Why are dual axle TTs made with the wheels in the middle?

Hard to imagine a rv trailer with wheels at the corners on a 35' long trailer. It would take the whole intersection to get around a corner....making it impossible to pull it around campgrounds and forget backing any where but in my 22 acre hay meadow.

Lots of old hay trailers still around but the ag industry modernized and gave us hay trailers with the wheels towards the the center. Much much easier to maneuver (forward and backing) and can be pulled down the road at highway speeds.

I would add that axles in "middle" of a TT allow it to PIVOT when turning...allowing easier backing up as well.

The farm trailer discussed here is correct as well...unhitch and its stable. Not intended for "major" highway travel.

Lastly, as I'm sure many here are, you get "really good" at backing a TT after doing it so many times. It's amazing how you can literally pinpoint exactly where you want to be, and put 'er there by knowing you pivot points.

mike-s wrote:
Why not just mount an axle on the roof, where the brakes/bearings/tires would never wear out?

You might be on to something here. Would this make the trailer usable in Australia as well?

theoldwizard1 wrote:
Eliminates porpoising on rough road. That is why farm trailers have axles set apart.

"Porpoising" has nothing to do with it, there's no suspension on a tractor for that to be an issue. On farm trailers because you can simply unhitch them while loaded without needing to do anything to keep them stable.

mike-s wrote:
Steering axles are expensive and can be unstable at highway speed. For what advantage?

Eliminates porpoising on rough road. That is why farm trailers have axles set apart. Yes, you need a steerable front axle and it is a lot more expensive than a solid axle.

Ever drive behind a farm tractor pulling a hay wagon or grain wagon? They are all over the road. And backing up, forget about it

Because you can not back up a trailer like that. Consider a tow vehicle. I have one. I cannot back it up because the front wheels immediately turn to full lock, then the towbar/hitch binds up.
The axles are in the middle, more or less, on a trailer to give it the ability to back it up.

Backing would be pertnear impossible without 4 wheel steering on a tow rig.

Back when Desert Shield / Desert Storm happened, I had to get certified to tow an eleventy-million pound Missile pylon that carried 6 ALCMs on the wing of a B-52.

It was transported on a trailer that had wheels at the rear corners and a tow bar attached to a set of wheels at the front. It was towed by an ancient aircraft tug, which had rear steering. operating that mess was a nightmare when backing up. The rear steering was a lever at your left knee.

Good question.
I suspect, as others have stated, it is because backing would be a nightmare. Yes, I used to backup hay wagons when I was kid.
I am less sure about the stability argument, as I see double and triple semi trailers all the time, they seem to work fine.

One of the great advantages of the typical travel trailer design is that it tracks behind the tow vehicle pretty darned closely. A steer axle in front with tires at all four corners would result in lots of damaged tires and curbs with black marks.