Originally Posted by
Kedosto
If your bike was factory equipped with 35c tires, you'll be just fine running 38's. Closer to 45? I doubt it. They may seem a lot wider, especially if the 35's you were running weren't an actual 35 - some are closer to 32-33. Possibly popping off? Seriously doubt that too (as long as you keep them inflated properly). Any bike will handle "awkward" when the bars are turned sharply. I'm pretty sure you're going to get the hang of it eventually.
Off they came, back to 35s, bike steers like it's on rails, tracking a line consistently. Hands free at any speed, even around corners.
-Kedosto
Or..... OP could have altered the trail enough to induce/increase wheel flop. I know that sounds crazy but I have experienced exactly that. I went from a 100% slick 35mm (measured) tire to a 100% slick 45mm (measured) tire and the steering and handling became nasty. Significantly. The bike wanted to fall into turns all on its own. And once into a corner, it wanted to tighten the line all by itself. It required constant rider input to maintain a line. PITA and didn't feel safe. Hands free? NO chance.
Granted, my bike was probably already at the extreme end of high trail and the larger tires pushed it over the edge into no man's land, but it could be possible that OP is experiencing the same thing.