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发帖数: 19210 | 1 http://triathlete-europe.competitor.com/2013/05/07/qa-carbon-cl
Question: Would please give a brief explanation for the advantages and
disadvantages of carbon tubular and clincher wheels? Is there more to it
than the weight savings of the former and the easy flat-fixing of the latter?
Answer: The carbon tubular rim is lighter due to the lack of bead walls. The
tires corner better because they are round in cross section rather than
lobe-shaped like a clincher. They are usually a bit lighter as well, having
no beads and being able to use a lighter inner tube. For events and road
conditions that warrant it, high-end tubular tires can generally be inflated
to higher pressures than clincher tires of the same size. They are harder
to pinch-flat than a clincher (due to lower, more rounded rim walls and
tougher latex inner tubes). Tubulars are safer to ride when flat, as they
are still glued to the rim, whereas a flat clincher can come off of the rim.
And unlike a clincher where higher pressure in the tire applies higher
outward pressure on the carbon rim bead walls, the tire pressure in a
tubular tire has no effect on the rim (other than to compress it uniformly
radially inward, thus reducing spoke tension slightly, something that
happens with all tire types).
The disadvantage of a tubular is cost and the time and skill required for
gluing it on. With enough braking heat, the glue has the potential to melt
and allow the tire to come off (remember Joseba Beloki’s horrific crash?).
Clinchers are quicker to install, the tires are generally cheaper than
tubular tires, and flats usually require only replacement of the inner tube
and not the entire tire.
Clincher rims are heavier, and clincher tires are also a bit heavier than
tubulars of similar casing and tread. While heat buildup in any clincher rim
can be an issue during extended braking (see the melting glue problem
mentioned above), it’s more of an issue with a clincher. The latest carbon
clinchers from top brands, when coupled with the brake pads recommended by
the manufacturer, are not likely to fail in this circumstance, but many
carbon clinchers in the past have done so. Carbon is very strong under
tension but not under compression, so asking it to form a rim wall capable
of constraining the pressure of tire beads trying to push it outward is a
big ask in the first place. Couple that with the fact that at some
temperature, any resin holding the carbon matrix together will soften, and
you can have rim walls that fold out like limp taco shells under hard
braking. Again, this is a thing of the past for the top brands with the
correct (and heavily studied) brake pads under riders who are not beyond a
certain weight (and this weight will depend on the rims, braking style, the
road steepness and curve sharpness, and the ambient temperature). |
