What Is Axle?- Definition, Types, and Uses

What is an Axle?

An axle or axletree is a central shaft that rotates the wheels and supports the weight of your vehicle. Axles are essential components of any vehicle and come in three main types: front, rear, and stub.

On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported.

In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type of axle is referred to as a spindle.

How Many Axles Does a Car Have?

The number of axles in a car depends on the type of vehicle. In most cases, cars have two axles to turn the wheels. Larger vehicles that carry more passengers and have more wheels can have more axles.

It’s easy to identify the number of axles your car or other vehicle has. Just look at your car from the side and then count the pairs of tires. Most cars have a total of four tires or two sets of tires, one in the front and one in the rear. Two sets of tires correspond to two axles.

Engineering Choice The Biggest Learning Platform

Factors That Decide the Type of Axle in a Car

Several factors determine which type of axle a vehicle needs. For example, the technical requirements and the force generated play a major role in the decision on the type of axis.

Some vehicles have pre-built axles in standard formats. Others have bespoke axles that meet the needs and specifications of the car. Custom axles are best for cars as they allow more individual control over the wheels. These axles can fine-tune the speed and torque of the wheels.

Types of Axle

Axles come in three standard types:

  1. Rear axle: This axle is responsible for the power supply to the drive wheels. It comes in two halves, called half-waves, which are connected by the differential. In most cases, the rear axles are under tension, meaning that they rotate with the vehicle’s wheels.
  2. Front axle: This axle is located in the front of the vehicle and is responsible for assisting in steering and processing bumps on uneven road surfaces. They consist of four main parts: the beam, the swivel pin, the tie rod and the stub axle. The front axles must be as robust as possible. That is why they are usually made of carbon steel or nickel steel.
  3. Stub Axle: Stub axles are attached to the vehicle’s front wheels, with kingpins connecting these axles to the front axle.

Types of Rear Axle

Not all rear axles are the same, as the support and mounting methods there are three types of rear axles:

  1. Semi-floating axle: This rear axle connects the wheel to the flange on the outside of the axle shaft and holds it securely. One bearing supports the axle shaft and the other is in the axle housing. Since it has two bearings, a semi-floating axle must be larger than the other options to produce the same torque. Semi-floating axles are used for automobiles, SUVs, and medium-sized trucks, Pickups with half a ton and low power.
  2. Full-floating axle: As the name suggests, thanks to two bearings, this type of axle effectively floats in place and maintains its position. It only transmits the drive torque. Fully floating axles are best for larger vehicles, e.g. heavy trucks. Some medium-sized trucks with larger towing capacity or those with all-wheel drive can also benefit from fully floating axles.
  3. Three-quarter floating axis: It is more complex than the semi-floating axle and also more reliable. It helps in maintain wheel alignment and handles side thrust and driving torque.

Types of Front Axle

There are vehicles have two main types of front axle.:

  1. Dead Front Axle: These axles stay in place and don’t rotate with the wheels. Most dead front axles and differentials have housings that prevent them from coming into contact with water or dirt.
  2. Live Front Axle: Unlike dead front axles, live front axles deliver driving power from the gearbox to the front wheels.

Types of Stub Axle

As The Engineers Post explains, there are four types of stub axle:

  1. Elliot: This type uses a kingpin, a yoke, and a cotter to connect to the front axle.
  2. Reverse Elliot: This type has the opposite arrangement of a standard Elliot stub axle.
  3. Lamoine: This stub axle type has an L-shaped spindle instead of a yoke-type hinge.
  4. Reverse Lamoine: It has the opposite layout of a standard Lamoine stub axle.

How to Know When Your Axle Is in Disrepair

Because axles are essential to your car’s operation, it’s important to keep them working properly. if you see one of the following signs, you can tell that your axle is in disrepair:

  • You hear a loud clunk when you put your car into gear.
  • You feel vibrations when you operate your car.
  • Your vehicle won’t move forward or backward even though it’s running.

How to Choose the Right Axle Ratio for Your Pickup Truck

In addition to unique torque, engine, and transmission specifications, many trucks also have custom axle ratios. An axle ratio like 3.55: 1 means that the driveshaft will turn 3.55 times every time the wheel turns once.

In most cases, a standard final drive ratio works well for most drivers who are not expecting large loads. However, if you are pulling heavy trailers or want to pull large loads, you may want the highest final drive ratio possible.

Axle Issues to Consider

When choosing the right axle ratio for your vehicle, keep a few things in mind. Remember:

  • A vehicle’s window sticker reveals the fuel economy data for the standard axle ratio. If the truck has a custom axle ratio option, the fuel economy is automatically lower.
  • It’s impossible to compare different automakers’ optional axle ratios. The various tire sizes affect the system gear, which impacts the final figure.
  • Many dealers prefer to lower axle ratios as tall gears and higher axle ratios as short gears. The former usually have better gas mileage, while the latter can generally haul heavier loads.