Trailer fuwa type leaf spring

The various shapes of leaf springs correspond to the type of load they can support. You know your truck has adequate support when its wheels stay on the ground going over bumps and the bed doesn't sag when full or during towing. Depending on how you use your truck, you may need OEM or heavy-duty leaf springs.

The shapes of the springs also make a difference. Not all leaf spring shapes apply to truck suspension systems. Common shapes you may encounter include elliptical, transverse and platform leaf springs.

1. Elliptical Leaf Springs
Elliptical leaf springs come in quarter, semi, three-quarters and full shapes. For trucks, the most commonly used are semi-elliptical springs. These springs have a parabolic shape and appear on both rear and front axles of trucks, and rear axles only on cars.

Older models of small cars used the less efficient quarter-elliptical leaf springs. These looked like half a semi-elliptical spring. By combining this type of elliptical spring with a semi-elliptical, manufacturers made three-quarters springs. However, like quarter springs, these fell out of favor and only appear on older cars today.

Some manufacturers thought that if semi-elliptical leaf springs worked well, putting two of them facing each other into a full elliptical spring would be better. This design option failed, though, because the pressure from the spring adversely affected alignment.

2. Transverse Leaf Spring
Transverse leaf springs have the same shape as semi-elliptical models. However, these springs fit under a truck with the base of the curve toward the chassis, rather than facing the ground. In addition to their change in orientation, these leaf springs also have a different location from their semi-elliptical counterparts. This upside-down installation goes along the sides of the vehicle instead of on the front or rear axles. Today, it's rare to see transverse leaf springs on trucks or other vehicles.

3. Platform Leaf Spring
Platform leaf springs use a pair of semi-elliptical leaf springs — one facing down, and the other pointing up. When affixed to the vehicle, the springs support three points of the vehicle's weight along each side.

Another consideration for how to choose leaf springs aside from the shape is the number of leaves they have. Two leaf spring suspension types exist – mono and multi.

Mono leaf springs only have a single piece of metal. Often, these mono-leaf springs will have a thicker center that narrows in depth toward the edges to provide some similar support to multi-leaf springs that have more springs in the center and fewer along the edges.

While mono-leaf springs suffice for lightweight vehicles, if you have a truck or do any towing, you likely need the additional support of more leaves. Multi-leaf springs have several pieces of metal that increase in size from the bottom to the top.

Multi-leaf springs need spring clips between the layers. These specialty clips permit each leaf to move as needed while staying in alignment with other leaves. A center bolt passes through the thickest portion of the multi-leaf spring, holding all layers together. To prevent the spring from squeaking and wearing out over time, each layer has a friction-reducing insulator between it and the leaves above and below it.

Just as the different types of leaf spring shapes exist, so do various capacities related to the number of leaves and leaf spring sizes. Look at the specs for the capacity of the leaf spring.

Another essential aspect of how to choose leaf springs is to know the capacity you need. Regularly exceeding this carrying ability can cause excessive wear and premature failure of your leaf springs.

Look at your truck's owner's manual to determine the stock carrying capacity. If this amount is too low for your typical hauling weights, you should upgrade the rear leaf springs to provide more support in the back of your truck. Find springs that offer a higher weight capacity than your vehicle currently uses. To choose the right springs, you may need to upgrade to heavy-duty leaf springs from the stock springs on your truck.

The number of leaves on multi-leaf springs allows for better support. When comparing mono to multi-leaf springs, the latter offers a higher carrying capacity because the added leaves increase the stiffness of the spring.

The device must have at least two springs to qualify as a multi-leaf spring. Most leaf springs will have between three and five leaves. However, for some heavy-duty applications, the leaf springs will have even more layers.

Choosing leaf springs with too many leaves can create too much stiffness in the suspension. This situation makes the ride stiff and less controlled. However, if you don't have enough leaves in the spring, you will lose carrying capacity from a lack of suspension.

While the number of leaves on your multi-leaf springs is a critical factor, you should focus more on matching the springs' load capacity to what you typically carry in your truck. When you choose suspension parts that match the way you use your vehicle, you will improve your performance and not have premature spring failure from carrying too much.

Well a leaf spring suspension is made of a series of relatively long strips of steel attached at both ends to a frame and suspending the axle in the middle. A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. Coil springs as the name suggests, look exactly like how one imagines a spring to look like. It sits on top of the axle or at the lower control arm and the chassis. A coil by definition is a mechanical device which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces.

Leaf spring suspensions are much simpler in terms of functionality as the axle is suspended by the spring, and does not require the arduous suspension geometry of the coil-spring set-up. Leaf springs are also much sturdier as compared to the coil springs. They are capable of handling much higher loads with less deflection than coils. Trucks with leaf springs are also easier to raise or lower.

The leaf springs' simplicity is as much of a curse as a blessing. Since this spring is attached at fixed points on the chassis, it leaves a minuscule room for adjustability and customization of the suspension geometry. These springs also flex a great deal less than coil springs, resulting in a loss of wheel-to-ground contact under extreme conditions.

Coil spring suspensions offer more range of suspension movement, and allow the user a wider tuning envelope through the suspension range than leaf springs. Practically all high performance applications use coil springs where possible and if the budget permits.

The two main drawbacks to a coil spring suspension are cost and load-bearing. Cost isn't so much an issue if the vehicle is originally equipped with coil springs, however the retro-fits can be quite expensive and time consuming. Coils are not ordinarily preferred for very heavy vehicles, as the coil on axle setup isn't remotely as stable or strong as a proper leaf spring.

This brings us to a conclusion that each of these suspension systems have their applications unique to their functionality and are used accordingly! Leaf springs will usually do an acceptable job and prove themselves a durable choice in the case of heavy, industrial or budget-limited applications; However, there are a very few applications which will benefit from choosing a leaf spring over a coil spring when it's a matter of performance.