Dual vs triple axles...

zekester

Member
Jul 25, 2009
74
Lake Huron
Boat Info
1987 Donzi Hornet3
1990 Searay EC310 twin 7.4 inboards
Engines
330 TRS, 7.4 merc inboards
If you have two trailers, both rated at 12,000 pounds, but one is triple axle, one is dual, what are the pros and cons of each? Is the triple a better handling trailer? with the dual being easier to manouvre? is the dual something to stay away from?
 
If you have two trailers, both rated at 12,000 pounds, but one is triple axle, one is dual, what are the pros and cons of each? Is the triple a better handling trailer? with the dual being easier to manouvre? is the dual something to stay away from?

I've run both and currently run a triple rated at 11k. You are correct that a triple will handle better on the highway, tracks straighter, etc. The double will turn better. But here are some other things to consider...

1.) If a tire blows on a double, you loose 25% of your capacity. If it blows on a triple, you only lose 16.7%

2.) Breaks, on a triple you get 50% more breaking power assuming you put breaks on all axles.

For these reasons a triple can "limp" along better, stop better and run smoother.
 
I actually blew a tire on a dual once, with my 270 DA on it, the tire blew, the hub snapped off so i was down to 3 tires, with one not flat but gone completely...

for more fun, it happened going down a hill approaching a bridge I ended up across two lanes, with the outdrives inches off the ground...

The triple is sounding better : )
 
I just lost the middle tire on a triple axle, and it was a non-event. There was no change in vehicle handling. The tire just blew up, it was about 5 years old and could not take the hot road.

However, I have come to the conclusion that with my triple axle trailer, I need two spares on a long trip. When you lose your last spare, you dare not venture far. Well, maybe you dare, but not me. It just worked out that I have two spares now. On my last trip of about 700 miles RT, I put on one new tire before leaving, and lost two on the trip.
 
I just lost the middle tire on a triple axle, and it was a non-event. There was no change in vehicle handling. The tire just blew up, it was about 5 years old and could not take the hot road.

However, I have come to the conclusion that with my triple axle trailer, I need two spares on a long trip. When you lose your last spare, you dare not venture far. Well, maybe you dare, but not me. It just worked out that I have two spares now. On my last trip of about 700 miles RT, I put on one new tire before leaving, and lost two on the trip.



Hi Dave,

That sounds like excessive tire issues.

Do you have an explanation on why you are going thru so many trailer tires?

Did you carry spare bearings, grease and tools to change a bearing?

This may be a northern climate issue, but here goes. This issue does not apply to campers & other non-marine trailers.

The trailer gets submerged in water as you are launching and retrieving the boat. A small amount of water remains by the seal. The trailer gets put into unheated storage for the winter. The water freezes and expands, causing a gap in the seal. In spring the trailer gets used and as its used the grease or oil leaks out then the bearing gets hot and fails.

Driving down the highways I think I see more boat trailers left on the side of the road with the hub off, meaning the bearing failed, not a blown tire.
 
I'll chime in for the pros. of the dual axles..

The tire thing is kind of mute really. If you lose a tire on any trailer, there you sit until you get it fixed. On a dual axle there are four chances to lose a tire, on a triple there are six. Also, with the braking both trailers have the same amount of weight on the axles, so they will stop about the same. Triple may be a bit better, but it is a pain doing mant. on three axles. Tight turns and steep grade changes are easier on the axles with a twin, the three axles bind up. Also, with twin axles you can run torsion bar suspension (mine is) and it is a much better system than the traditional leaf springs in my opinion.

The difference is really two heavy duty axles, bearing, and brakes or three normal axles, bearings and brakes. When is the last time you saw triple axles on a typical semi trailer?
 
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I'll chime in for the pros. of the dual axles..

The difference is really two heavy duty axles, bearing, and brakes or three normal axles, bearings and brakes. When is the last time you saw triple axles on a typical semi trailer?


The number of axles on a semi-trailer (all non self supporting trailers are semi-trailers) determines the load that is both carried by the axle tire combo, and the load in contact with the pavement. Increasing the number of axles lowers the per tire contact load with the pavement and improves both tire and pavement life.

