Trailer Load musings

[tpenfield]

As for musings . . .

My Tri-axle trailer's tongue weight is at 9%, which I think is a bit on the high side for a 3-axle set-up. Maybe 7% would be better.

I have thought about some re-engineering, but there is not much wiggle room of the bow-stop, axles, bunks, etc.

I did approximate that the center of weight (gravity) will be moving aft about 9" when I complete the conversion to outboards this year. So, maybe that will be enough.

I've also thought about the trailer tire psi . . . It seems that recommendations for trailer tires are to be at their maximum ratings. That differs from cars in that the recommendations are set by the car manufacturer (and tend to be about 70% of the tire maximum rating). I wonder about the science behind all that . . . trailers vs. cars/light trucks.

 

[Pmt133]

The pressure is a balance of ride and fuel economy. For a vehicles pay load, the factory specified pressure will give you the weight carrying the car needs at the set pressure. For the trailer you only get the maximum carrying capacity of the tire at max pressure. (Which is true for all tires) That's all.

And again, the tires supplied on most trailers are about maxed out at the trailers rated full load in most cases. So it makes sense to be inflated all the way.

 

[Lou C]

In many cases trailers seem to have only 10% safety margin meaning that the tires are loaded to 90% of their full capacity when the trailer is carrying its rated load. Vehicles have more like 25%. If you had the room to do so, one thing you could do is go to the largest diameter wheel you can use (in most cases 16") which will allow you to use a wider variety of tires including full steel trailer radials and LT radials. Now this doesn't increase load capacity per se but it does increase safety margin. When was the last time you saw a truck or SUV with 15" tires like most trailers? Oh yeah my '98 Jeep has those lol. 30"x9.5-15, largest you can fit on a stock ZJ Grand Cherokee. I use 225/75-15 Load Range E on my single axle. 2830 lbs each @ 80 psi.

 

[dingbat]

Tandem don't have tongue weight issues?

You can, but the load dynamics are entirely different with the second axle in play.

With a single axle trailer you’re playing teeter totter. With the single point of balance, the loads on each side must be fairly precise to maintain equilibrium.

The axles on a tandem are spread roughly four feet apart to distribute (balance) the load equally between the two points. Load variability with two points of balance, four feet apart is a whole lot greater than one

 

[bruceb58]

The axles on a tandem are spread roughly four feet apart to distribute (balance) the load equally between the two points. Load variability with two points of balance, four feet apart is a whole lot greater than one

Unless you have a trailer with torsion axles(like I do), the equalizer causes each tire to have the exact same weight. I hate torsion axles...wish I had regular leaf springs.

 

[Lou C]

I share your opinion Bruce, I think they’re overpriced and un-repairable whereas changing springs on a spring axle is easy and inexpensive (like $170 for a good pair of 5 leaf springs). And on multi axle trailers they don’t load share. I think trailer companies like them because they might be faster/easier to install….

 

[Pmt133]

They're quieter, articulate independently and tow nicer. That being said I can replace a spring pack with my normal trip pack out. Torsion I'm SOL. I have both and don't have a preference either way.

 

[tpenfield]

Doing some quick math on the actual load vs. 100% of trailer capacity . . . I should inflate my trailer tires to 70 psi . . . (I'll do that . . . they are currently about 60 psi vs. 80 psi max rating)

 

[redneck joe]

If a mod would like to change the thread title to 'trailer load musings' or similar i'd be ok with that. Lots of good stuff as ancillary info to my original post. Im enjoying the read.

 

[bruceb58]

They're quieter, articulate independently and tow nicer. That being said I can replace a spring pack with my normal trip pack out. Torsion I'm SOL. I have both and don't have a preference either way.

If you hit a bump, with a tandem torsion axle trailer, all the force of the impact will get transferred to the forward axle....not so with a leaf spring trailer. Its one of the reasons so many people have bent spindles on torsion axles. They don't share the load between axles like a leaf spring tandem trailer does.

This is a great article talking about it. It also explains why a torsion axle tamdem trailer is not independent which many people believe is the case.

Why Shouldn't I Use Torsion Axles In Tandem? Or in Triple?

We see Torsion Axles in Tandem or Triple a lot . . . Is something wrong with it? Here is Engineering to show how axles function. You decide.

mechanicalelements.com

 

[Pmt133]

If you hit a bump, with a tandem torsion axle trailer, all the force of the impact will get transferred to the forward axle....not so with a leaf spring trailer. Its one of the reasons so many people have bent spindles on torsion axles. They don't share the load between axles like a leaf spring tandem trailer does.

This is a great article talking about it. It also explains why a torsion axle tamdem trailer is not independent which many people believe is the case.

Why Shouldn't I Use Torsion Axles In Tandem? Or in Triple?

We see Torsion Axles in Tandem or Triple a lot . . . Is something wrong with it? Here is Engineering to show how axles function. You decide.

mechanicalelements.com

Yes. My tandems are all leaf. The only torsions I own are singles and that is the only application where I felt the cost is kind of worth it and you get a benefit. Tandems tow so much better to begin with that I wouldn't bother.

 

[tpenfield]

Interesting article/video. . . . My triple axle trailer is torsion style, but not much that I'm going to do about it.

 

[Lou C]

The author of the article has a very interesting video of how torsions can be made to load share with what's called the walking beam design. No reason why this couldn't be used other than cost. The reality is that the trailer companies are using torsions now almost exclusively. If you wanted a new trailer with tandem spring axles I think it would be hard to find one. A possible partial solution mentioned by the author is to get a trailer with higher capacity axles that can cope better with the brief overload from going over bumps. What I don't like especially is that after the rubber strips inside fail the axle (at a high replacement cost) is junk. A good galvanized axle can last indefinitely and you change springs (less than $200 per axle) when needed. Planned obsolescence and high replacement cost like everything else today....

 

[bruceb58]

Interesting article/video. . . . My triple axle trailer is torsion style, but not much that I'm going to do about it.

My brother had a trailer built for his 26' Formula and the guy that made it told him he had to go torsion with a triple axle because of how the spring perches wouldn't work with leaf springs on that particular trailer. Sounded like a bunch of BS to me. No way a 26' boat needs to be on a triple or have torsion axles.

One huge drawback with a torsion axle trailer is that unless the trailer is perfectly level, one axle will have more weight on it that the other. Not a huge deal if you are level but I have seen lots of boats and travel trailer trailered not level.

 

[cyclops222]

I am lucky. All my trailers have passenger tires. Never a crack or split or blow out. Sits in full sunshine for decades.

 

[bruceb58]

I am lucky. All my trailers have passenger tires. Never a crack or split or blow out. Sits in full sunshine for decades.

If you use passenger tires, you need to derate the weight carrying by 10%. I have never owned a trailer that I could buy passenger tires for and have enough weight carrying capability....not even close!

 

[tpenfield]

IIRC, my sailboat trailer had passenger tires . . . not a heavy boat . . . around 2K lbs.