Ronaldo said Cristiano Jr often teases him that Bale is faster in an interview in which he admitted becoming a dad has changed his life.
Both Bale and Ronaldo are set to star for Real in the Champions League final in Milan on Saturday as they look to give the club an 11th European crown and second in the space of three years.
But Ronaldo is adamant that no-one else is up to speed with him in the world game, even the 26-year-old Wales star.
Speaking to Spain’s leading TV football programme Jugones de la Sexta Ronaldo said: “My son has changed my life in many aspects. I always said it was a dream to have a son, he changed me a lot.
“Sometimes he comes at home and says ‘daddy Bale is faster than you’. And I say ‘what are you on about? No one is faster than your dad’.
“And he says ‘yes but at school they told me he is faster and in an interview Messi said that he’d like to have your right foot.’ He comes up with these things and it gives me joy, he’s a kid.”
Last year a study carried out by Mexican Premier League club Pachuca and backed by FIFA claimed Cristiano Jr is indeed correct.
It said Bale was the world’s fastest footballer, clocking a speed of 36.9km/h. That compared to Ronaldo’s top speed of 33.6km/h and Lionel Messi’s 32.5km/h.