/64" removed from the bottom of the inset. I thought I had accounted for this additional tolerance, but who knows at this point. I also have to shim the top studs more than I want to. I have already entered the new measurements into the program to solve any issue that came up. Additionally, I am also going to lighten the bracket in the center. For now I will make these ones work until I can get the next ones cut.
Notes on cut: Before I forget I wanted to document the conversion to CAM and Gcode process. The top cut you will need to extend out to get a square cut beyond the edge of the bracket. I have already converted to standard, but anyone having these made will want to ask ahead of time for what the machinist wants. Very helpful to give your machinist a 3D drawing print out with all the measurements on it. Make sure you write down the drill bit size for tapping to 3/8-16 and 12x1.25. It is also helpful to have all your start corners be the same corner. To make the bracket you will only need the front and the top dxf files.
I will have to get back to you on the total stock weight.
One piece rotor and hat stock front for GT: 8.912 lbs (Used for many years); most likely the rotor starts at 9 lbs.
Brake caliper without pads stock front for GT: 6.202 lbs without bolts and pads, and 7.338 lbs with pads no bolts. My original guess of 6 to 8 lbs was correct.
total weight: 8.912 +7.338 = 16.250 lbs + the weight of the bolts
Front Hat: 1.7lbs - the hole cutouts- bore diameter = 1.4lbs
Front 11.75" x 0.80" Rotor with bolts: 8lbs + 0.208 lbs = 8.208 lbs
Front Brake Bracket (aluminum) with studs, shims, nuts and bolts with lock washer and flat washer: 1.1 to 1.2lbs
Front calipers without pads: 4.1 lbs
Total weight: 15.1 lbs
Weight savings probably of 1lbs. Remember though this is for an increase from 250 mm rotors to 298 mm rotors.
My wheels are 10lbs which if you compare it to another 15" wheel your looking at roughly 4 to 5 lbs weight savings right there (some of them are a lot heavier. However if you are comparing it to a stock 14" alloy GT(i) I believe they are 9lbs. A stock 14" steel I believe is 12 to 14 lbs. My front spacers are only 1/2 lbs to 3/4 lbs. My 14" aluminum alloy wheels with tires where heavier than my 15" wheels. If I went with a summer tire I could shave another 3 to 4 lbs per tire off the total weight.
Compared with an average 15" wheel and the brake combo I am shaving as much as 7.5 lbs each front wheel and as much as 15 lbs off the front.
The rear stock:
8.5 lbs rotor hat one piece.
brake caliper with e-brake bracket: I'm guessing 10lbs
steel stock mount bracket: 3 to 5lbs guessing
stock setup total: as much as 23.5lbs
my potential setup:
hat: 1.350 lbs after being drilled
rotor: 7.154 lbs + 0.156 lbs for bolts = 7.310 lbs (only six bolts instead of 8)
rotor + hat after being drilled + bolts = 8.660 lbs
caliper: 4.012 lbs with pads (3.142 lbs without pads)
aluminum bracket: 0.954 lbs
Total for rear setup without spot caliper: 13.626 lbs + six bolts for mounting
spot caliper: 3.300 lbs with pads
spot caliper mounting bracket: 0.5 lbs or less (yet to be determined)
Flange bolts for caliper will be 3/8-24 which will be slightly lighter than stock.
Two of four hub mount bolts will be the same 10 mm x 1.25 x 30 to 35 mm, and the other two will be slightly longer.
total: 17.626 lbs (still need to weigh bolts and spot caliper bracket)
Final weigh in is not posted but it is still looking like there is 5 lbs off the stock setup even with the spot caliper.
I called K-sport today for their dual piston hydraulic hand brake. It is indeed inline which means that it will work with our front left, rear right and front right, rear left setup. However, the unit is quite expensive and on top of that the line installation kit is over $100 for each side. Additionally, it can not be used horizontally, and there is no emergency brake lock. Parking would rely on leaving it in gear. I don't believe there is room to leave both parking brake and hydraulic brake. The good is that the unit does not use separate reservoir, and the piston are 3/4 which will mean that they can lock the rears with more clamping force than the stock master cylinder even if the stock emergency brake was hydraulic. I did also get the in and out threads for unit. In is 7/16-20 UNF, and out is 3/8-24 UNC. What I will try to find is the right fitting to slip on hard steel lines. There is no advantage and no need to having a flex line where I want to connect it. This should save me at least $100.
The rear bracket is closing in on being ready to have produced. It will be possible to add a spot caliper for an emergency brake, but that bracket will be an add on to the rear brake mount. However, I think what I will do is go with the rear Dynapro lug mount calipers with the hydraulic hand brake, and then use what Richard said about the hydraulic stop valve that can be used to lock the rear brakes to use as my emergency parking brake. The problem would be that I would have to add two of them. Another option I am throwing around is to switch to two master cylinders; one for the front, and one for the rear. This would allow me to use a single hydraulic hand brake, and a single stop valve. I could still run proportioning valves on the rear and even the front.