I am guessing a few people run mountain bikes to complement there road bikes.
My question is this, Do you ride the same size mountain bike compared to your road bike?
I have been looking around at websites for bike fitting on mountain bikes and road bikes and by chance my road bike was almost spot on.
I am lucky enough to have 2 mountain bikes a small specialized epic and a medium trek fuel which I have recently built up. According to the competitive cyclist website I should be better off on the medium trek. But I feel a little better on the smaller framed epic.
This got me thinking,So I measured the theoretical top tube length of the epic it came in at 54cm the same as my road bike. And the stem to front of the saddle measurement is within 5mm on both bikes.
So do other people run similar sized bikes or am I going to be causing myself problems down the line?

Don't worry so much, if the mountain bike feels good, you are good to go. I'm the opposite, I got a road bike to train and ride when I can't go to some decent trails. You move a lot more on a mountain bike to jump, drop, lift the wheels over rocks, climb a steep trail with slippery roots, use your body's velocity to make the bike go through a hard line... You need a size that will let you do all that easily and confortably, that let's you move your weight way back for steep downhills and way up front over the front wheel to climb nasty walls.