The torsion axle requires less space; it doesn't need clearance around it for the axle to bounce around. Allows the trailer floor to be lower to the ground.
If that's not an important factor, straight axle with leaf springs is cheaper.
Almost all trailer suspensions are waaaaayyyy too stiff.
Torsion axle likely has better damping (rubber insert). May have dynamic toe problems. Not likely to have brakes.
Torsion axle has fixed spring rate, you get what they stuffed in there plus tire deflection. Same with ride height. Over-slung or under-slung. Buy a new, heavier motor, and you need a new trailer.
Solid axle with leaf springs can be altered easily by adding or removing leaves. Break one on the highway and you will need a tow truck. Break a spindle on the highway with a solid and you buy just a new axle or insert, then change it out.
Torsion axle less likely to drag home seaweed, fishing line(s) and the other crap that hangs around boat launches. Just don't back up into something that will block the wheel. Something will get ripped off (been there).
You can air bag torsion axles to be progressive, and adjustable. They do have models with brakes.
Personally I'd go torsion on a nice small trailer, but I will never have a big truck or SUV to tow with, in which case I wouldn't care so mucht.
If I did it myself I'd get those bag springs that are designed to fit around a shock shaft. That way you could put it around the rubber spring for redundancy.
If you had a dual axle you'd have some redundancy
Imagine unloading a trailer with air bags. Just let all the air pressure out and you're inches closer to the ground.
I can't say I'd use it for a boat trailer. I'm already crazzy about boat trailers anyways. People get those axles under water when they're hot off the highway and never think to lube their bearings. And they don't even rinse it off with the hose when they're done. A used boat trailer is like a ticking time bomb unless you go over all the neglected parts. You don't want to get stuck on the side of the highway with a seized bearing.
That being said straight axle trailers have the advantage that if you do have a problem almost any trailer shop will be able to get you up and going again if they have a big enough collection of parts. And more cheaply too than a torsion axle.
Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology
The rubber springs in the normal commercially-available rubber-torsion axles are so stiff that it's pointless to add airbags - they hardly move anyhow.
I've only seen air suspension on really big trailers - heavy-duty trailers for 18-wheelers - where it's commonplace.
I've seen coil springs and hydraulic shock absorbers used on smaller trailers with a linkage-located straight axle (as opposed to the trailing-arm geometry of the commercially-available rubber torsion axles). In fact, I converted my own leaf-sprung straight-axle trailer to use coil springs and shock absorbers with the axle located by a simple linkage. I did this because I got sick of the rough ride from the leaf springs beating up everything in the trailer, shaking tie-down straps loose, rearranging cargo, etc. This worked very well, and you could drive over rail crossings - or I-75 south of Detroit! - with impunity.
If you can fit coil springs, you can fit airbags, but there's more to go wrong.
It would not be impossible to take a coil-sprung twist-beam axle from any common front wheel drive car, and make that fit a trailer. The mountings for a twist-beam axle are pretty straightforward to fabricate. I haven't seen it done.
I don't like torsion axles on boat trailers because of the long term internal corrosion issues.
At least with coil or leaf springs you can see them.
My cousins trailer uses leaf springs (under mounted) with leaver action air shocks. The leaver action keeps the profile low and the air pressure can be adjusted for the load.
How much too stiff are most boat trailers? We took a 5 leaf spring pack from a trailer with the same supposed rating and took 3 leaves out of it.
And Bearing Buddy is the way to go. Then you only have to worry about keeping them serviced. (We did install a grease fitting to inject grease between the spring leaves)
I think you'll find it funny to see a car towing a car. You'd never see that in America. The standard here is to have the biggest tow vehicle possible, even if you're just going to move the ride on mower once a year over to your buddies house when his breaks. That and I think the max you're allowed to tow with most cars or pickups here is like half the weight of the vehicle but they don't have an allowance to tow more with trailer breaks and anti sway bars?
Some other parts of the world allow you to tow the whole weight of the vehicle! (assuming you have met some wild safety standards, trailer breaks, anti sway bar, etc. etc.)
All this is if I remember correctly. But I remember seeing some wild things like in europe a car towing a small non-pop up camper.
Marine greases do suck sometimes, but some are actually environmentally friendly as in biodegradable within our lifetime.
Personally I just bought an electric grease gun and I just pump everything on a trailer full of grease until I see clean stuff start to come out. Takes a while sometimes.
Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology
Pardon my 3am blunder, you are correct! I should have only said cars.
If you can find cars and (not trucks) that don't say this in the manual:
"Toyota does not recommend towing a trailer with your vehicle.
Toyota also does not recommend the installation of a tow hitch
or the use of a tow hitch carrier for a wheelchair, scooter, bicycle, etc. Your vehicle is not designed for trailer towing or for the
use of tow hitch mounted carriers"2019 camry manual
You can find a plethora of cars and small crossovers which have a tow rating of half their weight or lower.
Almost all of the cars on that list have a tow rating of LESS than half of their weight. Look up the curb weight of a malibu for example.
Here's what I was talking about for other countries:
Here the limit is 1000 lbs without trailer brakes.
With trailer brakes?
Engine: 6.6L V-8 turbo diesel
Horsepower: 445 @ 2,800 rpm
Torque: 910 lb-ft @ 1,600 rpm
Transmission: 6-speed auto
Tow Rating: 20,000 lbs. conventional/ 22,700 lbs. fifth-wheel
(The 2020 model will tow 35000 lbs.)
Bill
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"Why not the best?"
Jimmy Carter
