Offroad trailer suspension

[ai4kk]

I was figuring out the suspension I want to use on my next teardrop and ran into Deepmud on another site and then again on here - I tried to email him on the other site but it kept crashing on me. he had a thread a few years back at http://tnttt.com/viewtopic.php?f=39&t=27386 that I found fascinating for it's use of rear torsion bar suspension for an offroad trailer. I found out through his thread on here that he used a mid-80s Subaru suspension as seen here so no longer needed to contact him.

I was wondering, given the difficulty of finding suitable donor Subarus or VWs, what about an aftermarket VW suspension like at http://www.appletreeauto.com/TRAILING-A ... 2-TA3X3T2/ ? I wonder if the manufacturer could even be persuaded to offer a lower-cost version of that setup with only stub axles for trailers? Thoughts?

[deepmud]

I think the board would have emailed me if you tried messaging - I used the same handle on all forums - probably not very secure. You'll never guess my gmai....

For an off-the-shelf new-parts build, I'd try Timbren - modular, compact, easy to build a frame around it. They call it "axel-less"

http://www.sdtrucksprings.com/timbren-s ... /axle-less

[Shadow Catcher]

AT Adventure has some of the best information on off road suspensions http://adventuretrailers.com/suspension/

[Dave Nathanson]

I just got that Timbren suspension. So far I really like it...

When I fully emptied the trailer to take it to the shop for the suspension to be installed, the leaf springs had it bouncing all over the asphalt. I mean, really! This is a regular paved city road.

On the way back home with the Timbren installed, it was smooth riding all the way. Same road, different suspension.

It was a real education getting the details. What I wanted was heavy duty metal, but lighter springs because the TD is much lighter than a loaded utility trailer. I have what Timbren calls "Offroad tires," mine are are 30"x9.5" and the bolt pattern matches my Jeep. The Timbren spindle is offset for these wider tires.

But in spite of taking lots of measurements & talking with Timbren on the phone, the new suspension came out considerably lower than the old one. (By about 3"). I'm going to have to do something about that, probably buy & install the Timbren 4" lift spindle.

Btw; eTrailer.com had the best deal by a mile. I bought part number ASR1T-HDS02. It came with the straight spindle P024 (no lift, no drop, offset for wide tires). The 4" lift spindle is part P025. It is a bolt on, but you have to shim it to get the alignment right.

The metal is all very thick, (much heavier duty than I expected) rated for 3500#, the rubber springs are 1500#, & longer offset spindle 8.5" from hub face to frame. Timbren rated this kit as 2000# for Offroad use. I was able to reuse my standard Dexter hubs & brakes. Did need new seals of course.

[deepmud]

I just got that Timbren suspension. So far I really like it...

Cool! I was wondering - is there a brace across your frame where they mount? Seems like they will try to twist the frame a bit. The ride-height difference isn't something I'd considered. Barring a drop spindle, I suppose welding a "frame drop" section would help - it might add to the twist that might be there (but so would a drop spindle?).

It's good to see such an off-the-shelf system working well. The rubber springs aren't a new technology so this seems like a good option.

Erik

[irgod32]

I've always been torn between these type axles and a straight one. My opinion is that with off road type trailers, you can't crawl over terrain any higher that the axle on your tow vehicle. Another reason is, unless the bottom of the trailer is solid steel, do I really want something hitting the under side of my trailer? So I for one decided to use a straight axle since I'm not going over really rough terrain. But this is why I love home built trailers, everyone has such great ideas of how to build the perfect trailer to fit them personally

[Dave Nathanson]

I just got that Timbren suspension. So far I really like it...

Cool! I was wondering - is there a brace across your frame where they mount? Seems like they will try to twist the frame a bit. The ride-height difference isn't something I'd considered.

Yes, there is definitely a 2" square brace bar - much like an axle but a bit higher. I'm not really interested in the lack of an axle because after 13 years of wheeling with a straight axle, I have never had a problem with the trailer axle hitting anything or hanging up on a rock. Just doesn't happen. But I am very interested in a softer ride that won't break leaf springs and knock teeth loose. I fully expect my whole trailer will last longer with this Timbren suspension instead of the overly-stiff utility trailer leaf springs. I believe I have figured out why I was breaking leaf springs (has to do with the wrong way the shocks were mounted) but I am still really excited about this Timbren suspension.

I feel it is important to distinguish between the Timbren Axle-Less suspension and a Torflex suspension. Although both include rubber & metal, they are completely different things. Completely different. The Timbren is similar in design to a Trailing Arm suspension.

