In BikeCAD version 8.0 you can now zoom in on your model by scrolling the mouse wheel towards you. Scrolling away zooms out. Note that if you scroll over a specific part of the bike such as the stem, BikeCAD zooms in on that particular point.
For space efficiency the old slider bar has been removed from the BikeCAD interface. However, if you prefer, you can turn it back on in BikeCAD Pro by clicking View >> Customize and selecting the Zoom check box. Remember to click Save settings before quitting the dialogue box. The next time you launch BikeCAD, the slider bar will be included in the interface.
If you are using the BikeCAD applet embedded in another web site, scrolling to zoom in on the model can be a problem if the web page also scrolls. However, in Internet Explorer, if you press on the mouse wheel while scrolling, the BikeCAD model will zoom and the web page will remain fixed.
Also remember that if the model ever gets away on you, you can always click the refit icon 
to bring the bike back into view.