Any one out there have a handle on the physics behind the "road force" numbers and what they mean?

Just completed a 15K mile checkup and the dealer said I had excessive "road force" in three tires. It's been a while since I've had to worry about tire balancing. So, the term "road force" caught me a little off guard. I was told normal is less than 18 something and that my tires were as much as 30. Did I notice any vibration?

No, the tires rode OK to me. Tires were rotated. They still ride OK. The dealer said that they might give me trouble as they wear.

The dealer tried to explain the difference between balancing and road force. Something to do with the weight of the vehicle as the tire rotated? Could it be due to flat spots caused by the vehicle sitting for some time?

Thanks