Would be good if u can post a screenshot to show me but i think you would need to change the materials, not easy in the begining but you are doing better fast, trust me. Reed this guide: http://www.lfsforum.net/showthread.php?t=19763 and the chapeter "fix the tires", that might will help you.
I hope you meant an open top as in an open roof. I've just started making a XRT Targa top (I know it's been done a few times already) and now rendering it with your skin on it. Be done in 20 minutes.