one axle vs. two axles on short TT (20')

[SkiMore]

I was wondering what the pros/cons were of one axle vs. two axles on a short/lite TT. I'm talking about something less than 22' and 3500 LB dry.

I guess I should also ask about wheel size too.

[69_Avion]

westend wrote:
If considering alike travel trailers, one having single axle and the other, a tandem set, I would choose the trailer that is built better. There is a lot unknown how a trailer will tow, regardless of axle count. Tandem axles will support more weight and for some, that is a great attribute. I have a 22' with tandem axles supporting 5K lbs. It tows like a train and stops adequately.

Even though I respect Avion69 quite a bit for his trailer building skills (and he's helped me a ton), I'd differ a bit on the ride quality of sprung axles over torsion bar for a small TT application. My current TT has two torsion axles with shocks (I've forgotten the ratings). It is the smoothest towing trailer I've owned (current count is 6). Part of that may be due to the low attitude but the torsion axles are a highway dream.

The issue isn't as much the ride as it is the stress when one rubber torsion axle has to carry most of the weight of the entire trailer when you hit a bump that is greater (or close to) the travel of the axle. When you hit a 6" speed bump and the axle only travels 5", one axle will carry the entire weight of the trailer for that bump. A leaf spring has an equalizer so you get the travel of the equalizer plus the travel of the leaf springs. If you aren't hitting large bumps, a rubber torsion tandem trailer should tow real nice and ride nice as well.
If I were picking the "ride" of an individual axle, I would pick the rubber torsion over the leaf spring. The other issue is lateral stress when cornering. It isn't real bad with tandem axles, but it can be tremendous with triple axles. Some rubber torsion axle manufacturers don't recommend their RT axles for triple axle configurations because that stress can pull the rubber swing arm right out of the axle tube.
They all have their positives and negatives. Most of the time a person doesn't get their choice when buying a trailer. Another down side of the rubber torsion axle is that the rubber is usually only good for about 25 years. Then it is time to buy a new axle because you can't replace the rubber. In many cases the TT needs a rebuild by that time anyway. A positive attribute to the rubber torsion axle is that it can be used as part of the structural integrity of the trailer frame and it is easier to install. A real nice positive attribute to the rubber torsion axle when using the Flexiride axle is that the torsion arm angle can be adjusted in about 30 minutes. That can come in real handy.

[Sondy132001]

Mine is 18ft and a 1982 and it's a tandem axel

[AH64ID]

Ever tow a single axle trailer and watch the tires? They spend a lot of time airborne, a lot more than most people realise. I wouldnt want that for a TT.

Personally I will only try to own tandem axle trailers, even if the GVWR is low. The simple tow so much nicer.

As far as most trailers under 23'being single axle I call BS. Very rare TT's are single axle. I have owned a 22' tandem axle, and been around many trailers under 23' that are tandem axle and maybe 1 single axle.

[westend]

If considering alike travel trailers, one having single axle and the other, a tandem set, I would choose the trailer that is built better. There is a lot unknown how a trailer will tow, regardless of axle count. Tandem axles will support more weight and for some, that is a great attribute. I have a 22' with tandem axles supporting 5K lbs. It tows like a train and stops adequately.

Even though I respect Avion69 quite a bit for his trailer building skills (and he's helped me a ton), I'd differ a bit on the ride quality of sprung axles over torsion bar for a small TT application. My current TT has two torsion axles with shocks (I've forgotten the ratings). It is the smoothest towing trailer I've owned (current count is 6). Part of that may be due to the low attitude but the torsion axles are a highway dream.

[Jebby14]

I have a newly acquired 1991 prowler 19e. its got doubles and pulls fine. cant imagine it being nearly as friendly to tow on singles.

[Capt_RonB]

double axles increase the tolls.

[atreis]

NanciL wrote:

atreis wrote:

My current trailer has two axles (and weighs 3300 fully loaded and is 21' - there are MANY shorter lightweight trailers with two axles).

