Buses Glossary

Here you can find a list of terms useful when looking for a bus for sale. You can learn about the various key components that define a bus and what to ask about when you want additional information on buses for sale.

Bus Terminology

Bus Body

The body of a bus refers to the exterior shell. It typically does not contribute to load support or function, it is simply the 'jacket' of the bus. Examples of bus bodies include turtle top, champion, and krystal.

Bus Chassis

A bus chassis basically includes all parts of the bus and excludes only the bus body. When someone refers to the chassis of the bus, they are referring to the 'frame, wheels, and machinery' (dictionary.com) of a bus. Bus machinery would include the engine, transmission, suspension, differential(s), driveshaft, etc. The key difference between the idea of the bus body and the idea of the bus chassis is that the chassis' job is to support the bus body and move the bus. The bus body, then, is a sort of 'clothing' for the bus. Bus Chassis are distinguished by their manufacturer (eg. Ford, MCI, Van Hool in the case of buses), and they do not imply a particular engine type, transmission, etc. Oftentimes, someone will refer to the 'make' of a bus, which is just a word in common use meaning the 'chassis'.

Bus Model

The model of the bus is a reference to a particular design of a bus from a given manufacturer, and therefore the chassis. For example you'll always see a Ford E450 (where E450 is the model), Ford E350, Ford F550. You'll see Van Hool T2145 (T2145 being the model), but you WON'T see a Ford T2145 or a Van Hool F450.

Bus Brakes

Most bus brakes fall into one of two major design styles, disc brakes and drum brakes.
Disc Brakes : Basically a disc brake is a mechanism composed of brake pads and a disc. The disc is attached to the wheel and when the brakes are applied some force (be it hydraulic, air, or electro magnetic) puts the pads in contact with the disc, creating friction and slowing down the wheel. The benefit of disc brakes is that they are more resilient to wear. The heat caused by friction with brakes wears on these mechanisms regardless, and all brakes are susceptible to water reducing their effectiveness. However disc brakes recover from heat and water defects more quickly.
Drum Brakes : Drum brakes also use friction, but instead of a disc with pads that create friction on the outside, drums are a hollow ring that come into contact with the pads on the inner portion of the drum. The most significant feature of drum brakes is that due to their design, the very act of applying the brake strengthens the force of friction and therefore these brakes have more stopping power. However, this effect also makes it more difficult for the driver to manage the sensitivity of the braking force.
Air Brakes : This term refers to how the force which puts the pads in contact with the discs/drums is applied, specifically compressed air. Air can be pulled from a tank or filtered from the atmosphere. When these brakes incorporate air tanks, be careful because the design allows for water and compressor oil to leak into to mechanisms which can cause brake failure.

Bus Engine

Diesel Engines for buses tend to be far more efficient than gas engines. They weigh more than gas engines, requiring more force to move the bus, but even so they can be roughly 20% more fuel efficient than a gas bus engine. Also, they are more fuel efficient than gas engines when idling, and the life of the engine is much greater. A diesel bus engine's life may be double that of a comparable gas bus engine. One disadvantage of diesel is that in cold weather there may be greater difficulty getting the bus started due to the physics of the engine. Generally, though, you're going to want a diesel bus engine in any large buses you are looking at, though minibuses can sometimes afford to be gas powered buses.

Bus Transmission

Two main types of transmissions exist for buses. Manual bus transmissions require manual shifting of gear ratios (often simply referred to as 'gears') and automatics do not. Manual buses tend to be more fuel efficient and allow the driver greater control, but automatic buses are simpler to operate. Indeed, the operation of a manual ubs transmission is a skill to be learned. The basic purpose of a bus transmission is to adjust gear ratios for greater or lesser torque. To accelerate a 3 ton bus from 0 mph to 10 mph requires much greater force than to accelerate the same bus from 40 mph to 50 mph, due to inertia. Therefore different torque outputs are more effective at different speeds, and a bus will need to shift gears in order to achieve these outputs. Hence, transmissioons are a key component of any automobile, be it bus, car, motorcycle, etc.

