1955 Cadillac Coupe DeVille Disc Brake Conversion – Stop, Swap, And Roll

Unlike Chevys and Fords of the era, higher-end ’50s domestic marques such as Cadillac aren’t as “upgrade friendly” when it comes to adapting modern equipment – namely complete disc brake systems.

Thanks to the complex (and now antiquated) Bendix HydroVac system, trying to incorporate a newer vacuum-based setup is rather difficult – it’s not impossible, rather, just not as easy as, say, Tri-Five Chevys, where you’ve got numerous companies offering kits in all shapes and sizes. More so, the difficulty stems around the master cylinder and its hydraulic assist, as you’d need to go to somewhat great lengths, either configuring an under-dash pedal/master cylinder setup or manage to squeeze a booster-equipped master into the very tight framerail confines, in order to convert to a dual-circuit system.

That said, better stopping disc brakes are still an option — a very viable one.

Classic Performance Products (CPP) offers an 11-inch rotor disc brake kit for ’50-’55 Cadillacs (as well as ’57-’60 and ’61-’68) that works with the stock spindle uprights. A rather simple swap, the procedure requires basic handtools and, with the use of supplied spacers, the kit works with most stock 15-inch wheels.

As previously mentioned, you have to work “with” the factory HydroVac system, so before we had CPP start tearing the front drums off this ’55 Coupe de Ville, we not only made sure the power assist unit was in good, working order (if not, a rebuild is necessary, and kits are available online), but went ahead and rebuilt the stock master cylinder as well as the rear drum brakes (the latter of which was done to ensure a decent front-rear brake bias). Plus, retaining single-circuit system, you want to make absolutely sure that every single component is in top working order, replacing any/everything necessary in the process.

Follow along as CPP brings this stately cruiser’s braking system closer to modern standards — greatly improving its stopping power in the process.

As with every drum-to-disc swap job, first order of business: lose the drums. With the vehicle supported safely, remove the wheels and disassemble the stock drum brakes…

…down to the spindles, as such, leaving the steering arms attached to the tie rod. Thoroughly clean and inspect everything, especially the spindle shafts, checking for any excess damage/wear (replace if necessary).

The caliper brackets point rearward, with the bend facing out toward the fender opening, as shown

A spacer is provided to compensate for the lower rear factory steering stop bolt; it’s used with the longer of the four caliper mounting bolts, the bolt head now acting as the stop.

Securely tighten all caliper bracket hardware; inspect and replace (if necessary) any vital steering/suspension components, such as tie-rod ends.

Factory left-side lug studs are left-hand thread—the new CPP aluminum hubs are supplied with 1/2-inch right-hand studs; you’ll need to acquire new lug nuts, which CPP offers as well. (Note: factory left-hand thread hardware is typically marked to indicate such; the Caddy lug nuts feature a machined groove on the face.)

While on the topic of wheel studs, they will need to be installed into the hubs. Add thread-locker to the last five threads; torque the studs down to 90 lb-ft (shown here using the rotors placed in a vise equipped soft jaws to help with leverage).

Hand-pack both inner and outer sealed wheel bearings with high-temp disc brake grease; add grease to pre-installed bearing races as well. Install rear seal with appropriate driver (available at Harbor Freight) or a similar, non-marring device.

Again with the left-handed hardware: this time, the axle nut, which must be retained with the stock left-side spindle (relief cuts on the lower corners indicate its thread orientation).

Set bearing preload, seating the bearings first by slightly tightening spindle nut (no more than 12 lb-ft) while spinning the hub; once tight (but not enough to stop hub from rotating), back nut off to closest cotter pin hole and secure. Install dust cap when finished.

CPP’s slotted/cross-drilled rotors are directional; ensure you install correctly based on the arrow indicating direction.

When installing the calipers make sure that 1) the inner bushings are pressed flush with the caliper ear (to clear the rotor) and 2) the rubber O-rings are “not” pushed out when tightening the caliper bolts.

Since the stock drum brake line fitting is the larger 7/16 thread size (rather than a more modern 3/8 fitting), CPP provides the adequate stainless flex line (but double-check to ensure regardless). Secure lines with the supplied clip once fittings are tightened.

On the caliper side of the flex line, install using the one copper compression fitting on each side of the banjo fitting, as shown.

And with that, the front brake install is complete, but the entire brake job itself is not done quite yet.

As mentioned, to avoid the new front disc brakes from being the dominant “force,” the rear drums were completely rebuilt, including new drums themselves.

As for the stock master cylinder, it was removed and tore down for a quick rebuild, which also included a fresh coat of Eastwood Master Cylinder paint.

Prior to installing the fresh internals, the cylinder bore was lightly chased with a hone.

And prior to going back in the vehicle, it was adequately bench bled.

The one somewhat major component that wasn’t addressed as such: the factory HydroVac power assist unit, as it remained in fairly good working order. If need be, rebuild kits are available online.

When it comes to bleeding a HydroVac-assisted system, however, it’s highly recommended that you do so using the “pressurized” method versus vacuum or even manual (via brake pedal) processes. This is easily done with a small syringe pushing fluid through the system from the reservoir (using an adapted cap plug, as shown, with access for the syringe).

Finally, once the system is pressurized and free of air, not to mention you’ve got sufficient pedal pressure, install the necessary amount of wheel spacers in order for the Cadillac’s stock wheels to avoid contacting the brake calipers. In a safe environment, road test and break in the new front brake pads.