Whats the grammatical explaination for these two sentences. "would it be ok if I (borrowed-borrow) your tent?"

If I borrow and borrowed are teh present and past tenses of the verb. Often in English we interchange the tenses with some verbs. For example "would it be OK if I walk / walked with you, skate/skated, etc. I guess the reasoning would be that although you do the action in the present, the moment the action is underway, you refer to it in the past.