An implantable drug infusion device includes a pump tube for holding a liquid to be pumped. A race is configured to support the pump tube. A roller assembly is configured to compress the tube against the race at one or more points along the path, and the roller assembly includes at least one roller. A drive assembly drives the roller assembly relative to the tube along the path so as to move the liquid through the tube. At least two biasing members are operably connected to the roller to bias the roller against the tube, the two biasing members forming an angle.