Dual-Piston Front Brake Upgrade for the 1G Acura CL (Legend Calipers, Prelude Rotors)

This upgrade pairs dual-piston front calipers from a 1994 Acura Legend GS 3.2L with the larger front rotors from a 1996 Honda Prelude VTEC. Order the calipers as Raybestos loaded units, part numbers RC10627 and RC10628, so they arrive complete with pads, hardware, and mounting brackets and require no separate bracket sourcing. For the rotors, specify part number 39796374R and confirm the 11-3/32" (11.5") diameter version rather than the smaller 10" rotor that some applications used. This combination suits the 4-lug 2.3CL.

If you want painted calipers, finish that while the units are clean and on the bench. Degrease each caliper with brake cleaner, then mask off the piston and its rubber dust seal so no paint contacts the sealing surfaces. Suspending the calipers on wooden skewers makes it easy to coat them evenly and let them cure undisturbed. Be aware that the original installer later regretted painting: the finish is easily ruined by brake fluid during bleeding and by any subsequent rework, so leaving the castings bare is a reasonable choice.

Loosen the front lug nuts, raise the front of the vehicle, and support it securely on jack stands before removing any wheel. Take the front wheel off to expose the brake assembly. Do not attempt this job with the car resting on a jack alone.

Back out the caliper slide (glide) bolts and lift the factory caliper off its slides, then unbolt the mounting bracket from the knuckle. Leave the flexible brake hose connected for now and rest the caliper where it cannot hang from or strain the hose. Detach any clips that route the hose along the suspension so you gain slack to work; this also prepares you to renew the hose in a later step.

This is the step that most often goes wrong. The replacement calipers are stamped R and L, but they must be installed on the opposite corners from those markings: fit the R caliper on the left and the L caliper on the right, viewed from the driver's seat. Because the two pistons are different sizes, this orientation matters, and it is what keeps each bleeder screw at the top of the caliper. Installed as marked, the bleeders sit low, trap air, and make the system effectively impossible to bleed; getting it backwards on the first attempt cost the original installer a $200 shop charge to reverse. If you have already mounted them as marked, one reader's workaround is to loosen the lower slide bolt and pivot the caliper upward until the bleeder is the highest point before bleeding, the same motion used for a pad change.

Bolt the new mounting bracket to the knuckle. Apply a thin film of slide-pin grease so the pads move freely, seat the pads, and fit the caliper over them. Run the slide bolts back in and confirm every fastener is properly tightened before continuing.

With the hose already free, this is the ideal moment to install a fresh front brake line; aged rubber lines swell under pedal pressure and bleed off braking effort, so new lines restore a firmer pedal. Connect the new line to the caliper and secure it to each suspension anchor, leaving the upper end near the hard-line fitting. Crack the old line loose at the steel hard line and thread the new line on promptly to limit fluid loss. Keep the master-cylinder reservoir topped up throughout.

Bleed this corner before touching the other side. With the reservoir full, have a helper pump the pedal until firm and hold it down; open the bleeder to release fluid and trapped air, then close it before the pedal is released. Repeat until the fluid runs clear and free of bubbles, refilling the reservoir constantly so it never runs dry, because drawing air into the system forces a full re-bleed. Working alone, a gravity bleed is an alternative. As a final check, start the engine and confirm the pedal holds the same firmness with the booster active as it did with the engine off.

Repeat the entire procedure on the remaining front corner. When both sides are complete, refit the wheels, lower the car, and test-drive at very low speed in a safe area to confirm the brakes bite correctly and the pedal is solid before driving normally.