Quick approximations: cross section of 20cm², cylinder length of 2m (probably about right for 26″ mountain bike wheels), that’s about 4L; the stuff is generally

Quick approximations: cross section of 20cm², cylinder length of 2m (probably about right for 26″ mountain bike wheels), that’s about 4L; the stuff is generally somewhat denser than water, assume something like 1.25kg/L and this tube of yours is now 5kg. Much heavier than is desirable (especially for rotating weight: gyroscope effects will make it harder to handle), without stopping to consider its shock-absorption and road-holding properties.