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Steel is Real and Carbon is Lighter



 
 
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  #111  
Old June 24th 19, 12:17 AM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 4,300
Default Steel is Real and Carbon is Lighter

On Sunday, June 23, 2019 at 3:05:17 PM UTC-7, Tom Kunich wrote:
On Saturday, June 22, 2019 at 8:10:16 PM UTC-7, jbeattie wrote:
On Saturday, June 22, 2019 at 7:29:10 PM UTC-7, John B. wrote:
On Sun, 23 Jun 2019 05:17:38 +0700, John B.
wrote:

On Fri, 21 Jun 2019 09:15:50 -0700 (PDT), Tom Kunich
wrote:

On Wednesday, June 19, 2019 at 9:49:48 AM UTC-7, duane wrote:
On 19/06/2019 10:25 a.m., jbeattie wrote:
On Tuesday, June 18, 2019 at 8:06:37 PM UTC-7, Frank Krygowski wrote:
On 6/18/2019 1:24 PM, jbeattie wrote:
On Tuesday, June 18, 2019 at 9:49:50 AM UTC-7, Frank Krygowski wrote:

For ordinary riding? No, most tiny improvements make no noticeable
difference. Even though we all know the near-magic power of red paint.


What is a "tiny improvement"? The frame on my Emonda probably weighs less than the Columbus steel forks off my last custom racing bike. Those things were suitable for clubbing baby harp seals or home defense. Weight and stiffness do matter when climbing. If we're talking about aero bits, that's harder call -- except that dopes on aero bars riding in packs can result in a massive worsening of your riding experience. Wearing aero shoe covers may keep your feet warmer on chilly mornings, which might make you faster. It all adds up.

Stiffness probably does not make a detectable difference, unless the
frame is so flexible that things are scraping. Remember the discussion
we had about the bike magazine's test of modern stiff CF frames vs.
older, heavier steel frames? The test riders gushed about how the
stiffness improved their climbing, but the math showed the speed
difference was precisely what would be predicted by the weight difference.

Weight matters when climbing. If getting to the top of the hill before
your buddy is really, really important, a lighter bike will help by
whatever the percent difference in total bike+rider weight. If a 160
pound rider changes his 20 pound bike for an 18 pound bike, he should be
about 1% faster up a steep hill. Whoopee!

Make that a 5lb weight difference. You need to borrow a well-fitting modern 15lb racing bike with an appropriate gear range and then do a long ride with lots of hills. It's not a subtle or imagined difference compared to a T1000 or old-school steel sport touring bike, particularly if you're trying to keep up with others.

-- Jay Beattie.


5lbs? My Tarmac is probably closer to 12 lbs lighter than my cro moly
Volpe.

And no in reality it's not a subtle or imagined difference. And no,
it's not just about weight unless everything else is exactly the same.

I changed my Look pedals from CX 6 cyclocross pedals which are very easy to get into and put 206's on which were much lighter. Then since I had those 50 mm deep clinchers just sitting there I installed those The "out-the-door" weight was 21.7 lbs. for the Pinarello. I'm pulling my Basso apart to refinish it and I have another set of cheap Chinese tubeless wheels that I'll install when it get's back together. Also I think that my 44 mm bars are too wide so will reduce this to 42 mm. Chinese carbon bars as well. I think that I can keep a steel bike and have it about the same weight as the Colnago. Granted that the Colnago is not an ultra-light but my friend is touring Italy and he went to a bike factory and they advised him against buying carbon. They said that they support a racing team with these ultra-lights but that they are replaced every single race. They say that there's no way that you can get any reliability out of a piece of cloth that tears with resin on it that cracks.

That last is a rather strange statement given that practically all
modern recreation and work boats are made from a mixture of cloth and
resin. Do you mean that my 15 year old, 40 ft sloop, that had sailed
across the pacific ocean and that I sailed from Thailand to Australia
and back was prone to crack?

Or is this just another of your poorly thought out and wild eyed
statements.


