I hope you powerfly owners can help me validate your head angle. Can PF9 owners verify what their fork angle is?
I was checking the fork angle on the PF4 FS. Trek web site say 66.5 degrees head angle for all PS4 FS sizes which have 100mm forks.
PF4 FS: SR Suntour XCR 34, air spring, LO R damper, hydraulic lockout, tapered steerer, 41mm offset, oversized crown for eMTB, Boost110, 15mm bolt-on thru axle, 100mm travel
PF9 FS: SR Suntour Zeron 35, air spring, LO R damper, hydraulic lockout, tapered steerer, 44mm offset, Boost110, 15mm bolt-on thru axle, 120mm travel
I have replaced the 100mm Suntour fork with a 120mm Rockshox fork (44mm offset) so I expect it to be slacker. Trek is listing the Powerfly 9 FS which comes with a 120mm fork as 66.5 degrees head angle.
I measured the fork on my PF4 and it is 65 degrees which I expected with the longer travel. Every 20mm of fork length you gain about 1 degree slacker head angle.
I also went to a 27.5x2.6 tire which slackened the angle too.