Here is a photo of the inside drivers side wheel, looking from back to front. You can't see the cross bar, but you can see the spindle height, which is pretty close to the trailer frame height. This is the straight spindle. I'm going to get the 4" lift spindle in next week. That huge shiny bolt is the suspension pivot.

[working on it]

... I'm not really interested in the lack of an axle because after 13 years of wheeling with a straight axle, I have never had a problem with the trailer axle hitting anything or hanging up on a rock. Just doesn't happen. But I am very interested in a softer ride that won't break leaf springs and knock teeth loose. I fully expect my whole trailer will last longer with this Timbren suspension instead of the overly-stiff utility trailer leaf springs. I believe I have figured out why I was breaking leaf springs (has to do with the wrong way the shocks were mounted) but I am still really excited about this Timbren suspension....

You have a lot of off-road experience with your trailer, whereas I have only a few miles of rutted dirt roads with mine. But, I feel that you're not giving enough credit to leaf spring axles, which came first, and still remain. Look at 4wd vehicles & off-road-specific trailers: all types of springs are used (leaf, coil, and airbag/hollow rubber -Aeon, Sumo, Timbren-). But, if leaf springs were so insufficient to do the job, why were all Jeeps (the first brand most people think about when 4wd comes to mind) leaf-sprung until '97 (56 years)? True, leaf springs are old-school, can be rough, and jarring. But, if one breaks out in the wild, you can use a ratchet strap to secure it, and get to civilization to find a replacement (if using common sizes, no problem, they're everywhere), or if using re-purposed automobile springs, junkyards. Coil springs have no temporary fix, nor broken airbags, that I'm aware of. And the hollow rubber springs: unless you carry a spare rubber "donut, puck" with you, replacements are rare in the wild. I have had a leaf spring break once or twice, and limped home with it that way. There were two places within 5 miles of my house with matching replacements in stock! Another thing I feel favoring a leaf-spring axle is the usually strong spindle-to-axle weld: I know of no one that had their spindle break off, while I know of occasion where a spindle broke off a torsion axle (same sort of working motion on a Timbren; I was wary of that when I was deciding an axle upgrade. I upgraded a weak leaf spring axle setup awhile back, and chose a Dexter 3500 lb axle with brakes, for $400 ( after adding installation hardware, shackles, springs, etc)... The other system I considered was a Timbren with brakes, for $800+ (I don't know what it would've cost to install it). With either choice, I would've had to (and did) beef up my frame with heavy steel reinforcement, for $75 more. I chose the Dexter because of familiarity, trust, experience, and cost. I, perhaps, put too stiff of springs on it (3000 lb set) since my trailer is about 1750 lbs, loaded, but I can easily step that down to less, since new 25.25" springs are under $30 each.If you order the wrong rating with Timbren, it's $100-200 to change the spring rating (torsion axle- you can't change the rating, coil springs- replaceable like leafs= cost unknown). It's a choice worth considering well; buy/install what you're comfortable with (figuratively, physically, mentally, financially).

[Dave Nathanson]

I feel that you're not giving enough credit to leaf spring axles, which came first, and still remain.

Your points are good & well taken. I have indeed managed to get home after breaking leaf springs, frames, and trailer tongue. This time I am very interested in a sturdy yet softer ride. Instead of trying again with a longer, softer leaf, I'm trying something new. Good or bad, you can be sure I'll let you know how it works out! :-)

[working on it]

I left one point out of my dissertation above: both times that I've experienced broken leaf springs (and the one-unmentioned shackle tear-off) there was no bumpstop to cushion/limit the flexing of the spring past its' working arc limits. In the case of Dave's spring breakage, the leaf spring had nothing limiting it from flattening out, or even reversing its' normal arced shape (except for the shock bottoming out), resulting in a severe jolt, and breakage.

TD leaf Spring axle travel 2014b.jpg (113.62 KiB) Viewed 17204 times

Now, even Timbren recognizes the problems of over-travel in their suspension, and sees the need to "progressively" absorb the energy before the absolute "stop".

Timbren active bumpstops.PNG (116.75 KiB) Viewed 17204 times

I chose not to use shock absorbers with my new leaf spring suspension (with relatively little travel), reasoning that the shock absorbers couldn't absorb enough energy in their limited motion to do much good before their absolute stop was reached.And, I was going to add a bumpstop to prevent the possible overtravel of the leaves past the flattened arc stage. So, I combined the functions of shock absorber and bumpstop into one, using a Daystar progressive bumpstop, made of resilient polyurethane, as an active part of the system (always in contact with, and following the motion of the axle); sorta like Timbren does with their component. I described my "active bumpstop suspension" in my thread: http://www.tnttt.com/viewtopic.php?f=35&t=59570#p1075076.

