Wheel Sanding & Graphite

I'm sure theres a topic in the archives echoing this problem I'm having. RLD competition has signifiantly improved since I last was active, I'm trying to step up my mods to keep up.

Tonight I ran a test where I found two stock cars of equal speed and all I did was sand the wheels, polished the wheels, and apply graphite to one of them. I was hoping to evalaute the difference these simple techniques impact performance. 

Well, to my frustration, the sanded/graphited car dropped about a care length. Is there any reason either of these techniques could be done incorrectly to negatively impact performance? In the same token, what is the best way to get postive results from these steps?

Thanks guys!