theres 2 ways, theres a tensioner in the middle, with 13mm nut, normally a bit rusted try tightening it up.
The best way but harder is to take off tyre. when handbrake is off if you turn brake disk, and look through inspection hole you will see tensioner, like a nut, depending on which side it it turn it a few times up or down to tighten.
Ben, January 2009
