After installing my Bullitt Brake Upgrade, I noticed a big difference in stopping power and brake pedal feel. After bleeding the system and letting my pads break in, the Bullitt calipers were solid as a rock. Stopping distance was decreased, and brake fade was completely gone.

 

Uncle Bens Assassin - "After installing my Bullitt brakes, I noticed a big difference in stopping power & brake pedal feel. The Bullitt calipers were solid as a rock, stopping distance was decreased & brake fade was completely gone."

Oops, I accidentally posted before I was done (please re-read the completed thead). Anyway, I am not questioning the advantages of going w/PBS type brakes. Even tho you have a slightly smaller than OE brake pad (about 4%), the big difference is, of course, is the dual piston design of the caliper. Maybe, it's the old "If some is good, more is better & too much is just right" philosopy, but I would like to go w/the Brembos. However, I want to make sure that everything functions correctly when done. And, right now, I think that there are a lot of folks driving around out there in their Brembo braked Mustangs just as happy as a pig in slop, but, in reality, are not getting the stopping power that they paid for.

 

I am planning on installing a set of '00 Cobra R Brembo brakes on a '98 GT. Here is my problem ... everybody says just bolt 'em & head on down the road, but you just can't install larger brakes on a car & expect to use the same proportioning that you had w/the OE (or smaller) brakes. You may have better brakes, but the simple rules of brake physics say that you are not optimizing the larger (Brembo) brakes by not making any other changes to the system. Others say that as long as you have ABS (which I do), that "everything is fine." All the ABS will do is keep things from locking up, but you are still deceiving yourself if you think that you are obtaining the full benefit of the larger brakes because ABS does not affect proportioning (I suppose you could say that it does, but only in a compensatory way).

I called Ford Racing & they said ... "That's a good question!" Hell, I KNOW it's a good question, what I want is a good quantified answer!!!

When you make a 'little' change, like going to the Cobra/PBS brakes, you could probably get by by not making any other changes to the system. However, even then, I would go w/the Cobra brake m/cyl & pro/valve. Using that same logic, I would think that a change to the '00 R brake m/cyl & pro/valve would be the logical thing to do to insure that everything is correctly proportioned & you are getting full benefit from the larger Brembo brakes. My question (finally!) is will the '99 Cobra R brake m/cyl & pro/valve fit a '98 GT w/o any mods?

Somebody, please, give me some answers or chase my in the right direction. Thank you.

Personally,
I wouldnt waste your money on the 4 piston 13" kit...the 4 piston calipers cost 1k more then the 2 piston and dont offer that much of an improvement (little distance, some fade)...I would go with the 13" Cobra 2 Piston PBR OEM kit or the 14" 4 Piston Alcon kit...the alcon kit is pricey, but if your were going to spend and extra 1 k for just the 4 Piston calipers.....

As far as the proprtioning I would contact Baer, Alcon, or Willwood. I know when they made the FR500 and used 13" cobra brakes off the front and put them in back, i forget what they used in front, they didnt update the ABS system and the car didnt stop any faster then with the stock brakes...

 

I know this thread is half a decade old, but did Geezer ever get an answer? I did this accidentally and am looking for additional info. By "accidentally" I mean that I took a 96 GT with complete brake system (ABS included) and transplanted all the mechanicals from my wrecked 96 Cobra into it. Drivetrain, wiring, brakes, suspension. So, hardlines, ABS unit, MS, and hydroboost are GT. The 'sprung' parts of the brakes are from the wrecked Cobra. I assumed that the master cylinder and prop valve were the same. I also have the 00 R Brembos, so I've effectively upgraded the GT system once out back (to Cobra spec) and twice up front to (Cobra R spec). Anyone know if there's a difference in the master cylinder and prop valve for the Cobra and GT? This is car road raced ONLY and I feel like (but don't have data) the brakes were better before the transplant.

 

I read somewhere that the proportioning valve is different on the cobra's, but on the 95 cobra r, they used a GT proportioning valve to reduce "nose" dive.

 

I think people like to complicate alota things just to make things compicated.

A simple brake PAD upgrade on even the stock GT calipers is gonna make more of a difference than going to a 4 piston caliper with a regular street pad.

Alota people seem to want some big ass 70 piston brake caliper on a 19" rotor so "it'll stop better". The reality is, people seem to put the crappiest or average brake PAD on the car while doing so.

I used a set of HAWK HP+ pads on stock 99 GT calipers/rotors. I upgraded to a Cobra brake system for the larger rotor for heat disapation for track days. I ran the stock Cobra pads because they came with the rotors. I thought the brakes SUCKED, but knew it was just the pads. Replaced the pads with HP+'s and all is kosher again.

