More details about the components on your new bike are in order. There may not be any chainrings available for your crank in 42 teeth. Your previous triple did provide you with low gear options that you would lose completely by switching to a 42 tooth small ring. Perhaps you need to take some time to get used to your new setup. It all likelihood, depending on your actual crank, the largest small ring available may be a 36 or perhaps a 39 tooth small ring. However, because shift gates may no longer match properly, front shifting could be significantly degraded