The shoe polish / talk technique is a way to measure tire roll. You put it on the near the edge, make a run, and see how much of the polish gets rubbed off. It should just take off the outer edge, on the tread-portion of the tire. Too much rubbed off means you are really rolling the tire over; Bad for the tire, and handling. Add more air. If none was rubbed off, you aren't deflecting at all; not bad, but you have some room to let some air out.
Try doing a search on the internet for a better explaination. I suck at explaining it.
2003 Ford Focus ZX3 2.3l N/A = 221 HP, 162 ft-lbs, email@example.comMPH - SOLD
2006 Ford Fusion 2.3l Turbo = 244HP, 247ft-lbs
2014 Ford Fiesta 1.0; Turbo