Combined Braking System (CBS)

    American Honda
    Dec 09, 2013

It’s a system that has been in place since the early days of automobile design: simultaneous actuation of the front and rear brakes. However, in motorcycles this is not the case; from early models on to many of today’s most modern machines, the front and rear brakes continue to be actuated by separate controls. Except, of course, when it comes to Honda; for several decades now, Honda has introduced multiple systems that synchronize front- and rear-wheel braking.

A variety of Honda’s systems can be grouped together under the heading of Combined Braking System (CBS). Honda’s first street motorcycle with such a system was the 1983 GL1100 Gold Wing®. Called Unified Braking at the time, the system was derived from a “works” RCB1000 that won numerous world endurance race victories several years earlier.

Today, a number of Hondas offer sophisticated variations of CBS. For example, the Gold Wing 1800 uses dual full-floating 296mm front discs with three-piston calipers and a single ventilated 316mm rear disc with one three-piston caliper. A second master cylinder and a three-stage proportional control valve couple the three-piston calipers of the dual-front and single-rear brake discs. On the Gold Wing, using the front brake lever activates the outer two pistons of the front right-side caliper and the center piston of the front left-side caliper and—acting through the secondary master cylinder and an inline proportioning control valve—the outer two pistons of the rear caliper. The rear brake pedal operates the center piston of the rear brake caliper, the center piston of the front right-side brake caliper and the outer two pistons of the front left-side caliper. A delay valve sensitive to the rider’s pedal pressure helps smooth front-brake engagement. Other models, including the ST1300 and VFR1200F, offer variations of this system.

Specifically, the ST1300 also uses a second master cylinder and a proportional control valve (PCV) to couple the three-piston calipers of the dual-disc front and single-disc rear brakes. Application of the front brake lever activates the outer two pistons of the front calipers and the two outer pistons of the rear caliper. Rear pedal engagement activates the center piston of the rear brake caliper and the center pistons of the front calipers, and a delay valve slows initial front brake response to minimize front-end dive

Some Honda scooters also employ a CBS that only applies front braking force whenever the rear brake is operated. With the Silver Wing®, which is equipped with a three-piston front caliper and a twin-piston rear caliper, rider application of the front-brake lever activates the two outer pistons of the front caliper. Application of the rear-brake lever mounted on the left handlebar activates the dual pistons of the rear caliper and the center piston of the front caliper. When only the rear-brake lever is used, an inline delay valve helps smooth the application of the front-caliper piston.

The Metropolitan® scooter also incorporates a variation of this system. Rider application of the front brake lever activates the front drum brake in conventional fashion. Application of the rear brake lever, mounted on the left handlebar, activates the rear drum brake and the front brake together; when only the rear brake lever is used, a proportioning mechanism gradually applies the front brake.

Regardless of the model and the specifics of the CBS system, it’s easy to see that Honda designs variations of CBS to fit specific needs. These applications of CBS systems are a reflection of the many ways Honda maintains its longstanding commitment to rider safety, a commitment that will continue to lead the industry in the years to come.

Honda Powersports
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