Tri Axle Question

[HowieE]

I have read a lot of the comments on axle replacement posted here but have addional questions.

My 91 34 ft Excella has always sat very low to the ground. The factory ID plate shows 2,300# axles and a GVW of 8,900#. The math doesn't add up. While I had never weighed the trailer empty it does weigh in at 10,000#s for a normal trip. The axle arms do have a positive angle, the rear of a center line drawn through the arm is above a line parallel to the frame. This angle is about 10 degrees positive by eye.

My first question is what are other tri axle owners seeing as far a factory plate, trailer height when sitting level, and axle arm angle.

My second question. Has anyone changed out the axles on there tri axle and if so what axle rating did you use.

I have spoken to Airstrem with no result. and have spoken to Henschin with the results that they say the positive angle is OK but claim they never made a 2,300# axle.

With over 90,000 miles I thought it was time to look in things

[stp2136]

I had a 1987 34' Excella that had similar ratings. The axles were 2800# each (totaling 8400#) and a gross weight rating of 8900# which implies 500# on the hitch. I suspect you have 2800# axles as well. If you really weigh 10,000# loaded you are way overweight!

[RoadKingMoe]

My axles are 3200# each for a total of 9600#. GVWR is 9800# which one might take to imply a 200# tongue weight.

However... with a 1100# tongue weight and 9800 lbs total weight, each axle would be carrying 8700/3=2900 lbs... IF, AND ONLY IF the trailer was perfectly level! If it's nose down, the front axle will be carrying more than the rear axle and vice versa. THAT's why the axles need to have a margin of extra capacity.

I'm not sure what's up with your trailer, but I find it interesting that yours is 8900 vs 9800 and 2300 vs 3200 with a transposition in the first two digits of each.

As I mentioned in private messages, my spindle centerlines are below the axle centerline, but that's with only perhaps 600#s on board. I'd believe they'd be closer to level with a full load.

[85MH325]

I checked my trailer's info the other day for Howie. My '94 tri-axle has 2800lb rated axles and a gvwr of 8900 lbs. The dry weight on mine is 7100lbs. If you consider the tongue weight at the rated 800lbs, it leaves about a 300lb (roughtly 3%) margin of error in the GVWR of the axles before overloading.

Howie PMd me and discovered after the umpteenth time of checking his trailer that his axles are also 2800lb rated. Apparently his GVWR tag was just difficult to read, and the "8" looked like a "3".

Obviously the newer wide-body trailers are heavier than the older 34s, and need heavier axles for their heavier GVWR.

Roger

[RoadKingMoe]

Originally posted by 85MH325
Obviously the newer wide-body trailers are heavier than the older 34s, and need heavier axles for their heavier GVWR.

Good point, Roger. I'd forgot about the narrow/wide body difference when I saw the transposition.

[Inland RV Center, In]

The 34 foot trailers had 2800 pound axles.

They can, in time, settle, causing a positive angle.

Generally speaking a positive angle, when loaded, means bottoming out will occur.

Replacement axles for the 34 foot trailer can be 3200 pounds, or if usually heavily loaded, they can be 3500 pounds each.

Different rating axles must never be used together.

Andy

[bake315]

Originally Posted by Inland RV Center, In

Replacement axles for the 34 foot trailer can be 3200 pounds, or if usually heavily loaded, they can be 3500 pounds each.

So, if I'm understanding this correctly, if I have an older 34' with 2800 pound axles in need of replacement, I can do so with either 3200 or 3500 pound axles, giving me a bit more leeway in terms of loading than I had previously?

[Inland RV Center, In]

Dave.

Absolutely correct.

Andy

[bake315]

Cool beans!

Thanks Andy!

[j54mark]

I thought the axle load rating applied only to what the axles carried, which would not include the axles themselves, while the GVWR is the whole load. In other words, even ignoring tongue weight the axles need only to carry the weight loaded upon them.

Or am I missing something?

Mark

[Inland RV Center, In]

What does that have to do with increasing, if desired, the maximum carrying capacity?

Lets keep this out of engineering theories, so as not to confuse the true issue of increasing weight carrying capacity.

Andy

[Tarheel]

Andy after pulling my tri axel for 25,000 miles or more I finally got around to weight it. the truck weighs 7160 solo, 7880 with the trailer on it but trailer wheels not on scales and 16640 truck and trailer. My question is tongue weight I only have 720 lbs on the tongue of a 9480 lb trailer or 7.6% it rides level but should I shift some more weight up forward? Getting ready to make a cross country trip on the Southwest Caravan and want to be as safe as possible.

Rick

[Inland RV Center, In]

Rick.

Tongue weight should be between 10 and 15 percent of the gross trailer weight.

By various tests, a 12 percent tongue weights seems to be the ideal.

