Tech Corner: Wilwood’s Mopar B-Body Disc Brake Swap

1968-1970 Mopar B-bodies might be the greatest vehicles ever, and don’t argue with me. They’ve played an incredible role in the history of high-performance vehicles due to their excellent styling and legendary power under the hood. However, stopping these monsters can be a serious issue—especially by today’s standards. Now I know, there are lots of guys who can drive the hell out of a car with drum brakes all around—and I give them props. But if, like me, you don’t care for drum brakes and if, like me, you jump at the chance to swap in some disc brakes up front, then read on. Today’s Tech Corner is tackling a B-body disc brake swap, and we’re turning to some of the best in the biz for a little help: Wilwood.

Why Wilwood?

Why choose Wilwood for your Mopar B-body disc brake swap? Because, while the aftermarket is jam-packed with great brake kits for these vehicles, I personally feel the performance you get from a Wilwood product is well worth the investment. Plus, the company has an excellent reputation, cultivated since it opened its doors over 40 years ago. And did we mention the great selection?

Wilwood offers a whole line of disc brakes for Mopar B-bodies, tailored to each driver’s performance tastes. Want to maintain a more traditional wheel size? Wilwood has kits that fit 15-winch wheels. After higher piston counts and larger rotors? Wilwood’s got that covered, too. And while most people who own a classic Mopar B-body will want to convert their front brakes, the company offers kits for the rear as well.

And for you non-Mopar fans who happen to still be reading—Wilwood offers disc brake conversion kits for all popular hot rods and a similar, if not more extensive, selection.

Prepping for a B-Body Disc Brake Swap

Converting your Mopar B-body to disc brakes is going to deliver great results and—bonus—the installation isn’t all that difficult. Additionally, if you’re tackling both the front and the rear, the process will be very similar with the exceptions of a parking brake setup for the rear brakes.

So, you got your hands on a Wilwood brake conversion kit for your Chrysler. First step? Crack open those directions and read them. That might make this article seem redundant, but trust me, reading the manufacturer’s instructions will better acclimate you with the process—not to mention all the nuts and bolts. Speaking of which, make sure everything that should be included is there. Missing parts happen. Would you rather find out now or later?

Once you know everything’s there…

Familiarize yourself with it. The brake rotors and calipers will likely need little introduction, but you should also find a hub that is separate from the rotor and a mounting bracket. This bracket is going to be mounted in place of the factory drum backing plate. On front brakes, it will be used to mount the caliper alone, while on the rear it will host the caliper and the parking brake assembly.

If you’ve purchased a front brake conversion kit, you won’t find too much more besides the mentioned parts and necessary hardware. Rear disc brake kits will be a little different. Along with the caliper and brake pads, the parking brake assembly will be included as well. Because of this, the bracketry will be a bit different, as it will mount the parking brake assembly, caliper, and parking brake cable. The rotors will also be different, as they mount to the hub portion of the existing axle. Because of this, the rotor will be designed to fit—meaning you won’t need to preassemble it to a hub like you would front disc brakes.

Pro Tip: With front brakes, consider setting up the rotor and hub assembly now, as it will make the installation process on the vehicle that much shorter.

Tearing Down Your Mopar

Obviously, you can’t begin your B-body disc brake swap until you tear down your vehicle. Regardless of whether you’re tackling the front or rear, you’ll need to get the wheels and brake assembly off of the car. This means getting right down to the axle or the spindle.

If you’ve been performing routine brake repairs, this step should be easy. Although, the backing plate may require some extra elbow grease if it’s never been removed before. On 1968-1970 Mopar B-bodies, this plate is held in place by four bolts. Use a wire brush and some heat to help remove them, and then you can pop that bad boy right off.

On the rear, you will have the additional step of removing the axles so that you can fit the disc brake assembly to the differential assembly. This means you will need to remove the rear differential cover, as well. And of course, this means stocking up on seals and fluids. I also recommend grabbing a new wheel bearing and seals, which you can install after this step.

