BENDIX COMMERCIAL VEHICLE SYSTEMS has an air disc brake product ready for the North American market. The new brake system was shown at the Mid-America Trucking Show.

The new system is known as the ADB 225 and will be available in the fourth quarter 2002. In a major change from air disc brakes already in use in Europe, the ADB 225 system weighs 30 pounds less per wheel than its European counterpart. The weight reduction comes from eliminating component mass associated with compounding, a European brake standard that uses separate systems to apply the service brakes and the emergency brake. Compounding is not required in North America, allowing Bendix to reduce total system weight.

Air disc brakes have improved dramatically from earlier versions where weight, cost, and system balance issues made them less than attractive to fleets, says Ron Bailey, Bendix technical sales manager. Most important, however, is improved performance. Compared to conventional S-cam drum brakes, air disc brakes offer a 26% shorter stopping distance and exceed the federal standards for stopping a 10-wheel tractor by 39%, he says.

Tests of the air disc brake system were performed in October 2001 on a stretch of I-70 just below the Eisenhower Tunnel west of Denver. The test course used eight miles of 7% downgrade. In tests of brake fade during prolonged used, the disc brakes required only 4% additional air pressure to maintain braking performance as brake temperature rose compared to 25% more pressure required for drum brakes. In a test simulating freeway off-ramp braking, the ADB 225 system required 29 to 40 psi for brake application compared to 60 to 70 psi for drum brakes. In a downhill panic stop simulation, drum brakes decelerated the truck at 20 feet per second and were unable to activate the anti-lock system. The disc brakes activated the anti-lock system when vehicle deceleration reached 24 to 25 feet per second.

The ADB 225 system is designed for 22.5-inch wheels. It is compatible for use in combinations with drum brakes and works with ABS.

At present, Bendix air disc brakes are manufactured in Europe through a relationship with Knorr-Bremese, parent company of Bendix. The company is investigating options for manufacturing the systems in North America.