I have a Hardrock Sport Disc 2006. It comes with Tektro IO mechanical disc brakes. If I upgrade to Avid BB7s, do I need to put on the Avid disc, too, or can I leave on the Tektro disc and just add the Avid calipers? I'd sell the Avid discs to recoup some of the upgrade cost. WIll the Avids calipers perform equally well on the Tektro disc, or do I need to add the Avid disc to realize the BB7s full performance?