Correção de frase: ''I have carefully ridden...''

Something makes me wonder...I would say "I rode a/the bike carefully".

Also possible: I have been riding bikes carefully (since childhood, for example).

Something makes me wonder...I would say "I rode a/the bike carefully".

Aí não teria que falar quando?

I would say that not necessarily had to, it´s implicit. The temporality being denoted by the verb tense. Techniclly speaking, I mean.
And, generally speaking, when you have stated that sentence you have already more or less expressed it in context.

As you see, the present simple stablish "a short time span" (or the effect continues up to the present),
Many people use the rule of thumb of some event that happened in the last twelve hours or so, that is, until yesterday (if you are speaking of something today.)
When the action is finished, or happened before that, then enters the defining words "yesterday/last week/last month, etc" OR when the effect doesn´t persist.

Anyway, I can be mistaken. So, I leave the grammar minutes in the experienced hands of Donay
And/or the natives, teachers and the like.

=
One has also to be aware that "ride" can be transitive or intransitive, depending on the meaning.
http://www.thefreedictionary.com/ride

Sim, no presente perfect, eu sei que o tempo não precisa ser expresso, mas nesse exemplo que você deu "I rode a/the bike carefully". não está no present perfect, aí precisaria expressar quando a ação ocorreu, ou estou errado?

Obrigado pela atenção!

Não precisa, fica subtendido que foi uma ação no passado, já completada.