On Nov 9, 11:24 am, Doug Cimperman <
dcim...@norcom2000.com> wrote:
> Concerning radials, bias-ply tires and What Lies Beyond :o
> ------
>
> The fundamental question here is (assuming the tread is thin and evenly
> applied) do typical bicycle tires all inflate to perfect circular cross
> sections, where they are free of the rim edges?
>
> Consider a theoretical clincher tire that is a radial, with the threads
> crossing perpendicular to the tire. Each thread (which makes a complete
> crossing of the tire casing) cuts a perfect circle around the tube, as
> that would be the shortest path. And there are no other threads in other
> directions to redistribute stresses, so a radial clincher will inflate
> to a 'perfect' circular cross-section.
>
> Now consider a typical bias-ply bicycle clincher, with the bias set at
> 45 . The threads are perpendicular to each other so it will resist
> inflation pressure equally in circumference as well as laterally--but
> the path that any single thread follows is not circular. The thread's
> path is a slightly-flattened oval, wider than it is taller.... Is the
> tire's cross-section still circular, tr is it a
> slightly-laterally-flattened oval?
>
> Now.... consider a bicycle tire that has a casing with a bias WAY more
> than 45 ..... say, 75 . The threads are no longer perpendicular to each
> other, and are very resistant to circumferential stress, but not lateral
> stress. Will this tire inflate to a circular cross-section, or an oval?
>
> Cast your votes
To add a point of observation, in a radial casing with (theoretically)
non-elastic circumferential threads, the cross section _could_ be
flattened by constraint of the tire's circumference by the those
threads. Like adding an additional set of "beads" in the center of the
tread. But I don't envision that happening with threads running bead-
to-bead even with a very large longitudinal component.
In others words, I vote circular.
DR
Has your experimentation provided an insight into the has