As an addendum to the above I found a site that had tested a number of
carbon composite samples. The average of 4 separate test samples was
982.5 MPa or 142,499psi. In comparison the ultimate tensile strength
of "mild steel" (Aisi 1018) is 440 MPa or 63,816 psi.
http://www.scielo.br/scielo.php?scri...92006000100016
https://www.azom.com/article.aspx?ArticleID=6115

As an aside, the carbon composite samples appeared to show no
elongation before fracturing during the tensile strength testing while
the mild steel specifications show a 15% elongation before failure.
Also the tensile strength necessary to produce elongation of the mild
steel is 370 MPa. Which illustrates a major difference between carbon
composite and steel. The steel bends or elongates prior to complete
failure while the carbon just breaks.
--
cheers,

John B.


This is fascinating, but I think your first comment was correct -- Tom is either hallucinating or getting smoke blown up his a**. All my CF bikes have lifetime warranties, including an exceptionally light Emonda SLR. My brother flew CF Dreamliners and lived to retirement. The factory making disposable, one-race CF bikes is made-up by someone.

-- Jay Beattie.


Jay - I realize the Trek gives a lifetime warranty on the frameset. And my friend has exercised that three times. Another friend had a Lynskey titanium frame and I warned him to watch for cracks since the material is EXTREMELY sensitive to oxidation in the welding process. He laughed in my face and the very following week I pointed out a crack around the upper headset.


Yup, things break. And with your history of breaking CF forks, I might warn you away from anything CF, even a bottle opener. https://images.bonanzastatic.com/afu...74/s-l1600.jpg If I broke a pair of forks, I might be leading the Grant Peterson anti-CF parade with my wool shako and steel baton. However, after 25 years, I've yet to break a set.


-- Jay Beattie.
Ads
  #112  
Old June 24th 19, 02:23 AM posted to rec.bicycles.tech
jOHN b.
external usenet poster
 
Posts: 1,179
Default Steel is Real and Carbon is Lighter

On Sun, 23 Jun 2019 10:53:31 -0700, sms
wrote:

On 6/23/2019 8:42 AM, jbeattie wrote:

snip

Yes, like this anecdote. And for a lawsuit counter-anecdote, I've been representing Trek and Specialized in Oregon for over 20 years. It's like being the mythical Maytag repairman. There is not an epidemic of old CF frame failures resulting in lawsuits.


Be careful there..."Among dishwasher owners, 13 percent of Maytag
purchases required repairs, more than Bosch (7 percent), Whirlpool (8
percent), Miele (9 percent) and Kenmore (11 percent). Among
refrigerators, Maytag ranked third, behind Kenmore and Samsung while
among washing machines, it was tied for fourth with Whirlpool, behind
LG, Samsung, and Kenmore."

Your comments seem rather, well "strange", as I researched your
figures and I find that based on 34,687 service calls during 2018
YALE Appliances and Lighting stated that in their experience:
Maytag - Shipped 29, service required 3, service ratio 10.3
Bosch - Shipped 2735, service required 303, service ratio 11.08
Whirlpool - Shipped 1030, service required 44, service ratio 4.27
Miele - Shipped 1078, service required 155, service ratio 14.38
https://blog.yaleappliance.com/most-...shwashers-2019

In short your figures seem to have no basis in reality..
(as do many of your other "facts")

The Maytag repairman isn't so lonely anymore.
https://www.nytimes.com/2014/01/09/business/media/maytag-repairmans-new-job-keeps-him-busy.html.

It is true, though, that CF fails differently than steel and some internal damage is not apparent. When my Supersix was trashed in a roof rack incident, I had it inspected by Ruckus. https://ruckuscomp.com/inspection. They confirmed that it was indeed trashed, and in some areas I had not expected. So I got a new bike. I would have spent a similar amount repairing steel and getting a paint job -- particularly if I went with wet paint. Gads, nice paint is incredibly expensive these days. The moral of the story is that if you're worried about internal frame damage, have the frame inspected.


Someone buying a used CF frame is unlikely to be the kind of person that
will spent several hundred dollars on a proper inspection.

You can get failures in any product, and high volume products have ascertainable defect rates, generally very low with reputable manufacturers. The good news is that most bicycle failures result in warranty claims and not personal injuries. The exception is forks. Reputable manufacturers have spent lots of time and money on getting forks right -- and they police their contractors. CF forks are the standard now, even on steel and aluminum bikes. And note that steel forks are not without their problems. https://www.cpsc.gov/Recalls/2013/Sa...-Bicycle-Forks But if CF forks are too scary, get steel. They're still available. I've been riding on CF forks since about '92 when I got first generation Kestrel forks, and I haven't looked back.


