If only infallible authorities can give you information about religious truths, then what infallible authority informs you that Rome is infallible?
ou don't need an infallible authority to give you information about religious truth, though it is nice if you have one.  You do need one to settle disputes on specific matters of doctrine.  The Bible is not an "authority" per se because it cannot settle such disputes.  Look at all of the disputes among Protestants.
The infallible authority that tells us to look to the Magisterium of the Catholic Church is Jesus.  This is what has been taught by Tradition from day one.  It is Christ who established the hierarchy and left St. Peter in charge as his vicar.  The Bible bears witness to this in Matthew 16:18 and the other Petrine authority passages, but Papal authority does not come from the Bible.  It comes from Christ himself.  Jesus is, by definition, THE infallible authority.  If you believe in Christ, then you must accept the authority of his Church.
Art Sippo