69 FB Brake conversion and Wheel Q's

FallujahMedic said:

Ok, this is a 2 part question. I've searched, but still havent found the answers I'm looking for. These questions are in ref to my '69 Fastback, manual front/rear drums.

a. I've seen many a kit for disc brake conversions, but which is best? I like the price of "Mustang Steve's" front end conversion and Currie Ent. kit for the rear, but I'm concerned about having a cobbled together brake sys. I'd love to have fronts and rears by the same folks if possible. Any Ideas? If it helps, my front end has been torn down into many pieces. Could I buy a complete front '70 disc brake kit and replace it?

b. I've seen Dodgestang's wheel fitment guide, but wonder what else is open to me as far as rear wheel/tire combos?
I'd like to put the widest possible combo in the back without rubbing or sticking past the lip (running reverse eye leafs).

Thanks

Click to expand...

Answer a.: Insofar as having a cobbled together brake system, anything you use will be slightly cobbled together because there was never a '69 Mustang built with 4 wheel disks that was factory balanced for that use. However, that is precisely the reason that any good 4 wheel disk setup uses an adjustable proportioning valve to balance the front to rear braking ratios. Given that fact, I wouldn't be too concerned with a matched system.
IMO, Mustang Steve's Cobra front disk conversion kit offers far more in the way of bang for the buck than any other system. The only "downside" is that you'll have to use at least a 17" wheel, which is no downside at all in my book, but it may be in yours.
A couple of things you need to understand are as follows: First, somewhere between 65% and 75% of your braking comes from the front. The most important factors in terms of braking power are the size of the rotor and the number of pistons in each caliper clamping that rotor. The Cobra rotors are 13" units, which are as big as Baer's most expensive kits if I'm not mistaken, and Cobra's also have 4 piston calipers. The bottom line is that you would probably have to spend nearly twice as much as Mustang Steve's kit to receive any better performance, and even at that it would be only marginally better (diminishing returns).
Second, and inextricably intertwined with what I said above, is that since most of the braking power comes from your front brakes, your rear brakes are not AS crucial to begin with. That is why the manufacturers used disks on the front and drums on the back for a long time. A much smaller rear brake system will suffice, but the balance you are speaking of could be achieved by using an aftermarket Baer system or the like on the rear. As previously alluded to, though, it won't make a huge difference in your overall braking performance, especially in comparison with the front.

Answer b.: Dodgestang's wheel fitment guide does show you what others have found as the biggest wheel/tire fitments available. I'm not sure as a '65 owner how much '69 owners have pushed the limits, but look at all of the info provided on that chart. Rolled fenderlips will give you approximately 1" to 1.5" in additional clearance. The most important thing is getting a wheel with the maximum backspacing that will work. For whatever reason, the maximum backspacing seems to vary on these old cars.
Other options are relocating the rear leaf springs to give you additional room along with mini-tubbing the rear wheelwells for additional clearance or changing suspension systems to get away from the inherent limitations of our leaf sprung vehicles. This post is already too da** long, so I won't go into details about those mods, nor have I done them myself.

I hope all of this helps, and keep us informed on your decision.