True Fitness PS75 - Manual (Page 35)

PS Treadmills Owner’s Guide
35
Treadbelt Tension
Chapter Five: Care and Maintenance
Turn both rear roller adjustment bolts counter-clockwise until
treadbelt just begins slipping when walking on it, then turn both
rear roller adjustment bolts clockwise in equal quarter turn
increments until treadbelt stops slipping.
Note: Be sure to run on treadbelt to ensure that the treadbelt
does not slip while under load.
Treadbelt
Tension