Bus G.V.W.R

Gross Vehicle Weight Ratio, or GVWR, is the total weight of a bus including the bus itself, passengers, fuel, and cargo. Buses over 3 tons have restricted access to certain roads, and buses with gvwr over 4.25 tons are typically not subject to state emissions tests.

Bus Tires

Tires are the casing of a wheel, made of various materials such as rubber or plastic. They can be solid or pneumatic (pressurized with air). Bus Tires are often identified in bus sales with a code similiar to 225/60r16. The '225' refers to the width of the bus tire in millimeters. Though sometimes a bus tire's width is referred to in inches. The '60' refers to the bus tire's aspect ratio, which is the ratio of the height of a cross section of the bus tire to its width. So in this case, 60% of 225 millimeters is 135 millimeters, which is roughly 5 1/2 inches. In other words, the distance from the tire's inner diameter to outer diameter is 5 1/2 inches. The '16' refers to the diameter of the wheel, which for ease of understanding could be roughly equated to the inner diameter of the bus tire. Many times when looking for a bus for sale, you will also see tires described with just a percentage. This is an informal way of telling you about the bus tire tread depth. Tire tread depth is important because over time tires lose tread and eventually would be dangerous to drive on for various reasons. So when you see 'tires 50%' it means roughly half of the tread is worn... and you may want to consider buying new tires for this bus.

Bus Wheels

Often times when looking for a bus you may see some additional information about the bus wheels. When buying a bus, be sure to inquire about what the wheels are made of, and what difference it would make if they were constructed out of some other metal. Steel is a very common metal used for bus wheels. Sometimes they can be plated with chrome or aluminum alloy. One thing you may see is information about covers. These are largely for aesthetic value, and do not add much to the way of function or bus performance. They may offer a small degree of protection to your rims and hubcaps, but don't forget that what you are mainly 'paying for' when it comes to bus wheel covers is style, not performance.

Bus Suspension

Bus suspension is the system of mechanisms (including springs, shock absorbers, and joints) that connects the chassis of a bus to its wheels. The purpose of the suspension is to insulate the the bus from the shocks that the bus wheels transmit while driving. In other words, poor bus suspension could cause damage to a bus if road conditions are poor. Additionally, the bus suspension serves to make the ride more comfortable for the passengers, as absorbing the shock of the road prevents those inside from ever feeling it. Bus air suspension is a typical suspension type for buses, because it uses compressed air instead of springs, which allows for adjustable suspension. Therefore, when buying a bus you may want to inquire about the quality of the suspension. Better bus suspension means less wear on the bus as well as more comfortable bus rides. There are many factors that go into the quality of bus suspension, so rather than ask the technical questions that the bus seller may not even be able to answer, it may be better to ask some more general questions about your bus purchase.
1) Does the bus have air ride suspension? (air ride suspension is good for buses)
2) How well does the bus handle loads that vary from the norm? (for example a bus could be a smooth ride when the seats are full but when they are empty the bus' suspension may not be designed to handle so well)
3) How old is the suspension? (suspension technology is improving and an old bus with outdated and worn bus suspension should be notably less expensive)
The best way to get a feel for the bus' suspension is to test drive the bus. If you can, take note of how smooth the ride is with no passengers. If its a smooth ride its probably a good suspension because most bus suspensions are built to expect a load 1-5 tons greater than mininum bus occupancy. Air ride suspension is the norm for buses, and should provide a smooth ride regardless of occupancy.

Bus Drive Shaft

The bus drive shaft is the bar that runs from the front axel of the bus to the rear axel and its purpose is to transfer power from the bus engine to the wheels.

Bus Differential

In automotive terms, the differential serves to adjust and distribute torque. Torque is rotational force, and when buses are driving straight the torque is the same for all wheels. When a bus turns, however, the torque needs to be different on each wheel. The bus differential is what allows this to happen, hence the name. Typically one can find a differential built where the driveshaft meets the axel for whichever axel allows for steering. In the case of all wheel drive, differentials are built into both bus axels, and there is also often a third in the center of the drive shaft. When it comes to buying a bus, inquiring about the differentials is not exactly necesary; the relevant question would concern whether the bus is a front, rear, or all-wheel drive bus.