Chapter 8

Setting the preload

The spring has been in its seat since before the arm went in. Now that the arm and the motor are there for it to push against, the grub screw behind the seat sets how hard the clutch is pressed on the filter disc.

Step 1 Set the preload with the grub screw

• The M4 × 14 grub screw goes into the M4 insert in the outer wall of the box, behind the spring, and presses on the back of the cup. A 2.0 mm hex key.
• Run it in until you feel the spring start to load, then give it 2.4 mm more: the spring goes from 13.5 to 11.1 mm and pushes with about 13.5 N. Through the arm's lever that is roughly 7 N of the clutch on the disc, once the wheel is in. The cup has 2.0 mm of travel either way from there, to add or take off preload.
• Check the arm: it must still swing freely and come back by itself. If it sticks, the trouble is in the pivot, not here - go back to chapter 5.
• You will set this again for real in the last chapter, with the wheel in and the motor turning. What you want now is a spring that is loaded, not a spring that is crushed.