Solid axle versus independent suspension

[MOAK]

I run a dexter ez lube 3500 lb solid axle. It has at least 40,000 miles on it and with a bit of maintenance has never failed. A few years ago I upgraded from slipper springs to double eyed leafs and shackles. A friend is looking to buy a trailer and insists that an independent suspension is the only way to go. I say no. Unless you have tandems suspension articulation is a myth. The trailer will articulate at the hitch well before any suspension will compress or droop. If the dexter ever fails it is easily replaced. Not so true with the independents. Hey, I may be completely wrong in sticking with my KISS methodology. However, It is worth the discussion. Have at it and educate me a bit.

 

[smritte]

I just had this conversation. If you actually understand how suspension works, you would see how little the bolt on independents benefit you. There is the cool factor though.
Basic suspension theory. Everything not supported by the springs is called "unsprung weight". As your tire moves up and down, this weight becomes kinetic energy. Kinetic energy is absorbed into your suspension and converted to heat. Springs support the weight and shocks control the speed. The shocks main purpose is controlling the speed of the unsprung weight and converting kinetic energy to heat.
With that out of the way

Independent.
The Good. Less unsprung weight, less kinetic energy, great for track racing, great for long travel off road, smooth, one tire doesn't effect other tire.

The Bad. More body roll, the trailer manufactures run two types of springs. Torsion and rubber. Torsion's are good, rubber is not. Most don't run shocks. The energy needs to go somewhere. That means it will be absorbed into the spring and the energy is not being properly controlled. The rubber springs have very little travel and can "work harden" over time.

Solid.
The Good. Less expensive, easier to maintain, can be made smooth if the springs are longer with the proper shock, less body roll.
The Bad. Heaver, more unsprung weight to control, most people run short, over stiff, unshocked, trailer springs.

Which is better? Independent is nice if set up properly. Most run too high of spring weight, no shocks and rubber springs with about 3 inch's of compression (spring travel not arm travel). I wouldn't mind building a nice long travel, trailing arm suspension for my trailer. I would either use a coil spring or a torsion. Tune a nice gas shock and be able to pull it faster down a dirt road. But no, I cheaped out and built a long spring solid axle with a gas shock that is tuned pretty close out of the box.

Some years ago I did video footage of my M100 and my buddies similar build. I used long springs with no shocks and he had the normal short, heavy trailer springs with no shocks. 40 mph down a dirt road, mine bounced all over but still towed ok. His was all over.
Both towed just fine on the street.
When I added shocks to both, his trailer had a bit of movement, with the suspension doing most of the work and my trailer box barely moved, with the suspension doing all the work. About a year later I led a group over the Mojave Road. One of the guys had the Timbren suspension. On the rougher roads, his trailer was bouncing quite a bit, mine was not. When I suggested he run a shock and showed him some video of his trailer, his reply was, this suspension is designed to not have shocks and I don't have any problems with not running shocks.
Years later, I have watched different off road trailers and their mannerisms off road. The only ones that impress me at all are the torsion/trailing arm if the proper shock is added. I can build any design I want and have built or helped build a number of desert race, rock crawl and track suspension systems.
My new trailer has a solid. KISS

Hopefully no one is insulted/hurt by my findings. I'm sure someone will chime in and say they never have issues. That's not the point of my post. My point is, here is how they work. If your not happy, understanding the differences will help you make yours better if needed.

Remember, just because the latest trend is to do something, doesn't make it the best. If it were true then all those smokers who have been smoking for years and "never have problems", would be correct also.

 

[MOAK]

I just had this conversation. If you actually understand how suspension works, you would see how little the bolt on independents benefit you. There is the cool factor though.
Basic suspension theory. Everything not supported by the springs is called "unsprung weight". As your tire moves up and down, this weight becomes kinetic energy. Kinetic energy is absorbed into your suspension and converted to heat. Springs support the weight and shocks control the speed. The shocks main purpose is controlling the speed of the unsprung weight and converting kinetic energy to heat.
With that out of the way

Independent.
The Good. Less unsprung weight, less kinetic energy, great for track racing, great for long travel off road, smooth, one tire doesn't effect other tire.

The Bad. More body roll, the trailer manufactures run two types of springs. Torsion and rubber. Torsion's are good, rubber is not. Most don't run shocks. The energy needs to go somewhere. That means it will be absorbed into the spring and the energy is not being properly controlled. The rubber springs have very little travel and can "work harden" over time.

Solid.
The Good. Less expensive, easier to maintain, can be made smooth if the springs are longer with the proper shock, less body roll.
The Bad. Heaver, more unsprung weight to control, most people run short, over stiff, unshocked, trailer springs.

