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Numbers, Numbers, Numbers


Don Risdon

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OK, folks. . . . . . . . It's help the newbie time. I am pouring over the not too distant purchase of either an MDT or an HDT. As you are aware, the numbers: axle weight front and back, pin weight capability, trailer specs, engine output, etc. etc. etc. can be/are be overwhelming. The tag from inside the door jam of one of the models I am considering identifies the following information:

 

Gross Axle Weight Rating:

Front 12,350 lbs

Rear 19,000 lbs

 

Gross Vehicle Weight Rating: 50,350 lbs

 

My question is this: Since these were the numbers assigned to the vehicle at date of manufacture; and since the rear axles have gone from two to one (singled long in this particular case) wouldn't the GVWR and rear axle numbers have changed significantly? If the answer is "yes," then how would I determine the true numbers? If the answer is "no," then please explain in Newbie terms why not. Thanks

 

DWR

 

Here's the actual tag:

 

post-54251-0-90087200-1473622175_thumb.jpg

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Given that tag, either it was built as a factory single, or the builder had engineers on staff to do the required work to re-tag the rear axle weight rating. I suspect the weight you have listed as GVW is in fact GCVW, as the addition of the front and rear axles doesn't add to 50+ thousand lb.

 

Edit to add: If there was 2 axles originally, the rear axle weight capacity would be approx double the value you've given, or the sticker would have 2 places for rear ratings.

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I may be wrong but the rear axle rating should still be the same at 19,000 lbs. but the GVWR would be 31,350 lbs. with only one axle. Original GVWR was 19,000 +19,000+12,350 =50,350. New is 19,000+12,350=31,350.

Given that tag, either it was built as a factory single, or the builder had engineers on staff to do the required work to re-tag the rear axle weight rating. I suspect the weight you have listed as GVW is in fact GCVW, as the addition of the front and rear axles doesn't add to 50+ thousand lb.

 

Edit to add: If there was 2 axles originally, the rear axle weight capacity would be approx double the value you've given, or the sticker would have 2 places for rear ratings.

Hey Darryl, please educate me what I got wrong in my calculations. Love to learn from you guys.

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Hey Darryl, please educate me what I got wrong in my calculations. Love to learn from you guys.

Don't see anything wrong, except you carried an extra 19k. If Don comes back with what his tag actually says, we'll know for sure. In the mean time, I'm guessing as much as the next guy. 38k isn't a common rear rating, so I guessed at factory single. Our KW tag has 2 spots for rear capacity, each with 22, 000 lbs. A tri-drive will have 3 spots for rear capacity. The shop that singled it didn't do the engineering to have the tag changed, so that's what I'm stuck with, regardless of common sense.

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Darryl- For what it's worth, our '98 Volvo came with tandem 19k Rockwell axles. Door says 38k rears, 12.5 front.

Good catch. I got my head all wrapped up in tandem/2, and plumb forgot there's a whole wide world out there. Locally, the tandems in demand are 40 or 44's. 38's would get you sent back to town to get a real truck. :lol:

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12350 rating is usually something built with 14 ply low pros in the front. A 19K rear axle is usually one that looks normal but has 3/8 wall axle tubes. Traditionally 3/8 tubes can't be used in a trailing arm suspension but with special testing, analysis, etc they can get away with it.

 

The two ratings don't always end up equaling the GVW because of the 121 hill hold requirement. Single springs on tandem axles, not using long slacks on a single, specing skinny shoes, certain linings, etc, all can reduce the GVW from the norm. Just about the time you get it all figured out something comes along and changes it...

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Volvo created a lot of confusion with the way they worded that first tag, but all of the information is there, and it indicates that it was built as a tandem axle truck.

 

What is confusing is that, instead of itemizing the two rear axles at 19,000# and 19, 000#, they simply said "19,000 (EACH)", which, combined with the FAWR of 12,350 and the GVWR of 50,350, declares by implication that it's a tandem axle truck.

