that's what i run on mine
if you are using a taller tire, you need shorter gearing to compensate for it.
basically, stock is 16/40 with a 190/50, if you change to 15/40 and a 190/55, you are only getting a 3.2% shorter gear
if you use 15/43 with a 190/55 you'll have a gearing change of 9.7%, which is nice for the rc.
i have a 180/60 on the back of mine, which is a bit taller than the 190/55, so i'm at 8.6% shorter. the bike is very nice this way.
a lot of people will say that 15/41 is perfect, but with a 190/55 and 15/41 you're 5.5% shorter, which isn't really much at all.
here's a really simple calculator for figuring this out
gearing commander works well too, but is more complicated than necessary i think