Pro-Form TOUR DE FRANCE CBC User Manual page 22

HOW TO ADJUST THE DRIVE BELT
If you feel the pedals slip while you are pedaling, even
when the resistance is adjusted to the highest level,
the drive belt may need to be adjusted.
To adjust the drive belt, locate the Idler Cover (36).
Remove the M4 x 12mm Blunt Screw (80) and the Idler
Cover.
80
36
65
22
Then, tighten the M10 x 60mm Screw (65) until the
Drive Belt (not shown) is tight.
When the Drive Belt (not shown) is tight, reattach the
Idler Cover (36).