Yes, fork failures have been the most common and most likely to cause
injury. For a while Rivendell was offering a replacement program,
offering their steel forks at a discount when exchanged for a CF fork.
http://web.archive.org/web/20100801102119/http://www.rivbike.com/products/show/carbonoms-fork/50-718
"Our offer:

The fork sells for $200, and we won't have them 'till August 1. Call
800-345-3918 or email to pre-order. Or, if you send us your carbon fork
(write your name on the steerer tube, address below, along with your
contact info), we'll sell you its replacement for $115. We will
permanently remove your fork from circulation. That is the point, after
all. If you sell it on eBay, the problem is still out there."

--
cheers,

John B.

  #113  
Old June 24th 19, 02:25 AM posted to rec.bicycles.tech
jOHN b.
external usenet poster
 
Posts: 1,179
Default Steel is Real and Carbon is Lighter

On Sun, 23 Jun 2019 04:36:57 -0700 (PDT), wrote:

On Sunday, June 23, 2019 at 10:35:04 AM UTC+2, Tosspot wrote:
On 23/06/2019 03.29, John B. wrote:
On Sun, 23 Jun 2019 05:17:38 +0700, John B.
wrote:

On Fri, 21 Jun 2019 09:15:50 -0700 (PDT), Tom Kunich
wrote:

On Wednesday, June 19, 2019 at 9:49:48 AM UTC-7, duane wrote:
On 19/06/2019 10:25 a.m., jbeattie wrote:
On Tuesday, June 18, 2019 at 8:06:37 PM UTC-7, Frank
Krygowski wrote:
On 6/18/2019 1:24 PM, jbeattie wrote:
On Tuesday, June 18, 2019 at 9:49:50 AM UTC-7, Frank
Krygowski wrote:

For ordinary riding? No, most tiny improvements make no
noticeable difference. Even though we all know the
near-magic power of red paint.


What is a "tiny improvement"? The frame on my Emonda
probably weighs less than the Columbus steel forks off my
last custom racing bike. Those things were suitable for
clubbing baby harp seals or home defense. Weight and
stiffness do matter when climbing. If we're talking
about aero bits, that's harder call -- except that dopes
on aero bars riding in packs can result in a massive
worsening of your riding experience. Wearing aero shoe
covers may keep your feet warmer on chilly mornings,
which might make you faster. It all adds up.

Stiffness probably does not make a detectable difference,
unless the frame is so flexible that things are scraping.
Remember the discussion we had about the bike magazine's
test of modern stiff CF frames vs. older, heavier steel
frames? The test riders gushed about how the stiffness
improved their climbing, but the math showed the speed
difference was precisely what would be predicted by the
weight difference.

Weight matters when climbing. If getting to the top of the
hill before your buddy is really, really important, a
lighter bike will help by whatever the percent difference
in total bike+rider weight. If a 160 pound rider changes
his 20 pound bike for an 18 pound bike, he should be about
1% faster up a steep hill. Whoopee!

Make that a 5lb weight difference. You need to borrow a
well-fitting modern 15lb racing bike with an appropriate gear
range and then do a long ride with lots of hills. It's not a
subtle or imagined difference compared to a T1000 or
old-school steel sport touring bike, particularly if you're
trying to keep up with others.

-- Jay Beattie.


5lbs? My Tarmac is probably closer to 12 lbs lighter than my
cro moly Volpe.

And no in reality it's not a subtle or imagined difference.
And no, it's not just about weight unless everything else is
exactly the same.

I changed my Look pedals from CX 6 cyclocross pedals which are
very easy to get into and put 206's on which were much lighter.
Then since I had those 50 mm deep clinchers just sitting there I
installed those The "out-the-door" weight was 21.7 lbs. for the
Pinarello. I'm pulling my Basso apart to refinish it and I have
another set of cheap Chinese tubeless wheels that I'll install
when it get's back together. Also I think that my 44 mm bars are
too wide so will reduce this to 42 mm. Chinese carbon bars as
well. I think that I can keep a steel bike and have it about the
same weight as the Colnago. Granted that the Colnago is not an
ultra-light but my friend is touring Italy and he went to a bike
factory and they advised him against buying carbon. They said
that they support a racing team with these ultra-lights but that
they are replaced every single race. They say that there's no way
that you can get any reliability out of a piece of cloth that
tears with resin on it that cracks.

