Why do different numbers appear on your helmet after certain sessions?

If you mean the Manufacturers or Nations Championship races it's becuase the lobby gets ranked by their current DR rating and is given a driver number to reflect.

So if you have the most DR in the lobby for example you'll have driver number 1.
 
No, I see it quite often whether in Sport Mode or internal campaign. When I complete a practice session, or any given race, when the driver appears during the post event payouts and turns his head sideways different numbers appear just below the drivers ear. I've seen numbers 1 thru 10, and they never seem to correlate to where I placed in whatever event.
 
If your car has a number on the livery or as part of your ranking during Sport Mode (per @Mercia's post), this is the number that appears on your helmet.
 
Gotcha, copied what he said as well, that answers the helmet numbers for Sport mode. I see that now. I never thought about comparing the car # to the helmet #, because I had been seeing them before I ever jumped into sport mode. But like I was saying to @Mercia , I've seen them just as often in campaign mode. I've had them pop up after most internal events; License tests, Missions, Circuit Experience laps, etc. ? Just curious, but hey, at least I know what they are in Sport mode, thanks a bunch to both you guys for answering!
 
Back