I've had a flat on this trailer, and it went fine... My previous trailer had a single axle. I also had a flat on that trailer, and it also went fine. No sudden sway or other danger. So long as your setup is good - a good hitch, properly adjusted - it really doesn't matter much.

But I'll bet you didn't five five miles on that one wheel when the other one blew out !

Jack L

Assuming you meant something like: "I'll bet you didn't drive five miles..."

Correct. In neither case did I drive very far at all. I could have driven further with the tandem axle, at the potential risk that the damaged tire may have shredded and tore up the wheel well - not a good thing. Also, for most tandem axle trailers the one good tire would be severely overloaded. Just because you can do something doesn't mean you should.

[69_Avion]

mr61impala wrote:
Obviously wind resistance is the greatest constant load to your tow vehicle but is not rolling resistance the 2nd largest constant load? (Terrain being a variable).

Considering two otherwise identical trailer boxes would it not require more energy to tow the one with 4 tires as opposed to the one with 2?

FWIW our very first TT back in the late 80's was a 1965 Avion single axle that was around 20-21 feet long. Used W/D hitch, no issues at all.

You are correct. You also have more rotational force when stopping with tandem axles, but when I build trailers, I put brakes on all axles, which increases stopping power. You also have more "scuffing" with tandem axles, but that is a small price to pay for more load bearing area on the trailer. When the weights gets over 5,000# or so it really pays to have the second axle.

Most RV trailers currently being built don't have the aerodynamic qualities of a silver Avion.

[mr61impala]

Obviously wind resistance is the greatest constant load to your tow vehicle but is not rolling resistance the 2nd largest constant load? (Terrain being a variable).

Considering two otherwise identical trailer boxes would it not require more energy to tow the one with 4 tires as opposed to the one with 2?

FWIW our very first TT back in the late 80's was a 1965 Avion single axle that was around 20-21 feet long. Used W/D hitch, no issues at all.

[NanciL]

atreis wrote:

NanciL wrote:

Last month coming home on I-95 going 65 MPh I had a blow out on one of the trailer wheels. All I heard was a pop, and the trailer never even swerved.
I don't think I would have been as lucky if I only had one axle!

My current trailer has two axles (and weighs 3300 fully loaded and is 21' - there are MANY shorter lightweight trailers with two axles).

I've had a flat on this trailer, and it went fine... My previous trailer had a single axle. I also had a flat on that trailer, and it also went fine. No sudden sway or other danger. So long as your setup is good - a good hitch, properly adjusted - it really doesn't matter much.

But I'll bet you didn't five five miles on that one wheel when the other one blew out !

Jack L

[69_Avion]

With a trailer of 3,500 empty, you are probably going to be in the 5,000# plus range loaded. My recommendation when you get over 5,000# is to go to a tandem leaf spring combination.
The last "camper" trailer I built used a 7,000# rubber torsion single axle configuration and it tows great. Because of the configuration I was limited to a single axle and I wanted the tires and wheels to match the truck. Otherwise, I would have built it with two 4,000# axles with leaf springs.
As far as tongue weight, I like to have over 10%, as long as the TV can handle it. Excess tongue weight (within the limits of the TV) won't hurt you, whereas too little tongue weight can kill you.

Safe Camping

[SkiMore]

