In BikeCAD, by default, scrolling the mouse wheel up zooms out, and scrolling the mouse wheel down zooms in. This behaviour is consistent with a lot of other CAD programs. However, if you are accustomed to using Google Maps, you will notice that scrolling the mouse wheel up in Google Maps zooms in and scrolling the mouse wheel down zooms out. In BikeCAD Pro version 9.0, you can reverse the effect of the scroll wheel on zoom by going to: View >> Customize and unchecking the box that says Scroll down to zoom. You will then need to hit the Save settings button and restart BikeCAD Pro. After doing this, BikeCAD will zoom in and out in a way that is consistent with Google Maps.
In the free version of BikeCAD, you can reverse the effect of the scroll wheel by clicking View and unchecking the box labeled Scroll down to zoom.