Harley Dual Disc Caliper Rebuild (1977-1983)
Article by Vintage Vinny
Rebuilding brake calipers is usually less expensive than replacing them, plus it keeps the bike more original. This article covers rebuilding Harley dual disc brake calipers.
First seen on the 1977 XLCR Cafe Racer and FXS Low Rider, Harley dual disc brakes were standard equipment on 1979 through 1983 Sportsters, 1980 through 1983 FLHT models, and several FX models (Wide Glide, Fat Bob, and Low Rider).
Looking through old Harley parts books, it appears that 1977 through 1983 Harley dual calipers are interchangeable, but the right caliper only fits the right side, and the left caliper only fits the left side. Internal parts are the same for either one.
Rebuild or Replace Calipers?
Most, but not all, motorcycle brake calipers can be rebuilt. There are three reasons why calipers would not be rebuildable:
The caliper housing is cracked. This could happen if the bike was in an accident, or through damage.
Rebuild kits are not available. This is never a problem with classic Harley motorcycles. Rebuild kits are available from dozens of aftermarket suppliers.
The piston bores are too badly damaged. A badly pitted piston bore may cause a piston to stick, but corrosion is usually not an issue with aluminum-bodied calipers.
If you have a slight amount of pitting on the piston bore surface, it can often be sanded or honed out, but if there are any deep nicks or grooves, it's best to replace the caliper.
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After sitting idle for several years, both front calipers on this 1981 Sportster had frozen up. There were two options; rebuild them or replace them.
After checking to see what replacements would cost, the decision was made to rebuild the old ones.
NOTE: If only one caliper is frozen or leaking brake fluid, it's advisable to rebuild or replace both sides. If you find that only one is rebuildable, it's OK to rebuild that one and replace the other one.
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What's Involved
A brake caliper rebuild will involve removing, disassembling, cleaning, and then reassembling the caliper with new seals. On older bikes that have sat for awhile, you may have trouble removing a stuck piston.
Parts Needed
If needed, caliper seal kits can be purchased online.
Shop: Harley Dual Disc Seal Kit
The original Harley caliper rebuild kits had part numbers 44151-77 and 44153-77. Each caliper requires one seal and one dust boot. Aftermarket kits usually service one caliper only.
If the brake pads are worn or have brake fluid on them, replace them.
Shop: Harley Caliper Rebuild Kit
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Other Parts Needed
You won't know what else you'll need until the calipers are off and disassembled. On a 40+ year-old caliper, you'll often need to replace other parts, such as a caliper piston, caliper pins, or a stripped bleeder screw.
Tools and Supplies Needed
Tools needed include a 3/8" drive socket set, open and closed end wrenches, and Allen keys or sockets.
Flare nut wrenches, also called line wrenches, are designed to remove steel brake lines and other hydraulic fittings without damaging the nut. A standard wrench will work, but you stand a chance of stripping the fitting.
You'll also need a can or two of brake parts cleaner, some DOT 5 brake fluid, and shop towels or rags.
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Before Removing The Calipers
Spray the mounting bolts, bleeder screws, and brake line fittings with WD-40 or similar penetrant. The longer you allow the penetrant to soak, the better it will work (overnight is best).
It's usually easier to loosen the bleeder valves while the caliper is still mounted to the fork. Once loosened, tighten them up by hand so they don't leak while taking the caliper off.
Some brake fluid may come out of the brake hoses after they're disconnected from the calipers. Have a piece of cardboard underneath to catch any overflow and brake fluid.
Remove the mounting bolts, washers, and locknuts (two each per side).
Once the center caliper bolt is loosened, the outer and inner halves should easily separate.
Spray/clean all parts with brake cleaner.
Remove all dirt, rust, abrasives and old brake fluid. Dry with compressed air.
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Removing a Frozen Caliper Piston
Even with 100 psi of compressed air this piston would not budge!
Read: Remove Stuck Brake Piston
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Removing a Stuck Bleeder Screw
On one of the calipers, the bleeder screw head was stripped. To remove, the caliper was placed in a vice between two soft jaw pads. Once securely in place, penetrating fluid was sprayed on and left to soak for a few minutes.
Bleeder screw removal was now easy with a 1/4" drive 6-point deep socket.
Above: old and new bleeder screw.
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Brake Caliper Inspection
Once the piston was unstuck, all metal parts were cleaned with brake parts cleaner and shop towels, then blow-dried with compressed air.
After cleaning, look inside the bore for any nicks or grooves. If you can, run a fingernail inside the bore.
With a flat-blade screwdriver, lightly scrape out any corrosion out of the grooves where the caliper O-ring will seat.
The caliper is now ready for reassembly.
Before installing, dip the new seal, new piston boot, and piston in brake fluid (DOT 5).
The caliper pins had a little corrosion on them, and were sanded smooth with Emory cloth.
If your caliper pins need replacement, their part number is 44162-77.
Left and right calipers have identical brake pads, assembly plates, and pins.
Assembly procedure is: inner plate, brake pad inner, brake pad outer, and then outer plate. The caliper bolt (with flat washer) is torqued to 60 to 65 foot/pounds.
Before re-installing, check old brake pads for wear or damage. If they've been contaminated by leaking fork oil, or had brake fluid on them, replace them.
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Notes and Misc
It's not necessary to remove the front wheel to remove the calipers.
Take pictures during the removal process.
If your old calipers cannot be rebuilt, you can buy replacement calipers here.
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Related Articles:
Remove Stuck Brake Piston
Sportster History 1980-1985
Harley-Davidson FX Models
Harley-Davidson Cafe Racer
