Methods and devices for biasing a balloon catheter are disclosed. In one example, a medical device may include a catheter shaft and a balloon assembly coupled to a distal region of the catheter shaft. The balloon assembly can define a chamber configured to be inflated and deflated using a fluid supplied from the catheter shaft. A biasing member may be positioned in the chamber of the balloon assembly and may be configured to bias the balloon assembly to a longitudinally extended state without obstructing an exhaust lumen of the catheter shaft. In some cases, the biasing member may be a spring. In other cases, the biasing member may be a coiled portion of a fluid supply line.