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-   -   Spring vs torsion? (https://www.airforums.com/forums/f437/spring-vs-torsion-87104.html)

Aktundra 01-30-2012 08:45 PM

Spring vs torsion?
 
I am a bit behind in my research. I have a 1963 Bambi. About 1,800 lb dry weight on the axel.

This is a small trailer, and the tow rig will likely be a lifted truck. I do not have much experience with travel trailers, so not clear I understand all the implications of ANY variation to just replacing the original axel with as close to original set-up as possible. My research to-date has lead me to replacing the original axel with a 3,500 lb replacement. ( I have read the debate on whether this is to heavy, but I think it is the way to go)

Various parts shops have suggested an increased ride height from a leaf spring axel, if I am concerned about towing a small trailer with a lifted rig. I came running home tonight to research leaf springs vs torsion, and do not see a recent discussion on the forum. Are leaf springs totally ridiculous for a travel trailer? Like I said, I really have no experience with travel trailers, I just could not resist the challenge of restoring a 1963 Bambi.

I am doing a full monty, so all running gear options are on the table.

JimGolden 01-30-2012 09:19 PM

Hi AKTundra,

You will find varied opinions on this topic on here. But let me be the first to chime in :brows:

First, a little bit of history. Airstream used leaf springs for many years. I am not sure of the exact year they stopped, but I know that they still used leafs in 1958. I believe it was right around 1960 that they switched to the rubber torsion axles.

Why did they switch? From what I have read, Wally Byam (the founder of Airstream) wanted to make the trailers more robust and less problematic. Wally led caravans in the mid 1950's all over the place, through jungles and swamps and places you wouldn't take a Land Rover. One of the things that broke a lot on these trips were spring shackles. He switched to the rubber torsion axles because they are even simpler than a leaf spring setup and are very robust.

The only problem with the rubber torsion axles is that they wear out in 15-20 years. So you will have to replace them eventually. Wally wasn't really worried about having to swap the axle out in 20 years, he wanted an axle that worked great now and had a lower parts count and was bullet proof simple in the field. So he made the switch.

OK, so what about your specific case? When you say a full monty, are you making a new frame as well? If you switch from rubber axles to leaf springs, you will have to change/add spring mounts. Not that big a deal, but it will have to be done. Will you be towing where there are lots of ruts, rocks, etc.? If so, I would recommend you stick with the rubber axle for the same reason Wally went to them fifty years ago. If you get fifteen years of service out of it, then the $600 or so to replace it will seem cheap.

You can specify the "down angle" of the swingarm on the new axle, as well as its weight capacity, when you order it. If you want your trailer to sit higher, tell the axle manufacturer (most guys use Dexter or Axis now, but Henschen was the original maker and if you want a Henschen, get hold of Andy R. at Inland RV on here and tell him what you want to do and he'll work with you to hook you up) you want a 35 or 45 degree down angle instead of the normal 22.5 degree down angle.

I have read on here somewhere (don't recall exactly where...) that you shouldn't exceed 35 degrees down angle. I'm not sure why, but that's something to look into.

If you really want to jack it up high, then you may have to get radical and modify the frame and go to leafs. But if you just want a few extra inches, then you'd be OK with the rubber ones.

In fact, I'd bet you $100 your original axle is shot and is actually showing a negative down angle (meaning the rubber chords inside the axle have collapsed so much that the trailer is sitting way low from where it used to and the axle swing arms are actually angling up...as in the center of the wheel is higher than swingarm pivot point....) so that even a stock new rubber axle would probably lift you 3". So if you went to a 35 degree up angle new axle as compared to your old worn out one, you might see a 5" or so lift.

If you do go with Dexter, you'll want the biggest brakes you can get. Either with a leaf setup or a rubber one, get the 5000 or 6000lb rated axle with the big brakes. If you get the rubber axle (I believe it's a #11), you simply have them shorten the rubber chords inside it to give you the softer spring rate. That way you get the big heavy duty axle but it's soft enough for your trailer.

Hope this helps a little!

slowmover 01-30-2012 09:38 PM

Let me add to the above that torsion axles make for true independent suspension which means much greater resistance to tripping hazards, and a lower roll center. Better handling, in all respects. This is important. See the A/S video on their site of pulling an A/S through a slalom versus a square white box. While low center of gravity and good weight balance play their part, it is to the suspension type that that video makes the case for torsion arm suspensions.