Which is better? Independent is nice if set up properly. Most run too high of spring weight, no shocks and rubber springs with about 3 inch's of compression (spring travel not arm travel). I wouldn't mind building a nice long travel, trailing arm suspension for my trailer. I would either use a coil spring or a torsion. Tune a nice gas shock and be able to pull it faster down a dirt road. But no, I cheaped out and built a long spring solid axle with a gas shock that is tuned pretty close out of the box.

Some years ago I did video footage of my M100 and my buddies similar build. I used long springs with no shocks and he had the normal short, heavy trailer springs with no shocks. 40 mph down a dirt road, mine bounced all over but still towed ok. His was all over.
Both towed just fine on the street.
When I added shocks to both, his trailer had a bit of movement with the suspension doing most of the work and my trailer was still with the suspension doing all the work. About a year later I led a group over the Mojave Road. One of the guys had the Timbren suspension. On the rougher roads, his trailer was bouncing quite a bit, mine was not. When I suggested he run a shock and showed him some video of his trailer, his reply was, this suspension is designed to not have to and I don't have any problems with not running shocks.
Years later, I have watched different off road trailers and their mannerisms off road. The only ones that impress me at all are the torsion/trailing arm if the proper shock is added. I can build any design I want and have built or helped build a number of desert race, rock crawl and track suspension systems.
My new trailer has a solid. KISS

Hopefully no one is insulted/hurt by my findings. I'm sure someone will chime in and say they never have issues. That's not the point of my post. My point is, here is how they work. If your not happy, understanding the differences will help you make yours better if needed.

Remember, just because the latest trend is to do something, doesn't make it the best. If it were true then all those smokers who have been smoking for years and "never have problems", would be correct also.

Long live KISS method !!

 

[MidOH]

Torsion is preferred. But I fail to see why it would matter to overlanding. Tandem axle 10 000# trailers for sure. But only, if not for heavy equipment. Like a tandem dually flatbed trailer. Solid axles are best for that.

But for overlanding wee lil trailers?

 

[Boostpowered]

Using a axle from an old truck or jeep even the trailing arm axle off a mini van would be stronger than most commercial trailer axles and give better flex.

 

[JCarter]

Independent suspension fail. Not my video 15-sec video, but demonstrates the issue with independent suspension.

I did not have any issues taking that line using a front solid axel.


Update: My apologies @MOAK, I posted based on the title of the thread. I failed to realize it was under the trailer section of the forms. ¯\_(ツ)_/¯

 

[madcratebuilder]

Driver and high CG, just my opinion.

 

[MOAK]

Torsion is preferred. But I fail to see why it would matter to overlanding. Tandem axle 10 000# trailers for sure. But only, if not for heavy equipment. Like a tandem dually flatbed trailer. Solid axles are best for that.

But for overlanding wee lil trailers?

Yea, I used to think the same. My trailer had a 1,700 lb axle and it blew out the spindles, once each side. I’m a slow learner, so my third axle is big enough. The 3,500 lb spindles and bearings can take the beating of off road terrain that our 1/2 ton trailer gives them.

 

[m_lars]

Independent suspension fail. Not my video 15-sec video, but demonstrates the issue with independent suspension.

I did not have any issues taking that line using a front solid axel.

He's talking about trailers, not how awesome your Jeep is...

 

[m_lars]

It seems those ultra fancy camp trailers like to tout high ground clearance because there's no axle in the middle. Yes, there's a clear expanse in the middle but those giant swing arms with the dual shocks hang down farther than a straight axle does.

 

[MOAK]

It seems those ultra fancy camp trailers like to tout high ground clearance because there's no axle in the middle. Yes, there's a clear expanse in the middle but those giant swing arms with the dual shocks hang down farther than a straight axle does.

Yes, I’ve never understood that. My solid axled trailer has 14.5” of clearance and the deck sits 24” off the ground which is more clearance and way better break over angles than any tow vehicle.

 

[RoyB]

Independent, torsion type axles are nearly universally used on horse trailers because of a much smoother ride on the horses legs. There are videos showing this somewhere. Many torsion axle trailers , even with rubber springs, have thousands upon thousands of miles with no issues.

My next camping trailer will have torsion so my gear gets a smooth ride......

 

[smritte]

Independent, torsion type axles are nearly universally used on horse trailers because of a much smoother ride on the horses legs. There are videos showing this somewhere. Many torsion axle trailers , even with rubber springs, have thousands upon thousands of miles with no issues.

Without building a custom suspension, I would agree. What is offered out there as a kit, the torsion in my opinion is the best.
The data though on the rubber springs and or the torsion horse trailers is street with a small section of graded dirt thrown in. My only complaint with the bolt in systems is the lack of choices on the spring rate. For the most part they work. I would like to see if you can choose the rate and if you can get the suspension with shock mounts or if you have to "mod it" yourself.