With trailers for larger boats the geometry often works out that the trailer is carrying the majority of the weight of the boat. In any event determining whether you can use duals, or triples depends on the weight of the trailer and boat minus the tongue weight. Divide that by the weight rating of the axle/tire combination and you have your answer after you also apply a safety factor

To answer BC's question, lots of times. Under the Federal Law that covers interstate trade, commercial truckers are required to stay within a set of axle to pavement loadings that is based on a formula (the 'Bridge Formula') whose parameters are weight and weight rating on each axle, number of axles, and the distance between same. State laws apply to intrastate trade, and non commercial vehicles, but all work on roughly the same concept. And unless you are a boat hauler working off an interstate bill of lading, boat trailers fall under specific state regulations.

Typical applications for tri-axles are container chassis, dump trailers, heavy haul flatbeds, tank trailers etc. In Canada where the GVW is roughly 100,000 pounds (it varies by Province), the tri-axle and tridem is more common than tandems.

Henry
 
Zeke,

You hit the nail on the head as to the pro's/con's. And I'd agree with the other's comments on the pro's/con's as well.

I will add this story. I will point out that this happened with a ShoreLand'r trailer (tandem axle), which I believe to be one of the best built trailers out there. But, they are expensive. This was towing the boat in my signature - plus quite a bit of extra gear in the boat.

Twice, I blew a tire at high-way speeds. Complete blow-out - tread separated and everything. None of my passenger's had any clue what was going on. I barely knew. The first time I didn't know until I caught a glimpse of it in my side-view.

The second time, I felt a very slight vibration in the steering wheel - very slight. I looked in my mirrors but didn't see anything - thought it might just be road conditions. About 45 seconds later I saw smoke and figured it out. I started to pull off the road and my passenger's asked why I was pulling over. They still had no idea there was a flat.

Both times, there was absolutely no damage to anything else. The three good tires held everything up perfectly.

Point is, I think it ultimately depends on the quality of the trailer. I'm not saying that the ShoreLand'r is the be-all-end-all of trailers. But stick with a high-quality brand trailer, rated for the correct capacity, and a tandem will do just fine. But, a triple will still be better.

Saying all that, a triple will still afford a greater "margin of error" should something happen. The only real downside that I see to a triple is maintenance costs. Let's face it, you're not going to try move a trailer of this size around by hand. You'll always be using a vehicle. Just use a bit more of the skinny pedal in your truck and you'll be fine. :smt001
 
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I've had both duals and triples and will never go back to duals due to the safety issues mentioned. The weight distribution on duals is higher which adds to the possibility of flats over triples. I like to stop too and the extra set of brake disks is a big plus. They track much better and they should last a bit longer due to weight distribution. An extra set of tires will not break the bank but rather afford an extra level of peace of mind. For the same price for either duals or triples, no contest...
 
Also, with twin axles you can run torsion bar suspension (mine is) and it is a much better system than the traditional leaf springs in my opinion.


You can get torsion suspension on tri-axles as well. This is how the majority of new trailers I've researched are set up.
 
I have a triple. I've had 3 flat tires over the last 6 months. WTF? Anyway, I'll tell you I limped in one of them slowly to a tire shop that replaced the tire. I fell much better having the triple. It tows very well and 6 brakes are great.
 
. When is the last time you saw triple axles on a typical semi trailer?

It is fairly common here to see semi trailers with three axles, and probably half of them have a fourth axle that can be raised, and is only put down when needed to comply with the state load per axle requirements and their trailer weight at the time.
 
You can get torsion suspension on tri-axles as well. This is how the majority of new trailers I've researched are set up.

Yes, my triple axle trailer is torsion. So if you are planning to buy one of these, you should look under there and see how you would jack up a single axle to change a blown tire. I think you will find the manual says not to place a jack under the arm that the spindle goes in to. I think it can be safely done, but I am not sure, as I don't know the construction of those components.

Also, torsion arm suspension on a triple axle suspension arm trailer does not distribute weight evenly between axles, so if when you go over uneven surfaces, such as pulling into a gas station, you will have times when one axle carries very little load. For this reason, and others, trailer tires are designed with much more overload capacity than other tires.

To change a tire on the road, I carry a complicated set of wooden blocks that I can place under the other two axles, and back onto them a foot at a time, until the bad tire is off the ground.
 
Hi Dave,
Do you have an explanation on why you are going thru so many trailer tires?

Yes. The first boat tire this year was a replacement from Les Schwaub tires, and the newest tire on the trailer. It was on the rear axle, and had ALL the tread scrubbed off from turning. It was about 4 years old, had less than 2000 miles on it. A triple axle trailer is very hard on tires when you turn tight corners on pavement, such as at the boat ramp I normally use. I am trying to learn how to make to U turn at the ramp in two parts, so I don't scrub the tires sideways so bad. Anyway, I just replaced the tire as it had no tread, and was obviously not a good a quality as the Goodyear Marathons on the rest of the wheels.