While any suspension ought to be re-done every so often (leaf suspensions are ignored, but ought to be taken fully apart, not just eyeballed), a torsion suspension tends to dry rot if not used, so this single advantage goes to horse wagon crude leaf spring. Exercise that trailer -- don't let it sit for a few years -- and the torsion will last up to fifteen years.

.

Friday 01-30-2012 10:07 PM

CHeck out Timbren suspension if you want another option...

Frank's Trailer Works 01-31-2012 04:49 AM

I am going to throw in here and then enjoy the debate you opened us all up to...

I have never replaced a set of leaf spring axles(without the client insisting I convert them) I have however replaced dozens and dozens of torsion style axles. I would consider yourself lucky for right now you have a technology that may not give a true independent suspension, it does give you something that works well.
I restore trailers. I do not sell axles(but sure replace a lot of torsion style). My point of view is different than that of some others on this forum.

perryg114 01-31-2012 06:05 AM

I have to agree with 62overlander. A simple leaf spring system with cheap components you can buy at tractor supply is an asset. I am not looking forward to the cost of replacing my torsion axels. A simple axel is a fraction of the cost of the torsion axels and they should last for decades.

Perry

slowmover 01-31-2012 07:17 AM

A simple axel is a fraction of the cost of the torsion axels and they should last for decades.

I think you should run a complete set of numbers before this statement is made.

"Simplicity" is not much of a virtue unless the leaf spring suspension is taken fully apart on some schedule. Broken out there are a heckuva lot of parts. Trusting it to work correctly, otherwise, is a gamble. They fail, and it isn't pretty when it's a spring hanger or the main leaf.

A torsion axle simply isn't that expensive, especially given its' advantages. It's more of the drum brake or bias ply tire or friction bar hitch "arguments". Pennies saved . . . .

.

ROBERT CROSS 01-31-2012 07:49 AM

Just my experience....
 
Last year had a pair of 58 year old leafs re-built. $325 w/new U's, shackles, bushings and bolts. Plus my R&R.

Bob

perryg114 01-31-2012 07:53 AM

It depends on what he is going to do with the trailer. If it is going to sit the majority of its life like 99% of all trailers do then it is silly to spend several hundred dollars on a rubber axel. If he is going to pull it often and far then yes a rubber axel is going to be better.

As far as the 3500lb solid axel goes, it really does not matter if it is bigger than needed because the leaf springs determine the spring rate and not the axel rating. He does not want the trailer to be over sprung.

Perry

Short563 01-31-2012 08:02 AM

Can you please help me understand why a rubber axle pulls better?

perryg114 01-31-2012 08:13 AM

The rubber axels on the left and right sides are independent of each other and the wheel moves up and down. With a solid axel, if you hit a pot hole on one side the other side might bounce off the ground. The rubber axels are also self damping to some degree because the rubber has some friction as well a spring. One of the biggest advantages of the rubber axels is they allow the trailer to sit closer to the ground which lowers the center of gravity. With a straight axel you have to have room for the springs above the axels. They do make drop solid axels but they may cost you as much as a rubber spring axel.

The rubber axels are going to shake your trailer less and make it less likely to pogo or bounce off the road if you are in a really bad road situations such as any dirt road or driving down pop hole filled I-65 in Birmingham, AL.

Perry

markdoane 01-31-2012 08:46 AM

Gee, I have leaf spriings and I don't have any of those problems.
And I bought a new drop axle for a fraction of the cost of a rubber axle.

perryg114 01-31-2012 09:04 AM

Both systems can work well. Trailer manufactures use rubber axels to lower trailers and they have fewer moving parts to deal with during installation. I have nothing against solid axels. They would make my life easier. There is nothing wrong with staying with leafs and solid axels. Both systems work fine. The rubber axels might give you some advantages in really rough situations.

Perry

samb 01-31-2012 09:17 AM

I have five trailers right now and I use them all. Each one has a different purpose. Four of the five have leaf springs and one has the rubber torsion axle. I prefer the "horse wagon crude leaf spring". My leaf spring trailers range from 21 to 63 years old. On one of those I had a broken leaf. A visual inspection caught this early. Easy fix and not expensive. Repair parts were locally available. On another I upgraded to a higher rated axle, but retained the leaf spring set-up that matched the weight of my trailer.

If all my trailers had torsion axles that lasted the 15 years I would have had to replace 13 axles so far.

A leaf spring suspension system can be maintained. A torsion system can be replaced.

