Rear Disc Brakes Conversion

 

Covers:

First generation GTs were the only first generation Probe to come standard with rear disc brakes. In 1990, they became optional on LXs. If you own an LX and you didn't get that option, or you own a GL, your Probe has rear drum brakes. Those with rear drum brakes aren't forced to deal with the 'satisfactory' performance they offer. Converting your drums to discs is a relatively easy procedure, which I did myself on my '89 LX.

My '89 LX is loaded with every option, but since rear disc brakes weren't available on LXs for that model year, I was very disappointed. I wanted to upgrade my brake system, but they don't offer cross-drilled drums... besides, drums don't look good when they show behind a nice set of wheels. I looked into converting my drums to disc brakes and found that it wouldn't be hard at all. That was always a consideration until it became a reality when I decided to part out my '89 GT. Anyone with rear drums can go to local savage yards or put in a part request through the internet to get the parts they need. See the Web Links page for sites that offer used parts.

Parts Required

Tools Required

First, I highly recommend using NEW discs instead of used ones. If you get new ones, you'll also need two rear wheel bearings, two bearing retaining rings, two grease caps, and ten lug bolts. You can get these at your local Napa. Go to a local shop and have the bearings pressed into the rotors... don't try this yourself unless you have the equipment to do the job. Snap the retaining clips in and tap in the grease caps down. Now, to install the new studs in the rotor... stand a tire up, hold the rotor behind it where the wheel should mount to it. Put the five studs through the rotor and screw the lug nuts onto them. Once they're hand tightened, use a torque wrench to tighten the nuts to a good 80-85 ft/lbs. This will seat the studs into the rotor. They may not slide completely home... it'll take some use for that to happen. Remove the rotor and do the same for the other one. Once both rotors are finished, you're all set to begin.

Drum Disassembly

  1. Block the front wheels and release the parking brake. Raise and safely support the rear of the car. Remove the wheel.
  2. With the parking brake off, remove the two 12mm parking brake cable mounting bolts on either side. Remove the parking brake cable from the drum and push out of the way.
  3. Pop off the hub's grease cap. Using a punch or screwdriver, tap out the stake in the hub nut. Use the 1-1/4" socket to remove the hub nut. Slide the drum off the spindle.
  4. Use a 10mm wrench to loosen the rubber brake line at the end where the hose meets the Probe's body (you don't need this hose). Remove the two retaining clips holding the hose in place.
  5. Remove the four 14mm mounting bolts holding the rest of the drum assemble to the spindle. Remove the assembly as a whole.
  6. Remove the 17mm nut at the end of the Lateral Link to Spindle bolt. Remove the entire bolt. This may be a bit difficult if the spindle rusted itself onto the bolt. Don't hammer it out, since hammering can damage the threads. Use WD40 generously. If necessary, replace the nut partially on and tap the nut with a hammer to protect the treads.
  7. Remove the 17mm Trailing Arm to Spindle bolt from behind the spindle. Remove the two 17mm Spindle to Strut bolts and remove the spindle.

Disc Reassembly

Make sure you differentiate between the left and the right parts.

  1. Holding the spindle in place, install the two 17mm Spindle to Strut bolts and tighten the nuts to 69-86 ft/lbs.
  2. Install the 21mm Lateral Link to Spindle bolt and tighten the 17mm nut to 64-86 ft/lbs.
  3. Install the 21mm Trailing Arm to Spindle bolt and tighten to 64-86 ft/lbs.
  4. Install the dust shield and install the four hex bolts.
  5. Slide the rotor onto the spindle. Install a new hub nut and tighten to 73-131 ft/lbs. Stake the hub nut using a punch or screwdriver. Replace the grease cap.
  6. Install the caliper onto the spindle and tighten the two 14mm mounting bolts to 33-49 ft/lbs.
  7. Install the brake pads into the caliper, swing the caliper shut, and tighten the 12mm bolt to 12-17 ft/lbs.
  8. Place a new copper washer onto the brake hose banjo bolt and connect the brake hose to the caliper, tightening the banjo bolt to 16-20 ft/lbs. Place the hose onto the two holding brackets and install the two retaining clips. Connect the brake hose to the brake line and tighten.

Emergency Brake Cable Removal

  1. From under the car, remove the two 12mm mounting bolts from each end of the cable. Remove the other two 10mm bolts on each cable along the length of the cable, mounting it to the chassis. Remove the 10mm bolt holding the cable mounting bracket in place, just behind the return spring (should be directly under the emergency brake handle now).
  2. Remove the retaining clip on each cable end and slide the two cables out of their holders, just behind the return spring.
  3. Disconnect the return spring from the chassis mount.
  4. From inside the car, remove the Phillip's screw from the right side of the emergency brake handle and remove the three plastic cover parts.
  5. Remove the emergency brake adjustment nut's metal clip. Using a 10mm socket, remove the adjustment nut and separate the emergency brake cable from the handle.
  6. Use a long screwdriver to push the rubber seal around the emergency brake cable where it meets the chassis, out towards the ground.
  7. From under the car, remove the old emergency brake cable.

Emergency Brake Cable Installation

  1. From under the car, fit the replacement emergency brake cable into place and push the single cable end through the hole where it will lead to the emergency brake cable. Push the seal into place.
  2. Connect the spring to the chassis mount.
  3. Slide the two cables into their holders, just behind the return spring, and replace both retaining clips. Hold the bracket in place and install the 10mm bolt.
  4. Install the other four 10mm mounting bolts along the cables. Install the two 12mm mounting bolts on either side of the cable ends.
  5. Fit the cable tips into the hooks on the calipers. Slide each cable into place on their mounting bracket just before the end of the cable. Tighten the 14mm nuts.
  6. From inside the car, slide the emergency brake cable into the handle and tighten the adjusting nut. The emergency brake should click about 10 times when applying. Replace the adjustment nut's metal clip.
  7. Replace the three plastic handle cover pieces and install the Phillip's screw.
  8. Replace the wheel and tighten the lug nuts to 65-87 ft/lbs. If you bought new rotors and installed new lug bolts, tighten the lug nuts to 85 ft/lbs.
  9. Lower the car. You're done. The brake system may take a few days to brake in, so take it easy on it.

NOTE: If you installed new rotors with new lug bolts, make sure you periodically torque the studs down to ensure proper seating.


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