I have first hand knowledge on the KZ frames that most owners will not due to experiences on a previous TT we owned. Day after we owned it, we discovered major issues in the frame. The spring hangers were all bent to one side by around 1/2". The bottom flange of the frame got distorted above all hangers as a result of them flexing side-side. I temporarily tied a camcorder under the frame and went for a drive. The spring hangers were swinging left/right like a pendulum every time I turned a 90 degree corner! The hanger movement is harder on the spring bushings and ours were all shot in just the 2K mile trip to the dealer. The welds throughout the frame were terrible and substandard. Got delivered in the winter and didn't take long for rust to develop on the frame and components.
Frame flex combined with marginally rated axles allows for considerable camber change in the wheels. Not only is there higher lateral movement, the vertical up/down bounding while travelling stresses the aluminum superstructure and can even cause welds to fail.
The frame on these (unless they've changed recently) is made from 3 pieces of 1/8" sheet steel and welded together. It flexes a LOT more compared to the more common 1-piece rolled beams. Fatigue cracks can develop above the spring hangers and I know someone with a KZ who has had this happen.
Not to blame KZ alone, I have seen the identical frame on a few other brands/models. If I were ever looking for a new TT again, I would look for anything with a non-Lippert frame. There are some brands, like Jayco and Lance for ex. that use a BAL frame and Northwoods products out of Oregon that make their own. At one point KZ wanted to switch to BAL frames but Norco could not commit to providing enough quantity. As evidence, you can find the BAL frames on early 2014 Connect TTs.
I put the blame entirely on Lippert for continuing to crank out the same poor frames year after year. They alone design and manufacture the frames are liable for any defects. What the RV manufacturers are at fault for is continuing to purchase and use the same poor frames when they absolutely know that there are problems with them (ask me why I know, pffft). If you plan to keep the TT a long time and/or plan to put a lot of miles on it, I'd look for at least something with the more common 1-piece frame design. Some brands with the same frame have additional strengthening like gussets for ex. Sadly, frame failure or issues are usually blamed on an owner by Lippert regardless except in our case we only owned it one day but they still said initially it was within spec.
