Single vs Tandem Axle

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Single vs Tandem Axle

Postby arbakken » Mon Sep 19, 2016 1:45 pm

I have compiles a list of the Pros and Cons of single and tandem axles, as well as my thoughts on them. I am planning on doing a ~6.5x12 ctc camping trailer, with the intention of towing it fairly long distances including lots of off road (gravel, washboard roads, light off road trails, not rock crawling!, etc) I figure that the trailer fully loaded will probably be ~2500 lbs.

Single Pro:
weigh less - yeah, like 150 lbs less
cost less - a few hundred bucks, who cares
more maneuverable -that is a concern
don't have to level - I'll have a hitch that is setup perfectly, so whatever
doesn't need brakes - yeah, but then it doesn't have brakes

Single Con:
less payload - not a concern
doesn't have brakes - can have brakes, I'd kinda like to have brakes
harder on tires due to weight - that is a concern

Tandem Pro:
more stable at highway speeds - sounds great
flat tire much less catastrophic and easier to change - sounds great
safer due to blowouts and having brakes - sounds great
less prone to sway - sounds great
track straighter in wind - sounds great
bounce less - sounds great
more payload - who cares?
better approach and departure angles - I added this one, I think it's significant

Tandem Con:
costs more - a few hundred bucks, who cares
weighs more - even if 200 lbs more, whatever
road tolls - don't have tolls around here, so would be uncommon on trips
more maintenence - also more redundancy!
have to tow flat - again, hitch height would be set perfectly


At some point in a few years, I am considering taking a trip literally around the world with the trailer. After considering all the pros and cons, it seems like a no brainer on a trailer of that size to do tandem axles. I think it'll help out significantly off road, and the redundancy seems worth it for the small weight and cost increase. I especially think halving the load on the tires will help reduce the chances of puncture Anyone have any thoughts on the issue? I would probably be putting ~2000 lb axles on a tandem, or a 3500 lb axle on a single.

Also, what is everyone's thoughts on spring vs torsion? I originally wanted to do torsion axles as they ride smoother and have better ground clearance, but it sounds like they don't hold up as well on washboard roads, and spring axles work together going over bumps and rocks.

Thanks!
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Re: Single vs Tandem Axle

Postby Padilen » Mon Sep 19, 2016 3:46 pm

Actually a 3500 single will have brakes. Have you talked to a builder to see what they would recommend ?
For your use have you thought about bigger wheels tire's?



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Re: Single vs Tandem Axle

Postby yrock87 » Mon Sep 19, 2016 4:07 pm

Not to be a negative Nancy, but I think a single axle would likely suit you better. 1 ton military trailers are all single axle. They have high mobility, and the redundancy vs cost is not trivial. It will cost you $200 for the axle. Plus another $200 for cheap tires. If you want quality titles and wheels add another 100-200. If you want brakes add another $200 for that axle. So $400 minimum, easily a such as $800+ on the high end to add that second axle. for what? The need to and cost to maintain twice as much running gear? Sure bearing are only $10 a tire, but you doubled that cost from $20 to $40. And doubled the amount of time it takes as well.

Not to mention that if this trailer is literally going around the world, you WILL be paying fees for that second axle.

I'm not opposed to double axle trailers as a whole. They are great for greater than 3500lb trailers. If you were going to have a 3000-3500 build it may be worth considering, but if you are going to be at 2500... I don't see the benefit.

You are likely enter off getting quality components and full size wheels and tires for a single axle as far as weight, mobility, dependability goes. Vs going with two small axles to try to spread the load.

Also, you are less mobile if you underrated your axles/tires and go with two. While it is true that your tires will be closer to both the TV and the rear of the trailer. You cannot go over terrain that I'll push your vehicle to the limits because if you run twin 2k axles, and you go over harsh terrain, one axle may end up taking all 2500lb of your trailer in certain instances (very high approach / departure, or coming down/up a ledge.) that is a liability to me,not an asset.

Not to mention that most property designed tandem axles share a center spring mount. That is a single Pont of failure for both axles. Last point(I promise) you will need to carry twice as many spares. If you hit a nailed board on the highway, and loose both driver side tires, you will need two in order to get going again. (yes you can limp on a single tire with a tandam set up, but you don't really want to do that. You are better off carrying two spares with a single axle if punctures are a concern to you.

Okay, I'm done.

Your build sounds interesting, but there is a reason most tnttt, td, or of road camp trailers don't have tandam axles. It just doesn't make sense for a variety of reasons, with a small trailer. I wish you luck and look forward to watching your build.
Last edited by yrock87 on Mon Sep 19, 2016 4:52 pm, edited 1 time in total.
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Re: Single vs Tandem Axle

Postby MtnDon » Mon Sep 19, 2016 4:35 pm

A normal ST205/75Rx15" tire has a load rating of a little over 2000 pounds. At a ready to go weight of 2500 lbs two tires on a single are all you need. Rather than drag the tandem axle trailer I'd carry a spare hub and two spare wheels/tires and go single.

