According to an article in National Dragster, the NHRA's weekly, any combo that is titled at 25001 (uh oh, might be 26001) needs to have a CDL. I. E. if your truck has a GVW of 11k, and your trailer is at 16k, you need CDL. If possible, get ahold of a copy of ND, as they just did a great article on towing etc... .