Anyone use the calibration feature in the Nav?

I just replaced the stock tires and wheels with something a little more "shiny". I've read all the forums on doing this and understand pro's and con's. In anycase, I found out how to reset the TPMS and saw the calibrate feature on the third page of the nav systems set up menu. It has a specifc button for changing tires. OK, I hit it and it say "going into calibration mode", switches back to the nav map and that's it. No further feedback.

Has anyone else done this? I'm planning on following a car with stock tires and wheels and see if my speedo is reading correctly now. Just wanted to see if there was an expert out there to tell me how this system works.

(I did (upgrade/downgrade) to some chrome 16" wheels and new Goodyear Assurance Comfortreds).