The ultimate bike doesn't exist. It would be solid enough to hit potholes dead on all day long without damage, the tires would roll without friction but give a nice comfy ride on rough roads and would never need to be topped off. It would have a Rolhoff hub that somehow got 99%+ efficiency and weigh 5 ounces, and a belt drive that could go 50,000 miles without maintenance and was also as efficient as a chain. It would have fenders for the rain but they would be invisible so it looked nice. It would have disc brakes for foul weather yet weigh no more than rim brakes. It would be able to tow a trailer or mount full waterproof panniers front and back for grocery getting and touring. It would have a ton of reflective stuff and 1000 lumen full cutoff beam multi-level dynamo lights but still look nice.
And it should weigh no more than 20 pounds at most.
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Work: the 8 hours that separates bike rides.