69 Avion wrote:
The OP was asking about a trailer with a GVW of around 3,500# and a length of 22' or less.
As stated many times there are advantages and disadvantages of both. Having built trailers on and off for around 40 years I will express my experience with them.
First off, being a single axle or tandem axle has nothing to do with how well they back up. It is the distance from the hitch (coupler) to the center of the axle (or center of tandem axles) that determines how well they will back up. The shorter the distance, the harder they are to back up. Most folks don't realize that this distance also affect how well they tow. The shorter the distance the more any issues, like sway, will be magnified.
To the OP's question, in the 3,500# weight range it is hard to find decent axle arraingements with tandem axles. Most axle manufacturers start getting into their decent axles in the 3,000-3500# range. You aren't going to put two 3,500# axles on a trailer with a 3,500# GVW. Take a look at a 1500-2000# axle and you will see what I mean. The spindels, hubs, springs are not in the same league as the quality axles. I like tandem axles in most cases, especially with leaf spring instead of rubber torsion axles, because of the equalizer. Rubber torsion tandem axles can have all the weight on one axle when going over large bumps. That can create a huge problem.
Would I rather have a single axle trailer with a quality 3,500# axle or a tandem axle trailer with two 2,000# axles? I would take the single axle trailer every time. I recently built a single axle trailer with a 7,000# rubber torsion axle. It works great, but for that weight load I would prefer tandem leaf spring axles, but the length of the trailer didn't reasonably allow for that.
Most of the trailers that I built over the last 40 years were tandem axles, but there is a need, and use for single axles, just as there is for triple axles.

Interesting. Does axle placement vary much with TTs of a similar size? If the axle was father back wouldn't that translate to a greater portion of the weight in the front and a higher tongue weight? Assuming your truck can handle it is a higher tongue weight a problem?

I originally asked about a dry weight of 3500#, but I get what you are saying. That is an interesting idea about the weight rating of the axle(s). I looked at the specs of a couple of 1 and 2 axle 22' TTs. The dry weights were similar. The 2 axle ones had about 2000# CCC vs. 1000# for the 1 axle ones. I was wondering why it was only an extra 1000# for the 2 axles models. Your post cleared that up.

[69_Avion]

The OP was asking about a trailer with a GVW of around 3,500# and a length of 22' or less.
As stated many times there are advantages and disadvantages of both. Having built trailers on and off for around 40 years I will express my experience with them.
First off, being a single axle or tandem axle has nothing to do with how well they back up. It is the distance from the hitch (coupler) to the center of the axle (or center of tandem axles) that determines how well they will back up. The shorter the distance, the harder they are to back up. Most folks don't realize that this distance also affect how well they tow. The shorter the distance the more any issues, like sway, will be magnified.
To the OP's question, in the 3,500# weight range it is hard to find decent axle arraingements with tandem axles. Most axle manufacturers start getting into their decent axles in the 3,000-3500# range. You aren't going to put two 3,500# axles on a trailer with a 3,500# GVW. Take a look at a 1500-2000# axle and you will see what I mean. The spindels, hubs, springs are not in the same league as the quality axles. I like tandem axles in most cases, especially with leaf spring instead of rubber torsion axles, because of the equalizer. Rubber torsion tandem axles can have all the weight on one axle when going over large bumps. That can create a huge problem.
Would I rather have a single axle trailer with a quality 3,500# axle or a tandem axle trailer with two 2,000# axles? I would take the single axle trailer every time. I recently built a single axle trailer with a 7,000# rubber torsion axle. It works great, but for that weight load I would prefer tandem leaf spring axles, but the length of the trailer didn't reasonably allow for that.
Most of the trailers that I built over the last 40 years were tandem axles, but there is a need, and use for single axles, just as there is for triple axles.

[GWolfe]

No issues with my single axle, tows nice and has around 1000 lbs CCC. I haven't had a flat yet but have had a few on the old boat trailer and was never an issue.

[atreis]

NanciL wrote:

Last month coming home on I-95 going 65 MPh I had a blow out on one of the trailer wheels. All I heard was a pop, and the trailer never even swerved.
I don't think I would have been as lucky if I only had one axle!

My current trailer has two axles (and weighs 3300 fully loaded and is 21' - there are MANY shorter lightweight trailers with two axles).

I've had a flat on this trailer, and it went fine... My previous trailer had a single axle. I also had a flat on that trailer, and it also went fine. No sudden sway or other danger. So long as your setup is good - a good hitch, properly adjusted - it really doesn't matter much.