Trailer Suspension options... for overland trailer

[SnowLizard]

this trailer is strictly cargo. no RTT or kitchen, or electricity...

here's my setup right now...
20150701_000729 by Richard Gunn, on Flickr
20150701_000704 by Richard Gunn, on Flickr

I need to replace my axle and I figure I'd get the best I can... and swap the tires to match my 4runner bolt pattern.

I took some pictures of some boat trailers that really show off the type of suspensions... I'll let you ORDER them from best to worse in terms of smooth/overland/capacity/strength...

A) current.... torsion bar
20160604_173205 by Richard Gunn, on Flickr

B) dual leaf springs
20160604_173218 by Richard Gunn, on Flickr

C) single leaf spring, 3 link variant
20160604_173026 by Richard Gunn, on Flickr

D) dual coils with shocks, 3 link setup!!
20160604_172250 by Richard Gunn, on Flickr
20160604_172239 by Richard Gunn, on Flickr

In my opinion the weakest to strongest I'd put it this way...
A) 10 yrs old and it sags...
C) idk about the side to side roll with 1500-2000lbs on top of the axle like that
B) proven solid
D) didn't know you could to this!!!

if you were going to swap the axle out, which suspension would you choose?

 

[toymaster]

If I understand your question, you want to understand your options for suspension on your light weight trailer.

Out of those you have listed torsion is the 'best' then a leaf spring setup. The rest (that are pictured) I would not touch with a ten foot pole.

A torsion axles is a trailing arm setup and each side works independently, very little force is translated to the other side when one side hits a bump. The shock absorption is between the tire/rim/bearings and the rest of the system. All-in-all a good way of doing it. One set up from that is the timben style: http://timbren.com/axle-less/

Leaf springs have simplicity going for them. Tried and true, reliable, inexpensive, little to no maintenance. Since the shock absorption is between the axle and the frame all the force is translated to the other side of the axle as a result the axle always has a seesaw effect with the fulcrum being the center of the axle.


I would like to bring up the downfall of each of these systems. They are all fixed rate springs. Meaning if you have 1,000lbs on a 3,500lb spring you get a rough ride, this is a huge deal when we are talking light weight trailers. If you 'fix' this issue by using lighter springs then you have a less capable trailer. I guess you could swap out springs for what ever load you happen to have that day but then who is going to do that?

The absolute best suspension in terms of adjustability, versatility, and smooth ride is a trailing arm with an airbag. The amount of air pressure in each bag can be adjusted to achieve the proper spring rate for the load. (You can picture the timbren link above but with an airbag instead of a rubber springs) The downfall of this system is that it is high maintenance and high cost.

 

[SnowLizard]

that is some great food for thought, thanks for warning me about the spring loads, saved me lots of grief there...

the Timbren Axle-less is a cool setup, I'd probably go for a 2000 lbs setup. the rubber is accessible so I'd probably be able to swap it out over time.

leaf would be the tried and true setup...

I currently have a setup like pic A, and that's the 'best'? didn't expect that cause it's all sagging.. it's a 2005 trailer...

IF it's in the budget I'll go timbren, if not, I'll go leaf...

I don't want another torsion bar unless you can think of something to convince me...

 

[anickode]

It's tough to beat an old school straight axle with leaf springs. If your load doesn't change much, it's by far the most durable in the long term. You can add shocks to aleaf spring setup, just like a truck has. If you want more travel, go with longer springs and shackles.

The single leaf spring is a horrible idea. Any unevenness in your load side-to-side, and it's going to lean badly. Also, the total weight of the trailer is concentrated on a single cross member. Not at all what you want.

The coils, shocks, and 3-link is silly for a trailer, especially all flimsy like the one pictured here. One hang up on the trailing link, and your trailer isn't going to track straight anymore.

Rubber torsion axles are good. The big downside to most factory torsion axles is there's no way to mount shocks to them. Plus their suspension travel is quite limited, and the rubber breaks down over time. Faster if you do a lot of rough terrain.

My first choice would be a Spring over Axle leaf spring setup with shocks. Its tried and true, cheap, and easy to maintain. Bust a spring, and you can weld it in an emergency and find a replacement in just about any town.

Second choice would be trailing arms with bags and shocks or adjustable coilovers. Downside is the initial cost, extensive fabrication, and difficulty finding replacement parts. Fleet and Farm doesn't typically carry Heim joints and air bags. Blow an airline or bag, and you're traveling with zero suspension.

I find it humorous that the serious off road guys wouldn't touch an independent suspension vehicle with a ten foot pole, but when it comes to a trailer, they love to hate on straight axles, pointing out all their downfalls.

