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Why do some forks and frames have brake rotor size limits?



 
 
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  #31  
Old October 25th 17, 03:48 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-10-24 17:50, John B. wrote:
On Tue, 24 Oct 2017 11:39:39 -0700, Joerg
wrote:

On 2017-10-22 18:05, Frank Krygowski wrote:
On 10/22/2017 11:07 AM, Joerg wrote:
On 2017-10-21 17:19, Frank Krygowski wrote:
On 10/21/2017 4:07 PM, wrote:
On Saturday, October 21, 2017 at 7:12:03 AM UTC-7, Joerg wrote:
When researching upgrades to larger rotors I read that there may be
limits for frames and forks. Why?

Explanations were usually scant and contradictory, with some saying it
doesn't matter and some saying it does. After all, when increasing the
rotor diameter by a couple of inches the brake force on the caliper
goes
down by about 30% and then due to it being positioned farther out this
should cantilever back into the same +30% into the frame or fork
bosses
as before. The maximum deceleration achievable on each wheel
remains the
same, until it is very close to locking up. So it should be a wash,
shouldn't it?

Now THAT is something that Frank should be able to answer. I don't
believe that leverage forces are linear are they?

Give me a photo and I'll see what I can do.


This is what I am planning to do:

https://ep1.pinkbike.org/p4pb12868017/p4pb12868017.jpg

The fork has this kind on there right now because the rotor is 180mm
(or in my case 7") and the fork is native 160mm:

https://ep1.pinkbike.org/p4pb12873429/p4pb12873429.jpg

First, to really do a proper job on this I'd need to see a clear side
view of the entire disc brake and rotor (or rotors), plus lower end of
the fork, plus (ideally) the lower portion of the wheel. I haven't given
tremendous attention to disc brakes, because I'm not going to be needing
one. I'm having to make some guesses based on what I can glean from your
photos, plus a few others I found on the web.


This is the front brake:

http://www.analogconsultants.com/ng/...rontBrake1.JPG

The rear brake:

http://www.analogconsultants.com/ng/bike/RearBrake1.JPG

Next is the whole MTB. I'll do a separate post with that because it can
help people with increasing the payload capacity on full-suspension bikes:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

This is the kind of adapter I am planning to use:

https://erpimgs.idealhere.com/ImageF...963c864243.jpg

It'll move the caliper outwards and also sideways for (hopefully) a
total of 21.5mm increase in distance from the axles. I am not an ME but
my guess is that the load on the swooped upper rear post would increase
by 15-20%. That post has a lot of meat, about 0.400" by 0.400" and the
welds look beefy as well.


I think that you are talking about the difference between a 160mm disc
and a 203mm disc. The radius of the 203mm disk is 101.3mm and the
radius of the 150mm disk is 80mm. Thus the moment arm of the larger
discs is ~26.6% longer then the smaller.

But this is a two way street as any force applied to the wheel will be
multiplied 1.26 times with the larger disc and of course the effect of
any force applied to the rim of the larger disc will be multiplied
1.26 times at the center of the wheel with the larger discs :-)

A 6061 - T4 aluminum, a common aluminum alloy, has a yield strength of
21,000 psi. 0.4" x 0.4" is 0.16 square inches so the theoretical load
that will cause it to bend the mount bracket might be as high as about
3,360 lbs, or 1.68 tons :-)



I am cutting back on beer consumption so I won't get to the required
weight for that :-)

--
Regards, Joerg

http://www.analogconsultants.com/
Ads
  #32  
Old October 25th 17, 03:53 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-10-24 17:21, John B. wrote:
On Tue, 24 Oct 2017 11:47:12 -0700, Joerg
wrote:

On 2017-10-24 07:27, wrote:
On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote:
On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 12:48:29 +0700, John B.
wrote:

On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 07:02:08 +0700, John B.
wrote:

But re disc brake cooling F1 car brakes appear to work with
the discs red hot. In the 1,000 degree (F) range. And they
use Carbon Fiber discs too :-) And everyone knows that CF
is better.

"Thermal Conductivity of Carbon Fiber, and other Carbon
Based Materials"
http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html


"So...Is Carbon Fiber a good heat conductor?
As usual the answer is "it depends." The short answer is NO
not when regular carbon fiber is made up in regular epoxy and
expected to conduct heat across the thickness. IF a highly
carbonized pan fiber with graphite or diamond added, is
measured for heat transmission in the length of the fiber it
is very good and can rival and exceed copper."

