I thought this might be a ;little late in the year for an April Fool's joke. Air is easily compressed and water is not so if you really filled your tires with water the bike would ride as hard as if it had solid rubber tires. This one is a nightmare for weight weenies. Water is 8 pounds per gallon but air weighs nearly nothing. Sure would add weight to the bike, Here is one brand you might look at - Slime