older TTs with wheels on the rear frame/bumper

Dtaylor wrote:
Most of those sit low to the ground. They are there to "roll" when going over grade changes that would otherwise drag the frame or bottom of TT. BTW, they are still available should you wish to add them

My new TT sits very high off the ground - much higher than the previous TT. But even the previous TT never dragged on the ground. I take it older TT models had smaller tires and a lower suspension?

It makes sense on real long TTs, but the ones I saw were 25' max.