On the other hand, they seem to work pretty well :-) See
https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual
indication of heat dissipation. :-)

Impressive. I'll assume it's a carbon-carbon rotor, since all F1
cars seem to using them.

Undoubtedly so. But if the advantage of "carbon" bikes can be
extolled that a carbon-carbon frame must have twice the bragging
rights :-)


http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/


(4 pages)
"A typical road car uses a cast iron brake disc with an organic
brake pad. In an F1 car, though, the same material is used for
both disc and pad, and this material is known as carbon-carbon -
a significantly different material to the carbon-fibre
composites used in the rest of the car" In other words, the F1
brakes are NOT made from CF.

Some detail on Formula 1 brakes:
https://www.youtube.com/watch?v=ev6XTdlKElw

Fun destroying brakes:
https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting
at 4:45 sure looks like CF but I'm not sure.

Maybe twin disk brakes would be easier?
http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg


https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg
https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg


https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg
https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg
https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268

Given the coefficient of friction between a 1.25" wide rubber tire
(32mm) and a wet road probably dragging the feet will work. :-)

Joerg's experience is with full suspension MTB's. These things are
incredibly heavy and long wheelbased. He has his judgement of disks
and it is no doubt quite accurate for his experience and riding.

I have disks on a much lighter and shorter wheelbased bike. I know
the failings up close and personal. I simply cannot imagine WHY a
person would want a more complicated system than that offered by the
Campy Skeleton brakes.


The reason can be summed up in one word: Rain :-)


But last Sunday I started out my "weekend" ride in the rain. It had
been raining nearly all night and the roads had a lot of water on them
- note we have been having floods here in Bangkok lately - but it
appeared that the rain was ending so off I went.

Unfortunately my weather forecasting facility wasn't working very well
and I rode 20 Km of a 30 Km ride in light rain and flooded roads in
many places. I was splashing through water in some places and cars
were splashing through (and splashing me) in others.

Of course, Sunday is much lighter traffic then on work days but still,
Bangkok is rated as one of the cities with the most chaotic traffic
in the world, and I did have to stop suddenly several time, on flooded
roads with wet wheels and brakes.

My brakes worked just as they do in the dry. Back brake stops me
somewhat slowly and front brake stops rather suddenly, both brakes
together provides best stopping. No long wait after grabbing a brake
lever although I did think of you with your stopping problems and I
have the feeling that the brake lever pressure might be a tiny bit
more to stop in the rain but if it was it was so little that it
couldn't be quantified.

But of course I am using quality brake pads. Why it costs me US$12.12
a wheel just for pads alone.... but they do last a year or more.



It seems Californian rain and Thai rain aren't the same. When it rains
heavily and I have to do a surprise emergency stop after not having used
the brakes for a while there is 1-2sec of nada, absolutely nothing. It
makes no difference whatsoever whether I use $17 high-falutin Koolstop
rain-rated pads or $4 Clarks pads. The experience of other riders around
here and in this NG is similar.

--
Regards, Joerg

http://www.analogconsultants.com/
  #33  
Old October 25th 17, 04:59 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,345
Default Why do some forks and frames have brake rotor size limits?

On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, John B. wrote:
On Tue, 24 Oct 2017 11:47:12 -0700, Joerg
wrote:

On 2017-10-24 07:27, wrote:
On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote:
On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 12:48:29 +0700, John B.
wrote:

On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 07:02:08 +0700, John B.
wrote:

But re disc brake cooling F1 car brakes appear to work with
the discs red hot. In the 1,000 degree (F) range. And they
use Carbon Fiber discs too :-) And everyone knows that CF
is better.

"Thermal Conductivity of Carbon Fiber, and other Carbon
Based Materials"
http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html


"So...Is Carbon Fiber a good heat conductor?
As usual the answer is "it depends." The short answer is NO
not when regular carbon fiber is made up in regular epoxy and
expected to conduct heat across the thickness. IF a highly
carbonized pan fiber with graphite or diamond added, is
measured for heat transmission in the length of the fiber it
is very good and can rival and exceed copper."

On the other hand, they seem to work pretty well :-) See
https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual
indication of heat dissipation. :-)

Impressive. I'll assume it's a carbon-carbon rotor, since all F1
cars seem to using them.

