3 ms·

They could have made basically the same thing except with a sprocket to help drive the chain.

• ryukoposting 2mo ago
  Chain moves side to side with gear changes, and adding extra chain tension with an extra drive sprocket could make the deraileur angry. Also, chain-tube geometry varies a lot. Not impossible, just more complicated than it might seem. I ride an all-original 1970s steel-frame road bike, which seems like a prime candidate for this sort of product. I'm certain no sprocket-based design would fit it. I'd buy one of these if there was any way to lock it up.
  • andrewshadura 2mo ago
    It does not if you use hub gears.
    • Toutouxc 2mo ago
      Yes, but a tiny minority of bikes use those, and the product is meant to go on existing bikes. Also, even on hub-geared bikes (or single-speeds) you’d still need to switch to a longer chain or significantly move the rear wheel to be able to mount the powered sprocket in the right place, so that it wouldn’t skip.
      • andrewshadura 2mo ago
        Not a tiny minority. Depends on the country, of course, but from my experience the majority of city bikes use hub gears. And they can be retrofitted.
• Toutouxc 2mo ago
  Go ahead, sit down with a piece of paper and try to design it in a way that doesn’t prevent shifting, doesn’t skip under load, doesn’t require you to use a longer chain, works with rear suspension and doesn’t interfere with your legs.