Tuesday, June 25, 2024

What Size Leaf Springs For Boat Trailer

Is This A Thing

Trailer Leaf Springs

Lets start by looking at some standards. Because the most popular axle capacity for DIY is 3500#, well use this as our example. Other capacities have similar standards and effects.

To get a feel for sizes, well turn to the Dexter Axle publication on 3500# axles. This graphic below gives a lot of information, but focus for a minute on the red circle items. There are at least 3 popular-ish spring lengths indicated. Looking at other sources we also find 27 is sort of common , as well as 25.

The info here is from Dexter, and since they are probably the biggest manufacturer, it makes sense to consider what they think is important to publish. Another big one to check is eTrailer.com And a quick search there shows similar available trailer leaf spring length. Heres a partial screenshot.

As you can see, there really isnt a true standard. However, from experience, the sizes that are close will all work with the same mounting. And, if youre building new, its best to follow the manufacturers suggestions for spacing anyway. Even with our trailer plans, we specify the spring mount positions then, defer to the components you want to buy rather than forcing you to do it as we say.

The Breakdown: Trailer Suspension

For a lot of customers, trailer suspension is often something not always thought about. After all, isnt it just coils, spring hangers bolts, springs, and shock absorbers? But are things really that simple? In truth, its a lot more complex than one would think. It entails knowing the basics of a trailers suspension and more importantly suiting the right trailer suspension to your intended trailer purpose. This article breaks down everything you need to know about trailer suspension.

The Wrong Way To Measure Leaf Springs

The wrong way to measure springs is eye to eye. You know, taking the tape and measuring the spring straight from one end to the other.

Its wrong because springs flex up and down depending on the weight applied, which changes the length of the spring a different amount depending on the springs rate So that method doesnt tell you your springs size at all.

Worse yet, it also doesnt tell you where your center bolt is located. The location of the center bolt is where your axle and spring meet.

Do I need to stress the importance of making sure your spring is connected to the axle correctly? No? Oh, good.

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Products Related To This Search

A trailer trailer leaf spring is used for vehicle & trailer suspension. It consists of a stack of slightly curved narrow steel strips which are called “leaves”. The curve in the steel allows it to absorb the energy transmitted through the tires by the bumps on the road. There are two types of leaf springs:

Double Eye Leaf Springs are used with the shackle-type suspensions.

Slipper Leaf Springs are the heavy-duty springs used with slipper-type suspensions.


When selecting a trailer leaf spring for a new trailer, or matching to replace an old spring you need to take the following measurements into account:

1. Width of spring: A measurement across the bottom of the spring leaves. Corresponds with the width of the spring seats

2. Free Length: A measure of the length of the spring from eye to eye

3. # of Leaves: A count of the number of strips of steel stacked together. Count at the centre point.

4. Flat Length: A length measurement which follows the actual contour of the spring. This measure is better than the Free Length measurement because old/used springs “relax” after use. Flat length is measured by taking the length from the centre of one eye to the centre bolt on the sping, repeating on the other side, then adding the two together.

5. Eye Size: When building a trailer, the eye size of the spring is necessary to select the other hardware pieces that bolt to the spring.

What Leaf Springs And Bearings Can I Purchase At Anaconda


ARK products are in demand with Australian road users. As a 100% Australian owned and independent company, ARK understands Australian conditions, and the best ARK products are proudly supported by Anaconda. Leaf springs available include 3,4,5 and 7 leaf galvanised springs for lightweight and heavy duty trailers, with features that include:

  • 45mm x 6mm leaf pieces with 1/2″ nylon bush
  • Galvanised steel that can handle all outdoor conditions
  • Leaf spring weight bearing capability from 600kg to 1350kg per pair

In other words, you can pair your trailer and outdoor style with ARK products that are tailor-made. With ARK leaf springs attached, you will appreciate a more comfortable and balanced towing experience.

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Final Thoughts On Leaf Spring Length

The concepts of trailer leaf spring length are not something to lose sleep over. While there are differences for performance, choosing one length over another will not make or break the trailer. We bias toward longer springs because its the right direction, but other factors can influence that decision more. A tandem axle trailer with really small tires, for instance, might want short springs just for maneuverability. There is nothing wrong with that choice.

The biggest factor in choosing springs should be the availability of correct components to give you the action and function you want from the trailer. All other things being equal, choose long.

Why Choose Ark For Leaf Springs And Bearings

ARK is an innovator ahead of its time. ARK was the first company in Australia to introduce the lockable jerry can holder, tow ball shin protector and quick assembly mechanisms. ARK manufactures state of the art towing systems that can be adapted to suit almost any type of motor vehicle. ARK products are built to handle tough Australian conditions and long distance journeys. These leaf springs and bearings are highest quality, constructed from heavy-duty materials so you can have confidence in your trailer and towing equipment for short trips or long distance journeys.

