2000lb or 3500lb axle for TTT

[TheOtherSean]

Hello, fellow trailer enthusiasts! I'm looking for some advice.

I'm working on plans for a tiny travel trailer with a projected dry weight less than 1400lb. Given full tanks and loaded with food, clothes, etc. , it should still be well under 2000lb, but once a few people are inside, there could be 2500lb inside. Do I need a 2000lb or 3500lb axle?

[Walt M]

torflex makes a 2200 lbs axel. and they might even be able to make a custom weight. if that helps. Walt

[Nitetimes]

Hello, fellow trailer enthusiasts! I'm looking for some advice.

I'm working on plans for a tiny travel trailer with a projected dry weight less than 1400lb. Given full tanks and loaded with food, clothes, etc. , it should still be well under 2000lb, but once a few people are inside, there could be 2500lb inside. Do I need a 2000lb or 3500lb axle?

It kinda depends on what type of axle you are using, torflex or spring?
If it's a torflex a 2k would work fine, if it's a spring axle I would just use the 2k axle and 2k springs (it actually becomes a 2500lb. axle if brakes are added sooo) unless you find you are much over that. The load at camp won't hurt anything.
You really don't need a 3500lb axle unless you are going with a drop axle then that's what I'd use as others I know have, just for piece of mind and use 2k springs on it. You can get springs in a lot of different load weights.
You definitely won't want a 3500lb torflex unless your desire is to beat your trailer to death!
Just what I've learned after building a 1k or 2.

[GregB]

Rich,

I'm using a Torflex #10 3500 lb. axle after talking to the engineers at Dexter for my 1600 lb. tear, though the rubber will be de-rated to 2K. As it turns out, you can run a 79" hubface distance with a frame that is only 48" wide by upgrading the axle. Normally you should have a maximum of 10" or so distance from the hubface to the frame rails where the axle is mounted and I have about 15.5". I have 15" wheels so there will be some pretty considerable weight hanging off the ends of those axles. My trailer sat too high with the wheels inside the body, so I am buying another axle (my third!) to put the wheels outside the body and lower the whole trailer. It's an odd situation, to be sure, but one reason to buy a #10 over a #9.

Greg

[Nitetimes]

Rich,

I'm using a Torflex #10 3500 lb. axle after talking to the engineers at Dexter for my 1600 lb. tear, though the rubber will be de-rated to 2K. As it turns out, you can run a 79" hubface distance with a frame that is only 48" wide by upgrading the axle. Normally you should have a maximum of 10" or so distance from the hubface to the frame rails where the axle is mounted and I have about 15.5". I have 15" wheels so there will be some pretty considerable weight hanging off the ends of those axles. My trailer sat too high with the wheels inside the body, so I am buying another axle (my third!) to put the wheels outside the body and lower the whole trailer. It's an odd situation, to be sure, but one reason to buy a #10 over a #9.

Greg

Can't argue that. And I have used heavier axles than necessary on occasion myself, usually for pretty much the same reason. A deep offset wheel or an odd frame configuration sometimes gives you more overhang outside your springs than is good to have on a 2k axle, that's when ya wanna move up to the next size and be safe. You can do pretty much the same thing you did with springs, use the heavier axle and lighter springs, there are exceptions to every rule but it all comes out in the wash.

[doug hodder]

For what it's worth...I always get more axle that I need from the get go....any variations in the design are covered, it's just not that much more weight or $$$$, 3.5K axle, 4" drop on the last 4 tears, but I build with springs, weights...between 960 and 1200#. Build what'cha want. Doug

[Nitetimes]

For what it's worth...I always get more axle that I need from the get go....any variations in the design are covered, it's just not that much more weight or $$$$, 3.5K axle, 4" drop on the last 4 tears, but I build with springs, weights...between 960 and 1200#. Build what'cha want. Doug

No doubt. Unless you're really, really weight conscious the extra axle weight won't hurt a thing!

[kennyrayandersen]

I kind of don't get it. Generally the axles are rated for the weight you plan on carrying. They are designed to mitigate the shock based on that weight. It you are significantly over-capacity then it doesn't work as designed. When you get a extra big axle, you don't just get more capacity, or extra margin of safety, you get much more weight adn stiffness as well. The weight jumps from 50 to nearly 80 Lb going from a Dexter #8 to a #9. An 8 is rated up to 1100 Lb and a # 9 up to 2200 Lb. That’s a pretty heavy tear. I don’t see so many (any?) of the builds that have gone that heavy (at least and not regretted it). I'm sure that even at the rated weight they are designed to handle peak loads in the neighborhood of 3gs, which means that there is already some headroom there for big bounces and whatnot.

