Tire pressure gauges

[TK4]

Yamaha, among others, played with "air suspension". Use air volume as a spring, use pressure to adjust preload (works GREAT on paper... sucks in practice)

Motion Pro had ( maybe still do ?) a low pressure syringe type pump with a gauge on it for doing those stupid forks and monoshocks.
My XV920R had both, it seemed like every time I went to go for a ride they'd both leaked down to zero. PITA.