The second tire and wheel I lost at Anacortes, trying to maneuver to a place where I could park so my wife to walk to a hardware store and get a crab license. I managed just clip a curb with the front axle, and rolled the lip of the wheel up enough to let out the air. I thought I had also punctured the tire, but now it seems I did not. It is holding air, and I have used a hydraulic jack to restore the rim to near original shape, and put it back on the trailer for local trips to test the tire and wheel. But at the time, I had to use my only spare, I was 350 miles from home, and could not buy a Goodyear Marathon within a reasonable travel distance. So I had to buy another Les Schwaub tire as a spare to get home. So that flat you can attribute to 'operator error'.

The third tire I lost in the heat of the day. Road surface temps were about 150, and the tire treads were running about 145 degrees. This was too much for the old tire, which was about 4 1/2 years old, and it blew. This is a common failure mode for Goodyear Marathons. I read a comment on them by someone who said their good points are that they are made out of rubber and they are round.

This tire suffered from age, triple axle turning abuse, surge brakes, and heat. The reason I say surge brakes is that the 350 mile trips includes 5 to 6 percent grades of 10 miles or more in length. I can't prevent the surge brakes from being applied coming down those hills. I stopped at the bottom of one, and the brake drum temp was about 200 degrees. This does not help keep the tire cool, as some of the heat must be being transferred into the wheel, and on the the tire. I am seriously thinking about switching to all electric. I was travelling with Jim Larson, and his triple axle trailer with a bigger boat but electric brakes had brake parts that were only about 130, just a bit over ambient tempterature.

I was not the only one with tire issues, there were probably 10 dead tire carcasses per mile along the road.
Did you carry spare bearings, grease and tools to change a bearing?

I do in my fifth wheel trailer, it has greased hubs. I don't for my boat trailer, it has fluid filled 50 weight oil, and I can easily drain the oil and replace it. So I don't feel it has the same issues as one with grease.

The trailer gets submerged in water as you are launching and retrieving the boat. A small amount of water remains by the seal. The trailer gets put into unheated storage for the winter. The water freezes and expands, causing a gap in the seal. In spring the trailer gets used and as its used the grease or oil leaks out then the bearing gets hot and fails.

I don't have grease in the hubs. I still may get a small amount of water, but I can easily flush the oil. I don't have an issue with freezing, as the boat and trailer are kept in heated space in the winter.

So I think with three axles, you are going to lose tires unless you replace them at about 4 years just based on time. I understand people thinking it is unusual to lose tires like that.

On my small boat that I have had since 1968, single axle, I never carried a spare, and never needed one.

On my fifth wheel, I carry one spare, and I think that is adequate. I also carry a greased spare bearing set and tools.

On my boat trailer, now I have two spare tires, on won't go on long trips with less. No spare bearings, I can keep track of how they are doing by looking a the fluid the measuring their temp with an infrared temp gun.

This all pertains to the Pacific Northwest, where there are long hills, and it may be 100 miles to the nearest location to get tires if you have a flat. And if it is on Sunday, then it just becomes more difficult. Better to be prepared.
 
I would go for the triple for stability.

As far as tires... I have been towing heavy boat trailers for 20 years, and heavy horse trailers before that. I have commonly had blowout problems with radials, and very rarely had blowout problems with bias. A tire guy explained to me that radials cannot take the additional flexing necessitated by the heavy load and limited travel suspension of trailers.

Regarding torsion axles, as someone else mentioned, you can run them on triples. I had them on the triple under my 260. I like them. Smooth, quiet, and simple. Since they don't articulate, they do occasionally put higher stress loads on individual axles.
 
lots of great comments and opinions, thanks guys....
 
OT, but, I saw a hydrolic trailer at a marina this spring.
It had dual wheels on two axles. The tires were not that tall either and I imagine very heavy rated. That trailer would probably easily move a 50' boat.
It seems like this would be the way to go.

Are there any manufactures that make typical boat trailer this way?

It seems like it would be the best of both worlds for a larger boat. Especially a boat with any beam greater that 8'6.
 
In all the discussion of flat tires, did anybody mention this...

For two trailers with equal load limits, triple axles will have smaller tires compared to a double. This can lower your clearance which can effect bridge clearances and loading your boat at the ramp. Also, there can be other pros/cons for tire size.
 

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