Oh, and i'm running cheap-o NAPA brake pads in back with no fiddling with MC or any prop. valves. My car stops and stops well.

 

Well, FWIW, I went from 98GT brakes to Bullitt (Cobra) brakes and the pedal needed a little more effort, but I actually liked it because it gave me better feedback. I subsequently went to the 2000R Brembos and the pedal feel was about the same. No booster or MC changes were done.

 

Lets not forget one simple factor that most people overlook when it comes to brakes. Your brakes are only as good as the tires that are applying the resistance to the pavement. With that said, you can have 18 wheeler brakes on your Mustang, but if you have a set of $30 walmart h rated tires your not going to stop any faster than you would with stock brakes. If your car is primarily used for street use, there are few street tires that are going to provide a dramatic increase in stopping power between stock and upgraded brakes. There are some tires that will but most will not. Traditionally, the major difference you notice is with brake fade and brake torque. A 10.5in rotor is obviously not going to achieve as much torque per pound per square inch of pressure as a 13in rotor. For this reason you will apply moe pressure to achieve the same stopping power. You will likely generate more heat on the smaller rotor because of this as well. But... the moment your ABS kicks in, your brakes are no longer the limiting factor in your ability to stop quickly.

Lets assume you have very sticky tires (as most brake tests I have read use race rubber on the car). If this is the case then you will notice a huge difference in ability between stockers and cobra 13" brakes in all aspects. The upgrade from 13" dual-piston PBRs to the Cobra R Brembos is going to net minimal advantages, though, for the price. By minimal, I mean, you will see a little more stopping power but the primary advantage is heat dissipation and resistance. These brakes were designed for track use so they are made to dissipate heat and resist fade better than the stock Cobra brakes. If your a heavy tracker, or the car only gets used for track, this may be an asset to you, but in most cases, the Cobra 13" brakes are more than sufficient and can be made to be just as useful in track applications as the Brembos, for cheaper. Again, if your tires are not top notch, your not going to notice a major difference.

As far as brake pressure is concerned (keep in mind this is what I was told by an owner of a Cobra R and also from what I have read) to the extent of my knowledge, the HydroBooster and the Master Cylinder is the same on the GTs and Cobras. Now, an owner of an 00R told me that as far as he has been able to find, the same holds true for the 00R. From what I have been able to find, the proportioning valves are the same on the GTs and Cobras. I don't know about the R's. If there is a difference, it cant be that huge just based on the dynamics of the car and weight ratios and such.

To summarize, the tires will limit you before brakes (in most cases). The Cobra 13" brakes are more than sufficient for 90% of applications. You can add Cobra brakes to an existing GT application and they will work just as well. I have the 13"F/11.65"R setup on my car with stock GT hardlines w/ steel braided soft lines, ABS, prop valve, and booster/mc. They work just fine and are more than my tires (race or street) can handle.

I hope this helps a little

 

Assuming your replies are for me and if so, I appreciate the feedback...my car is road raced ONLY. I run 20-40 minute races. The heat dissapation is a number 1 priority. Loss of braking due to fade is why I had to take a wrecked car and a non-wrecked car to make one good one.
I have good pads. I have good tires. I am only looking to maximize what I have before spending the next 2 grand on the stoptech kit.
Based on my continued research, I think the hydroboost is the same between the GT and Cobra. I still don't know if the prop valve is the same or not. I have seen in several places that the master cylinder IS different. Bore diameter of 15/16" vs 1-1/16". My plan is to remove the oem prop valve and my the manual one and tune it myself. Then I'll see if I can get any more out of it. I still feel like my rear brakes aren't working hard enough.
I may also experiment with pad compounds. My fronts are one level more aggressive than my rears now.

 

I got to tell ya, with all the Mustang braking kits I have experimented with, I have not seen one yet that really has exceptional stopping power from the rear. A good portion of that is due to the geometry of the suspension on the car, but more than that, the rears just never seemed to have much clamping power. The GT stockers and the Cobra stockers barely hold on the parking brake, much less provide any exceptional braking torque. The Baer Claw 13" rear kit is really cool but caused the ABS to kick in prematurely because of the lightened rear end under hard braking. The IRS seems to help with the nose dive and allows the rears to do more because of the difference in the geometry of the suspension, but its still nothing to write home about. If you are looking into the absolute maximum braking force you can achieve from your setup, your going to have to focus some attention to tires (which you have) and suspension geometry (as it pertains to weight distribution and nose dive).

 

the cobra's have a smaller MC
the bigger MC of the gt is advantageous when you need to push all that additional fluid for the 4 pots
i have cobra rear brakes and cobra r fronts, while my overall stopping power didn't increase that much(previously has the 2 pot cobra pbr's on front), pedal feel is much better with the 4 pot calipers on the front, along with fantastic fade resistance