I would be very careful about changing tire size unless your willing to spend the time and money to treat it like an experiment and go back to the original size if needed. A 180/55 is reportedly 4 mm taller than a 190/50.
The 190 will cause a weight shift to the rear of the bike. If anything I think the Bird needs weight shifted forward not back. The lower back end will increase the trail on the front end slowing steering.
Also, for a given turn at a given speed the wider the tire the farther you have to lean it over to hold a given line.
A 180 has all the capacity needed for holding back the horsepower of a stock Bird. I wouldn't do it.
And the 190 costs more.