Installing a Timbren (or other) axle

WilliamA

I said I would start a dedicated thread on the axle installation and I'd better step up. A lot of information already posted will show up on this thread but there are some big holes in the data that I'd like to fill in. I'd also like to calm GigHarborTom down so he can sleep at night again.

The "WHY":

(NOTE: Before we start, I'll remind folks that I've had my loaded trailer weighed on a CAT scale and it came in at 1685 lbs. Minus the 210 lbs tongue weight and you get 1475 lbs of axle weight...)

There has been a lot of bashing going on about the Dexter axle. Some of that has been mine. First, and to be fair, let's put a couple misconceptions (and Tom) to bed. I have said in the past and still believe that the Dexter axle my T@G came with is a good piece of hardware. Used properly for what it was intended, it no doubt is up to the job of holding up a trailer. Mine suffered through 50,000 something miles of hard thrashing and outright abuse without too many problems. For a "road trailer" I don't doubt it's capability. Sleep tight, Tom.

Most of my own axle-related sleepless nights have come from the fact that because the axle is too narrow for my trailer, causing the tires to rub on the body, I've been forced to run wheel spacers. Properly used, wheel spacers are safe and functional. Assuming that one didn't get them from eBay, they are as safe as any add-on. This does NOT hold true for the stress associated with moving the wheels another 1 1/2" outboard of the centerline of the hub. That puts considerable additional stress on an otherwise reliable axle, causing all manner of other problems with wheel bearings and spindles over the long haul. I've run spacers for a lot of rugged miles and have had zero problems, but that doesn't mean I liked it. I've been a mechanic all of my life and just because someone says no one has had any problems with a thing doesn't mean they won't. It's a matter of time in most cases. If you push the automotive envelope, it will almost always push back. In short, the axle had no role in my own need to run wheel spacers. That was a trailer design problem. The axle was just an innocent bystander. That I elected to fix the problem by adding wheel spacers is on me. I "could" have solved the problem by putting smaller (narrower) tires on my trailer, but I wanted the wider tires it came with for reasons involving the off-road use of my trailer where narrow tires would be a detriment. Looking back, I can ironically postulate that the thing more than any other that has probably saved my axle from destruction was my decision to get the larger of the two T@Gs. There were (are!) A lot of places I wanted (and attempted in some cases) to go where my trailer simply wouldn't fit.

What the Dexter axle "isn't":

The Dexter is NOT an off-road capable axle. It's not a design flaw as I don't believe it was ever designed to do that. It simply doesn't have the travel, spring rate and robust design needed to seriously expect it to do that. It's a utility trailer axle designed to run down the road. That it ended up underneath what has been sold as an offroad-capable trailer has a lot more to do with marketing and less to do with engineering.

If I know anything about mechanics, it's that the automotive God's will always get their pound of flesh. Good design and good parts always pay back. Bad ones always bite back. It's fair to say that "Use as intended" has a broad range of meaning and most of us, admit it or don't, push that envelope by mis-use or outright abuse. I've pushed that to the point of needing to recognize that it's time to throw some money at the potential problem before it IS a problem. I've still got 60 more miles of the Mojave Road to finish and a broken/bent axle in the middle of a 20 mile salt flat would put a serious kink in that goal.

Getting serious:

So what IS an off-road suspension? Well, more than anything it's about wheel travel and bearing size. The Dexter has, maybe, an inch and a half of usable wheel travel out of a couple inches of full travel. It pretty much impossible to get a true progressive spring rate with so little. My trailer hardly settled at all when I put the weight down on it. That means that the spring rate is higher than the trailers' loaded weight and there's next to no rebound damping. If I hit a bump, there's little to control rebound so the trailer would pogo and bounce, with the tires providing most of the rebound (secondary) bounce. In addition, the Dexter axle has an anxiety-provoking amount of apparent camber-flex. When I'd hit a bump or go around a corner, I could SEE (in the rearview mirror) the camber visibly change. This is caused by axle flexing. That tendency, in addition to me having actually seen it many times, is apparent in the rubber burns on both sides of my trailer from the top of the tires rubbing against the body. Some of that rubbing has no doubt been the result of frame flexing at the axle mount (no intermediate crossmember to prevent it) but as I noted, I've SEEN the camber flex in my own travels. This camber flex is exacerbated by the addition of wheel spacers needed to to eliminate the tire rubbing, and on and on.

For those running smaller tires, I should note that smaller diameter/width tires dramatically reduce most of the flex/deflection problems as the "lever" is just much shorter.

But off-roading needs ground clearance. The easiest way to get that is with larger diameter tires. Couple that with the need for good control of compression and rebound and you need a long control arm.

I'll be adding to this as I get time but I wanted to lay out some basics as good for thought...

WilliamA

WilliamA

There are a number of different types of springs. I'll keep my comment within three categories:

Leaf springs.

Coil springs.

Torsion springs.