That last is a rather strange statement given that practically all
modern recreation and work boats are made from a mixture of cloth
and resin. Do you mean that my 15 year old, 40 ft sloop, that had
sailed across the pacific ocean and that I sailed from Thailand to
Australia and back was prone to crack?

Or is this just another of your poorly thought out and wild eyed
statements.


As an addendum to the above I found a site that had tested a number
of carbon composite samples. The average of 4 separate test samples
was 982.5 MPa or 142,499psi. In comparison the ultimate tensile
strength of "mild steel" (Aisi 1018) is 440 MPa or 63,816 psi.
http://www.scielo.br/scielo.php?scri...92006000100016


https://www.azom.com/article.aspx?ArticleID=6115

As an aside, the carbon composite samples appeared to show no
elongation before fracturing during the tensile strength testing
while the mild steel specifications show a 15% elongation before
failure. Also the tensile strength necessary to produce elongation of
the mild steel is 370 MPa. Which illustrates a major difference
between carbon composite and steel. The steel bends or elongates
prior to complete failure while the carbon just breaks.


Which is what makes CF frames incredibly rigid. They are fun to ride
because you feel that every erg on the pedal converts to KE without
loss. I've never owned one so can't comment on the 'rough ride'
criticism, but I could believe it.



When do the old farts learn to understand that the properties of CF depends on the direction. Today CF frames are one of most comfortable frames.

Lou


"properties of CF depends on the direction"?
You mean that a CF bike is more comfortable headed north than it does
when heading south :-?
--
cheers,

John B.

  #114  
Old June 24th 19, 02:41 AM posted to rec.bicycles.tech
jOHN b.
external usenet poster
 
Posts: 1,179
Default Steel is Real and Carbon is Lighter

On Sun, 23 Jun 2019 22:17:25 -0000 (UTC), Duane
wrote:

wrote:
On Sunday, June 23, 2019 at 10:35:04 AM UTC+2, Tosspot wrote:
On 23/06/2019 03.29, John B. wrote:
On Sun, 23 Jun 2019 05:17:38 +0700, John B.
wrote:

On Fri, 21 Jun 2019 09:15:50 -0700 (PDT), Tom Kunich
wrote:

On Wednesday, June 19, 2019 at 9:49:48 AM UTC-7, duane wrote:
On 19/06/2019 10:25 a.m., jbeattie wrote:
On Tuesday, June 18, 2019 at 8:06:37 PM UTC-7, Frank
Krygowski wrote:
On 6/18/2019 1:24 PM, jbeattie wrote:
On Tuesday, June 18, 2019 at 9:49:50 AM UTC-7, Frank
Krygowski wrote:

For ordinary riding? No, most tiny improvements make no
noticeable difference. Even though we all know the
near-magic power of red paint.


What is a "tiny improvement"? The frame on my Emonda
probably weighs less than the Columbus steel forks off my
last custom racing bike. Those things were suitable for
clubbing baby harp seals or home defense. Weight and
stiffness do matter when climbing. If we're talking
about aero bits, that's harder call -- except that dopes
on aero bars riding in packs can result in a massive
worsening of your riding experience. Wearing aero shoe
covers may keep your feet warmer on chilly mornings,
which might make you faster. It all adds up.

Stiffness probably does not make a detectable difference,
unless the frame is so flexible that things are scraping.
Remember the discussion we had about the bike magazine's
test of modern stiff CF frames vs. older, heavier steel
frames? The test riders gushed about how the stiffness
improved their climbing, but the math showed the speed
difference was precisely what would be predicted by the
weight difference.

Weight matters when climbing. If getting to the top of the
hill before your buddy is really, really important, a
lighter bike will help by whatever the percent difference
in total bike+rider weight. If a 160 pound rider changes
his 20 pound bike for an 18 pound bike, he should be about
1% faster up a steep hill. Whoopee!

