Tandem or Single Axle? - Fiberglass RV


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Old 03-24-2009, 04:22 PM   #1
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I'm looking for a light, small, fully self-contained trailer that's tall enough for me (I need just over 6 feet interior height) and has a bed long enough (again, just over 6 feet).

Because of the light weight, some trailers come with single axle, while others are tandem.

To my mind, a single axle trailer sounds more attractive for the following reasons:
1. No scuffing while turning.
2. Fewer tires to replace every several years when they "age out".
3. Less overall weight, especially unsprung weight.
4. Single axle trailers tend to use larger wheels and tires, which better deal with pot holes and washboard.

What are the advantages of a tandem axle beyond the greater load-carrying capacity?

And what are the disadvantages of single axles that I have overlooked?
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Old 03-24-2009, 05:25 PM   #2
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What are the advantages of a tandem axle beyond the greater load-carrying capacity?

And what are the disadvantages of single axles that I have overlooked?
In the 17' and under size range, single axles with 13" tires (and up) are pretty much industry standard. Most manufacturers begin double axles in the 19' to 21' range. Unique to small fiberglass trailers, The Fiber Stream put double axles under a relatively small 16' trailer, going to smaller 12" tires.

My Fiber Stream is the most stable, not-even-a-wiggle of sway, towing trailer I have ever experienced. While I have a friction anti-sway bar, I only put it on the hitch if I expect to be towing in an area with very high cross-winds.

I have heard that others experience sway and have gone to great lengths to minimize it.

Also, having a flat tire on a double axle trailer is less traumatic; you loose only 25% of your support, not 50%.

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When the [b]right-front trailer tire blew on our way to Bandon last summer, the ONLY clue I had was a tic-tic-tic sound of the deflated tire slapping. The trailer's handling and stance did not change in any way. When I pulled over to inspect the trailer, I started at the front LEFT and went around the rig in a counter-clockwise direction... scratching my head all the way until I found the problem in the last place I looked.
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Old 03-24-2009, 05:41 PM   #3
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Boy -- that's quite a rupture!

Do you have any idea of what precipitated that event?
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Old 03-24-2009, 05:51 PM   #4
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Do you have any idea of what precipitated that event?
Not a clue!
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Old 03-24-2009, 06:57 PM   #5
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Interesting topic.

We are in the process of trying to find a Bigfoot 5th wheel, we would prefer the dual axle but there seem to be fewer of them. Our preference for the dual axle is as Frederick says, we have never had sway with a dual axle trailer (Though I know it can happen I've seen it). Plus the idea of spreading the load over four high rates tires seems safer to us. I tend to pack "the kitchen sink" too it seems as our 13 ft Boler is one of the heaviest Fred has weighed.

We have never found there to be enough scuffing while turning to be a bother. Our tires age out before wearing out.

I'm interested to see what others have to say about this.
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Old 03-24-2009, 09:27 PM   #6
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The primary reason, beyond load capacity, for using tandem axles is ride quality. Tandem axles ride more smoothly with less bounce.

Roger
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Old 03-24-2009, 11:49 PM   #7
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We have a Bigfoot 5th wheel single axle and a Nissan Frontier crew cab pickup. There is no bounce, the ride is smooth. It's much smoother towing the 5th wheel than it was when we towed our old 17' Bigfoot with our pickup. I just wish Nissan made extendable towing mirrors for the truck. Back when we were on a hunt for our 5th wheel, we were looking for a single axle because it made quite a difference in weight and we have more interior headroom. Then again, to each his own!

Chris
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Old 03-25-2009, 07:27 AM   #8
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We have a Bigfoot 5th wheel single axle and a Nissan Frontier crew cab pickup. There is no bounce, the ride is smooth.

Chris
Chris, the tandem axle may not always play out as advertised, but a smoother ride is alleged. I had a triple axle Airstream for several years, and much to my amazement, even over VERY rough roads, items left on the dinette didn't move at all. I see an improvement in the ride quality of our Bigfoot 25 over our Bigfoot 17, not that the single axle 17 was 'bad' by any means.

I'd guess that part of your smooth ride with your Bigfoot fifth wheel has to do with how much weight is over the truck axle as well, and that the fifth wheel hitch mechanism transfers more of the movement to the truck axles and frame. It's very difficult to compare the handling of a hitch mount trailer to a fifth wheel mount trailer. The dynamics are very different. I'd guess that towing a Scamp 'fifth wheel' is very different from towing a Bigfoot fifth wheel, since the scamp really only uses a standard ball mount in a higher location. That wouldn't dampen the trailer's movement much, where a standard fifth wheel plate and pin would have a much greater damping effect.

