how to select replacement leaf springs for a trailer

Buying replacement parts for your trailer isn&#;t always the easiest thing to do. More often than not, you don&#;t know what to call a particular part & you certainly don&#;t know which type or size you need. Our goal is to make buying replacement parts easier for our customers. In this article, we are going to tackle how to select the correct replacement leaf spring for your trailer.

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First things first, you need to determine which type of leaf spring you need. There are 5 different types of leaf springs that fall under two main categories &#; double eye leaf springs & slipper springs.

Notice that all of the springs shown have a bolt &#;eye&#; on the front end of the spring. That is how the spring attaches to the trailer frame. The other end of the leaf spring is more interesting. Notice that all of the springs are arched. When your trailer is loaded & you are driving along, the spring moves up & down vertically as your tires hit bumps & variations in the road. This up & down movement &#;flattens&#; out the spring causing it to grow in length. The spring is attached in a fixed position on the front end, so the back end moves back & forth. The slipper springs slide (or slip) back & forth against a stationary surface to easily compensate for the changes in length. The stationary surface can be a specific bracket attached to the trailer frame, or sometimes the trailer frame itself is used as the contact surface of a slipper spring. Here is an example of a slipper spring attachment on the movable back end:

Double Eye leaf springs get their name because they have a bolt eye on both the front & back of the spring. This type of spring deals with the changing length by adding pivoting shackle links to the rear of the spring. Here is an example:

Now that you know the different types of leaf springs, you can select the appropriate style & move on to measuring for the correct replacement. The number of leaves & the weight capacity of the spring is also very helpful to know.

Here are some terms that are important to know regarding leaf spring measurements:

Overall Length &#; The complete overall length from one end to the other

Length &#; Depending on the type of spring the length is determined slightly differently. Double eye leaf springs are measured from center of eye to center of eye. Open eye slipper springs are measured from center of eye to center of open eye. The remaining types of slipper springs (flat end, radius end & hook down) are measured from center of eye to contact point. (See below for the 3 different length measurement diagrams)

Axle Location &#; The axle location is measured from center of eye straight across to the point where the leaves are all bolted together.

Stack Height &#; The thickness of the springs where all leaves are stacked.

Width &#; The width of the leaf spring.

 Use the charts below to find the correct leaf spring for your trailer. Just click on the part number & you will be taken directly to that leaf spring on our online trailer parts store. If the part number does not have a clickable link, that means that the part is no longer available.

Double Eye Leaf Springs

Part # Leaves Capacity Overall Length Length Width Stack Height Axle Location EXP- 3   20&#; 1.75&#;     TDE- 4 26.75&#; 25.25&#; 1.75&#; 1.50&#; 12.5&#; UGC-UNA-030 4   20&#; 1.75&#;     UGC-UNA-050 3   26&#; 1.75&#;     UGC-UNA-051 4   26&#; 1.75&#;     UGC-UNA-052 5   26&#; 1.75&#;     UGC-UNA-053 6   26&#; 1.75&#;     UGC-UNA-111 5 27&#; 25.25&#; 1.75&#; 2.01&#; 13&#; UGC-UNA-115 1 27&#; 25.25&#; 1.75&#; 2.01&#; 13&#; UGC-UNA-124 4   26&#; 1.75&#;     UGC-UNA-167 4 22&#; 20.5&#; 1.75&#; 1.13&#; 10.5&#; UGC-UNA-168 3 700 21.75 20.25&#; 1.75&#; 0.67&#; 10.5&#; UGC-UNA-169 3 21.5&#; 20.25&#; 1.75&#; 0.79&#; 10.5&#; UGC-UNA-188 5   24&#; 1.75&#;     UGC-UNA-210 4 28.5&#; 27&#; 1.75&#; 1.38&#; 13.5&#; UGC-UNA-212 4 26.5&#; 25.25&#; 1.75&#; 1.27&#; 13&#; UGC-UNA-216 3 24.5&#; 23.25&#; 1.75&#; 1.08&#; 12&#; UGC-UNA-217 3 26.75&#; 25.25&#; 1.75&#; 1.04&#; 13&#; UGC-UNA-219 3 26.5&#; 25.25&#; 1.75&#; 0.94&#; 13&#; UGC-UNA-220 3 26.75&#; 25.25&#; 1.75&#; 1.16&#; 13&#; UGC-UNA-221 4 26.75&#; 25.25&#; 1.75&#; 1.5&#; 13&#; UGC-UNA-223 6 26.5&#; 25&#; 1.75&#; 2.05&#; 13&#;

Radius End Slipper Leaf Springs

Are you interested in learning more about Single Leaf Spring? Contact us today to secure an expert consultation!

Flat End Slipper Leaf Springs

Part # Leaves Capacity Overall Length Length Width Stack Height Axle Location TDE- 2 30&#; 28&#; 1.75&#; 0.69&#; 13.5&#; TDE- 4 30&#; 28&#; 1.75&#; 1.44&#; 13.5&#; UGC-UNA-039 3 30&#; 29&#; 1.75&#; 1&#; 13.5&#; UGC-UNA-040
4   30&#; 1.75&#;    