Make that a 5lb weight difference. You need to borrow a
well-fitting modern 15lb racing bike with an appropriate gear
range and then do a long ride with lots of hills. It's not a
subtle or imagined difference compared to a T1000 or
old-school steel sport touring bike, particularly if you're
trying to keep up with others.

-- Jay Beattie.


5lbs? My Tarmac is probably closer to 12 lbs lighter than my
cro moly Volpe.

And no in reality it's not a subtle or imagined difference.
And no, it's not just about weight unless everything else is
exactly the same.

I changed my Look pedals from CX 6 cyclocross pedals which are
very easy to get into and put 206's on which were much lighter.
Then since I had those 50 mm deep clinchers just sitting there I
installed those The "out-the-door" weight was 21.7 lbs. for the
Pinarello. I'm pulling my Basso apart to refinish it and I have
another set of cheap Chinese tubeless wheels that I'll install
when it get's back together. Also I think that my 44 mm bars are
too wide so will reduce this to 42 mm. Chinese carbon bars as
well. I think that I can keep a steel bike and have it about the
same weight as the Colnago. Granted that the Colnago is not an
ultra-light but my friend is touring Italy and he went to a bike
factory and they advised him against buying carbon. They said
that they support a racing team with these ultra-lights but that
they are replaced every single race. They say that there's no way
that you can get any reliability out of a piece of cloth that
tears with resin on it that cracks.

That last is a rather strange statement given that practically all
modern recreation and work boats are made from a mixture of cloth
and resin. Do you mean that my 15 year old, 40 ft sloop, that had
sailed across the pacific ocean and that I sailed from Thailand to
Australia and back was prone to crack?

Or is this just another of your poorly thought out and wild eyed
statements.


As an addendum to the above I found a site that had tested a number
of carbon composite samples. The average of 4 separate test samples
was 982.5 MPa or 142,499psi. In comparison the ultimate tensile
strength of "mild steel" (Aisi 1018) is 440 MPa or 63,816 psi.
http://www.scielo.br/scielo.php?scri...92006000100016


https://www.azom.com/article.aspx?ArticleID=6115

As an aside, the carbon composite samples appeared to show no
elongation before fracturing during the tensile strength testing
while the mild steel specifications show a 15% elongation before
failure. Also the tensile strength necessary to produce elongation of
the mild steel is 370 MPa. Which illustrates a major difference
between carbon composite and steel. The steel bends or elongates
prior to complete failure while the carbon just breaks.

Which is what makes CF frames incredibly rigid. They are fun to ride
because you feel that every erg on the pedal converts to KE without
loss. I've never owned one so can't comment on the 'rough ride'
criticism, but I could believe it.



When do the old farts learn to understand that the properties of CF
depends on the direction. Today CF frames are one of most comfortable frames.

Lou


I mentioned that once and got blasted by a bunch of people here. I doubt
any had ridden a decent CF road bike. So I stopped paying attention to
their posts.

Although I have to admit that the age of old farts seems to be a moving
target.


Well, Yes! After all , as the song would have it "another day older
(and deeper in debt)".
--
cheers,

John B.

  #115  
Old June 24th 19, 03:47 AM posted to rec.bicycles.tech
Joy Beeson
external usenet poster
 
Posts: 1,410
Default Steel is Real and Carbon is Lighter

On Sun, 23 Jun 2019 09:29:05 +0700, John B.
wrote:

The steel bends or elongates prior to complete
failure while the carbon just breaks.


Veering sharply off-topic, that reminds me of the plastic clothespin
that snapped and cut my hand. A wooden clothespin will also be
destroyed by exposure to sunlight, but when it fails, it just sighs
and gives up.

I haven't seen plastic clothespins in the stores recently.

I've got a mouthful of plastic that got stronger when exposed to
ultraviolet. I don't expect to test its resistance to sunlight -- I'm
not *that* happy a cyclist!