 

[toymaster]

....I find it humorous that the serious off road guys wouldn't touch an independent suspension vehicle with a ten foot pole, but when it comes to a trailer, they love to hate on straight axles, pointing out all their downfalls.

That is because of physics and the different purpose of a trailer vs. the tow vehicle. You want the trailer to float over obstacles with the least amount of resistance as possible. You want the vehicle to be able to obtain as much traction as possible. In other words, the transfer of weight on a solid axle helps you to get traction and hurts you in the application of a trailer.

Kinda' along the same line as deflating the tires on the vehicle to create a larger surface area to obtain more traction vs. keeping the trailer tires properly inflated to reduce rolling resistance.

 

[azscotts]

If your current torsion bar setup is sagging after 11 years, I'd say that's a pretty good ROI on your investment. A new Dexter Torflex without backing plates, etc. is around $400. Has your 4Runner gone 11 years without new shocks/struts? $400 doesn't seem like a huge investment for another 10-11 years of what seems to be regarded as one of the best axle setups around. That trailer looks pretty light so you'd probably get away with a 2,000lb axle. My build experience is with aircraft, so I don't have a ton of trailer build experience either...just for reference.

My build (currently in CAD and BOM stage) will be using a 3,500 Dexter Torflex. I figure if I have to replace the axle after 10 years, that's a pretty good lifespan.

PS) I had 2 different 3rd Gen 4Runners (highly modded). Loved them both!

- Deckplate Mod
- Tundra Brake Mod
- Performance Shocks
- SS Brake Lines
- Lots of electrical mods like hardwired GPS, power inverter, laptop, etc.

 

[skersfan]

Try contacting the US Army, Marine Corps, All NATO forces and check on the torsion axles. Every single trailer below 5K is using torsion axles, the last I heard both AlKO and Dexter were being placed on all 10K and above. 10K and above do come with air bags on the torsion axle. But above 10K likelihood of crossing ditches, rocks becomes less of a problem.

I have never tried the Timbren, but your frame needs to be quite strong, and if you go above 3K I believe they require a cross member that hangs down, actually making it a axle.

Cross bracing of the frame on the lower weight limits will be required. Or if you seriously off road it, it will look like a duck in a few years.

If you go torsion, have them built for you, you should be with in a couple of hundred pounds of max weight, IE 1800 pound trailer no more than a 2000 pound axle. Dexter makes axles down to 1800 with 3500 pound bearing and brake systems. It will cost you 500 bucks I think, but it will out last the others, be far more resistant to damage, simple. I have used them for many many many many years. Air bags form creases, get punctures. Get the right spring rate for your trailer with torsion and I guarantee it can go anywhere your tow vehicle can take it. Not just over a single rock in the middle of a road.

 

[SnowLizard]

Ok, I'm convinced... I'll stick with the torsion axle... sounds like it's the best out there for the buck...
anyone know where I can order a torsion axle with the custom setup? I also need to lift the trailer to make it ride lvl with the new hitch height... raised it 9.75 inches above stock.

AZscotts - are you in scottsdale? I too have modified my 99... my wifes 97 is stay'n stock... here's the same tow vehicle that I posted earlier...

20160528_091018 by Richard Gunn, on Flickr

 

[borison]

That's a good looking bumper.

 

[Semi-Hex]

FYI, I have matching 4runner wheels on my trailer but the threads are not metric so I have a different set of lug nuts (with shoulders or whatever the inners part is called) on my trailer.

 

[azscotts]

Nope. I'm in Gilbert. Been here since 1997, since before Gilbert was cool.

I'm right across the street from the Lifetime Fitness.

- Scott

 

[SnowLizard]

That's funny in in downtown Gilbert, rock on!

 

[IM1RU]

You can order any kind of set up you like from Dexter Axle, I just put a Trimbren set up on my trailer. http://www.expeditionportal.com/for...bren-3500HD-suspension)?p=2101359#post2101359

 

[SnowLizard]

took the trailer to 3 different shops, only one 'sounds' reasonable...

I'll probably go with the classic leaf spring setup, any setup I go I'm going to need a subframe...

the torsion bar has it's bolt points outside my 'tappered' trailer body... companies won't make them any other way...
the Timbren is the same concept, they hug even closer than the torsion bar against the body
the current trailer frame can't handle a leaf spring setup, it needs extra support.

I got quotes on each setup, and I'm not excited about the prices... waiting on one more shop before I do something I regret...

so far the quotes are are %160-%260 than my hopeful budget...

 

[Gizzard Stone]

I have a similar trailer (aerotow) with the original leaf spring setup and am wanting to go Torsion. If yours is like mine, and it looks like it is. There's just a strip of metal welded to the frame where the springs are attached.

Here's my trailer: https://www.youtube.com/watch?v=RXwNBErl79I

-M