In 35 years of towing single axle trailers I have yet to wear out the tread on a trailer tire. They age out first. I have never had a blowout in all those years. Maybe because I change tires before they hit 5 years of age, I check pressures before setting out and while traveling check temperatures of both tires and bearings at stops. I have had a couple flats over the years but those were slow leaks that provided ample warning.

Where do you get the info that a tandem tows without sway or that they track better in winds? Sway is virtually always caused by improper tongue weight (too light) and or a rearward slope. I have never been bothered by sway or winds with any trailer I have towed because I pay great attention to tongue weight. Hurricanes and tornadoes do not count.

The only reason a tandem most always comes with brakes is the GVW of the trailer and state trailer weight laws. Brakes can be added to virtually any axle except for the bargain basement things like HF sells. Any builder can build a single with electric brakes. I have a single open box trailer that could easily carry more than the rated 2990 lbs weight except for the fact that it does not have brakes.

For the weight you have described all I see are negatives for a tandem.

Tire load capacity can be increased by going to a 16" trailer wheel.
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Re: Single vs Tandem Axle

Postby Redneck Teepee » Mon Sep 19, 2016 7:12 pm

For a 2500 lb trailer go single axle... I'll back up what has already been stated, if you go tandem get ready to spend very good money on "Trailer ST Rated Tires" if you use car radials on a tandem, like you can on a single axle trailer you will burn thru tires faster than you can pay for them as they are always skidding sideways somewhat in a turn. Trailer rated tires are a harder tougher compound just for that reason. Stick with single axle and good car radials for the ride. Just my 2 cents worth :thumbsup:
The links below explain it very well.

http://www.tirerack.com/tires/tiretech/ ... techid=219 :D
http://www.discounttire.com/dtcs/infoTr ... reFacts.do
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Re: Single vs Tandem Axle

Postby KCStudly » Wed Sep 21, 2016 8:11 am

Single. For all of the reasons mentioned in the above posts. In particular for your stated usage of around the world travel on sketchy roads.

As far as leaf spring versus torsion, I say leaf spring. You are much more likely to be able to perform a bush or roadside repair on leaf sprung suspension.

Parts availability: You would be surprised at what can be bodged together and made to work to get leaf springs working again. Not so much for a torsion axle; you're looking at complete replacement and you better hope your axle is an off the shelf common version. Can you even get torsion axles in east nowhere land?

I am not a fan of torsion axles in tandem applications due to the possibility of overload from weight jacking (traversing uneven surfaces/transitions/rough terrain) and the lack of load leveling features (i.e. central spring rocker perches). (Maybe on a horse trailer?)

Brakes. Just do it. In some regions trailer brakes are required for gross weights as low as 1500 lbs (such as CA). And yes, axle cost does go up more than you are estimating once you up rate, add brakes, and decent tires. Just do it.
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Re: Single vs Tandem Axle

Postby Dale M. » Wed Sep 21, 2016 9:25 am

Two points where your research is faulty on tandem axles... One is they do not maneuver well, the tend to scrub going around corners ( they want to always run straight, not steer) and backing can be miserable also because of scrub factor.... As for stability, if you are think it will hold trailer lever and stable when parked, it wont, it will have tip/rock/roll maybe not as much as single axle but it will be there by the nature of pivots that support springs..... IF you want stable trailer when parked, use jacks, trailer suspension by design will not give you stable cabin...

And brakes,, If you are building trailer and have even consider tandem axles, you WILL NEED BRAKES... And they can be good even on light weight trailer...

Single axle is so much simpler than tandem.... I would rather tow and maneuver a single axle trailer anytime over my tandem axle trailer.....

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Re: Single vs Tandem Axle

Postby arbakken » Wed Sep 21, 2016 10:15 am

I can't lie, I was hoping you guys would all think my plan was awesome, and send me $1000 each for being such a genius. :lol: Oh well...

