03 Brake System

Brake System

• Front brakes are 17” air applied disc

• Rear brakes (Figure 3-1) double as parking brake

- Park brakes are spring applied – air released

- Two large 16.5 x 7” drum brakes

- Park brake remains applied even if air pressure is lost

• If air pressure is lost

- A buzzer and warning lamp will alert you

• Chassis is equipped with automatic slack adjusters (Figure 3-2)

- No brake adjustment required

The rear brakes on the PowerGlide chassis are also used as the parking brakes. This provides you the holding power of two large drum brakes to prevent your coach from rolling, even when fully loaded on a 20% grade.

A decrease in air pressure while driving will not cause an immediate loss of brakes. If a significant leak develops in the air system, at approximately 60 PSI you will be alerted by a lamp on the instrument panel, and by an audible alarm. As you apply the brakes, the air supply holding the park brakes in the released position will gradually be depleted. When system pressure drops to approximately 40 PSI the rear brakes will set. This allows you sufficient time to pull over to the side of the road.

NOTE: The rear brakes have dual chambers – one for the service brakes and one for the park brake. The service brakes are air applied and spring released. The park brake is spring applied and air released.

The brake system is equipped with automatic slack adjusters that avoid the need to manually adjust your brakes. Each time you step on the brake pedal, if adjustment is needed, the adjusters will take up the slack.

Compressed Air System

36’ and 40’ Bus Non-Tag Tank Drains

43' Bus Tag Tank Drains

Compressed Air System

The compressed air system is comprised of multi-air storage tanks. The primary tank stores and supplies air for the rear brakes, the secondary tank stores and supplies air for the front brakes.

When air is compressed it becomes hot. As it cools, condensed moisture forms in the system. The air system is equipped with an air dryer to remove most of this moisture. The dryer has an automatic moisture ejector that releases the trapped moisture back into the atmosphere. However, some moisture will form in the system beyond the dryer, and make its way into the storage tanks. As moisture collects in the primary and secondary tanks, it displaces the area needed for air storage, thus requiring that the tanks be drained periodically.

The air system is equipped with air tank drains conveniently located in the compartment with the DEF tank. Each drain is attached to a different tank. These drains should be opened regularly for a few seconds to remove any moisture trapped in the tanks.

Air Dryer

The Tiffin PowerGlide chassis air brake system features a Haldex Purest air dryer (Figure 3-3), which removes the condensed moisture from compressed air. The air dryer is equipped with a desiccant cartridge that needs to be changed every 36 months. The dryer is located on the driver's side (LH) frame rail (behind the rear axle).

Engine Compression Brake

The engine compression brake (Figure 3-4):

• Improves braking power

• Reduces the chance of overheating brakes on steep grades

• Works in conjunction with the transmission to help slow the vehicle

• Has two stages (low and high) for varying terrain

All brakes will build up heat when being used due to friction – this is normal. However, excessive use of the brakes when descending a grade can result in excessive heat and can cause “brake fade” or a loss of braking power, even with disc brakes. The proper way to use your brakes is to go slowly enough that a fairly light, occasional use of the brakes will keep your speed from increasing.

NOTE: DO NOT maintain continual brake pedal pressure when descending a hill with any type of brake system.

Rather, down-shift the transmission to slow the vehicle and make light, intermittent brake applications to control downhill speeds. By utilizing the transmission gears and compression brake, continual use of the brakes will not be necessary. When using the transmission’s lower gears to slow the vehicle on hills, be careful not to exceed the governed speed of your engine. If engine-governed speed is exceeded, the transmission will shift up to the next range, rapidly increasing the speed of your vehicle. If you find that you are continually using the brakes to maintain a safe speed and to keep the RPM within this range, slow the vehicle down even further and shift the transmission to a lower gear.

Warning

DO NOT USE the compression brake on wet roads, hazardous, or slippery conditions. As with any motorized vehicle, practice safety when on the road.

AIR FORCE ONE SUPPLEMENTAL BRAKING SYSTEM FOR TOWED VEHICLES

Your coach is equipped with Demco Products Air Force One supplemental braking system.

Air Force One is designed to provide proportionate braking effort in the towed vehicle by applying proportioned air based on the pressure in the coach’s braking system to the Air Force One braking system.

Air Force One uses the coach's air to create vacuum for the towed vehicle’s power-brake feature, and also uses the same air supply to proportionately apply the brakes in the towed vehicle. Since it uses the coach’s air supply, Air Force One does not need an electric pump. The Air Force One operating unit has no moving parts. The Air Force One operating unit is very small and fits under the hood of your towed vehicle. The brake actuator mounts on the brake arm

Be sure to have your towed vehicle’s brakes inspected for wear before towing. In most cases towed vehicles do not accrue mileage on the odometer while in tow, resulting in the brakes needing to be serviced before the odometer would dictate. For most vehicles it is recommended to have the brakes inspected/replaced every 20,000-30,000 miles. You must combine towing and driving mileage when determining the interval.

Federal Motor Vehicle Safety Standard (FMVSS) 121 requires that a separate air circuit and flow protection valve be installed when the towing vehicle’s air supply is used for a supplemental braking system. Air Force One is the only air brake system that supplies these components as part of the installation kit. Should there be any breach in the supplemental air connection, the air supply will be shut off: allowing you to stop your coach safely in every situation, even during a breakaway.

Tiffin Motorhomes does NOT install the Air Force One on towed vehicles at the Service Dept. in Red Bay, AL or anywhere else. However, a customer can purchase the towed vehicle kit from Tiffin Motorhomes parts and service dept. and have it installed anywhere they like.

The Tiffin part number for the Customer Vehicle Kit is 5087751

For more information, specifications, and manuals please visit DEMCO at: https://www.demcoproducts.com/rv-towing/supplemental-brakes/air-force-on