From the Feds:
https://www.fmcsa.dot.gov/registration/commercial-drivers-license/drivers
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Pursuant to Federal standards, States issue CDLs and CLPs to drivers according to the following license classifications:
Class A: Any combination of vehicles which has a gross combination weight rating or gross combination weight of 11,794 kilograms or more (26,001 pounds or more) whichever is greater, inclusive of a towed unit(s) with a gross vehicle weight rating or gross vehicle weight of more than 4,536 kilograms (10,000 pounds) whichever is greater.
Class B: Any single vehicle which has a gross vehicle weight rating or gross vehicle weight of 11,794 or more kilograms (26,001 pounds or more), or any such vehicle towing a vehicle with a gross vehicle weight rating or gross vehicle weight that does not exceed 4,536 kilograms (10,000 pounds).
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The way I read that is a combo over 26k OR a trailer over 10k.
My brother talking to a guy that does cdl license training realized he screwed up because he had registered his truck for full combination weight which is wrong. He registered for 18k. As soon as he hooked to the 10k trailer he was now at 28k gvw and technically required CDL. He’s in the process of fixing that. The combination can’t be over 26k but it’s that second part that gets you.
My two cents. It’s not my interpretation that matters though....it’s the DOT officer that matters.