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The Good Bad And Ugly Of Trailer Leaf Springs

The Good, Bad, and Ugly of Trailer Springs

Trailer springs are essential part of trailer suspension and as we all know you cannot go anywhere without your springs. Unfortunately, many of us do not pay attention to our springs and years can go by before we think of them. Usually, this thinking occurs when you are sitting on the side of the road or boat launch waiting on that expensive tow truck that is heading your way! And the worst thing about it? It can be avoided and all it takes is knowing what to look for before leaving on your fishing trip. A good trailer spring makes a happy fisherman and boater! Any of these problems and issues we will cover can occur on Double Eye Springs, C-Hook Springs, and Slipper Springs at any time. These types of leaf springs can be found on boat trailers, utility trailers, and enclosed trailer so make sure you check every trailer you may have to avoid suspension issues in the future.

Trailer springs should always be inspected for cracks and breakage to avoid failure of the trailer spring. Cracks typically appear near the philister bolt and near the eye of the bolt that connects your spring to your hanger. Anytime you see a crack or break in the spring it is time to replace them. When a trailer spring fails you can receive significant damage to your trailer and boat such as complete suspension failure, cracks in the frame, tire or hub damage, and trailer axle damage.

The Cracked Trailer Spring
The Separated Trailer Spring

Spring Leaf Suspension Tested And Proven

How to Measure Leaf Springs

Some of our competitors are pushing Torsion Bar Suspension. Not us. We like our system, it doesnt bounce when towed empty. It not only costs a lot less, but you dont have to replace the whole suspension system if it needs repaired. Also, the rubber inserts in the torsion system lose memory and strength if a loaded trailer sits idle for an extended period of time. At ROAD RUNNER, we use simple, tried, and practical technology the kind that makes sense.

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Does Anaconda Stock Other Towing Equipment Also

Yes, we do. At Anaconda you will find a wide range of towing equipment, parts and accessories. Our extensive product range includes adjustable towing mirrors, towbar shin protectors, tow ball covers, hitch steps, tiedowns, d-shackles, jockey wheels, coupling locks and much more. At Anaconda, we stock highest quality gear from premium manufacturers so we can provide you with the best products for the lowest available price.

If you are looking for trailer lights, webbing straps, wobble roller brackets, trailer adaptors, winches, trailer cable, or anything else to get you on the road, check out the amazing Anaconda collection.

Trailer Axle Leaf Spring Length Why

So, why do they have so many different spring lengths? What trailer leaf spring length should I use? Does spring length even matter?

Lets start with the last question, and work to the first. I dont have definitive answers, but Ill share some facts and perspective.

Does Spring Length Really Matter?

In a word, Yes. How much is debatable, and it depends on what youre doing with the trailer. So lets break it down into a few key points.

  • The biggest advantage to long springs is better ride. In general, longer springs give a better ride. You can see this in the evolution of pick-up trucks. As the years go, truck and SUVs are getting longer rear leaf springs. They support load just as well long or short, but the bump dynamics are better with longer springs. In general, longer springs have a lower deflection rate which helps to absorb bumps better. It allows more motion with smaller forces. For trailers, a longer leaf spring length means the trailer doesnt react as quickly to bumps, so it doesnt jar as much.
  • Longer springs spread forces more. With leaf springs, the load effectively divides from the axle so the front of the spring has half the load, and the rear has half. If we think about extremes, a super short spring puts all the force at one-ish point on the frame. A really long trailer leaf spring length puts two force points, half as much, far apart and that makes less stress in one area.
  • What Trailer Leaf Spring Length Should I Use?
    Why So Many Spring Lengths?

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    Small Size Trailer Leaf Spring For Light Duty Boat Trailer In American Market


    Small size trailer leaf spring for light duty boat trailer:

    For light duty trailer leaf springs, There are 6 end treatment styles:

    1. Double eyes slipper springs,

    2. Open eye slipper springs,

    3. Flat end slipper springs,

    4. Radius end slipper springs,

    5. Hook end slipper springs,

    6. Parabolic type springs.

    These leaf spring are very popular in North America, Australia and New Zealand markets.

    What’s the leaf spring ?

    Leaf Spring is one of cells in auto suspension system, the main function is transmitting all force and moments between wheels and car frame, relax impactive load caused by the road surface and realize vehicle guidance, makes vehicles normal drive. It is a necessary component of truck, trailer, special cars and other vehicles.

