question about tubulars

On Oct 26, 7:09 pm, "Tom Kunich" cyclintom@yahoo. com wrote:
"Dan Connelly" wrote in message

Boutique? Carbon wheels are substantially lighter for racing. Not for
training, or touring the Alpes. Who cares about 0.5% speed advantages
when you're touring or training?

Carbon wheels serve a purpose very well. They're not going to be as
durable as metal rims, but that's not their design point.

Well, I don't know about you Dan, but there's no reason I can think of to
use carbon wheels in any case. Can you name a single race that was won
because of carbon rims?

You can't ever name a race that was won because of
a component, other than maybe Lemond's aerobars
in 1989. You never know what the influence of a
component was, unless it breaks and causes a loss.
However, racing is a game of seconds, so at the
pro level, they have to take advantage of weight
shavings and so on, whether or not you can assign
any single victory to a component improvement.

At the amateur level, of course, carbon rims aren't
for racing. They're for showing off on the Saturday
ride.

Ben

On Oct 26, 11:22 pm, "Mike Jacoubowsky" wrote:
"Dan Connelly" wrote in message

Carbon wheels serve a purpose very well. They're not going to be as
durable as metal rims, but that's not their design point.

Dan

Why must a carbon rim not be as durable as metal?

Because, as Dan wrote, that's not their design point.
You could presumably make a carbon rim as durable as
an aluminum rim, but then it wouldn't be as light as
possible, and the reason to use a carbon rim is to
make it lighter (while being aero, perhaps, but
lighter).

Someone could make a magnesium stem as durable as a
Salsa steel stem by adding metal. It might still
be lighter than the Salsa. But that's not why
anyone buys magnesium stems, so they don't make them
that way.

Life is a series of engineering tradeoffs.

Ben

Tom Kunich wrote:

Well, I don't know about you Dan, but there's no reason I can think of
to use carbon wheels in any case. Can you name a single race that was
won because of carbon rims?


I seem to remember Millar losing because one disintegrated??

wrote:
On Oct 26, 11:22 pm, "Mike Jacoubowsky" wrote:
"Dan Connelly" wrote in message

Carbon wheels serve a purpose very well. They're not going to be as
durable as metal rims, but that's not their design point.
Dan
Why must a carbon rim not be as durable as metal?

Because, as Dan wrote, that's not their design point.
You could presumably make a carbon rim as durable as
an aluminum rim, but then it wouldn't be as light as
possible, and the reason to use a carbon rim is to
make it lighter (while being aero, perhaps, but
lighter)....

It is hard to imagine a CFRP (not solely carbon [1]) rim being as
durable as one made of even a relatively soft metal such as aluminium
alloy if rim brakes are used.

[1] A pure carbon (diamond) rim would have great resistance to brake
track wear, as it would be harder than the silica grit commonly encountered.

--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?

Mike Jacoubowsky wrote:
"Donald Munro" wrote in message
om...
Howard Kveck wrote:
I fixed it in front of your Cupertino store - thanks for the air!
Tom Sherman wrote:
Mike J. owns the air in front of his stores?
Howard Kveck wrote:
He's a business titan, let me tell you.
Lucky he's not from Seattle or he'd try to patent the air.

There was a thread here a while back about a shop in Paris that did, in
fact, charge 1.5 euro (about $2) for air, if you didn't buy the bike there.
Yikes!

Andrew Muzi advertises free air 24 hours per day:
http://www.yellowjersey.org/wru.html.

--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?

Mike Jacoubowsky writes:

Carbon wheels serve a purpose very well. They're not going to be
as durable as metal rims, but that's not their design point.

Well, I don't understand why a tubular on a carbon rim should slip,
even with heavy braking, since the rim is a non conductor and will
not appreciably warm its rim glue. The real problem is that the
brakes don't work with rims that have no heat capacity and do not
conduct because brake pads are even better insulators and will burn
off as they did with wood rims of yore. Braking with wooden rims
was a burning mess.

At the end of November, my carbon clincher wheels will be two years
old, with probably about 13k miles on them. And still on the
original brake pads, which simply refuse to wear. No problem with
braking power either. I will finally retire the pads at the two
year mark and measure their thickness vs new ones. It's all very
odd, since everything I've heard says that stopping power will be
diminished and pad life shortened compared to standard aluminum rims
with standard rubber (KoolStop) pads.

And you know where I ride; it's not as if I avoid hills. That's all
I do.

Most hills in that area (Santa Cruz Mts) don't demand continuous
braking, but rather short applications before curves.

I haven't tried descending with such rims so I don't know ho hot they
get. The energy has got to go somewhere as it does with all friction
brakes. They convert kinetic energy to heat. How hot do these rims
get? Can you touch them without burning your hand? I just came down
Mt. Umunhum, one of the most hazardous descents for rim overheating.
I've measured rim temperatures on this grade with an instrumented test
that showed 125 degC on Mavic MA-2 rims. That is hotter than I like
to touch.

