Race him." On the track " I knew two brothers with the same issue, one is dead, because the race took place back road style on Christmas day..
I love when my brothers and I argue.
Tell him to just prove it or ask him questions like why is it faster, then break it down gear by gear, HP to HP definitions. Maybe that way if you keep asking him why all time and why for ""EVERY"" question, he will just stop.. My brothers hate it and we dont talk for a week or so.