Undoubtedly so. But if the advantage of "carbon" bikes can be
extolled that a carbon-carbon frame must have twice the bragging
rights :-)


http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/


(4 pages)
"A typical road car uses a cast iron brake disc with an organic
brake pad. In an F1 car, though, the same material is used for
both disc and pad, and this material is known as carbon-carbon -
a significantly different material to the carbon-fibre
composites used in the rest of the car" In other words, the F1
brakes are NOT made from CF.

Some detail on Formula 1 brakes:
https://www.youtube.com/watch?v=ev6XTdlKElw

Fun destroying brakes:
https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting
at 4:45 sure looks like CF but I'm not sure.

Maybe twin disk brakes would be easier?
http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg


https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg
https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg


https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg
https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg
https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268

Given the coefficient of friction between a 1.25" wide rubber tire
(32mm) and a wet road probably dragging the feet will work. :-)

Joerg's experience is with full suspension MTB's. These things are
incredibly heavy and long wheelbased. He has his judgement of disks
and it is no doubt quite accurate for his experience and riding.

I have disks on a much lighter and shorter wheelbased bike. I know
the failings up close and personal. I simply cannot imagine WHY a
person would want a more complicated system than that offered by the
Campy Skeleton brakes.


The reason can be summed up in one word: Rain :-)


But last Sunday I started out my "weekend" ride in the rain. It had
been raining nearly all night and the roads had a lot of water on them
- note we have been having floods here in Bangkok lately - but it
appeared that the rain was ending so off I went.

Unfortunately my weather forecasting facility wasn't working very well
and I rode 20 Km of a 30 Km ride in light rain and flooded roads in
many places. I was splashing through water in some places and cars
were splashing through (and splashing me) in others.

Of course, Sunday is much lighter traffic then on work days but still,
Bangkok is rated as one of the cities with the most chaotic traffic
in the world, and I did have to stop suddenly several time, on flooded
roads with wet wheels and brakes.

My brakes worked just as they do in the dry. Back brake stops me
somewhat slowly and front brake stops rather suddenly, both brakes
together provides best stopping. No long wait after grabbing a brake
lever although I did think of you with your stopping problems and I
have the feeling that the brake lever pressure might be a tiny bit
more to stop in the rain but if it was it was so little that it
couldn't be quantified.

But of course I am using quality brake pads. Why it costs me US$12.12
a wheel just for pads alone.... but they do last a year or more.


This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it.

I see no reason whatsoever for disk brakes and their complications even on most MTB's since a good V-Brake is longer lasting, just as effective, cheaper and doesn't require special wheels and frame and fork changes.
  #34  
Old October 25th 17, 05:05 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,345
Default Why do some forks and frames have brake rotor size limits?

On Wednesday, October 25, 2017 at 7:53:09 AM UTC-7, Joerg wrote:
On 2017-10-24 17:21, John B. wrote:
On Tue, 24 Oct 2017 11:47:12 -0700, Joerg
wrote:

On 2017-10-24 07:27, wrote:
On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote:
On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 12:48:29 +0700, John B.
wrote:

On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 07:02:08 +0700, John B.
wrote:

But re disc brake cooling F1 car brakes appear to work with
the discs red hot. In the 1,000 degree (F) range. And they
use Carbon Fiber discs too :-) And everyone knows that CF
is better.

"Thermal Conductivity of Carbon Fiber, and other Carbon
Based Materials"
http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html


"So...Is Carbon Fiber a good heat conductor?
As usual the answer is "it depends." The short answer is NO
not when regular carbon fiber is made up in regular epoxy and
expected to conduct heat across the thickness. IF a highly
carbonized pan fiber with graphite or diamond added, is
measured for heat transmission in the length of the fiber it
is very good and can rival and exceed copper."

On the other hand, they seem to work pretty well :-) See
https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual
indication of heat dissipation. :-)

Impressive. I'll assume it's a carbon-carbon rotor, since all F1
cars seem to using them.

Undoubtedly so. But if the advantage of "carbon" bikes can be
extolled that a carbon-carbon frame must have twice the bragging
rights :-)


http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/


(4 pages)
"A typical road car uses a cast iron brake disc with an organic
brake pad. In an F1 car, though, the same material is used for
both disc and pad, and this material is known as carbon-carbon -
a significantly different material to the carbon-fibre
composites used in the rest of the car" In other words, the F1
brakes are NOT made from CF.