Pro Tip: Once the car is naked of its brakes, take the time and assess the condition of the brake lines. Even if they’re in good shape, it’s not a bad idea to replace them with something new for added peace of mind. Plus, now’s the time since an open wheel well makes life easier.

Assembling Your New Wilwood Disc Brakes

After tearing down the vehicle and addressing any issues, you can move on to the actual meat and potatoes of a B-body disc brake swap—installing your nice new purchase.

If you haven’t already assembled the hub and rotor kit of your front brakes, now’s the time because the rest of the process is going to rip past you.

For Wilwood front brakes, you’ll notice that the studs are separate from the hub and you will need to install them. These studs are torqued to the hub, but they use a normal thread pattern rather than reverse. Because of this, make sure you use red thread-locker so they stay secured in place. Otherwise, during the point where you reinstall the lug nuts and the wheel, they can back out—which is tremendously annoying as you will need to tear the whole thing back apart to apply it.

Speaking of wheel studs and thread pattern, your Mopar will no longer have reverse thread on the driver side with front disc brakes from Wilwood. Consider making a swap for the rear studs on the driver side. Because, if you’re anything like me, getting into the rhythm of tightening and loosening with three sets of one thread pattern and one wheel with another, is difficult. Confusion can set in and lead to disaster.

Installing Disc Brakes on Your B-Body

With that in mind, let’s move on to actually getting those Wilwood brakes on the car and completing the B-body disc brake swap. The first thing will be to bolt the mounting bracket in place of the factory backing plate. This is where front and rear brake installation is going to separate.

For the front, orient the caliper bracket so the caliper is placed to the rear of the wheel. Once the caliper bracket is installed, you can move to placing the rotor and hub assembly onto the spindle. With the wheel bearing in place on the assembly, place the retaining washer on the bearing and then the nut, the cotter pin to keep the nut in place, and then the supplied spindle cover. After that, you simply place the brake pads into the caliper, which can then be bolted in place.

On the rear, you will want to orient the bracket so the caliper mounts to the rear of the wheel, just as you would the front. Once the bracket is installed, move to the parking brake assembly. Much like modern vehicles with rear disc brakes, the parking brake is going to be a cable-operated drum brake system which mounts inside the rotor. The cable will be retained on the same bracket which mounts the caliper. Installing the cable before inserting the axle will make life easier.

With the parking brake assembly installed you can move to installing the axle. Then, after the axle is in place, install the rotor and caliper.

What about the master cylinder?

Okay, so a major concern with any disc brake conversion is the master cylinder. That’s because master cylinders intended to be used with drums are different than those for discs. With drums, an equal amount of fluid will be used for front and rear braking systems. But, with discs, the front will have a larger reservoir because more braking power is needed.

Luckily, Wilwood makes it possible to use the factory drum brake master cylinder. However, for peace of mind, I recommend swapping to a dedicated master cylinder meant for discs. Since ‘69 and earlier B-bodies didn’t come with disc brakes, I personally opted for a master cylinder out of a 70 B-body that came equipped with disc brakes from the factory. It bolted right up, no issues. It’s also important to remember that these kits can be used with manual or power-boosted master cylinders, too.

If you choose to install a new master cylinder, you can’t afford to skip bench-bleeding the unit. This is done with a bench vise and a brass rod. Secure the master cylinder in a vice, fill it with fluid, and then compress the piston to bleed out any present air bubbles before the unit is installed to the Mopar.

Plum, Bleed, Enjoy

Once the master cylinder is in place you just need to plumb everything up and bleed the brake system. With Wilwood calipers, there are two valves for this in order to provide versatile mounting solutions. You don’t need to bleed both, just the one positioned on the bottom of the caliper.

And that’s it. Really, that’s all there is to a B-body disc brake swap.

With just an hour or two worth of work, you can bring that big bad Mopar to a stop like nuts. And for those of you who don’t own a Mopar, but stuck around anyway, most classic applications will follow a very similar process.