I was thinking about this the other day…skateboards are flexible, bike tires are bouncy. Why aren’t there “performance” skates with shocks? Wouldn’t that be better for your knees?
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Skateboards flex for shifting momentum. Bikes have inflated tires for rougher terrain. Shocks on skates would absorb your push off and require much more work to move.
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On skates you push with the skate against the ground to accelerate. If you had spring you would first need to press against the spring and then against the ground to do the same acceleration. So it would be a lot harder or slower. On a skateboard you push with the leg that isnt on the board so there also isnt a bouncy thing in between. And for bikes there is also nothing to compensate between the pedals and the wheel.
Specifically roller or quad skates, they have rubber or some type of polyurethane “cushion” which acts as a damper and allows the truck to flex. It’s similar to a skateboard but they typically have a more angled geometry to the plate. The plate itself needs to be ridged in order to transfer the push energy to speed. If there was flex, they would be less efficient.
Everyone asserting that pushing off would be less efficient needs to go back and check their physics knowledge. The entire point of a spring is that very little energy is lost in its action. In any case, the spring constant would be chosen to minimize compression on push-off. The answer is really that springs give no benefit in most uses of in-line or roller skates. Springs would be nice in in large wheel off-road inline skates, though.
They tried with with hiking poles a couple decades ans everyone got tennis elbow and/or arthritis in their wrists. Sometimes it’s better to just let your body absorb the shock.
They really aren’t needed for reasons similar to how it’s not needed on a road bike – the surface is pretty smooth overall, and by riding with your knees slightly bent, your body is more than capable of absorbing shocked from road irregularities.
There are off-road in-line skates that have pneumatic tires or spring suspensions. Those things add weight, reduce durability, and/or increase cost. If someone is skating on mostly smooth surfaces, then the benefits aren’t worth the drawbacks.
Same reason that running on a trampoline is harder than running on solid ground. you need something to push off of to transfer as much as that energy as possible into horizontal momentum
On skates, just like skis, your thighs are the shock absorbers. Just never land with straight legs.
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