--
Joy Beeson
joy beeson at comcast dot net
http://wlweather.net/PAGEJOY/
  #116  
Old June 24th 19, 04:41 AM posted to rec.bicycles.tech
jOHN b.
external usenet poster
 
Posts: 1,179
Default Steel is Real and Carbon is Lighter

On Sun, 23 Jun 2019 22:47:40 -0400, Joy Beeson
wrote:

On Sun, 23 Jun 2019 09:29:05 +0700, John B.
wrote:

The steel bends or elongates prior to complete
failure while the carbon just breaks.


Veering sharply off-topic, that reminds me of the plastic clothespin
that snapped and cut my hand. A wooden clothespin will also be
destroyed by exposure to sunlight, but when it fails, it just sighs
and gives up.

I haven't seen plastic clothespins in the stores recently.


Here, I don't believe that I've ever seen a wooden clothespin.
Everything seems to be plastic these days.
I just asked my wife about wooden clothespins and she said that she
remembers them from when she was a little girl, 5 - 10 years old.

I've got a mouthful of plastic that got stronger when exposed to
ultraviolet. I don't expect to test its resistance to sunlight -- I'm
not *that* happy a cyclist!

--
cheers,

John B.

  #117  
Old June 24th 19, 10:15 AM posted to rec.bicycles.tech
SMS
external usenet poster
 
Posts: 8,677
Default Steel is Real and Carbon is Lighter

On 6/23/2019 7:47 PM, Joy Beeson wrote:
On Sun, 23 Jun 2019 09:29:05 +0700, John B.
wrote:

The steel bends or elongates prior to complete
failure while the carbon just breaks.


Veering sharply off-topic, that reminds me of the plastic clothespin
that snapped and cut my hand. A wooden clothespin will also be
destroyed by exposure to sunlight, but when it fails, it just sighs
and gives up.

I haven't seen plastic clothespins in the stores recently.


Ditto. Wooden clothespins are all that are available here. Ever since I
built my nuclear fusion powered clothes dryer (a clothesline) we've only
ever had wooden clothespins.

I seem to remember plastic clothespins but it's been decades since I've
seen them, but they can still be purchased online
https://www.aliexpress.com/item/32962556941.html.
  #118  
Old June 24th 19, 07:09 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 500
Default Steel is Real and Carbon is Lighter

On Monday, June 24, 2019 at 1:01:32 AM UTC+2, jbeattie wrote:


The assurance of a credible seller that a CF frame has not been crashed is probably adequate. I'm sure Lou was honest about his crash history, if any.


There are certain simple rules you have to follow when buying, using and for decent people also selling a high end CF bike. The rules are simple and you can look them up. I used that bike for 8 years with an average milage of 3500 km/yr. I wiped out in a corner once at low speed and my body (elbow and hip) took the hit. Only one of the limit screws of the rear derailleur was scratched a bit. Do you think I would sell a high end CF bike that took a severe hit to a friend or a stranger?
I mentioned it before, if you want to throw a bike in the back of a pick-up truck, stay away from 800 gr CF frames.

Lou
  #119  
Old June 25th 19, 12:26 PM posted to rec.bicycles.tech
SMS
external usenet poster
 
Posts: 8,677
Default Steel is Real and Carbon is Lighter

On 6/24/2019 11:09 AM, wrote:
On Monday, June 24, 2019 at 1:01:32 AM UTC+2, jbeattie wrote:


The assurance of a credible seller that a CF frame has not been crashed is probably adequate. I'm sure Lou was honest about his crash history, if any.


There are certain simple rules you have to follow when buying, using and for decent people also selling a high end CF bike. The rules are simple and you can look them up. I used that bike for 8 years with an average milage of 3500 km/yr. I wiped out in a corner once at low speed and my body (elbow and hip) took the hit. Only one of the limit screws of the rear derailleur was scratched a bit. Do you think I would sell a high end CF bike that took a severe hit to a friend or a stranger?
I mentioned it before, if you want to throw a bike in the back of a pick-up truck, stay away from 800 gr CF frames.


I cringe when I see how some people treat their CF frames. For example,
you want to use a specific type of car rack for a CF frame, one that
holds the bike by the wheels and that does not clamp the frame, but I
often see carbon fiber frame bicycles being carried incorrectly, with
the frame tubes tightly clamped into a rack. It only takes one time to
permanently damage the frame.