Some detail on Formula 1 brakes:
https://www.youtube.com/watch?v=ev6XTdlKElw

Fun destroying brakes:
https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting
at 4:45 sure looks like CF but I'm not sure.

Maybe twin disk brakes would be easier?
http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg


https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg
https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg


https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg
https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg
https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268

Given the coefficient of friction between a 1.25" wide rubber tire
(32mm) and a wet road probably dragging the feet will work. :-)

Joerg's experience is with full suspension MTB's. These things are
incredibly heavy and long wheelbased. He has his judgement of disks
and it is no doubt quite accurate for his experience and riding.

I have disks on a much lighter and shorter wheelbased bike. I know
the failings up close and personal. I simply cannot imagine WHY a
person would want a more complicated system than that offered by the
Campy Skeleton brakes.


The reason can be summed up in one word: Rain :-)


But last Sunday I started out my "weekend" ride in the rain. It had
been raining nearly all night and the roads had a lot of water on them
- note we have been having floods here in Bangkok lately - but it
appeared that the rain was ending so off I went.

Unfortunately my weather forecasting facility wasn't working very well
and I rode 20 Km of a 30 Km ride in light rain and flooded roads in
many places. I was splashing through water in some places and cars
were splashing through (and splashing me) in others.

Of course, Sunday is much lighter traffic then on work days but still,
Bangkok is rated as one of the cities with the most chaotic traffic
in the world, and I did have to stop suddenly several time, on flooded
roads with wet wheels and brakes.

My brakes worked just as they do in the dry. Back brake stops me
somewhat slowly and front brake stops rather suddenly, both brakes
together provides best stopping. No long wait after grabbing a brake
lever although I did think of you with your stopping problems and I
have the feeling that the brake lever pressure might be a tiny bit
more to stop in the rain but if it was it was so little that it
couldn't be quantified.

But of course I am using quality brake pads. Why it costs me US$12.12
a wheel just for pads alone.... but they do last a year or more.



It seems Californian rain and Thai rain aren't the same. When it rains
heavily and I have to do a surprise emergency stop after not having used
the brakes for a while there is 1-2sec of nada, absolutely nothing. It
makes no difference whatsoever whether I use $17 high-falutin Koolstop
rain-rated pads or $4 Clarks pads. The experience of other riders around
here and in this NG is similar.


And I find nothing of the sort. Riding through creeks and having to brake on the other side I do not find even a second's delay. And I ride in such a manner that any slight delay is accounted for.

Seeing your pictures of the staggering amount of weight that you have on your bike I can understand that you might have a longer delay but I think that a great deal of that is because of the weight you are stopping and not just the wet disks or rims.
  #35  
Old October 25th 17, 05:22 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default Why do some forks and frames have brake rotor size limits?

On Wed, 25 Oct 2017 06:58:57 +0700, John B.
wrote:

On Tue, 24 Oct 2017 10:15:53 -0700, Jeff Liebermann
wrote:

On Tue, 24 Oct 2017 16:19:42 +0700, John B.
wrote:

On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:
Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars
seem to using them.


Undoubtedly so. But if the advantage of "carbon" bikes can be extolled
that a carbon-carbon frame must have twice the bragging rights :-)


I don't think it would be a good idea to brag about having a bicycle
made from the same stuff that caused the Challenger space shuttle
disaster. The leading edges of the wings were made of carbon-carbon.
When the wings were hit by ice during takeoff, it punched some rather
large holes in the carbon-carbon.


?????????????
"Disintegration of the vehicle began after an O-ring seal in its right
solid rocket booster (SRB) failed at liftoff. The O-ring was not
designed to fly under unusually cold conditions as in this launch. Its
failure caused a breach in the SRB joint it sealed, allowing
pressurized burning gas from within the solid rocket motor to reach
the outside and impinge upon the adjacent SRB aft field joint
attachment hardware and external fuel tank. This led to the separation
of the right-hand SRB's aft field joint attachment and the structural
failure of the external tank. Aerodynamic forces broke up the
orbiter."


Sorry. Memory fault. I meant Columbia, which had the carbon-carbon
and ice impact problem:
https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster
"About 82 seconds after launch from Kennedy Space Center's
LC-39-A, a suitcase-sized piece of foam broke off from the
External Tank (ET), striking Columbia's left wing reinforced
carbon-carbon (RCC) panels. As demonstrated by ground
experiments conducted by the Columbia Accident Investigation
Board, this likely created a 6-to-10-inch (15 to 25 cm)
diameter hole, allowing hot gases to enter the wing when
Columbia later re-entered the atmosphere."

