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Disc vs. Drums

P92313 Image Large
Christian Hazel
| Brand Manager, Four Wheeler
Posted May 1, 2000
Photographers: Cole Quinnell

Let the Battle of the Binders Begin!

Step By Step

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  • Dziezyk begins by draining the differential fluid and removing the axleshafts. The hub and drum assembly is then removed.

  • With the bearings removed, the hub is separated from the drum by knocking out the wheel studs with a brass drift and hammer. Once the studs are out the hub lifts right off.

  • Using the old studs, the new rotor is pressed onto the hub using a hydraulic press. The bearings are cleaned, packed, and reinstalled with new seals.

  • The four bolts holding the backing plate to the axle are removed and the entire assembly is tossed. The emergency brake pedal, cables, and low-hanging brackets are also scrapped. More on that later.

  • The TSM caliper brackets lined up beautifully. The two-piece design allows the use of all four bolts on the axlehousing for increased strength and stability.

  • The hub and rotor assembly is installed and torqued to spec using a 29/16-inch spindle nut socket. The caliper is bolted to the bracket with the bleeder pointing up.

  • Since the calipers move as the brakes wear, flexible line should be used from the calipers to the axle. Dziezyk welded the supplied hose bracket to the housing and cleanly bent new hard lines along the axletube.

  • The stock proportioning valve containing the brake warning light, hold-off valve, and check valve stopped functioning properly some time ago. It was unceremoniously cut off and thrown on the trash heap.

  • The TSM-supplied Wilwood adjustable proportioning valve allows for up to a 57-percent pressure reduction. It was plumbed into the rear brake line and mounted on the fenderwell for easy access.

  • Dziezyk fabricated a sano mounting bracket for the Jamar Park-Lok. It was plumbed into the rear brake line between the master cylinder and proportioning valve.

  • The Park-Lok isn’t intended for use as an emergency brake. To operate it, depress the brake pedal, push the knob, and release the brake. The unit disengages itself when line pressure drops or when the brake pedal is depressed.

  • Dziezyk reinstalled the axleshafts, filled the differential fluid, and bled the brakes. Even with 12-inch rotors, we have room to run 15-inch wheels if we want to.

We’ve all heard the hype. Disc brakes don’t get clogged with mud and grunge off road, they cool faster, are less susceptible to fade, and are easy to rebuild. But will they stop your vehicle faster than drum brakes? To find out we took our ’85 Ramcharger to our secret desert test facility for some 60-zero mph floggings. Using a G-Tech performance meter by Tesla Electronics, we first tested the ¾-ton 12.82-inch disc/12x3-inch drum combo. Then we swapped the rear drums to discs, junked the factory proportioning valve in favor of an adjustable unit, and tested the vehicle again.

To convert the Dodge Dana 60 rear to disc brakes, we called TSM. In addition to offering kits to convert many vehicles from drum to disc brakes, TSM offers just about any parts you may need when performing a drum to disc conversion. For our application, we ordered a disc brake conversion kit that included brackets, Grade 8 hardware, and beefy 12-inch ’71-’87 Chevy ¾-ton four-wheel-drive front rotors.

We also had TSM ship us an adjustable proportioning valve, flexible stainless brake hoses, and calipers. Rather than opting for parking-brake-equipped El Dorado rear calipers, we chose ’71-’77 Chevy truck front calipers. They’re ultra-reliable units that are easy to replace and arrived loaded with pads. Besides, we desperately wanted to get rid of our low-hanging e-brake cables and brackets. We found a hydraulic brake lock in the J.C. Whitney catalog that seemed to be just the ticket for holding the vehicle in place on steep hills or while winching. For under $25, it was worth a shot.

We knew we’d need some custom bracketry to mount our hydraulic brake lock and would also need some custom hard line work since we were removing the factory proportioning valve containing the warning light, hold-off valve, and check valve and adding a Wilwood adjustable proportioning valve from TSM. With parts in hand, we went to M.I.T. Drivetrain Specialists where Rick Dziezyk performed a very clean and professional installation, despite the fact that the stock lines crumbled at the slightest touch.