On Tuesday, January 14, 2020 at 9:10:48 AM UTC-8, Mark J. wrote:
So I learned (?) something new (?) today reading Lennard Zinn's column
at Velonews:
https://www.velonews.com/2020/01/tec...blowoff_503717
What I learned was the term "crochet-type rim".
Looking it up, some sources say this is just another name for hook-bead,
BUT:
https://en.wikipedia.org/wiki/ISO_5775#Rims says:
Both crochet (C) and hooked-bead (HB) rims have inner profiles
that curve inwards near the outside diameter of the rim to
provide a hook that helps retain the tire bead under high
pressure. On modern bikes crochet rims are most common and
hooked bead rims are rare. The distinction is primarily that
hooked-bead rims lack the defined bead seat of straight side and
hooked bead rims. The tire is held in position radially by the
hook without a bead seat playing a role. Without a bead seat,
the primary designation of the diameter in terms of the bead
seat is not applicable, and the governing diameter is the OD.
Sentence #3 pretty clearly has a typo, but I can't figure out the
correction, and I cannot find any images on google that directly compare
hooked-bead and crocheted (also sometimes mis-named "crotched").
I suspect the "HB" in the quoted passage above is really referring to an
obsolete design, and that the quoted writer would even call the 70's
Mavic Mod E "crocheted" rather than "hooked-bead," even though we all
called them hooked-bead.
Can anyone clear this up with an authoritative source?
Mark J.
I'm sure there must be an ISO drawing somewhere.
https://en.wikipedia.org/wiki/ISO_5775 My sense is that we've been calling ISO "crochet" rims "hook bead" rims but that a true "hook bead" looks like an open hook ala the old steel rim design.
http://www.asia.ru/images/target/pho...Steel_Rim..jpg
-- Jay Beattie.
-- Jay Beattie.