Originally Posted by
Wilfred Laurier
What size mountain bike do you have? You will generally have to get the saddle the same distance from the pedals on a road bike as on a mountain bike... in the same ballpark, anyways. Measure the distance from the centre of the bottom bracket to the top of your saddle, and the horizontal distance from the seat post to the top of the frame's head tube, and compare these numbers to published geometry of bikes you are considering.
In general, a 5'4" person would fit on a 'small' size bike, but all manufacturers and bodies are different.
This is solid advice. I have 6 bikes and I have those critical dimensions the same on all them of them. It isn't easy, at least in these parts, to find high quality small bikes, most being made for riders between 5'7" and 6 '. I would take the time to read online on this subject and compare the descriptions of the components of bikes at different price points to get a sense of what components a quality bike is likely to have. In the interim, I would buy some light weight, road-type tires for the bike you have to replace the wide, heavy knobbies mtn bikes are usually sold with. You can also add bar ends to your handlebars to get closer to a roadbike feel. There are even bar ends that provide the same appearance and function as drop bars so you can see if you like that.