Daystar progressive bumpstops ku09016bk.jpg (45.43 KiB) Viewed 17204 times

I modified the Daystar bumpstop to be softer-acting (by cutting away the hard "bump" of the top of the piece, and curved the remaining body to slip-fit between my axle and frame (at full droop of the springs). With the top part of bumpstop so modified, the remainder relies on the two lower "ligaments" to progressively flatten out, before compression into the bottom layer, when the overtravel is finally prevented. I wondered how well it would work, as did may doubters on the forum, but I think it proved itself when I encountered a large chughole in the road at 75 mph. My truck and trailer both got bounced into the air, with my truck tires being the only damaged parts afterwards. In normal driving situations, I really haven't noticed any of the trailer bounce that I should be seeing, as a result of using too stiff of springs. In any case, the bumpstop at least kept the leaves from overflexing, preventing breakage. If I ever soften the suspension, and/or add conventional shock absorbers (if suspension travel becomes greatly increased), I will still use some form of progressive bumpstop to limit overtravel. I try different things, sometimes re-purposed from originally designed function, to do what I need them to. Sometimes it works....

[KCStudly]

The reason jeeps and Jeeps have had leaf spring suspensions for so many years probably has as much or more to do with the fact that they have live straight axles at both ends, precluding the use of independent suspension. Once that design choice is locked in, so to speak, leaf springs become one of the simplest manufacturing and assembly solutions.

The reason that modern day Jeeps have shifted to coil spring/link suspensions has as much to do with the market no longer tolerating harsh bouncy riding vehicles. As soon as the TJ came out (first with coil springs), Jeep sales boomed and the resurgence continues.

YJ or XJ leaf springs are much longer and softer than typical trailer spring packs, and are also load rated more closely to typical TD trailer weights.

If it wasn't for the higher cost (and I wonder about the total weight differences) I can see the attraction to the Timbren system.

[AzAv8r]

I remain paranoid about dragging an axle over a boulder. I feel pretty comfortable predicting where the tires and therefore the pumpkin will pass with my rear axle. Not so much the trailer axle (once the turns become extreme) because of the vehicle geometry. I find the notion of not worrying about hooking the axle on a boulder in a switchback a compelling feature.

Now, ask me again once I've tried it with the Timbren.

[Dave Nathanson]

I remain paranoid about dragging an axle over a boulder.

Put a wheel on it!
This is me taking Mengle pass. The trailer has a straight axle. By putting the wheels on the rocks, you go
over them. (instead of getting stuck behind them). And of course the axle rises out and out of the way
as the tires go over the rocks. Is your off road trailer too low?

[AzAv8r]

Exactly. Perhaps I was not clear. In most tow vehicles, it's trivial to put the rear wheel where you want it, and clear the axle. In *really* tight terrain, the line the trailer follows is vastly different than the line the tow vehicle follows, with the inside tire 18" to as much as 4' inside the tow vehicle's inside line. I know how to keep the axle from dragging (a spotter, or a very slow traverse), but I don't want to worry about it. And you do not have the same degree of control over the line the trailer follows. In my experience tight terrain usually has some large rocks at the inside of the switchback. If your tire rolls over the top of that, you are golden. If it rolls inside of it, you are going to have a long day. I have never hung an axle, but the time I've spent making the turns is excessive relative to the time on the trail. I'm there for the journey, not the challenge of the switchback.

[deepmud]

I remain paranoid about dragging an axle over a boulder.

Put a wheel on it!
This is me taking Mengle pass. The trailer has a straight axle. By putting the wheels on the rocks, you go
over them. (instead of getting stuck behind them). And of course the axle rises out and out of the way
as the tires go over the rocks. Is your off road trailer too low?

After over 20 years of hard use, I'm really happy with the massive clearance of the trailing axle design. You ignore the trailer clearance, just drive the tow rig - but it's not about primarily clearance - it's soft riding because it has low un-sprung weight, something a solid axle just will never have. Soft riding at speed over dirt roads with a few hundred pounds to half a ton or more of load - not clearance while crawling over rocks - although, my trailer clears rocks with little bitty tires as well as my solid-axle Suzuki with 39.5 Boggers.

here it is about 10 years ago with 2200 pounds of flooring on it - I've packed the bearings once since then. And put 15" rims on it. Durability test: passed. 20k miles of highway - passed. Soft riding, doesn't beat up my camping gear - passed.



Carries a crap-ton offroad? - passed



Of course, the 1989 Subaru axle may turn out to be more durable than a Timbren - but it looks pretty good - I'm looking forward to more input.