Canon ImageRunner iR8500 Series Service Manual page 678

Chapter 14
2) Adjusting the Front Non-Image Width
Place A3 test chart in the original tray of the ADF and make a copy of it
to check the front non-image width.
Standards: 2.5 ±1.5 mm
Adjustment:mounting position of the ADF original tray.
2.5 1.5mm
14-24
4+1.5mm,-1.0mm
F-14-48
F-14-49