Adapting an SUV IRS for a trailer?

TWX

New member
While cooped up at home I've been thinking about, among other things, trailers with the thoughts on what it would take to build something. Specifically because I have a '15 Nissan Frontier and it's recommended to run the same wheel bolt pattern, if not the same actual wheels and tires on both tow vehicle and trailer, what that means for a truck with 6 on 4.5" bolt circle.

It occurred to me that the Pathfinder, like the Frontier and Xterra, is 6 on 4.5, but has an independent rear suspension because that was deemed the easiest way to accommodate a footwell for the third row seat. That IRS uses a large subframe crossmember along with three control arms and a suspension-knuckle instead of a steering knuckle to accept the hub and bearing assembly. Likewise, the Armada uses a similar setup, and even shares one of the control arms with the Pathfinder. It looks like the two might have the same bolt-pattern for attaching the hub to the suspension knuckle, but I have not been able to independently confirm this.

So, what do you think of the idea of taking either a Pathfinder or Armada independent rear suspension and using it for the basis of a trailer? Remove the differential and CV shafts, look into some kind of electric-over-hydraulic system for the disc brakes, even be able to use a handle to lock the parking brake assembly when the trailer is set up on a campsite. The Armada's setup is probably more useful since it's wider, but best would be if the Pathfinder's hubs and brakes were used, since they would match the tow vehicle.

This is very, very VERY much preliminary, but since these parts are plentiful in junk yards it seems like something that could make for an interesting thing to experiment with.
 

SDDiver5

Expedition Leader
I dig it and I dont see how it would be a difficult thing to do with general mechanic and fab skills. I've had ta similar thought but using an older explorer rear end when they did IRS mid 2000's.

I think a pathfinder would be better option since its smaller? I feel an armada would be a little too large?

What kind of travel trailer are we talking about? Teardrop style or something your family can sleep in with a kitchen/bath, bunks, etc?
 

Jnich77

Director of Adventure Management Operations
If you you can weld ans fab it's not that hard on paper.

Why not run a torsin axle and get the hubs machined or run spacers to match your truck?
 

TWX

New member
I dig it and I dont see how it would be a difficult thing to do with general mechanic and fab skills. I've had ta similar thought but using an older explorer rear end when they did IRS mid 2000's.

I think a pathfinder would be better option since its smaller? I feel an armada would be a little too large?

What kind of travel trailer are we talking about? Teardrop style or something your family can sleep in with a kitchen/bath, bunks, etc?
Long story short I don't entirely know what kind of trailer yet. The Frontier is 73" wide, the Titan is 80", I expect the Pathfinder and Armada to be similar, and the extra 3-4" on each side doesn't seem like it would be too consequential, especially with towing mirrors on my Frontier.

Now, I suspect that my wife would insist on at least a half-bath, and would probably prefer a 3/4 with a shower. There are three of us; the youngest is a toddler but obviously I would need to build for the future.

I'm actually thinking about seeing if I can find softer springs, and going double axle. There was a recent video where a Frontier CC SWB Pro4X got stuck while pulling a single-axle purpose-built off road trailer:


I don't want to find myself in that position if something double-axle could make that less likely.

Now all that said, I'm still not sold on pulling a trailer versus some kind of on-truck camper. Trouble is all options are pretty expensive and all have their compromises. A slide-in cabover popup has limited floor space and is much more difficult to have a proper bathroom in. A flatbed model has more space but there are weight limitations on the truck regardless. A full bolt-to-frame model can't be left behind at camp for a more aggressive offroad experience.

So right now this is mostly just brainstorming. A year or so ago I bought myself a tig welder and I've been studying up on various aluminum alloys including 5083 and 5086 that don't lose their strength when welded, so in some respects I'm itching to see what can be done with an aluminum frame.
 

Rbertalotto

Explorer
I had a friend that built bunch of trailers using VW Golf rear suspensions. This was a few years ago but it wasn't difficult.
 

old_CWO

Well-known member
If you you can weld ans fab it's not that hard on paper.

Why not run a torsin axle and get the hubs machined or run spacers to match your truck?
This.

It's an idea that makes for good bench racing talk (especially while bored holed up in the house), but doing it for real would probably be a fool's errand. Backyard engineering a cobbled up SUV suspension is going to be a lot more trouble than it's worth and will cost more in the end then just doing it right. There are already plenty of proven trailer suspensions available from the humble leaf spring to the "cool guy" air bag and trailing arm setups. Worst case scenario would be wheel adapters or re-drilling hubs to get the goofball Nissan bolt pattern and you are in business.

I think in this case I would consider using a common trailer hub, carry a spare and be done with it. the benefit there is it doesn't matter what's doing the tugging.

😷
 

billiebob

Well-known member
How much weight are you going to haul and how much does the suspension weigh and how much will your custom frame weigh ?

