cycling sucks wrote:
It's a hybrid bike but more geared towards a road bike design. The frame is very light, the wheels are thin, but the handles are flat bar. I got fitted so that shouldn't be the issue. I'll try to adjust the seat. Do you know a good rule of thumb for seat height?
A flat handlebar limits your riding position so that might be why you're getting back pain. On a drop handlebar, you can change your seated position by putting your hands on the hoods, the bar, or the drops. On a straight bar, your back stays in the same position. Maybe you could try standing on the uphills. That might help.
There's probably a way to vary the position on a straight bar. I've heard that bar end handles are dangerous if/when you crash so I would stay away from those. Maybe someone can give you another option.
A longer stem also changes position and lets you stretch out more. Whether that's a good thing or not... I don't know. I just replaced a 80mm stem with a 110mm stem on a small road bike. It changes the riding position.
As far as fit is concerned, you may have gotten professionally fitted, but if you're having pain somewhere, the fit probably isn't right for you even if the fit is "correct" according to the book definition.