    The main three styles of leaf springs:

    1. Multi-Leaf Spring This type of leaf spring has more than 1 leaf in its assembly. It consists of a center bolt that properly aligns the leaves and clips to resist its individual leaves from twisting and shifting.

    2. Mono Leaf Spring Consists of one main leaf where the materials width and thickness are constant. Example the leaf will be 2 1/2″ wide throughout its length, and .323 in thickness throughout its entire length. The spring rate is lighter than other styles of leaf springs and usually requires a device to control positive and negative torque loads as well as requiring coil springs to hold the chassis at ride height.

    The function of automobile leaf spring:

    Trailing Arm Independent Suspension

    Double Eye Leaf Springs For Boat Trailer

    When it comes to this suspension, theres zero impact transfer happening from one trailer side to the next. Wheels usually remain vertical all throughout the travel. Whats more, theres greater movement range. For those planning to travel off-road, its missing cross-vehicle axle beam makes for excellent ground clearance advantages.

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    S To Identify And Measure A Trailer Leaf Spring

    Step 1: Determine Type of Trailer Spring

    Determine the type of trailer spring. What do the ends of your trailer spring look like? Below are images of the most common types of trailer springs. You will need to know if you have a double eye spring or a slipper spring with a flat, radius, open eye, or hook end.

    Step 2: Measure Width of Spring

    Measure the width of the spring. The majority of trailer springs for boat, motorcycle, horse, camping, flatbed, and utility trailers range from 1-3/4 to 2 inches wide. To determine the width, measure across the top of the top leaf.

    Step 3: Measure Length of Spring

    Measure the length of the spring. If you are replacing a spring, getting the same length is important. To measure the free length, refer to letter C below. It is important that your trailer is unloaded when measuring the length. When determining length , measure from the center of one spring eye to the center of the other spring eye for double eye springs. Measurements will vary depending on the age and fatigue of your spring. We offer a large selection of trailer springs. Determining the length first, will narrow your selection down considerably and make finding the correct spring quicker.

    Step 4: Determine Capacity

    Step 5: Measure Free Open and Arc of the Spring

    Trailer Spring Capacity

    The capacity rating is per spring. If you have a 6000 lb. rated trailer axle with two springs, use two 3000 lb. rated springs.

    Change Springs in Pairs

    How To Select Replacement Leaf Springs For A Trailer

    Buying replacement parts for your trailer isnt always the easiest thing to do. More often than not, you dont know what to call a particular part & you certainly dont 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.

    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.

    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

    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.

    Double Eye Leaf Springs

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    We Help Maintain American Icons By Manufacturing Leaf And Coil Springs Right Here In America

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  • Spring Tech 101

    We have been manufacturing springs for American vehicles for over 80 years. Our process and expertise has been continuously refined and improved over the century and our Spring Tech section reflects some of that specialty knowledge.

    Browse our many articles, watch videos produced in partnership with AutoRestoMod, and learn all about your spring suspension here.

  • Buy Ford Manuals
  • Spring Tech 101

    We have been manufacturing springs for American vehicles for over 80 years. Our process and expertise has been continuously refined and improved over the century and our Spring Tech section reflects some of that specialty knowledge.

    Browse our many articles, watch videos produced in partnership with AutoRestoMod, and learn all about your spring suspension here.

  • How To Purchase At Anaconda

    How to Identify & Measure a Leaf Spring for a Semi Truck or Trailer

    Anaconda is Australia’s biggest camping, outdoor and adventure retailer, and we provide in-store and online shopping for your convenience. For first-hand experience of ARK products and other great towing gear, visit your nearest Anaconda retailer and speak to a product expert.

    If shopping online, simply make a wishlist, add products to your shopping cart, and proceed to checkout for speedy payment and delivery to your door. At Anaconda, we offer afterpay, gift cards, weekly specials, Anaconda Club deals, and the lowest available price on every stocked item. Explore great ARK products today and save money with every purchase.

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    How To Measure Springs

    Our Lund Boat with Heritage Trailer had four springs that each were three leaf. They were rated at 1250 lbs each. Since our boat, motor and trailer fully loaded was right at 5000 pounds we determined that we would replace all springs with stronger leaf springs, and moved up to springs that were four leaf, and rated 1500 lb each. This also meant that we needed to order longer U-Bolts for our axle mount. Next we measured the old leaf springs. Stengel Brothers Trailer Springs walks you through how to do this and offers a phone number if you have questions. They have springs of virtually every size, rated weight capacity, and choices of 3, 4 or more leaves. In order to double check measurements we traced the outline of one spring on a large piece of cardboard, then used a tape measure to measure the dimensions – we wrote down all the dimensions shown in the drawing above.

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