Time and money, when both are unlimited anything is possible but, wife and toddler I'm betting both are stressed already. If the goal is to get outdoors in comfort, shop for a good used trailer. When you say wife, toddler, shower, you are obviously not an RTT candidate. If you get a trailer with a straight axle on leafs a custom axle with the right track and bolt pattern to fit your Nissan rims is under $300. I just did this and paid $207 for a new 3500# bolt in axle. I did it for the same reason too, so 1 spare fits all around. And that gives me 3 spares for the truck.

Most guys doing funky things with trailer suspensions already have the components from a wreck or a dead truck and it becomes a quest to use those free parts. If you have to go source everything it can be a real money pit.
 
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Louisd75

Adventurer
I'm actually thinking about seeing if I can find softer springs, and going double axle. There was a recent video where a Frontier CC SWB Pro4X got stuck while pulling a single-axle purpose-built off road trailer:


I don't want to find myself in that position if something double-axle could make that less likely.
I don't think the number of axles would have mattered in the example video. That guy's truck was stuck. You could make the argument that it was due to the trailer wheel being in a hole. Take a look at how long the truck tracks were deep though compared to where the trailer tire got stuck... I'm not sure you can blame that on the trailer being single axle. I'm also suprised (actually, not really) that it looks like there was no attempt by the vehicle owner to get unstuck other than more skinny pedal. And are those paper plates on the trailer? Methinks he was in over his head as soon as the tires left the pavement.
 

ottsville

Observer
Their was a build thread around here based on a subaru rear suspension I believe...but that was way back and in what is now the manufactured trailer forum
 

Rath

Member
could it work? Sure!

is it a good route to go? Not at all imo. WOuld be more expensive, complicated to fab and even maintain, and is arguably the worst designed independent suspension for a trailer. swing arms going sideways wont have the same benefits of trailing arm style, or torsion style.
 

TWX

New member
So here's some of my thoughts.

Proper IS using long-arm trailing arms are best obviously, but pre-built assemblies for bolting in to a trailer are pricey. An order of magnitude kind of pricey.

Common trailer dead-axles perform worst off road. A solid axle is great for a driven-axle but seems prone to jounce and trailers seem to bounce around like crazy.

Torsion axles that use rubber have been failure-prone in the past. I cannot speak to existing products but Andrew White talked about an expedition trailer that failed on him in the middle of nowhere when a torsion axle gave out.

Likewise, newer rubber-block-suspended trailing arms seem more oriented towards low deck height instead of long travel or high ground clearance, and I have my long term concerns about the longevity of the rubber blocks.

The Nissan F-Alpha platform suspension is meant for vehicles intended to go well over 100,000 miles. It may not offer the travel of the heavy duty, purpose-built long arm suspensions, but looks like a good compromise of ground clearance, long term durability, cost, and field serviceability. It also looks alignable in a regular alignment shop and should remain well aligned as it articulates on pavement, as it had to in its original application on a passenger vehicle. Furthermore those trucks had 7000lb towing capacities on top of the original vehicle weight. It might be more an issue trying to find soft enough springs if the trailer weighs less than the original axle load had in the SUV.
 

Rath

Member
The problem with vehicle IRS in a trailer is that arm design is designed to push the tires outwards. Not a very good design for a trailer, especially if you are using the same heavy duty suspension from that vehicle, in a trailer.

Your ground clearance won't be that great compared to a solid axle, ground clearance also isn't as good with trailing arm. However trailing arm allows the suspension to be be dragged over obstacles with ease, vehicle IRS will not have this benefit.

Rubber torsion axles last a long time. Very long. I'm not sure where you heard otherwise, but they last.

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dreadlocks

Well-known member
Some guy who apparently everyone knows personally, 15y ago or so had a torsion axle fail him in Baha, and since then everyone brings it up and says torsion axles are not suitable for serious off roading.. but nobody can point to any other examples of failure, and if you point out the military uses em they just counter with military spec dont mean its good.. I dunno what the deal is, but I think they are great and they have never let me down.. If I didnt know any better I'd say Big Offroading is trying to squash a superior technology because its cheaper and simpler than a dual wishbone airbag setup.. I mean heck, look if you throw control arms on a cheap chinese POS its suddenly worth $60k+
 

Rath

Member
********, yeah nothing at all wrong with torsion axles. Anyone who says otherwise is on something, or had a defective part that should have been warrantied.

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dreadlocks

Well-known member
it seems to me most trailer performance on trail comes down to having shock absorbers, on a single axle leaf the suspension does very little at trail speeds.. the hitch is the pivot point so super flex suspension is worthless.. but having some dampening other than the tires when that wheel comes crashing off a rock or something will create the biggest results.. the problem is a solid axle leafs and shocks is a bunch of crap to get hung up on, but its durable and most failures can be field repaired w/a stick welder.

Torsions adjust to your load weight so they do great when you leave overloaded and return empty, act independently, provide dampening, and result in almost nothing to hang up on clearance wise.. Tandem Torsions crawl over stuff with very minimal deflection of the trailer and float down washboard roads silently.

Only reason I see for IRS setup is so u can have a super trick auto leveling/multi-height setup.. but thats alot of hassle and expense for such luxury.
 
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