Chris McReynolds said:In theory the only advantage now with sew-ups is that the rims can be
(and normally are) designed without any extra material to keep the tire
closed. That material accounts for a nominal amount of weight though in
well designed rims it is not worth considering.
What do you think that material is not doing? The entire cross section
of the rim supports spoke tension in compression as an arch and all of
it is necessary. You seem to think that the rim does nothing in
bending or compression while both of these characteristics are
essential to a durable wheel. It is the heavy deep "V" shape of the
16-spoke aero rims that make the low spoke count possible.
Quoted message said:However, if you are looking at the very top end of wheels (even most
pros don't use these wheels) then you either have to do without (a
clincher model) or you have to put up with a significant weight
disadvantage. I don't know if the current models are still made
this way, but the example I am thinking of is the ZIPP 303 and 404
models. When I looked at the clincher vs. sew-up weights there was
a 100+ gram weight difference per wheel. There are others that have
the same compromise where the sew-ups are all CF material but the
clinchers have a lip add-on that causes the extra weight. Again,
this may not be up to the minute but the last time I checked there
were very few sub 1200 gram clincher wheels.
To make up for that, former clincher wheels were more durable than
tubular rims although they weighed only 50g more. I didn't see a
single rim that I would buy or recommend while at InterBike.
All-carbon wheels may have surfaces where brake pads could run but
they do not absorb heat as aluminum does so the brake pads will burn
off as they did in the days of wooden rims.
Quoted message said:IMO, it pays to compare each time you buy new wheels. You wouldn't know
it by observation, but there is no reason I can see for one to have
both clincher and sew-ups available. If you are looking at your first
race set then most likely clinchers will serve you best. However, when
looking for certain niches of high performance race wheel, sew-ups are
definitely worth considering.
That's fine, but why? This sounds more like a mantra than a technical
explanation of why one should ride clinchers. You must have seen the
RR data:
http://www.terrymorse.com/bike/imgs/rolres.gif
with the RR losses due to rim glue. I'm sure if you are a regular
tubular user who descends with braking, your rims have aluminum grey
in the glue and the rims have cloth wear marks from the base tapes.
Tubulars move on the rim unless you have bare cloth base tapes and use
track glue. That's what it's there for.
Quoted message said:I stopped using sew-ups whenever there is no support vehicle(s). It is
too much of a pain in the ass to carry a spare sew-up tire. With
clinchers I carry 2 spare ultra-light (and compact) tubes and a small
patch kit. Lastly, it is worth noting that clincher rims are much
easier to damage when riding on a flat.
Quoted message said:Back in the day (20 + years ago?) I recall an occasional race won by a
guy crossing the line on a flat or near flat tire. Not only are
clincher rims more likely to become damaged this way, they are also
more likely to come off the rim in my experience.
Not to worry. I have ridden many miles on a flat 25mm clincher because
the rim was so deeply dented and would not take another tire. It is
only imagination that flat clinchers cannot be ridden.
Quoted message said:I have never had a sew-up come off the rim due to a flat but I have
had clincher tires come off more than a few times due to flats. WRT
equipment choices, one last consideration is that sew-ups are
getting very expensive I am sure due to the smaller volumes produced
these days and cheap sew-ups are more difficult to repair and some
times not worth the effort.
What sort of rags did you use for clinchers? I've used wire bead
avocets for years and the ones that I rode flat did not come off the
rim.
Jobst Brandt
