Machine Weight and Moving Equipment

Let me start by saying I know nothing about semi tractors and moving larger equipment then skid steers and backhoe loaders.

I have recently looked on truck paper at some semi tractors just to see what was around. I saw that they gave the axle ratings. Say you had a Kenworth W900. The rear axles are rated at 46,000 pounds and the front axles are rated at 13,200. This is a rating that I saw a few times. You will have a combined axle rating of 59,200 pounds.

A new cat 329D L weighs 64,460 pounds. If you had that Kenworth W900 your machine would be heavier then your combined axle rating. Does this mean that you will not be able to safely move a cat 329D L with that truck? Thansks guys.

Well your math is good - but you are forgetting about the trailer.

A trailer is something that you will need. Just looked on eager beavers site to get an idea of a trailer's weight and a 50 ton lowboy is about 22,000 pounds so the machine and trailer weigh 86,460 pounds.

So now could the above Kenworth w900 move 86,460 pounds.

I am not planning on a move of this type just something I am confused about.

Well, you have to subtract the combined tare weight from combined gross weight, and that is what the MANUFACTURERS (only) say you can carry for a load.

Now the combined gross weight comes from what? Do the axle rating have any relation to the GVWR?

The heavier the axles, the heavier load you can handle, but the state hiway depts limit the axle weights. 46k rear ends are on the higher side of axle capacities (there are also way heavier axle/suspension set ups available), and that truck would handle such a excavator fine, the problem is that over 80k gross typically requires oversize/weight permits. Thanks to a non standard system from state to state, I can't tell you what's legal where you are (I could tell you if I spent 1/2 a day looking, but I'm too lazy to). The rating from the manufacturer is just a way to tell you how heavy the rear end/ suspension/ axle systems are. I'm not sure if you're asking from a lawman position, or a "hey can I pull this with a truck like this" type of question. Either way in most states if your driving tandems scale 46k, you're probably not driving much further. If I'm not making myself clear, fire away with more questions.

I guess my main question is what does the axle rating on semi tractors relate to? And from the axle rating can you determine a GVWR?

With my trucks I deal with GVWR instead of axle ratings.

dieselnut said:

I guess my main question is what does the axle rating on semi tractors relate to? And from the axle rating can you determine a GVWR?

With my trucks I deal with GVWR instead of axle ratings.

Click to expand...

Well - if you add up the gross on all your axles, you should come up with manufacturers gross for the truck.
What don't you understand?

When the manufacturer says 13,200 front end, that means when you drive on the scales, the manufacturer doesn't want the scale to say more than 13,200 as weight. Typical rear tandem allowable weight by state laws is 35k (varies state to state). Why have 46k rears if the state only allows 35k of weight? Because of axle restrictions on a dump truck (for example) they add air tag axles (states allow a extra 10-15k per axle of weight). But as soon as the driver leaves pavement, he dumps the tag axles air suspension, adding the extra 10k to the 35k that was on the driving tandems (air tag axles don't push you through the mud, they hang you up) making the weight on the drivers be 45k. A tractor rear isn't rated for the whole load it is pulling, its just rated for the weight/down pressure put on it.

If you add all the axle weights you get the GVWR for the truck. Take a look at a Gross Weight Schedule, try to find the one for your state on google, that might help clear things up. My rig is 85k with a tri lowboy and a JD 200C, and I can gross 87 with the bridge I have.

Example for you of a dump truck, our 2006 Kenworth T800.

Front axle 20,000
Rear axle 46,000
2 8,000 lb lift axles

Total 82,000 lbs

Now bridge law only allows 20,000 on the front axle, 34,000 lbs on the rear axle, and it will allow 10,000 lbs on a lift axle but I got the super light weight ones since I don't need more than 8,000 on each. And bridge law will only allow 60,500 lbs total based on our wheelbase with the lift axles, and 50,500 if it did not have lift axles. The Truckweld dump trailer for this truck has 3 22,500 lb axles and with a wheelbase that allows 45,000 on these axles. The total legal bridge wheeelbase load for this setup is 105,500. I can haul 33 tons of gravel with this setup


Now from what I can remember of the Peterbilt tractor and Trail King TK70 and TK110 low boys we owned in the past.

The Pete had a 14,000 lb front axle, 40,000 rear axles, and a 10,000 lb lift axle. The Trail King had three 22,500 lb axles. The truck was light weight with air ride and weighed about 17,000 and the trailer was around 22,000. The legal bridge on this setup was 102,500.

Before the TK110 we pulled a TK70 without a lift axle on the truck we were only allowed to gross 80,000 even though the wheelbase would allow more. This was because of the limits of 34,000 on the tandems and only 12,000 allowed on the front axle. And we hauled our 42,000 to 43,000 lb 690D on it, just made it under the 80,000 lbs limit.