sixfrost

A question for brake experts. Something odd with my new brakes, please help me out, may be i am missing something...

Here is the situation: I have put together a brake upgrade: Brembo X-drilled/Slotted Cobra rotors (from ebay) and SVT cobra caliper kit: http://www.fordracingparts.com/parts...tKeyField=6455.

1st thing i wonder about: The front rotors on a 2001 GT are 11.65 correct? New rotors are 13 in. That install went fine - brakes bled and tested. Works fine. Two things seem odd - i am not noticing a dramatic difference in braking! It seems a bit better, but not by much... Is the upgrade not that big? And another thing - the area of the brake pad that is touching the rotor is about 75% of the available rotor area. Is that normal and as expected? Or are my pads smaller then needed?

2nd: New rear rotors were as big as the old FRONT ones, so about 11 in. They didnt fit. Looks like i either need a bracket to mount the calipers or different calipers alltogether. Is that correct? Is the 10th edition Cobra rear brake caliper mount different from a GT? Take a look at this kit http://www.fordracingparts.com/parts...tKeyField=6455. Is the rear caliper the same as stock GT? Is it even worth for me to put the rear one on? I left the stock rotor and just put the red caliper on.


Is this WHOLE package as i described it even a good upgrade? I thought i got a good deal on it - for 600 bucks all brand new. Was it worth it?

All the help is very much appreciated!

Thanks

groundpounder

six, I hope someone replies to you because I am about to do the SAME thing and someone spooked me by telling me that the rear has to have special caliper brackets because of the IRS vs solid axle, but I don't believe them. My research tells me that the IRS and solid axle caliper brackets are the same for the 11.65" rear rotors. And it's going to cost be $600 for the whole shebang.

A few points on your post:
2001 GT front rotors are 10.8" - rears are 10"
You received new front and rear Cobra pads in your caliper kit, right?
Your new rear rotors are 11.65". Your old ones were 10"
Did you receive new brackets for the rear? Because you will need them or your new caliper kit will not work. The 10th Anniversary Cobra does not have the same caliper bracket as an 01GT - those new rotors require a new caliper bracket since the new rotor is 1.65" bigger in diameter. That may be your problem if you didn't get a new caliper bracket.

You want to know the heck of it? EVERY Mustang from 1994-2004 (including the Cobra R's) use the SAME rear caliper - a 38mm single piston Varga unit. The rear rotor on all Cobras is 1.65" larger in diameter and slightly thicker, which is solved by using a taller axle to caliper bracket and thinner pads. There is no upgrade to the rear other than that. So you maybe didn't need the rear calipers from Ford Racing (unless yours were shot like mine). The ones you have stock are the same thing.

I will say that your upgrade is worth $600. What I think you need to do is spring for some rear Cobra caliper brackets and you will be set. And you might as well get anti-moan brackets for the rear as well. Then they will work in tandem together and you will see the difference you were looking for in the first place. And I think I answered my own question at the top of the post.

Good luck and let us know the outcome - I think you need new rear brackets.

groundpounder

And another thing...

Since you've upgraded to the 13� brakes in the front, your 01GT spare will not work - the cobras came with a special sized spare tire to fit the larger brake rotors. They aren't easy to find and can will probably take a bite outta your wallet when you do.

There is another solution. Keep the one you have but remember that spare will not clear the front 13� brakes, but will clear the rear brakes just fine. So if you get a flat on the rear, you're good to go. If you get a flat in the front, just put your spare on the rear and move the rear to the front. Only works if you have the same sized wheels at each corner. If you run a staggered setup like me, then plan to spend the money for the 94-95 or 99+ cobra spare. Or become a member of AAA like me!!

kasper

If you are looking for a dramatic decrease in stopping distance, you are not going to get it. The car still has X amount of weight and the laws of physics still apply. Braking is a combination of both brakes and tires. Your stockers will stop the car and even lock it up if you slammed on it hard enough. The question is how many times can you brake like that before you start to experience brake fade? The larger diamater rotors will give you the ability to use the brakes much more often without experiencing brake fade as soon. The larger caliper and dual pistons allow you to apply more pressure to the rotor surface via the pads. Use Ceramic pads and you can further increase that time. Of course if you get any brake too hot you have to start looking at possibly boiling brake fluid (not good), possibly warping the rotors. If you just use the car for everday street driving, and the occasional track run, the upgrade is more than adequite. IMO it was money well spent.

sixfrost

Thanks for the detailed reply man! I also posted same question on stangnet: http://forums.stangnet.com/showthread.php?t=601663 Got some replies, but yours was the most informative.

After doing some research myself - i came to find out exactly what you described... You are absolutely right - we DO need a cobra bracket if we want to put a cobra rear rotor/caliper on a GT. I didnt get the bracket with my purchase - it was from a private seller... My local ford dealer has NO idea what part the bracket is, even after looking at the micro fiche.

So i left the stock GT rotor and put the 10th annyversary red caliper on it. But i think there is no difference in the caliper itself... if there is something different in its design, it didnt do much in terms of brake performance improvement. What i also did is order stock size GT x-drilled/slotted rotors fairly cheap. Just to match the overall appearance, nothing more.

I have to say I DID notice some minor improvments with the new front calipers and rotors, but not as drastic as i might have expected. The pedal still feels mushy. So I ordered some stainless lines for the front - i'll see how much difference that might make when i install them. So all together this "upgrade" cost me about $750 in parts + labor. For about $1000+ i guess i could have gotten a mid level brembo grand tourismo or Baer package. And probably have better brakes Oh well, what's done is done

BTW, Thanks for the tips on the spare... i do have a staggered set up like you - 255 (or 245 in the front) and 295 in the rear. That is for the summer. My winter rim/tire combos are same at all 4 corners, so i should be fine for the next few months Then i'll need to find a cobra spare.

sixfrost

Thanks kasper. I was kinda looking for the positive confirmation on the money subject. I guess it looks good and it works a bit better and, as you said, enough for the street. AS LONG as the price is right. However, with the extra money in parts (see my reply to groundpounder) i am starting to doubt it. but most of the parts are ON and there is no returning them.

groundpounder

kasper, I LOVE your sig. I've heard that saying before and I like it!

On to the physics lesson:

six, I think once you get it all on, you'll get the bang for the buck you're looking for. The SS lines WILL make a difference and change that spongy feeling.

kasper, you are on the money with the brake fade stuff and weight and laws of physics statement, but there is a little more to the story: Braking is a beautifully complicated mathematic study in non-adiabatic heat dissipation, braking surface area, the undulating pressure applied to that area (think single, dual, 4 and 6 piston setups) and the diameter and weight of the rotating mass doing the whoa business. Bigger is better for many reasons, and small increments in size, both on the rotor and pad, make a big non-linear difference to the positive. It's not exponential, but it's close, and there is a point of diminshing return.
Without getting into the math, here are the numbers that tell an interesting rest of the story, and why that brake upgrade is a good idea and why six will eventually feel he got a steal:

60-0 braking distances for a 2003 Cobra run in the 116-120 foot range at 3,400-3,600 lbs curb weight. 2001GT numbers for the same distance are about 150-160 feet. That is a dramatic difference, and once you finish your setup you will see and feel that. 2001 GT curb weight is 3,000-3,300 lbs to boot, so using those tricky laws of physics, you have better braking capacity with lighter curb weight, so your results may even be better than a Cobra!! Depends on some other factors, though, so temper your expectations.

But you will notice a difference, six, it just all has to be there.