There are plenty of carbon-fiber car racks available now, but if you
didn't have a carbon fiber frame in the past you probably didn't spend
the extra money for such a rack. Alternatively you can buy a "carbon
fiber frame adaptor" i.e. https://www.amazon.com/dp/B0741DNNR7 which
spreads out the pressure from the clamp over a larger surface area to
prevent damage to the frame. Additional caution needs to be taken with
carbon fiber wheels to avoid compressing the rim during transport (pipe
foam is suggested by one person that writes on the subject, see the Car
Racks section of
https://www.carlhart.com/how-to/how-to-care-for-carbon-bikes-and-parts-pg220.htm.
And of course you shouldn't use a fork mount rack on a carbon fork with
carbon dropouts but most carbon forks now use alloy dropouts but there
are still some with carbon dropouts.

I wouldn't buy a used carbon fiber framed bicycle from someone I didn't
know to be honest and trustworthy, there is just too much risk in doing so.

Also, when it comes to used carbon fiber bicycles you're losing the
"lifetime warranty" which is what drives up the price of the name brand
CF bikes in the first place. Unless you're getting a heck of a deal, you
may want to look into one of the lesser known brands. You can buy a full
carbon Fuji with Ultegra for $1500, and other full-carbon models are
even less.


  #120  
Old June 25th 19, 04:39 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 7,800
Default Steel is Real and Carbon is Lighter

On 6/22/2019 4:24 PM, Frank Krygowski wrote:
On 6/22/2019 3:16 PM, Tom Kunich wrote:
On Friday, June 21, 2019 at 3:55:05 PM UTC-7, jbeattie wrote:

Today's ride:
https://localfreshies.com/wp-content..._2014_V1.jpg¬* Mt.
Bachelor.¬* The winds were howling at the top, and I almost had a
Froome moment coming down -- and I was on modest C35s and not super
deep-dish sails.

-- Jay Beattie.


This was why I wanted to make the point that these cheapo deep aero
clinchers do not run off on me - they are no more sensitive to side
gusts than some of those old Campy Proton wheels which were flat
sections.

I assumption is that it is the spoke tension but it may be the
directional stability of the Victoria Corsa G+ tires. I've used these
clinchers on the Aero frame of the Colnago and the very non-aero frame
of the Pinarello Stelvio and they seem to react that same way.


OK, my guess on crosswind stability and aero wheels:

With an old fashioned, unstreamlined sort of box section rim, the cross
section of the forward part of wheel is a simple bluff body. Air hits it
and goes turbulent no matter what the angle of attack - that is, no
matter if there's zero wind, or if there's a sidewind causing the air to
come at the rim at an angle. So the front and rear portions of the wheel
get roughly the same amount and direction of force.

The more a tire+rim looks like a teardrop or airfoil, the less that is
true. The airfoil shape will certainly give less drag if it's pointed
directly into the relative wind (that is, if there is no sidewind). But
for many values of sidewind, the relative wind is at an angle of attack
that causes a significant sideways "lifting" force on the front part of
the wheel. [Rather, it would be a lifting force if the airfoil were
horizontal, as an airplane wing.] On the bike, this is a lateral force
that tries to steer the front of the wheel away from the wind. The
backside of the wheel sees the same angle of attack, but its airfoil is
oriented backward so it's much less efficient at generating side force.
The sideways force there is much less, so the front and rear side forces
are much less balanced than for a normal wheel.

The more streamlined the wheel+tire, the better this works. So I'm not
surprised aero wheels would be sensitive to side winds.

I don't think loose spokes have anything significant to do with this,
assuming the spokes don't go dead slack. In fact, I don't think tighter
spokes increase the rigidity of the wheel. The stiffness (or modulus of
elasticity) of a spoke with 50 kgf tension is the same as a spoke with
100 kgf tension. They're both within the elastic range of the material,
where strain is proportional to stress, so the same force will cause the
same deflection.

That's what I think. We can discuss.


Yesterday's club ride was at a pretty relaxed pace, but one guy had
brand new and extremely deep section aero rims. Sorry, I didn't catch
the brand.

But as we passed him, I asked "How are those rims in crosswinds?" He
said "Terrible. They're actually scary, really scary."

--
- Frank Krygowski
 




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