The final word on allowable axle weights.

(n) Any vehicle subject to this subpart that utilizes an auxiliary power or idle reduction technology unit in order to promote reduction of fuel use and emissions because of engine idling, may be allowed up to an additional 400 lbs. total in gross, axle, tandem, or bridge formula weight limits.
(n)(1) To be eligible for this exception, the operator of the vehicle must be able to prove:
(n)(1)(i) By written certification, the weight of the APU; and
(n)(1)(ii) By demonstration or certification, that the idle reduction technology is fully functional at all times.
(n)(2) Certification of the weight of the APU must be available to law enforcement officers if the vehicle is found in violation of applicable weight laws. The additional weight allowed cannot exceed 400 lbs. or the weight certified, whichever is less.
[49 FR 23315, June 5, 1984, as amended at 59 FR 30420, June 13, 1994; 60 FR 15214, Mar. 22, 1995; 62 FR 10181, Mar. 5, 1997; 72 FR 7748, Feb. 20, 2007]

Thats straight from the FMCSA site on APU's.

 

§658.17 Weight.
(a) The provisions of the section are applicable to the National System of Interstate and Defense Highways and reasonable access thereto.
(b) The maximum gross vehicle weight shall be 80,000 pounds except where lower gross vehicle weight is dictated by the bridge formula.
(c) The maximum gross weight upon any one axle, including any one axle of a group of axles, or a vehicle is 20,000 pounds.
(d) The maximum gross weight on tandem axles is 34,000 pounds.
(e) No vehicle or combination of vehicles shall be moved or operated on any Interstate highway when the gross weight on two or more consecutive axles exceeds the limitations prescribed by the following formula, referred to as the Bridge Gross Weight Formula:


except that two consecutive sets of tandem axles may carry a gross load of 34,000 pounds each if the overall distance between the first and last axle is 36 feet or more. In no case shall the total gross weight of a vehicle exceed 80,000 pounds.
(f) Except as provided herein, States may not enforce on the Interstate System vehicle weight limits of less than 20,000 pounds on a single axle, 34,000 pounds on a tandem axle, or the weights derived from the Bridge Formula, up to a maximum of 80,000 pounds, including all enforcement tolerances. States may not limit tire loads to less than 500 pounds per inch of tire or tread width, except that such limits may not be applied to tires on the steering axle. States may not limit steering axle weights to less than 20,000 pounds or the axle rating established by the manufacturer, whichever is lower.
(g) The weights in paragraphs (b), (c), (d), and (e) of this section shall be inclusive of all tolerances, enforcement or otherwise, with the exception of a scale allowance factor when using portable scales (wheel-load weighers). The current accuracy of such sales is generally within 2 or 3 percent of actual weight, but in no case shall an allowance in excess of 5 percent be applied. Penalty or fine schedules which impose no fine up to a specified threshold, i.e., 1,000 pounds, will be considered as tolerance provisions not authorized by 23 U.S.C. 127.
(h) States may issue special permits without regard to the axle, gross, or Federal Bridge Formula requirements for non-divisible vehicles or loads.
(i) The provisions of paragraphs (b), (c), and (d) of this section shall not apply to single-, or tandem- axle weights, or gross weights legally authorized under State law on July 1, 1956. The group of axles requirements established in this section shall not apply to vehicles legally grandfathered under State groups of axles tables or formulas on January 4, 1975. Grandfathered weight limits are vested on the date specified by Congres and remain available to a State even if it chooses to adopt a lower weight limit for a time.


This is also straight from FMCSA as well.

 

Some states will ticket you for over on axel but not gross i know for sure VA is one of em i've bin sitted there for over on tractor axel but only 79200 gross.

 

not all states give allowance for apu, you can get a sheet from your safety dept that will show you what states do and don't. safe rule of thumb, don't exceed the limist period, don't go over 12,000 on steers, don't go over 34,000 on drives or trl, not sure what it is for spreads. follow that rule, you will never have issues. rolled into oregon, my load shifted slightly, was 650 over on steers, got warrning citation, what saved me was having a CAT scale ticket for the load that showed me legal, and it was only 30 min old. load shifted when came down hill and braked a bit hard when 4 wheeler cut me off for off ramp(was hauling those big sack bags filled with potato's). He gave me attitude, but only gave me a warrning no fine. Thanks to CAT.

 

This is your best bet overall. You can't go wrong with this.

However, there are certain instances in which you will not have a lot of choice...like the paper rolls from GP and the nearest public scale is over 50 miles away. In this case, get it as close as you possibly can and if you have to be a little over on an axle, make it your steers and no more than whatever your tires are rated for.

Regarding the APU, the only state I've heard of giving any grief over it was (of course) California. The information I have is you may be over on your drives, but not over gross weight for the vehicle...80K in most cases.

Pay close attention to bridge laws, also. Where you set your trailer tandem can earn you a hefty receipt...especially (of course) in California. Get a chart from your company if they have it. If not, the information is in your Motor Carrier's Atlas.

 

Wisconsin limits you to 12,000 on the steering axle, the last I heard. Didn't bother to check into it, just slid things around to get under 12K, 34K, 34K.

 

Not really. I've ran just about every corner of WI for the past ten years and have never been given any grief for steers over 12,000. Of course when you start getting outrageous with it like 12,600 or 13,000 It will probably raise red flags in any state. The 387 Petes i Occasionally drove with C15 Cat Engines were almost always around 12,400 with full tanks, even after pulling the 5th wheel far back.

 

I scaled out the other day because Tyson loaded me nose heavy and my pressure guage showed it. Big bins of chicken breasts and they were loaded tight. I questioned Tyson and they said they had to load it that way because they been having alot of damage putting singles in. To my surprise, I scaled out at 31800 on the drives with my axles all the way forward and about 12,800 on the steers. That was at a CAT scale. I think they were wrong and called CAT afterwards. So I ran late at night figuring all the scales ahead of me would be closed.
LA pulled me over and told me to come inside. She shows me I scaled 35,000 on my drives. It was fix it or pay a $10.50 fine, lol. I'm sure my load didn't shift because there was no where for it to go.

I asked her if I could put it on my steers. She said yeah, so I did and went on my way.

Moral of the story, most of these scale houses could care less about your steer tire/axle rating. Only during an inspection might it be a problem. I run 13- 13,500 many times with zero problems. My truck is nose heavy and I run with the 5th wheel about 2-3 slots from the back. I usually put more weight on the drives to counter the steers and it'll drop to around 12,500 then.

 

Sigh. DIFFERENT STATES HAVE DIFFERENT LAWS....

 

Missouri has been checking lately. There have been a few dozen of our trucks get tickets for over weight rating of the tire recently. Just FYI