Muscle cars might have been quick in the 0-60 department, but the 60-0 department was a whole other story. What was considered pretty cutting edge on the best performance muscle cars in the 1960s (Shelby, Z/28, Boss, etc.) would be bottom of the barrel today. In stock form, most can't even touch the numbers of a modern generic four-door sedan with all-season tires. Even worse, the four-wheel drums in most run-of-the-mill muscle cars will get you in serious trouble in an emergency braking situation surrounded by newer cars. Of course, none of them would be considered acceptable for any serious hard driving with lots of repeated heavy braking, especially with higher-powered engines or stickier tires.
For a dose of reality, we took our stone-stock, four-wheel manual drum-equipped '68 Mustang shod with 17x8 and 17x9.5 Vintage Wheel Works V50 wheels and Nitto NT05 tires out for a few 60-0 deceleration tests. Our very best result was 210.4 feet. Read that number again slower. That's over two thirds of a football field. Most modern 1-ton pickups can stop faster than that, and every single car built in the last 20-plus years can as well. If the tires on your vintage car are harder, or your drums haven't been checked lately, your stopping distance could be even worse.
So how much brake do you need? For bare minimum safety in today's traffic, all of which can stop much faster than any 1970s or older car, we'd recommend at least 11-inch discs up front with modern calipers. Like to drive fast or through the curves? It's time to look at better calipers and pads and get some discs on the rear too. Really enjoy pushing your car or getting it out on the autocross or track? Now it's time for some 13- or 14-inch rotors and big calipers, at least on the front.
For decades there were no real upgrade options available that didn't involve custom machining to adapt stock late-model or race car parts. Those days are long gone and most popular muscle cars have brake upgrade kits ready to purchase. But there's more than bolting on a set of calipers and rotors to creating a truly effective braking system; it takes a complete rethinking of the whole system to create something that works like a new OEM system. Thankfully, companies like Wilwood have stepped up and created exactly that: full proper disc conversions with just a few part numbers.
We've got a rearend swap planned for our pony, so for now we're just starting with the front brake conversion with a new master cylinder to get it safe. Slight spoiler alert: You're going to be blown away by how much improvement it netted us. We're not quite hanging with brand-new Mustangs yet, but it's close, and we will be soon!
Included in the SL6 Mustang front brake conversion kit is Wilwood's forged narrow Superlite 6R (FNSL6R) caliper. This is their newest version in the Superlite caliper series that adds versatile radial mounting to provide two planes of adjustment for accurate alignment over the disc. The kit is actually quite simple, and the swap can easily be done in a day at home.
Not only will your wheel choice determine the diameter of rotor usable on your swap, it may also determine the caliper that will be required for adequate clearance. Wilwood always recommends using the proper sizing chart (this one is for our 13-inch, six-piston kit) to check your wheels before ordering.
Those fitment diagrams are simple, but there's nothing low-tech at Wilwood. While the front 17x8 Vintage Wheel Works V50s were off, Wilwood scanned them to create this CAD image to show exactly how much space was available. As you can see, there is tons of clearance for huge calipers.
This is where we are starting, the same stock manual drum package that the vast majority of Mustangs were equipped with from the factory. Not only do drums stop slower and fade much more quickly after repeated hard use, they can become completely unusable if you happen to hit a big enough puddle in the rain, sometimes only on one side. Ask us how we know.
To give them a fair shake for testing, we made sure our drums were in good shape prior to testing. The shoes had plenty of good material and were in proper adjustment, and the wheel cylinders were new. Removing the drum is as simple as four bolts on the spindle. The hydraulic hose was left connected temporarily to prevent a mess.
The drums had never been removed from the spindle, but we thankfully had little rust to deal with. A wire brush was used to clean up the scale and make sure the bearing surface was free of corrosion.
The caliper mounting bracket is designed so that it can be used on either Ford disc or drum brake spindles, so both bolt patterns are included. Our Mustang's spindles are drum, so the four appropriate holes were lined up and the button head Allen bolts were installed.