Why do newer TVs have higher payload than older ones?

[daveinaz]

I was looking and the payload on our 2008 Ram dually is 4450. I think the max trailer is 19K.

I know that the newer trucks have greater payload and towing capacity, but I don’t know why they do. What is so different between our current truck and a newer Ram diesel that gives it so much more capacity? Did they just beef up suspension on them?

Thanks.