According to Pa.Dot it doesn't matter wether your private,commercial,or other wize,you must be regestered for your Gross combination weight if you pull a licenced trailer and the combination weight exceedes the gross weight of your tow vehicle.IE: if you have a truck that has a GVW of 10,000lbs and are towing a trailer with the laden weight of i0,000lbs you should register yourtruck for a GCVW of 20,000lbs,Rembember also any trailer over 10,001lbs or any truck or truck and trailer exceeding 26,001lbs requires a CDL licence and a health card. Also you must have a statement from the mfg as to the max combo towing weight.IE: My Dodge 3500 is 12,200GVW with a max towing GCVW of 23,000.I can't register my truck any higher unless it is modified and certified to do so.It is all based on axles,tire contact patch,braking capabilities,and structual design.
Also you must have a statement from the mfg as to the max combo towing weight.IE: My Dodge 3500 is 12,200GVW with a max towing GCVW of 23,000.I can't register my truck any higher unless it is modified and certified to do so.It is all based on axles,tire contact patch,braking capabilities,and structual design. 
