What is a car axle, and where is it located in your car? When you choose a car to buy, you often refer to your car’s axle indirectly, whether you’re aware of it or not. Remember choosing between a two-wheel, four-wheel, front-wheel, rear-wheel drive, or AWD? You were actually talking about axles.
So What Is A Car Axle?
A car axle is a rod, shaft, or a spindle located underneath your car’s body. It passes through a set of wheels to rotate them, maintain the position of the wheels relative to each other, and bear the load of a vehicle. One axle supports a pair of wheels, except in the case of a stub axle. The car you drive to work most likely has two axles, while a six-wheel truck has three. Axles are configured as either live or dead.
What Are Live and Dead Car Axles?
Live axles are fixed on the wheels and rotate with them. All vehicles that run on wheels have live car axles, which propel a set of wheels. This type delivers power and torque to the wheels and supports the laden weight of the vehicle.
In a word, live axles drive the wheels. For this reason, live axles are also called drive axles and thus are part of the drivetrain, while the wheels attached to them are called drive wheels. A two-wheel-drive car then has two drive wheels and one live axle.
Now, that leaves us the question of what dead car axles are. You may have guessed by now - it’s that axle with the non-drive wheels. A dead axle is attached to the vehicle, unlike live axles which are fixed on the wheels. In a dead axle, the wheels rotate around it, not with it.
What does a dead axle do then? Contrary to its other name, which is ‘lazy axle,’ a dead axle does not sit there doing nothing while it’s brother huffs and puffs to propel the vehicle. Dead axles are load-bearing axles, and in fact, heavy trucks and trailers employ various types of dead axles for load-bearing purposes.
What Are the Types of Car Axles?
Aside from classifying car axles based on configuration (live or dead), they may also fall under two main types of axles based on their location (front or rear) or a third type called stub axles. These three types are further divided into several subtypes, which are all described in detail below.
Front axles absorb shocks and support the weight of a vehicle’s front section and steering. Front axles can either be live (live front axles) or dead (dead front axles). A live front axle has the added job of driving the wheels as described above. Think of these drive wheels as ‘pulling’ the vehicle.
Rear axles are located at the rear of a vehicle and can either be live (live rear axle) or dead (dead rear axle).
So, can you guess which types of axles are in your front-wheel-drive vehicle? You’re right, you have a live front axle attached to the two drive wheels at the front, while your neighbour's RWD has a dead front axle and a live rear axle. It doesn’t stop there, however. Rear axles are further classed into three more subtypes depending on the support they provide and how they are mounted.
- Semi Floating Axles – carry the weight of a vehicle with a single bearing on the axle housing and another inside the axle casing. It is attached to the wheels and rotates to produce torque. This type of car axle is typically used in mid-size trucks and light-duty pickups.
- Full Floating Axles – are designed for transmitting torque. It consists of a wheel hub assembled to the axle shaft and axle tube supporting it with the help of two-wheel bearings and shifting the weight of the vehicle and cargo to the axle tube. You can find this type of rear axle used for heavy-duty trucks, mid-size trucks and four-wheel-drive vehicles.
- Three-Quarter Floating Axles – consist of an axle housing with an elongated axle tube and rotating axle shaft. It is most reliable as compared to the two others. These car axles help in handling driving torque and side thrust.
A stub axle, aka stud axles, supports only one wheel, as opposed to the other two main types of axles. In a rear-wheel-drive vehicle, a stub axle is attached to either end of the front car axle, while in a front-wheel-drive car, it is fitted in one end of the rear axle. It allows angular movement when steering and improves cornering.
There are four main types of stub axles, named and described as follows:
- Elliot – this stub axle is connected to the front axle at the yoke-type hinge using a kingpin and a cotter.
- Reverse Elliot – this stub axle also uses a yoke-type hinge attached to the front axle using a kingpin and cotter but in reverse order of the Elliot.
- Lamoine – commonly used in the front axle of tractors, the Lamoine stub axle has an L-shaped spindle instead of the yoke type and uses a kingpin to attach it.
- Reverse Lamoine – similar to the Lamoine but in reverse arrangement to standard Lamoine and is generally used in the front axle of a rear-wheel-drive car.
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