Open Eye (Hook Up) Slipper Leaf Springs

Part # Leaves Capacity Overall Length Length Width Stack Height Axle Location FRA- 3 825 23.75&#; 22&#; 1.75&#; 0.75&#; 11&#; FRA- 6 28.25&#; 26.5&#; 1.75&#; 2.13&#; 13&#; FRA- 4 25.5&#; 24&#; 1.75&#; 1.13&#; 12&#; FRA- 4 23.25&#; 22&#; 1.75&#;     FRA- 2 26&#; 24&#; 1.75&#;     UGC-UNA-263 3 28&#; 26.5&#; 1.75&#; 1&#; 13&#; UGC-UNA-264 4 28&#; 26.5&#; 1.75&#; 2.38&#; 13&#;

Hook Down Slipper Leaf Springs

Part # Leaves Capacity Overall Length Length Width Stack Height Axle Location TRP-SH- 4 31.25&#; 26.5&#; 2&#; 1.25&#; 14&#; UGC-UNA-161 6 26.63&#; 29.5&#; 2&#;     UGC-UNA-229 4   25.5&#; 2&#;     UGC-UNA-230 4   26.48&#; 2&#;     UGC-UNA-231 4 27.5&#; 25&#; 2&#; 1.44&#; 11.50&#; UGC-UNA-232 5 26.5&#; 24&#; 2&#; 1.80&#; 11.50&#; UGC-UNA-285 7 28&#; 25&#; 2&#; 2.52&#; 11.50&#;

Leaf springs are a very simplistic suspension design dating back to the beginning of the 18th century. With such a long history, leaf springs might seem a bit outdated for use on modern trucks. But their simplicity has led to their longevity. Leaf springs are the AK-47s of suspension. Both are still around because they are rugged, reliable, and cheap to produce, and effective at what they do.

Just because they are simple doesn't mean all leaf springs are the same. There are significant differences between a cheap set of leaf springs and high-quality ones. So what should you look for if you are looking for a new set of springs? Let&#;s dive into it and we will explain.

Thin Is In

Peer under the rear of your truck and you will see very basic factory leaf springs consisting of a few thick leaves. Thicker leaves are more resistant to movement and usually produce a rougher ride, but they are much cheaper to produce. OEM springs get around this lack of ride quality by having almost no arch or even a negative arch since a flatter spring moves easier.

This style of spring is fine for the vast majority of trucks that never leave the pavement. But the limitations of OEM springs quickly become apparent once in the dirt. With no arch, or even a negative one, there is very little upward travel and the stock springs quickly bottom out on bigger hits. With their resistance to movement, the thicker leaves also don&#;t absorb smaller hits well either. All of this adds up to a harsh ride and less control in the dirt. Add more payload to the bed of your truck and things get even worse.

Leaf springs with a multitude of thin leaves are more expensive to produce, but thinner leaves are more flexible than thicker ones and move more freely. This means a spring with multiple thin leaves can have more arch, but still produce a nice ride. Extra arch not only provides some lift, but it also yields more bump travel. And, lots of thin leaves stacked on top of each other makes the spring a lot more progressive. This allows it to absorb both smaller hits and larger ones for a much better ride and control in the dirt.

Military For The Win

Any high-quality set of springs should come with a military wrap. On a standard set of springs, only the main leaf wraps around the eyes of the springs. With a military wrap, both the second leaf and the main leaf wrap around the eyes of the spring. This might seem like a minor difference but can play a vital role if the main leaf ever breaks. Without a military wrap, there is nothing to keep your axle in place should you snap the main leaf. A military wrap acts as a secondary safety should the main leaf ever fail.

Trust us when we say that a military wrap is a feature worth having. We once snapped the main leaf in a spring without one on a trip in the Nevada backcountry. After getting creative with a bunch of ratchet straps, we were able to secure the axle somewhat. The 30-mile drive to the nearest pavement that normally would have taken an hour took six hours. With a military wrap, this would have been much less of an ordeal.

Less Friction

Just like in your marriage, workplace, or current relationship, friction in springs is not a good thing either. As a leaf spring cycles through its travel, the end of each leaf can rub against the leaf above it, causing wear. In extreme cases, this wear can damage a leaf or even cause it to crack eventually. While not as extreme, this friction can also make the leaf springs squeak as they absorb bumps. Anyone that drives a vehicle with squeaking leaf springs will eventually go insane.

Anti-friction pads in high-quality springs eliminate tip-to-tip friction and squeaking. Placed between each leaf, the smalls pads of polyurethane or Teflon keep the tips of each spring from making contact. Anti-friction pads keep you sane and keep your springs in good shape.  

Diamonds Are Your Friend

Not only does the tip of each leaf generate friction, but they can limit articulation as well. As one side of the axle goes to full droop and the other goes to full stuff, the spring twists in its mounts. With a standard cut leaf spring, the outside edges of the tip of each leaf can contact the leaf above it as it twists. This contact can limit articulation and cause friction affecting ride quality.

The solution to this problem is simple. Diamond cutting the edges of each tip at roughly a 45-degree angle eliminates the contact points. With those points of contact gone, the spring is now free to twist as much as it can. This allows you to get the maximum amount of articulation possible out of the spring.

Mini Packs

You might also be looking at mini packs if you are thinking about improving your rear suspension. How do they compare to a high-quality set of leaf springs? Well, mini packs are a half measure. Since you are sticking with most of the original springs, you don't get all the benefits that full replacement springs bring. For example, there is no military wrap with a mini pack. You also won't have diamond-cut ends on all of the leaves. And, since you are mixing thin leaves with some thicker ones, a mini pack won't be as progressive as a full replacement spring. However, a mini-pack can still add spring rate, lift, and some progression to an existing pack. And, while high-quality springs will always be better, mini packs are more affordable.

For more information, please visit Factory Steel Wheels.