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #36  
Old October 25th 17, 05:24 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 6,016
Default Why do some forks and frames have brake rotor size limits?

On 2017-10-25 09:05, wrote:
On Wednesday, October 25, 2017 at 7:53:09 AM UTC-7, Joerg wrote:
On 2017-10-24 17:21, John B. wrote:
On Tue, 24 Oct 2017 11:47:12 -0700, Joerg
wrote:

On 2017-10-24 07:27,
wrote:
On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B.
wrote:
On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 12:48:29 +0700, John B.
wrote:

On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann
wrote:

On Mon, 23 Oct 2017 07:02:08 +0700, John B.
wrote:

But re disc brake cooling F1 car brakes appear to
work with the discs red hot. In the 1,000 degree
(F) range. And they use Carbon Fiber discs too :-)
And everyone knows that CF is better.

"Thermal Conductivity of Carbon Fiber, and other
Carbon Based Materials"
http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html




"So...Is Carbon Fiber a good heat conductor?
As usual the answer is "it depends." The short answer
is NO not when regular carbon fiber is made up in
regular epoxy and expected to conduct heat across the
thickness. IF a highly carbonized pan fiber with
graphite or diamond added, is measured for heat
transmission in the length of the fiber it is very
good and can rival and exceed copper."

On the other hand, they seem to work pretty well :-)
See
https://www.youtube.com/watch?v=h5JcHAEmIYM for a
visual indication of heat dissipation. :-)

Impressive. I'll assume it's a carbon-carbon rotor,
since all F1 cars seem to using them.

Undoubtedly so. But if the advantage of "carbon" bikes can
be extolled that a carbon-carbon frame must have twice the
bragging rights :-)


http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/




(4 pages)
"A typical road car uses a cast iron brake disc with an
organic brake pad. In an F1 car, though, the same
material is used for both disc and pad, and this material
is known as carbon-carbon - a significantly different
material to the carbon-fibre composites used in the rest
of the car" In other words, the F1 brakes are NOT made
from CF.

Some detail on Formula 1 brakes:
https://www.youtube.com/watch?v=ev6XTdlKElw

Fun destroying brakes:
https://www.youtube.com/watch?v=KslGsXMgmqg The brake
starting at 4:45 sure looks like CF but I'm not sure.

Maybe twin disk brakes would be easier?
http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg




https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg
https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg




https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg
https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg


https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268

Given the coefficient of friction between a 1.25" wide
rubber tire (32mm) and a wet road probably dragging the
feet will work. :-)

Joerg's experience is with full suspension MTB's. These
things are incredibly heavy and long wheelbased. He has his
judgement of disks and it is no doubt quite accurate for his
experience and riding.

I have disks on a much lighter and shorter wheelbased bike. I
know the failings up close and personal. I simply cannot
imagine WHY a person would want a more complicated system
than that offered by the Campy Skeleton brakes.


The reason can be summed up in one word: Rain :-)

But last Sunday I started out my "weekend" ride in the rain. It
had been raining nearly all night and the roads had a lot of
water on them - note we have been having floods here in Bangkok
lately - but it appeared that the rain was ending so off I went.

Unfortunately my weather forecasting facility wasn't working very
well and I rode 20 Km of a 30 Km ride in light rain and flooded
roads in many places. I was splashing through water in some
places and cars were splashing through (and splashing me) in
others.

Of course, Sunday is much lighter traffic then on work days but
still, Bangkok is rated as one of the cities with the most
chaotic traffic in the world, and I did have to stop suddenly
several time, on flooded roads with wet wheels and brakes.

My brakes worked just as they do in the dry. Back brake stops me
somewhat slowly and front brake stops rather suddenly, both
brakes together provides best stopping. No long wait after
grabbing a brake lever although I did think of you with your
stopping problems and I have the feeling that the brake lever
pressure might be a tiny bit more to stop in the rain but if it
was it was so little that it couldn't be quantified.

But of course I am using quality brake pads. Why it costs me
US$12.12 a wheel just for pads alone.... but they do last a year
or more.



