the law is that on a tag trailer you need to have a wheel base of 51 feet to gross 80000lbs. witch means the truck would be a triaxle but then the truck would weigh to much and you would be at about 85000lbs with the 55000lbs trailer and 30000lbs triaxle "light truck" witch is not leagle in this state
there is no way to get the lenth with out the added weight to meet both laws
it needs to be moved on a goose neck with an over weight permite is the only legal way to move the mechine
i called the ct dot
My dump truck is NOT light. It weighs 24,130 pounds with no load but full of fuel. The dump bed is a "bomb grade demolition bed" (1/4" AR400 steel throughout, including the high lift tailgate). It's not a light bed. Maybe adding a drop axle would put another 6k# on it but I don't think so. I'm not sure why you would need a triaxle dump just to pull a 315 behind it anyway (let alone an over weight permit with a 5th wheel and a lowboy). My triaxle trailer weighs 11,000# empty. It's not "light weight" either. My 2003 Cat 315 CL weighs 40,000 pounds. It is equipped with the long undercarriage, long stick, reach boom, hydraulic thumb, hydraulic "quick-tach", and a 3' heavy duty rock bucket. The only thing, I can see, that may be possible to add weight would be the 28" grousers (mine are 24"). My machine weighs 39,900 pounds.
In summary:
Dump truck: 24,130 pounds
Triaxle trailer: 11,000 pounds
Cat 315: 39,900 pounds
TOTAL: 75,030 pounds
Unless I have done my math wrong you are not anywhere near 80,000 pounds. On a side note, the 80,000 pound rule is a federal rule that the states have adopted on the interstataes. In my state (I can't say that this is true for all states) I can run 85,000 pounds on secondary roads.
BTW I did some research to see if I could haul my 315 from CO to CA. I would have to go through New Mexico and Arizona to get there. All four state have different laws about weight. They are all based on what each state has adopted as a "bridge gap formula". This basically means that each state has different design criteria for bridge construction and expected life of the bridge (taking into account environmental/seasonal weather considerations). The closer together that your wheel base is equals more weight in a concentrated area. A longer wheelbase will spread out the load, and reduce the stresses on the roadway (and bridges). In CO I can put up to 62,000 pounds on a tridem (three axles in series within a specified wheelbase-which I can't remember the specific distance right now). In NM it's 36,000 pounds. The most stringent was CA. They do not even recognize the tridem so the weight of my trailer is restricted to the same as that of a tandem (two axles). In CA this is 34,000 pounds. Despite these restrictions I could load my 315 (all the way forward-against the head rail) and keep it under 34,000 for the tridem. Obviously this puts a lot of strain on the pintle hitch. I consulted the trailer MFR and they said that the trailer could handle up to 25% of its payload capacity (50,000 pounds or 25 ton) on the tongue. Even though the 315 was all the way up front it met the criteria.
I have offered the above to illustrate that it is possible to haul a 315 (on a triaxle, behind dumptruck) even with very restrictive regulations. You will have to research your states regulations. I would find out what the max weight is for steer axles, tandems, and tridems. Max GVW (you said 80,000 and I doubt you will reach that hauling a 315) must be met also. The bridge gap must be considered too. The bridge gap does not usually reduce the max GCVW (with possible seasonal exceptions). It will determine what your axle spacing will be.
BTW, in most states you can haul up to 40,000 pounds (20 ton) on a two axle (tandem) 20 ton trailer. The 20 ton trailer will weigh less than the 25 ton trailer.
