I have heard shock travel sensors are expensive , and an idea popped into my head about how to rig up a cheap (sorta) shock travel sensor?
A small air cylinder attached between the axle and the upper shock mount, tapped for an air line to a MAP sensor would read out a pressure change as the shock moved? That and a maximum travel indicator to calibrate it might be fairly accurate if the rate of sampling is quick enough? 100 per second ought to do it. The air cylinder would need to be small so as not to have too much effect on suspension, and set at zero pressure so it would graph shock motion in both directions. Any experience that might reflect on how this would work is welcome.