Most trailer springs are designed for one purpose, heavy weight support not smooth travel. Most spring rates are designed around the axle rating. If you want to haul #2500 you generally buy a #3500 axle with #3500 springs. My M100 has #600 springs on a #1400 trailer. That means my springs will compress 1 inch with #1200 of weight on them. With the way leafs deflect, I get about 3-4 inch of movement at 30mph on a rough dirt road and about 6 inch of total travel. The trailer box itself rides smooth.
Trailer manufacturers have to build a "max weight" trailer without having any way to know the final outcome. This limits our choices to either build your own suspension, designing it properly or buying a system and calling it good.

 

[HuddExpo]

I have had quite a few trailers from torsion to independent to leaf spring. The best riding and favorite setup is my teardrop where I swapped in long wide leaf springs from an older Land Cruiser with some shocks. The springs have the load carrying capacity I need, but are very soft. That softness along with the shocks make my trailer ride super smooth over all types of terrain. It is the first time I have had a trailer ride so smoothly that the food, drinks, salt, pepper, etc hardly move. Its very nice arriving to camp not having to worry about if the drinks are shaken or if anything inside has moved around. A leaf spring suspension is a super simple setup and proves that you don't need a complex suspension with all sorts of moving parts, etc. to get a nice ride. How well something rides normally comes down to the springs being used, not necessarily the type of suspension, especially in trailers. I will never do torsion or independent again, but I will always strive for a long, wide leaf spring setup.

 

[Rath]

It seems those ultra fancy camp trailers like to tout high ground clearance because there's no axle in the middle. Yes, there's a clear expanse in the middle but those giant swing arms with the dual shocks hang down farther than a straight axle does.

sure, but having things hang low that are RIGHT beside the tire, makes very little difference as the tire is what goes over things. The middle is where things will get hung up.

If you want ground clearance, independent is the way to go on trailers.

 

[Billiebob]

The best riding and favorite setup is my teardrop where I swapped in long wide leaf springs from an older Land Cruiser with some shocks. The springs have the load carrying capacity I need, but are very soft. That softness along with the shocks make my trailer ride super smooth over all types of terrain.

This will be the next step with my SquareDrop.

 

[Billiebob]

sure, but having things hang low that are RIGHT beside the tire, makes very little difference as the tire is what goes over things. The middle is where things will get hung up.

If you want ground clearance, independent is the way to go on trailers.

If you are running tha same tires on the truck and trailer, a straight axle on leafs will have more clearance than the pumpkin of the trucks rear axle. So why worry unless the tow vehicle has portals.

 

[Rath]

trailers don't follow exactly where your rig does, your rigs axle is much stronger, and can handle scraping on things a lot better. your rig will articulate a lot more than your trailer will. If you're doing hardcore wheeling with a trailer, it's a no brainer independent will be better for it. Handles bumps FAR better as well. where a solid axle rig will articulate to keep tires on the ground over uneven terrain, a solid axle trailer will not. independent will allow it to stay more even, and less chance of tipping, less strain on the hitching mechanism, the list goes on and on. also not everyone runs the same size tire on their trailer. I wont be. I will only have 31.7" tires on my trailer. so my clearance will be a lot less on the trailer.


that being said, I'm putting a solid axle under mine. as the pros of independent don't outweigh the pros of a solid axle for my application. They each have their place. It's about finding what works for you.

 

[m_lars]

sure, but having things hang low that are RIGHT beside the tire, makes very little difference as the tire is what goes over things. The middle is where things will get hung up.

If you want ground clearance, independent is the way to go on trailers.

I theory, yes. But that’s not how it plays out. Have you seen them in person? If they used a setup like an IFS truck (arms swing out from the center) it would be ok, but they don’t. The swing arms pivot in front of the axle and the back end is parallel to the ground well below the axle stub. I actually saw a smittybilt trailer on the road this past Monday. The gap between the two swing arms was about a foot and the swing arms were about 18” each. So, it had 3’ of swing arm hanging down low and 1’ of free and clear space between them. The Black Series trailers I've seen are wider, so the gap between them is more usable. Even so, I still contend they give you no advantage and likely the opposite.

On my trailer I run the same wheel/tires as my Land Rover and the springs are over the axle. Given the way it’s setup I’ve got way more ground clearance on the trailer than the vehicle.

 

[Rath]

I have seen them in person. And I have seen them on the trails too. you do realize there are different types of independent suspensions, right? Because what you're describing isn't the best if you want ground clearance alone. However, that system is still a better offroad option than a solid axle for a trailer.

Although I can understand why a lot of people would argue about its benefits. It's rare for someone to actually take a trailer through conditions that would most benefit from IS.

Most people mentioning torsional independant suspension also are not talking about what you are talking about. Most common would be a Timbren axleless suspension. seen here.

VERY low profile, takes up very little space. fantastic for rough offroad trails. if you see it vs solid axle on a rough trail you'll understand its benefits. But again, for most people, yeah, a solid axle will be suitable.