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Old 03-25-2009, 10:39 AM   #9
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I have driven both too, I like the extra stability of the tandem under most conditions, however when I drove the Alaska Highway I got into trouble, a muddy road made it a totally different game. The tandem axle on muddy roads or slushy ones was murder to pull, it was like pulling an anchor, the single axle just cuts though it. I have stayed single axle ever since because I boondock allot.

Harry
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Old 03-25-2009, 11:06 AM   #10
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Tandem axle doesn't reduce sway -- It's all still in the balance -- Just coincidence that dual axle was better balanced than the single axle -- I had dual axle boat trailer that wasn't properly balanced and had a LOT of sway until I changed the set-up.

Friend of mine has big diesel pickup truck and took jobs delivering trailers from factory to dealers and between dealers -- He kept meticulous records and said the dual axles invariably gave worse mileage than single axle, not by a major amount but noticeable (He also found they weren't paying him enough to make up for long-term wear-and-tear on his truck, so he quit doing that work).
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Old 03-25-2009, 12:22 PM   #11
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Friend of mine has big diesel pickup truck and took jobs delivering trailers from factory to dealers and between dealers -- He kept meticulous records and said the dual axles invariably gave worse mileage than single axle, not by a major amount but noticeable (He also found they weren't paying him enough to make up for long-term wear-and-tear on his truck, so he quit doing that work).
Pete, Isn't the trailers with tandem axles heavier then the single axle trailers? I would think mileage would have a lot to do with total weight, especially if pulling over the rockies for a western state delivery.

My take is that each axle is for carrying up to 3500 lbs. My 3200 lb. single axle Casita bounced like crazy and everything had to be tied down. My 25' Bigfoot has tandem axles and weighs about 6500 lbs. Stuff left on the dinning room table is still there when we arrive at our next stop.

When my Casita had a Blow Out on the freeway, it drop to the ground. My tandem axle trailer now won't do that. It seems safer to me.

With my Casita and Chevy Tahoe I got 14 MPG. With my 1 Ton Dodge diesel and 6500 lb Bigfoot, I get 17.5 mpg to 18 MPG towing even though it is much heavier. It is all about rig combinations. I have friends that tow a 44' 5th wheels weighing around 18,000 lbs and get 11 MPG. They tow with a modified Vovlo 610.
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Old 03-25-2009, 02:11 PM   #12
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For boondocking I can see several other potential advantages to a single axle:
1. It is easier to warp into narrow dogleg spots.
2. If you replace the brake drums with ones from a car or truck that matches your tow vehicle's wheels, you can use the same wheels and tires as on the tow vehicle. Now you have TWO spare tires that can be used on either the trailer or the tow rig. Another advantage of this setup is the overall tire width and diameter will likely be larger, giving you additional ground clearance as well as better flotation through loose sand, mud, or whatever. The downside, of course, is this can require a major modification of wheel wells, and potentially even the axle in order to use that brake drum.
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Old 03-25-2009, 02:23 PM   #13
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When my Casita had a Blow Out on the freeway, it drop to the ground. My tandem axle trailer now won't do that. It seems safer to me.
One thing people tend to forget is that when one tire fails on a tandem rig, the tire manufacturers strongly suggest that you replace that tire and also the one on the other axle and the same side as the failed tire. Makes sense if the blowout was due to a pothole or other abuse -- the tire on the other axle probably also encountered the same abuse.

So remember, for a tandem rig you really should carry two spares.

One time when we were coming down from Sonora to Merced on a very hot day we encountered a 18-wheeler tanker also going downhill but which had blown out all 8 driven tires on the tractor -- what a mess! What was surprising is that the area we were in was rolling grasslands miles away from any significant grades, so it didn't seem likely that the tires had overheated from braking. I don't know whether they had been properly inflated or not -- when I saw him he was creeping to a pullout with 8 very floppy tires.
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Old 03-25-2009, 09:22 PM   #14
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Weight makes a difference, but so do windage and rolling resistance -- He said he could feel the difference in the rolling resistance, and he was a Sheriff's Deputy for 30 years, so I believe him.

I have had one blowout/total tire failure on my single axle Scamp and it handled very well, so I am not concerned about control problems enough to take on the concerns of dual axles with twice as many brake sets, bearing sets and tires to be concerned about.

Although they are not a match-up for long-term replacement, I had 4x4.5 15" trailer wheels and tires on my previous Jayco and they fit on my previous Dodge truck's 5x4.5 wheels and tires for some get-out-of-trouble spares -- That was a comfortable feeling!

Trailer wheels are zero-offset and lug-centric mounting; tow vehicle wheels often have off-set and have hub-centric mounting, plus may need extra room for disc and drum brake hardware.
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