The combination of leaf springs and either a straight axle or drop axle will give you any ride height needed for your desired use.

Are torsion axles better for an Airstream and the owner than leaf spring suspension? It is a matter of opinion. Here you have my experience on the matter.
Sam

worldinchaos 01-31-2012 10:28 AM

Quote:

Originally Posted by samb (Post 1101140)
Are torsion axles better for an Airstream and the owner than leaf spring suspension? It is a matter of opinion. Here you have my experience on the matter.
Sam

Ah, as are so many things on the forums.

Personally, my decision to replace leaf spring setup with replacement in kind is motivated by quite the opposite argument of previous regarding lowering the trailer.... I have a 26" leaf setup with reverse drop that rides way too low for my offroad/ back area destinations. And I don't plan to drive at any sort of high speed through these areas-- If it takes me an hour to get down 5 miles of dirt road, so be it.

Then again, I have no actual experience with leaf v. torsion except my one 400 mile RT inaugural camping trip, in which the leaf setup seemed to work exceptionally well. Based on the physics, I wouldn't be surprised if the torsion would have been even MORE dampening of shocks and vibration while also providing Independent suspension, but that will be the accepted downside to replacing in kind.

To me, the bottom line is you should use those new axles to "Get your 'Stream On", and see as much of the beauty in our lands as possible. :wally:

Edit: On second thought, I really like that phrase. I might even make T-shirts. haha.

Jammer 01-31-2012 11:50 AM

Quote:

Originally Posted by Aktundra (Post 1100979)
Various parts shops have suggested an increased ride height from a leaf spring axel, if I am concerned about towing a small trailer with a lifted rig. I came running home tonight to research leaf springs vs torsion, and do not see a recent discussion on the forum. Are leaf springs totally ridiculous for a travel trailer?

In practice, either can work well, and as such, the choice is partly a matter of taste and tradeoffs.

Torsion axles are premium products that provide superior ride and handling. The suspension is fully independent, the unsprung weight is lower, and there is a degree of damping to the point where it is not strictly necessary that shock absorbers be used. The difference in smoothness of ride and stability is nothing to sneeze at -- comparable to the difference between cars of the 1950s and modern cars.

Torsion axles offer better ground clearance for the same ride height, because the axle tube is at frame height rather than at the center of the wheel.

There are some other benefits specific to tandem axle setups which don't apply to your situation.

Leaf springs are cheaper and are therefore more widely used on trailers (campers and otherwise), because making trailers of any kind is a cost sensitive business. Welding shops are more familiar with them and may recommend them for this reason alone. For travel trailers, it is necessary to use shock absorbers as part of the suspension design when leaf springs are used.

Neither suspension type lasts forever. Torsion axles fail with the passage of time, generally after 20 to 25 years though their performance may deteriorate somewhat sooner. Leaf springs fail with use, particularly with frequent articulation as occurs off-road or on poor roads. This manifests itself as leaf breakage, loss of curve, and failure of individual parts like shackles and bushings. It is necessary to replace shocks periodically when leaf springs are used.

A standard height trailer will ride fine behind a lifted truck as long as suitable drop hitching is used. Either leaf springs or torsion axles can be lifted if desired by using spacers or changing the spring/torsion geometry itself. There will be more stress on the springs and the frame when this is done, in either case.

Alumaholic 01-31-2012 12:33 PM

Jammer Nails It!
 
Airstreams are premium travel trailers with premium axles.
Leaf springs are cheaper to install, repair, and replace, but...
Torsion axles provide better performance and much better handling especially in emergencies.
By design, torsion axles dampen sway and oscillation.
There's a video on these forums someplace of a 500 HP sedan pulling both an Airstream and an SOB through a slalom. This video provides a graphic look at the difference between torsion and leaf-spring suspensions.
I'll link it when I find it.

perryg114 01-31-2012 02:01 PM

You would need to do the same test with an Airstream with leaf springs and one with Torsion Axels in order for the results to be meaningful. An SOB trailer has a much higher center of gravity and they are heavier and have the aerodynamics of a brick. Aerodynamics, weight, center of gravity, and axel type are all factors that improve handling and stability. Axel type is just one of those factors.

Perry

Alumaholic 01-31-2012 02:45 PM

Here's the Video
 
Watch this video, see what you think.

https://www.youtube.com/watch?v=7cMg42sW6NU

perryg114 01-31-2012 04:59 PM

The CG of that SOB is way higher than the Airstream.

Perry


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