I have to agree with Nitetimes. If you use too heavy-duty of an axle, you will increase the g-loading and will tend to beat it up. I say get the right-sized axle for the weight you expect with maybe a little headroom in case you go over a bit. I'd say a #9 would appear to be the right size. I'm only using a #8 on mine, but it will admittedly be a light build.

The weight of the wheels is insignificant in the overall axle loading.

[agpage]

but once a few people are inside, there could be 2500lb inside. Do I need a 2000lb or 3500lb axle?

I am not an expert, but most trailers have some sort of stabilizers or jacks for leveling the trailer at camp. Those should help carry the weight of the sleepers.

Andy

[aggie79]

I bought the #9 Dexter derated to 1500# instead of the #8 because I wanted the 5-bolt hub.

[kennyrayandersen]

but once a few people are inside, there could be 2500lb inside. Do I need a 2000lb or 3500lb axle?

I am not an expert, but most trailers have some sort of stabilizers or jacks for leveling the trailer at camp. Those should help carry the weight of the sleepers.

Andy

Exactly! you only have to get the axle rated for the going-down-the-road wieght.

Interestingly enough, I'm about to post some results from some computer modeling that I did for the uber-light. In the case of a 'frameless' trailer the critical condition for the floor is parked! But it is certainly not critical for the axle as it's designed to carry a 3g dynamic load. There would have to be some serious shenanigans going on to get a 3g people load when parked!

[madjack]

I bought the #9 Dexter derated to 1500# instead of the #8 because I wanted the 5-bolt hub.

...this is what I do for a torsion axle...and have been VERY satisfied with the results...

...for a spring hung axle, you should have around a 50% overcapacity, a torsion axle as not as critical....

...unsprung weight(wheels/tires/axle) should not be considered in these calculations..........
madjack

[GregB]

I kind of don't get it. Generally the axles are rated for the weight you plan on carrying. They are designed to mitigate the shock based on that weight. It you are significantly over-capacity then it doesn't work as designed. When you get a extra big axle, you don't just get more capacity, or extra margin of safety, you get much more weight adn stiffness as well. ...

The weight of the wheels is insignificant in the overall axle loading.

Kenny,

The more robust axle actually has no effect on shock loads as the rubber rating inside or the spring ratings determine shock absorption. Thus, an axle rated at 3500 lbs. won't make your ride any more stiff, by itself. The heavier axle, (which has the penalty of extra weight, as you note) is simply stronger, which is crucial. The weight of the wheels doesn't even pertain to axle loading (since it is unsprung weight) but is important to axle integrity. I don't want to snap an axle. In my case, you have to think of the overhang as the distance from a pivot point (where the axle is attached to the frame) or fulcrum. The entire wheel becomes a weight that is suspended from that fulcrum and acts like a lever, so that the increased force of that weight is actually the square of the increased distance from the pivot point. Since my wheel is about 40% farther away than recommended, the force on the end will be many times greater. At least that is the way I understand it.

GB

[brian_bp]

but once a few people are inside, there could be 2500lb inside. Do I need a 2000lb or 3500lb axle?

I am not an expert, but most trailers have some sort of stabilizers or jacks for leveling the trailer at camp. Those should help carry the weight of the sleepers.

Andy

Exactly! you only have to get the axle rated for the going-down-the-road wieght...

Exactly what I was thinking. I believe that the springs should be rated high enough for the loaded weight of the trailer as towed (thus not counting occupants at camp), and the rest of the axle should be rated that high, or greater only if some aspect needs upgrading for a special purpose (such as the large overhang such as Greg described, or a need for large-diameter brakes due to very large tire diameter).

Given the description of the trailer so far, a 2000 (or 2200) lb capacity axle, perhaps with springs rated somewhat lower, seems appropriate.

[brian_bp]

...for a spring hung axle, you should have around a 50% overcapacity, a torsion axle as not as critical....

I'm curious... why?
If a suspension system (axle, springs... the whole thing) is rated for operation with (for instance) a one-ton load, why would it not be suitable for use with a trailer which weighs one ton when loaded? If I'm reading this correctly, you would use a 3,000lb-rated axle for a 2,000 lb trailer.