The Timbren axle "looks" physically a lot like the Dexter axle, but they are quite different in operation. While the Dexter unit is a torsion spring, the Timbren is most in characteristics and function like a coil spring. Two coil springs, actually. One is for compression and the other is for rebound. They work exactly like a progressive coil spring, but instead of steel, are rubber. The big advantage is not in the spring itself but in the fact that it has two springs. This, coupled with a long control arm, is what gives it so much suspension control. With two springs, what happens is the primary spring holds the weight of the trailer right to the point where the trailer weight is mostly unloaded. When the suspension reaches that point of unloading, (going over a big bump) the axle pivots down until the rebound spring starts to load, causing the axle movement to progressively slow down. In a conventional coil spring or torsion suspension, the spring unloads until the suspension hits the travel limit and stops...violently in some cases.

For a torsion spring to have a lot of travel, it needs more length. As the Dexter axle isn't a true torsion spring, it's not possible to provide the same level of control. Couple that with the short, stubby control arm and mostly, the geometry works against all of the principles of smooth control of wheel travel. What you end up with is a short, choppy ride.

WilliamA

GigHarborTom

Thanks William....You are right. Dexter Axles are the go to for most the Vintage trailer folks we have hung with the 20 years or so. I have changed out two myself. One on our first teardrop and a 59 DeVille, Canned Ham style. I had the axle on the Avion done by a shop. Mostly because I am just not up to it anymore. All three axles were changed due to age,1940 something on the teardrop and 1961 on the Avion. The shop job was botched. Dexter is the go to and I had another shop correct. Was not paying close enough attention here. You are off road and we are not. Big difference.
All that , I do get a lot of pleasure reading you guys serious mods. Admire your skills a great deal.
Thanks

WilliamA

Well, I'm late again. I still haven't tackled the write-up/PDF for the Timbren suspension. Admitting one has a problem is the first step in solving it.

I HAVE, however, been shin deep in the interior remodel that is turning the pole she'd into DW's next pottery studio/mad-scientist HQ. I built a center wall and split the project in two, mostly to convince myself the whole job is only half as big as it really is. I've got all the new windows in, interior framing finished, rewiring finished, insulation done and most of the sheetrock up in the east half. The "shed" is already full with pottery reagents, a kiln, beekeeping supplies, gardening supplies and the like, so it's like building a ship in a bottle to do anything out there. My son and I are being gently but inexorably shown our hats so far as workspace is concerned. She did let us (so far) keep the welder and roll around toolbox out there.

But I digress.

I HAVE been putting the trailer through its post-modification paces by sneaking off with my son to goof off while DW is at work. Other than making some pigtail brackets for the parking brake cables:

and retorque-ing the lugnuts, I haven't touched the suspension since I put it in. We've thrashed it pretty well and I am pleased to say it's amazing. I was sure it would work better but had no clue how much of a difference it would actually make. The difference is astonishing. Washboards, rutted sand roads and railroad tracks are now more of a challenge for the Jeep than the trailer. That's saying a great deal. I'll get on the write-up.

WilliamA

GigHarborTom

Dang Nice.
TP

MattMc

I'm really wanting to do this mod and hope you might have found some time for a quick write up and any gotchas. Like watching all the mods you do and wanted to let you know how helpful they are!

daveandcorlene

Amazing mod!

WilliamA

Well, I'm no closer to moving the whole thread over here so for now, I'll post a link to the (hijacked) other half:

https://teardrop-trailers.vanillacommunity.com/discussion/988/tinfoil-dexter-axle/p2

Moving along.

I picked up a set of raised spindles from Timbren to get me a few more inches of ground clearance.

These will net me about 4" over the standard Timbren spindles. If I get the muse I'll get the trailer into the garage and stuff them on. That's not the issue though. Getting the 4" taller trailer back OUT of the garage is going to be the issue.

One beating at a time.....

WilliamA

zgfiredude

Deflate the tires........

WilliamA

I got my mechanic shirt on and got my spindles swapped.

Net lift is 3 1/2". Cleared the garage door by at least 2 sheets of typing paper...

WilliamA

LuckyJ

@WilliamA said:
I got my mechanic shirt on and got my spindles swapped.
Net lift is 3 1/2". Cleared the garage door by at least 2 sheets of typing paper...
WilliamA

Wow, this is pretty high clearance,so I'm sure it looks awsome behind the jeep.👍😊

But I sure do have a question, how confortable is it to get in and out of tge trailer. Tgis is one of my concerne about the air bags on my project. 🤔

WilliamA

It's way easier than getting into our rooftop tent! LOL. I have a tiny plastic folding step that rides behind my pillow next to the headboard. When I set up camp, it comes out for the purpose. Easy. I don't need the step for my "butt first" entries but it's nice for the boy and his herd of crumb snatcher cousins. I also like the step, even though I don't need it, because it's a dry spot to put my shoes on and off. I just leave my shoes on the fender, under the eyebrow awning.

Actually, the bigger issue that folks don't think about is the kitchen. I'm tall so more headroom means less chance of scalping myself on the kitchen hatch, but vertically challenged folks might take issue. My DW is also tall so it's not an issue for us.

WilliamA