I am not a LEO and will only speak of personal experience and my own opinion as to what I think to be correct.
Anyone can call the state DOT offices in any state as found on that states WEB site, although sometimes it is difficult to get through to a real live person to speak to that is actually qualified to answer your questions.
Texas allows one to register a pickup for whatever weight you are willing to pay the tax for, when using as a company vehicle hauling your own companies equipment(non-commercial), or if it is "for hire" or commercial use and in both cases the trailer has no weight applied to the registration (token trailer tag). Above 26,000# requires a DOT# as do most states. In the case of a private use pickup, it can only be registered for it's Fed label, and as Wadcutter indicates in IL, the RV trailer will have a registration fee for it's own weight rating. I believe Louisiana only allows you to register for the amount AS LISTED ON THE FED TAG reguardless of purpose(not recently verified). Each state will look at your plate and recognize the other's rules while you drive through, however, some states, like California and New York sometimes have additional rules. It's almost like going against the Fed regs, but I'm sure they will argue that they are just more strict and have added additional rules rather than ignoring Federal Regulations, as to what the states are allowed to enforce.
As to the troopers being referred to as DOT. In many states there are Troopers, and then the Troopers that enforce Weights and FMCSR regs. On the door of the vehicles they drive will usually have Department of Transportation, and other info. Most truckers call all of those types of troopers the "DOT" even if in some states that title is only used for the highway maintenance department.
Wadcutters other info is great, as well as the other LEO's however he is basing his info on IL regs and trying to convince all that the way IL does it regarding FMCSR regs applies nation wide. Not so. Also, as impeccable as his credentials are, the claims that all troopers or DOT officers will always be correct on the law is false. Doctors, Lawyers, Judges, and Carpenters all have made mistakes and do on a regular basis. Additionally some laws are either vague or misinterpreted. Otherwise, he has attempted to be very helpful to all in this discussion, and I'd put him up against any on IL regs and how they utilize the Fed regs.
Now, in case it hasn't been mentioned. The tire load rating is separate from the pounds per inch of tread width (or square inches of foot patch) which is usually generalized as axle weight, sort of like . . . the registered weight is only indicative of the amount piad to register, but is separate and different from the weight against the pavement, and possibly exceeding any other regulation. (one can be illegally over what they paid to haul when registering and be legal on Fed reg, tire load rate, axle load rate, GVWR, etc. And visa versa. One could register for a huge weight rating and be illegal on axle, or other limits, As Wadcutter has gone above and beyond to explain. Scale weight is relevant in both cases, but the fines are of totally different issues, different rules) Back to tire patch . . . there is a formula that includes tire diameter and width that determines it's foot patch size when at maximum rated inflation and with it's maximum rated load weight on board. This is how 20,000# maximum single axle weight is arrived upon as well as the entire 80,000 pounds limit, because anything beyond this applies more weight per square inch of pressure against the pavement and therefore more wear and tear on the highway as that vehicle travels along. Therefore, although undoubtedly this will never apply to an RV, big rigs pay for a permit for overweight transport for which the additional money will be paid to the road tax fund for maintaining our highways.
So, technically one could not be over the 20,000# axle weight but have narrow tires that are not rated for that amount. Texas DOT web site clearly state that a vehicle may not carry more that it's tires are rated for as seen in the last line at this address -- http://www.dot.state.tx.us/services/motor_carrier/weight_limits.htm
Wadcutter is correct in that most of the time RV'ers are rarely bothered. It is difficult to comply with all of the rules all of the time. Some states give little attention to RV's and others are a little more finicky, and have rules they simply have chosen to pay more attention to.
What I take from this entire string of post on this topic in order to be more prepared is . . .
1. Go to the scales and know your actual axle weights.
2. Check your tire rating.
3. Check to see if all states recognize your states style of registration as far as per max of Fed label rating, versus as per weight paid for at registration.
4. Be aware that you may need a written statement from your insurance company as to what reasons reguarding weight that they may deny covering an accident, and maybe more importantly, in what circumstances of weight overages will they guarantee to cover.
Others may add more items to check list in case I've left anything off, and remember, I reserve the right to be as wrong as anybody else.
Simply, food for thought.
Ken