It seems Californian rain and Thai rain aren't the same. When it
rains heavily and I have to do a surprise emergency stop after not
having used the brakes for a while there is 1-2sec of nada,
absolutely nothing. It makes no difference whatsoever whether I use
$17 high-falutin Koolstop rain-rated pads or $4 Clarks pads. The
experience of other riders around here and in this NG is similar.


And I find nothing of the sort. Riding through creeks and having to
brake on the other side I do not find even a second's delay. And I
ride in such a manner that any slight delay is accounted for.


Maybe the Sierra Foothills rain is diiferent from coastal rain :-)


Seeing your pictures of the staggering amount of weight that you have
on your bike I can understand that you might have a longer delay but
I think that a great deal of that is because of the weight you are
stopping and not just the wet disks or rims.


It isn't the weight, it is a delay with almost complete absence of
braking power, after which it usually comes on hard.

What is even worse with rim brakes is mud. The delay is more gradual
then but also 1-2sec. The nasty part appears afterwards when brake power
comes on and you hear that awful grinding noise yet, depending on the
situation, can't let go of a brake. You can literally hear the rim
material being eaten.

Disc brakes do not have any of those problems. Of course, they can have
other issues such as sudden fading.

--
Regards, Joerg

http://www.analogconsultants.com/
  #37  
Old October 25th 17, 05:37 PM posted to rec.bicycles.tech
Jeff Liebermann
external usenet poster
 
Posts: 4,018
Default Why do some forks and frames have brake rotor size limits?

On Tue, 24 Oct 2017 23:11:15 -0400, Frank Krygowski
wrote:

On 10/24/2017 8:13 PM, Jeff Liebermann wrote:
On Sun, 22 Oct 2017 09:06:07 -0700, Jeff Liebermann
wrote:

Have you considered adding a water mist brake cooling system instead?


Curses, it's not going to work. The problem is that a very fine water
mist sprayed at a red hot brake disk will vaporize (evaporate) the
tiny water droplets before they hit the red hot brake disk. That's
nice for evaporative cooling the air around the brakes, but does
nothing to cool the actual brake disk. To do that would require
larger droplets, a higher velocity droplet spray, or both. Dumping
liquid water on the brakes would also work, but that's like having
your own private rain storm, which was the original problem.

Grumble...


No problem. You pump it into the right end of a hollow axle, and provide
channels connecting that with the inner hollows in a double-sided disc
similar to an automotive disc, like this:
http://www.autopartsapi.com/eEuropar...169e817e2b.jpg

The water flows out radially, carrying heat with it but leaving the
braking surface dry.


Yep, that will work if we can figure out a way to get the water out of
the hollow axle, through a series of holes drilled into the axle,
without weakening the axle. Cooling channels would make the brake
disk rather thicker. Never mind spraying the bicycle and rider with
scalding hot water or steam while braking. Fenders for disk brakes?

I was hoping that it could be done without any major modifications to
the existing disk brake system. It might be possible to modify the
brake shoes to inject some cooling water. That would go directly onto
the hot brake disk, which is exactly where it's needed most. The
water would cause some slippage, but would evaporate instantly when
red hot. For lower temperatures, the water would simply be turned off
and not used. This might cause some "interesting" braking effects at
the transition point, but I think that can be managed with practice.

You keep forgetting that for Joerg, weight doesn't matter! ;-)


It should matter. Much of Joerg's ride is probably airborne, where
weight is important. Perhaps some fins or wings will make it feel
lighter.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #38  
Old October 26th 17, 06:22 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 10,538
Default Why do some forks and frames have brake rotor size limits?

On 10/25/2017 10:53 AM, Joerg wrote:
When it rains
heavily and I have to do a surprise emergency stop after not having used
the brakes for a while there is 1-2sec of nada, absolutely nothing. It
makes no difference whatsoever whether I use $17 high-falutin Koolstop
rain-rated pads or $4 Clarks pads. The experience of other riders around
here and in this NG is similar.


My experience: Koolstops are definitely better than cheaper pads.

Yes, in heavy rain, there's a bit of delay. It's never mattered to me,
probably because I don't seem to require surprise emergency stops. I'm
big on paying attention and anticipating problems. I always have been.

