why are leaf springs so stiff?

I was wondering this...

When towing my Escort without the Capri I can see the tires jump clear off the ground. With the Capri I see virtually no suspension movement.

Still somewhat on topic, my dad's 22' triple axle deckover for the backhoe seems to ride about the same.

Do leaf springs on trailer typically give any travel at all? Or are they just there to think there is? I mean vehicles with leaf springs ride fine though granted empty pickup trucks can hop a little.

One exception is my two place standup Jet Ski trailer...you can look in the mirror and see that thing floating along like a soft Buick back there

Literally, what gives?

Re: why are leaf springs so stiff?

A trailer is sprung to handle it's maximum capacity, when empty, the bare frame isn't nearly enough to make the springs work.
On an older trailer, make sure that the springs and hardware aren't all rusted and seized.

Re: why are leaf springs so stiff?

that is exactly why the boat has to be secure to the trailer. it take the bounce, jarring, away from the boat. the boat and trailer need to be one unit.

Re: why are leaf springs so stiff?

reelfishin said:

A trailer is sprung to handle it's maximum capacity, when empty, the bare frame isn't nearly enough to make the springs work.
On an older trailer, make sure that the springs and hardware aren't all rusted and seized.

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you hit the nail on the head. My little tinny rides the same way. it only weighs a few hundred pounds. rides a lot smoother with all the gear and a cooler in it.

In fact even my little Ford Ranger rides goofy with out any weight in the bed.

Re: why are leaf springs so stiff?

To put this in perspective, think about your car. If you happen to have a large, rear drive six passenger sedan, it likely weighs about 3800#. Six adults would average about 170# each for a total of 640#. If the manufacturer designed the car with a suspension for a 1000# load (4800 GVW) in this example, that load represents only about 20% of the total weight so suspension can be tailored for a nice cushy ride no matter what the load. A boat trailer must run empty (just a few hundred pounds on a single axle trailer) to its maximum GVW which would typiclly be either 2200# or 3500# on a single axle trailer. You can easily see the spread in empty vs loaded weights and why the springs need to be selected as they are. Trailer tires generally carry much higher pressures than cars as well (50 - 90 PSI).

Re: why are leaf springs so stiff?

reelfishin said:

On an older trailer, make sure that the springs and hardware aren't all rusted and seized.

Click to expand...

This is exactly what came to my mind. A siezed shackle.

For any arc type leaf spring to allow verticle bump absorption movement, the pivoting shackle needs to be able to do just that PIVOT

Re: why are leaf springs so stiff?

Polar_Bus said:

This is exactly what came to my mind. A siezed shackle.

For any arc type leaf spring to allow verticle bump absorption movement, the pivoting shackle needs to be able to do just that PIVOT

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If the trailer is more than a few years old, chances are the pivot points are seized or at least starting to. Especially if it's anywhere near saltwater. I pull mine apart every so often and grease them to avoid the problem.

Re: why are leaf springs so stiff?

Thanks for the points and input. When I get to it and before the rig gets back on the road I'll jack it up and see how the shackles and all are doing

Re: why are leaf springs so stiff?

thats a good tip. I never even thought of that when I went through my trailer. everything else got looked at or replaced but I didnt look at the shackles.