A little more, or, a little less than the 12 percent is OK, but certainly no less than 10 percent or more than 15 percent should ever be considered.

Tongue weight can easily be adjusted by placement of the variable load.

Always travel with a "FULL" water tank. It helps the tongue weight, "AND," lowers the center of gravity.

All of the above applies to those that use a "proper" load equalizing hitch, properly installed and properly adjusted.

If you tow an Airstream trailer with just a ball, sooner or later, you will become a statistic. The laws of Physics, says so.

Andy

[j54mark]

"I thought the axle load rating applied only to what the axles carried, which would not include the axles themselves, while the GVWR is the whole load."

Originally Posted by Inland RV Center, In

What does that have to do with increasing, if desired, the maximum carrying capacity?
Andy

Nothing, nothing at all. But then, increasing the maximum carrying capacity wasn't really the initial question, now was it? HowieE was trying to figure out how a coach with a GVW of 8900 lbs could have three axles, each rated only to 2300 (later corrected to 2800) lbs. I wasn't the one who wandered off into tongue weights.

So the question remains - three times 2800 is only 8400 lbs. The coach is rated to 8900 lbs. How is this possible? I asked the question, and I'll ask again using different words, is this because the axles CARRY 8400 lbs., while the entire coach weight cannot exceed 8900 lbs.? Or does an axle's weight rating include its own weight? If so, then we do come back to tongue weight after all, or so it would seem.

And If HowieE buys your 3200 lb. axles, what is the point? Does it increase his GVW? If so, what is the new GVW?

If this is too much "engineering theory", I will retire.

Mark

[markdoane]

Originally Posted by j54mark

I thought the axle load rating applied only to what the axles carried, which would not include the axles themselves, while the GVWR is the whole load. In other words, even ignoring tongue weight the axles need only to carry the weight loaded upon them.

Or am I missing something?

Mark

Mark,
I think you have put your finger directly on the main question. Howie's concern was why the GVWR and axle ratings didn't match. If you ignore the unsprung weight (axles, wheels, and tires), you could conclude that the axles were underrated.

Calling the unsprung weights an 'engineering theory' leads to more confusion. The axles and running gear probably weigh close to 1000 lbs total.

[Tarheel]

Andy do use a Reese weight distribution hitch as well as a sway bar. The galley was not loaded, we do take quite a bit of food under the dinnete table and always travel with a full tank of potable water. I was just really surprised at the tongue weight and didn't know if this was a normal condition. there isn't a whole lot I can do other than movable ballast as the stuff in the rear compartment is held to a minimum only the things that won't fit anywhere else, folding chairs and an olympic grill. Thanks again I will start shifting.
Rick

[HowieE]

An up date.
I weighted the trailer today. Total weight, with empty refigerator no water or sewage on but with a general complement of junk inside, 16,140 lbs. Trailer axel weight while attached to the truck is 8,100 lbs. In this configuration the trailer sits 13 in. off the ground to the bottom of the frame while parallel to the ground. The bottom of the hitch flange is 14 1/2 in off the ground and the axels have about a 5 degree positive angle.
As mentioned before the trailer has always sat very low from the day I bought it and has frequently bottomed out on the rear frame supports while crossing railroad track and deep driveways.
I am using the largest "high low" hitch mount Reese make, in the extende low position, with the hitch mounted at the bottommost position causing my chains to bottom out under the hitch frequently.
I guess my question at this point is how do my height measurements compare to other tri axels.

[Inland RV Center, In]

HowieE

You are describing a low chassis height, that can happen, if, the axles are gone.

Your normal underbelly clearance should be about 16 to 16 1/2 inches, above the ground.

A positive angle on the torsion arms, as you have posted, confirm that your axle rubber rods are toast.

Andy

[bryanl]

Originally Posted by Inland RV Center, In

If you tow an Airstream trailer with just a ball, sooner or later, you will become a statistic. The laws of Physics, says so.

Now that gets my attention ;-)

The implication is that load leveling is needed for reasons other than shifting tongue weight back to the axles and forward to the tow vehicle steering axles. What are those reasons? What is the statistic being referred to?

[Inland RV Center, In]

Leipper.

Proper loading (weight distribution) assures towing stability.

The statistic that I referred to was being in an accident, which sooner or later will probably happen, "unless", your rigged properly.

Proper rigging does not guarantee that an accident could not happen, but it does alter the statistics very heavily in favor of "trouble free" towing.

State of the art "rigging" is the very best anyone can do.

Unfortunately, some owners feel that the extra expenditure required to provide maximum safe towing assurance, is not worth it.

Those are the people that regard "safety" as an issue that only applies to others, as being "macho" is all they need...............

How sad, for them, and the innocent people they may also injure.

Andy