Volvo Service Bulletin 7-72-11

Product Section Group No. Date Title
B772111.85Air suspension, B10M with bogie

On the B10M with bogie, the rear suspension system has six air bellows, compared to four on the B10M without bogie.

The air bellows over the trailing axle are coupled in parallel to the drive axle air bellows. Moreover the air suspension for the bogie type has two extra solenoid valves. Otherwise the suspension system is similar to that on the B10M without bogie.

B10M Bogie/Tag axle/Trailing axle air bellows1. Trailing axle air bellows

The trailing axle air bellows are of the same type as those for the drive axle. Since all air bellows on the same side of the bus are coupled in parallel, they receive the same pressure from the levelling valve. However, the pressure in the trailing axle levelling valves can be exhausted separately with the help of two solenoid valves. By reducing the pressure in the trailing axle air bellows, e.g., when driving away on a slippery surface, we increase the load on the drive wheels and thereby bus traction.

B10M Bogie/Tag axle/Trailing axle solenoid valves2. Solenoid valves for engaging and disengaging compressed air to trailing axle air bellows

The solenoid valves are placed on the compressed-air line to the trailing axle air bellows and are operated by a switch on the dashboard.

Trailing axle air suspension system layout
1.Trailing axle air bellows
2.Solenoid valves for engaging and disengaging compressed air to air bellows, 1.
3.Levelling valves
4.Drive axle air bellows

Layout diagram of compressed-air suspension system for drive and trailing axles on B10M with bogie

Trailing axle air suspension system diagram

A. From four-circuit protection valve

Rear suspension levelling valve3. Levelling valves

Rear suspension levelling valve4. Drive axle air bellows


Compressed air from the four-circuit protection valve flows to the levelling valves (3) to regulate the pressure to the air bellows (4) and (1), in relation to the bus load. The height of the body above the ground thereby does not change, but the boarding height is maintained constant.

On its way from the levelling valves, the compressed air flows through two solenoid valves (2). Normally there is no current to the solenoid valves which allow compressed air to the air bellows (1). When the solenoid valves are activated, by a switch on the dashboard, the compressed-air line from the levelling valves and the air bellows (4) is blocked, at the same time as the compressed air in the air bellows (1) are exhausted.