Yes, a lot of folks have posted here with your same story.
You need to sit down and look him in the eye and ask why you two can't ride together without him wanting to teach you all the time; he's not your father.

Next; the fact is, if you are training for a tri; you really are taking a lot of time away from your relationship - remember, you used to ride together. He got a lot of joy out of playing coach with you; might even be why he got involved with you in the first place.
It's clear to me he's not happy with this new development.
You have to find a way to keep him happy if you want the relationship to continue. If all you do is TRIs and tri training, and he's not involved, you might be in trouble..
the golden word is compromise. You BOTH have to do it for a relationship to work.
M