These post-retirement days, I don't do much riding in the rain. (Well, I
did yesterday, but that was unusual.) But I can't see ever buying a disc
brake bike.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

And ISTM that this is yet another example of "safety inflation." For
decades and decades, cyclists rode in all weather using caliper brakes.
They removed their hands from the brake levers to shift gears. They rode
at night using halogen or even vacuum headlight bulbs powered by
dynamos, and in daylight with no lights at all. They had shoes without
custom attachments to the pedals. They wore cloth caps, or no caps at
all. They rode wearing clothing with natural, non-blinding colors.

Now every one of those practices is portrayed by some as scandalously
risky. Sheesh!

--
- Frank Krygowski
  #39  
Old October 26th 17, 06:37 PM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default Why do some forks and frames have brake rotor size limits?

Joerg writes:

On 2017-10-24 17:21, John B. wrote:
On Tue, 24 Oct 2017 11:47:12 -0700, Joerg
wrote:


[ ... ]

The reason can be summed up in one word: Rain :-)


But last Sunday I started out my "weekend" ride in the rain. It had
been raining nearly all night and the roads had a lot of water on them
- note we have been having floods here in Bangkok lately - but it
appeared that the rain was ending so off I went.

Unfortunately my weather forecasting facility wasn't working very well
and I rode 20 Km of a 30 Km ride in light rain and flooded roads in
many places. I was splashing through water in some places and cars
were splashing through (and splashing me) in others.

Of course, Sunday is much lighter traffic then on work days but still,
Bangkok is rated as one of the cities with the most chaotic traffic
in the world, and I did have to stop suddenly several time, on flooded
roads with wet wheels and brakes.

My brakes worked just as they do in the dry. Back brake stops me
somewhat slowly and front brake stops rather suddenly, both brakes
together provides best stopping. No long wait after grabbing a brake
lever although I did think of you with your stopping problems and I
have the feeling that the brake lever pressure might be a tiny bit
more to stop in the rain but if it was it was so little that it
couldn't be quantified.

But of course I am using quality brake pads. Why it costs me US$12.12
a wheel just for pads alone.... but they do last a year or more.



It seems Californian rain and Thai rain aren't the same. When it rains
heavily and I have to do a surprise emergency stop after not having
used the brakes for a while there is 1-2sec of nada, absolutely
nothing. It makes no difference whatsoever whether I use $17
high-falutin Koolstop rain-rated pads or $4 Clarks pads. The
experience of other riders around here and in this NG is similar.


I don't understand the difference myself. When it's really raining,
meaning there's a continuous film of water on the road and a rooster
tail shooting forward off the front tire, I ride like a little old lady,
because of the delay in braking. Especially when it's dark, and leaves
and other blown down crap cover the road.

--
  #40  
Old October 26th 17, 06:38 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,345
Default Why do some forks and frames have brake rotor size limits?

On Tuesday, October 24, 2017 at 4:59:06 PM UTC-7, John B. wrote:
On Tue, 24 Oct 2017 10:15:53 -0700, Jeff Liebermann
wrote:

On Tue, 24 Oct 2017 16:19:42 +0700, John B.
wrote:

On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann
wrote:
Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars
seem to using them.


Undoubtedly so. But if the advantage of "carbon" bikes can be extolled
that a carbon-carbon frame must have twice the bragging rights :-)


I don't think it would be a good idea to brag about having a bicycle
made from the same stuff that caused the Challenger space shuttle
disaster. The leading edges of the wings were made of carbon-carbon.
When the wings were hit by ice during takeoff, it punched some rather
large holes in the carbon-carbon.


?????????????
"Disintegration of the vehicle began after an O-ring seal in its right
solid rocket booster (SRB) failed at liftoff. The O-ring was not
designed to fly under unusually cold conditions as in this launch. Its
failure caused a breach in the SRB joint it sealed, allowing
pressurized burning gas from within the solid rocket motor to reach
the outside and impinge upon the adjacent SRB aft field joint
attachment hardware and external fuel tank. This led to the separation
of the right-hand SRB's aft field joint attachment and the structural
failure of the external tank. Aerodynamic forces broke up the
orbiter."

Given the coefficient of friction between a 1.25" wide rubber tire
(32mm) and a wet road probably dragging the feet will work. :-)


Good point. Perhaps an anchor and rope thrown overboard might be more
suitable for stopping the bicycle on a wet road?


The initial reports I read said that ice formed on the leading edges of the wings and caused holes from the tearing away of these surfaces on take-off. Then upon re-entry the aerodynamic imbalance caused the breakup.
 




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