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Good catch. I got my head all wrapped up in tandem/2, and plumb forgot there's a whole wide world out there. Locally, the tandems in demand are 40 or 44's. 38's would get you sent back to town to get a real truck. :lol:

Why would 40k or 44k be in demand? It's not federally legal unless they're well-spaced (aka far enough apart that they can be counted as singles).

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Why would 40k or 44k be in demand? It's not federally legal unless they're well-spaced (aka far enough apart that they can be counted as singles).

In the oil fields the heavy tandems are used for moving cranes and machinery around. 1 company in Texas ran triple axles with the front being a lift axle that were all 23k axles. They regularly hauled 130k loads down farm roads to one rig site to another. Trailers were 8 and 10 axle beasts.

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Don,

I'm wondering if you read the label for the rear gross in kg instead of lbs.

Go look at his original post. He edited it yesterday to include a picture of the actual tag. Don read it correctly (in lbs) and Carl's first post (post #2 in the thread) was on the money without digging into the things that Scrap is talking about, and since his truck has already been singled and the GVWR was not adjusted at that time, he is technically stuck with the GVWR on the sticker. Any actual weight questions and calculations from here on will be done using bridge law and tire weight rating.

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Why would 40k or 44k be in demand? It's not federally legal unless they're well-spaced (aka far enough apart that they can be counted as singles).

 

 

In the oil fields the heavy tandems are used for moving cranes and machinery around. 1 company in Texas ran triple axles with the front being a lift axle that were all 23k axles. They regularly hauled 130k loads down farm roads to one rig site to another. Trailers were 8 and 10 axle beasts.

That right there/\ /\ /\ /\. We also have to deal with wet fall seasons, and soft spring "break-up". During these reduced weight times, the roads will be de-rated by a percentage, so a higher rated truck-trailer combo can move more all year long.

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Big5er mentioned "bridge law". I never learned the rules of bridge even though everyone played it when I was young, but this may not the same bridge Big5er is referring to. What is a "bridge law"? Certainly "Don't jump!" has to be near the top of them. In Texas bridge laws for bridges over the Rio Grande are probably different from bridges over other highways and railroads.

 

Until this discussion it did not occur to me that my vehicle is now radically different in weight from when I bought it. Singling the truck, along with the decking and storage units have definitely changed the vehicles empty weight and gross weight rating. Since I clearly do not use the truck for commercial purposes, when will my GVW listed on the door be checked against the actual weight I can safely carry? I do not go into weigh stations where the subject might come up. I suspect that trying to officially change the trucks GVW would be somewhere between highly difficult to impossible.

 

I have no clue what my new gross vehicle weight is as I removed an axle and four tires/wheels. I know it can be calculated, but to me it doesn't matter as I know I'm way under what the truck can safely carry. (Actually, I'd calculate the new weights if I could, but that would require MATH, a four letter word, and much more knowledge about trucks than I have.)

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Uh, beat you to it. Read post #2. :)

There is no magic here....Post #2 had the result. And watch your weights, because with a smart on deck, full fuel, and a HEAVY trailer, you CAN exceed your weight limits. These trucks are very capable, but they still have limits. Anyone intending to carry a full-size vehicle needs to stay tandem, IMO. Especially with a heavier trailer in the mix.

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You guys are way tooooooooo much. If we ever get together, I'll buy the Dr Pepper (if it's still being made). I'm certainly glad that I, someone with no knowledge, could bring together a significant group of chaps with incredible knowledge, to have them create eighteen posts with semi-related, but distinctly original ideas. You all are my heroes.

 

DWR

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You guys are way tooooooooo much. If we ever get together, I'll buy the Dr Pepper (if it's still being made). I'm certainly glad that I, someone with no knowledge, could bring together a significant group of chaps with incredible knowledge, to have them create eighteen posts with semi-related, but distinctly original ideas. You all are my heroes.

 

DWR

Indeed we are........

 

I been waiting a long time finding a place to be a hero......

 

Drive on......(do all heroes have to wear the undies on the outside.......)

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