So I have an issue now that my head angle is far too steep. But I’m trying to be scientific rather than just buying new forks which are bigger.
I’ve put a longer shock on my Stumpjumper 120, an increase of 10mm shock length and 3mm stroke.
A 47mm stroke shock gives 120mm travel, so an extra 10mm of shock length pushes the rear wheel down by around 25mm, as well as an increase in BB height and steeper head angle. To counteract this I would like longer forks which will give a known output.
I’m currently using 2009 Revelations (130mm). I believe these have an axle-crown of 509mm. Using sketchup and some photo’s, it appears I’m running a head angle of 72 degrees.
I’m working on an output of 68 degree head angle, to produce this I need to move the headtube upwards around 73mm, ready reckoning of 0.5 degrees per 10mm gives me a near-as-dammit confidence check on that too.
Any arguments against my theory? If not, I just need to find a nice bargain fork (probably 160mm)!