The menu adjustment +/- 2.5% was enough to calibrate my 2011 to within 1 mi/hr. I tried to use the menu adjustment on my 2015 when I first purchased it, but the car automatically returned the setting to zero after driving a while. I eventually found that the speedometer was within 1 mi/hr of a fast-response GPS with the original tires inflated to 44 psi. I noticed no change with the first set of replacement tires. I recently purchased new tires one size larger so I planned to use the menu adjustment to compensate. Again, the menu adjustment returned to zero after driving. I then discovered that the speedometer was still within 1 mi/hr (fast-response GPS generally indicated 1 mi/hr higher than speedometer). I eventually concluded that the navigation system GPS must send a calibration signal to the speedometer periodically (it also sends the clock signal to the eyebrow display so the clock never needs to be set). It does not calibrate the odometer so it now reads about 3.5% lower than actual distance diriven.
Edited to add: I don't know when the change was made, but the clock in the 2011 required periodic resetting and the +/- 2.5% adjustment in the menu was effective. The 2015 seems to set the clock and calibrate the speedometer automatically from the navigation system GPS.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015