I read a lot of threads on other forums, and the people there seemed to think that tandem axle was better than single, but all of them were in reference to much larger, heavier trailers/loads. I still haven't given up on the idea, but it has lost a lot of luster and seems unlikely I'll pursue it at this point. The thing that scares me the most is losing a tire on a single axle trailer that is pretty high off the ground. Maybe I should cook up a height adjustable, trailing arm, airbag suspension! :twisted:

So, what do you think about torsion axles vs spring axles for my application?
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Re: Single vs Tandem Axle

Postby drhill » Wed Sep 21, 2016 11:02 am

I agree with all that has been said about the benefits of single axle. Unless you are over 3500 lbs, single axel is the best. As for springs vs torsion axle. One of my boat trailers has torsion axle and it rides nice - on the highway. Leaf springs would be my choice for anything that is going to be used a lot on gravel roads or trails in the bush etc. If something ever does break it won't be in your driveway. Parts for leaf springs are much more readily available and you can block the axle to limp along if needed. Breaking a spring is pretty rare and I am told is often the result of excessive bouncing of an under loaded trailer.
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Re: Single vs Tandem Axle

Postby Padilen » Wed Sep 21, 2016 1:08 pm

arbakken wrote:I can't lie, I was hoping you guys would all think my plan was awesome, and send me $1000 each for being such a genius. :lol: Oh well...

I read a lot of threads on other forums, and the people there seemed to think that tandem axle was better than single, but all of them were in reference to much larger, heavier trailers/loads. I still haven't given up on the idea, but it has lost a lot of luster and seems unlikely I'll pursue it at this point. The thing that scares me the most is losing a tire on a single axle trailer that is pretty high off the ground. Maybe I should cook up a height adjustable, trailing arm, airbag suspension! :twisted:

So, what do you think about torsion axles vs spring axles for my application?

I was thinking that if one person agreed with you you'd jump at it. Glad reasoning worked! But would have been fun to see success or fail.
As many have said leaf springs are easier to repair. Yes the axle is still low and could drag. That's why I had already suggest larger wheels on a single. FYI I haven't found inexpensive options of wheels / spacers etc., for my CTC. Cheapest for me was an axle flip kit.


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Re: Single vs Tandem Axle

Postby lrrowe » Wed Sep 21, 2016 2:37 pm

I have a 5000# Dexter Torsion single axle and have no regrets yet. I get no sway at interstate speeds, no unnecessary bouncing on Nation Forest roads and winds have not bothered me yet. I am guessing my tow weight is 2500 lbs.
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Re: Single vs Tandem Axle

Postby arbakken » Wed Sep 21, 2016 5:33 pm

lrrowe wrote:I have a 5000# Dexter Torsion single axle and have no regrets yet. I am guessing my tow weight is 2500 lbs.


Any reason you went that heavy?
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Re: Single vs Tandem Axle

Postby lrrowe » Wed Sep 21, 2016 9:10 pm

At the time, I had planned on being able to haul a motorcycle (which I do not have) with plenty of capacity to spare.
But now in retrospect, since the chances are slim to none that I will get one, I could have gone lower. I tend to over build in about all things I make which means I could have gone with a 3500 lb CT. I do not regret the Torsion set up though.
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Re: Single vs Tandem Axle

Postby swoody126 » Wed Sep 21, 2016 10:01 pm

as mentioned above, leaf springs are simpler and repair parts are easier to find WHEN you find yourself w/ an issue

if you tow very much you WILL have issues

TRACTOR SUPPLY as do many other farm stores carry common leaf spring suspension parts as do stores like ACADEMY SPORTS...

torsion axles are seldom "in stock" anywhere and can take a while to be ordered in

if you have a single axle you can maneuver it by hand while rolling on the tongue jack wheel

if your trailer has tandem axles you will be "challenged" to move it around by hand

as mentioned above tandems want to go straight and scrub tires unmercifully

15" tires come in up to 10 ply ratings that will carry any load your OP has described and then some

2 axles more than double the towing forces lowering your fuel economy

2 axles at least double maintenance times

2 axles more than double the building & maintenance parts $$$

most tandems that experience a catastrophic tire failure will have the other tire on that side fail within a short time meaning having 2 spares is advisable

having the trailer hubs w/ the same bolt pattern and tire size as the tow vehicle effectively adds another spare to the equation

the KISS method is highly recommended by this old man

btw, my experiences include tire failures on 2 wheel, 3 wheel, 4 wheel, 6 wheel & 10 wheel primary vehicles as well as on 2 wheel, 4 wheel & 8 wheel trailers over many hundreds of thousands of miles on personal & commercial vehicles and my recommendations/comments are based on personal knowledge not speculation

GOOD LUCK WITH YOUR BUILD

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Re: Single vs Tandem Axle

Postby arbakken » Thu Sep 22, 2016 7:14 am

swoody126 wrote:having the trailer hubs w/ the same bolt pattern and tire size as the tow vehicle effectively adds another spare to the equation


That would be sweet, but I've already got the oe 32" tires and will probably run 35" tires soon, so that's probably out. A small trailer on 35" MT tires would look badass though! 8)
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