First off, this is federal. All states are at least this restrictive. Some states are more restrictive. If you meet your state and meet federal, you can drive in ANY state, even if the other state is more restrictive.
So, for the federal and majority of state rules
If the GVWR (that is the RATING, not the registered or actual weight) is over 26000 pounds with NO trailer, it's class B.
If the GCWR (that is the combined RATING, not registered or actual weight) is over 26000 pounds AND the trailer is over 10,000 pounds, it becomes class A.
If the GCWR is 26000 pounds or less, no CDL is required regardless of the trailers GVWR.
If you have a load on a hauler that does not require a CDL by weight, but requires plackarding, you will have to get a class D CDL which is essentially a "regular" driver's license but is able to accept commercial endorsements. (Hazmat in this case).
Also note- None of the above has any classification about air brakes. Air brakes are NOT an endorsement or a requirement of a CDL. They are only a restriction if you fail to demonstrate a mastry of them during the skills exam. Below CDL weight, air brakes does not affect licensing.
Again, a few states are more restrictive in a lot of areas, a couple are more restrictive in a lot of areas, but this is the federal standard that states are held to.
post edited by Jake450s - 2008/09/02 17:46:37