Hi everyone, I recently started cycling, mtb to be specific, my boyfriend upgraded to a new bike, and I took his. Its a 19" frame Merida, and I really do not know if it is too big or not. I am 1.7m(just) tall. Is there a huge difference between a 18" and 19"? Any help would be appreciated as I do not want to sell the bike unnecessarily as it is a great bike.