Hicks Road, Metcalf Road, and Old Watsonville Road are brake burners.

http://tinyurl.com/3xkn7k
http://tinyurl.com/2r8whj
http://tinyurl.com/3adg2t

These roads have sections of 18% grades, dropping continuously more
than 1000ft.

Jobst Brandt

wrote in message
...
Mike Jacoubowsky writes:

Carbon wheels serve a purpose very well. They're not going to be
as durable as metal rims, but that's not their design point.

Well, I don't understand why a tubular on a carbon rim should slip,
even with heavy braking, since the rim is a non conductor and will
not appreciably warm its rim glue. The real problem is that the
brakes don't work with rims that have no heat capacity and do not
conduct because brake pads are even better insulators and will burn
off as they did with wood rims of yore. Braking with wooden rims
was a burning mess.

At the end of November, my carbon clincher wheels will be two years
old, with probably about 13k miles on them. And still on the
original brake pads, which simply refuse to wear. No problem with
braking power either. I will finally retire the pads at the two
year mark and measure their thickness vs new ones. It's all very
odd, since everything I've heard says that stopping power will be
diminished and pad life shortened compared to standard aluminum rims
with standard rubber (KoolStop) pads.

And you know where I ride; it's not as if I avoid hills. That's all
I do.

Most hills in that area (Santa Cruz Mts) don't demand continuous
braking, but rather short applications before curves.

I haven't tried descending with such rims so I don't know ho hot they
get. The energy has got to go somewhere as it does with all friction
brakes. They convert kinetic energy to heat. How hot do these rims
get? Can you touch them without burning your hand?

Since carbon is a poor conductor of heat, it is also a poor heat transfer
material (perhaps the same thing). You can go blasting all day long on a
motorcycle with a carbon exhaust and still touch it (not the metal bits). It
will be warm, but it won't burn you.

Carl Sundquist writes:

Carbon wheels serve a purpose very well. They're not going to
be as durable as metal rims, but that's not their design point.

Well, I don't understand why a tubular on a carbon rim should
slip, even with heavy braking, since the rim is a non conductor
and will not appreciably warm its rim glue. The real problem is
that the brakes don't work with rims that have no heat capacity
and do not conduct because brake pads are even better insulators
and will burn off as they did with wood rims of yore. Braking
with wooden rims was a burning mess.

At the end of November, my carbon clincher wheels will be two
years old, with probably about 13k miles on them. And still on
the original brake pads, which simply refuse to wear. No problem
with braking power either. I will finally retire the pads at the
two year mark and measure their thickness vs new ones. It's all
very odd, since everything I've heard says that stopping power
will be diminished and pad life shortened compared to standard
aluminum rims with standard rubber (KoolStop) pads.

And you know where I ride; it's not as if I avoid hills. That's
all I do.

Most hills in that area (Santa Cruz Mts) don't demand continuous
braking, but rather short applications before curves.

I haven't tried descending with such rims so I don't know ho hot
they get. The energy has got to go somewhere as it does with all
friction brakes. They convert kinetic energy to heat. How hot do
these rims get? Can you touch them without burning your hand?

Since carbon is a poor conductor of heat, it is also a poor heat
transfer material (perhaps the same thing). You can go blasting all
day long on a motorcycle with a carbon exhaust and still touch it
(not the metal bits). It will be warm, but it won't burn you.

Well? So where does the heat go if it doesn't go into the rim? As I
explained, wood rims also dissipated no significant heat and on hard
braking hot bits of melted brake pad burned the legs while brake pads
wore out rapidly.

Jobst Brandt

"Dan Gregory" wrote in message
...
Tom Kunich wrote:

Well, I don't know about you Dan, but there's no reason I can think of to
use carbon wheels in any case. Can you name a single race that was won
because of carbon rims?


I seem to remember Millar losing because one disintegrated??

You're sure he would have won excepting the wheel problem?

"Dan Connelly" wrote in message
. ..
Phil Holman wrote:

There is a more disturbing failure mode with carbon tubulars and
heavy
braking. The stem cuts its way through the rim until it gets to the
first spoke hole. Another negative aspect of carbon boutique
tubulars.



Boutique? Carbon wheels are substantially lighter for racing. Not
for training, or touring the Alpes. Who cares about 0.5% speed
advantages when you're touring or training?

Apparently quite a few riding up and down North Oracle Rd, Tucson.


Carbon wheels serve a purpose very well. They're not going to be as
durable as metal rims, but that's not their design point.


Yep, I have a pair of Zipp 404s just for racing.

Phil H