Cycling & bikes - Why do some forks and frames have brake rotor size limits?

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

On Wed, 25 Oct 2017 09:22:49 -0700, Jeff Liebermann
wrote:

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."

Just like bicycles. Proof positive that steel is better :-)
--
Cheers,

John B.

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

On Thu, 26 Oct 2017 22:45:42 -0700, Jeff Liebermann
wrote:

On Fri, 27 Oct 2017 11:04:29 +0700, John B.
wrote:

Years ago I saw heavy logging trucks, operating in the mountains near
the Yuba river in California, with what appeared to be water cooled
drum brakes. The water seemed to be piped from a tank directly to the
brake drums with - I'm guessing here - about 1/2" nominal water pipe
sized pips and hoses. It was quite obvious when they turned the water
on and off.

I did some Googling and found that the water cooling system was mostly
found in Hayes HDX logging trucks:
http://www.hankstruckpictures.com/hank_rabe_pacific_story.htm
"This truck also was equipped with two Williams exhaust brakes,
Lear electric retarder on the driveshaft and a water tank for
spraying water on the brake drums to keep them cool. This was
a state of the art modern and huge truck in 1963."

That was about the era when I was "prospecting" up the Yuba river in
California.

There are some YouTube videos of the Hayes HDX but none show the water
cooled braking system in action. There are some comments indicating
that it sometimes belched steam. Also, the water cooling seems to be
for emergency use, not for regular stopping.
http://www.eng-tips.com/viewthread.cfm?qid=339285
"The water idea was for a one-time emergency use, not continuous.
How much do you think would be needed to save overheated brakes
and slow the rig to a safe speed or stop it?"
Same with the bicycle idea. When the brakes get hot enough to melt
the pads, it's time for some water cooling.

When I saw them they were hauling very large tree trunks to the mill
and seemed to be using the water cooling on the downhill portions of
the haul road.

I also saw long gouges in the rock walls on the side of the road
where, apparently, someone's brakes didn't work.

At the copper mine, in Irian Jaya, the trucks and busses that ran from
the base camp up to the tramway, that made the final jump up the mine,
were all equipped with "Jacobs Brakes" which used the engine
compression to reduce speed.
--
Cheers,

John B.

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

On 2017-10-27 01:11, John B. wrote:
On Wed, 25 Oct 2017 07:53:11 -0700, 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.

Which, to be honest, I find a little mystifying as I've had pretty
constant success with conventional brakes.

Frankly, I can't believe this is solely because I'm somehow so
uniquely skilled or that y'all are all in the awkward squad

I do see a number of people here and many who are not here who seem to
have ridden for years using conventional brakes without complaint and
some of the blogs I read don't even talk about brakes. Dave Moulton,
for example. An old fellow, used to race bikes, came to the U.S. in
about 1979 and built frames commercially for years, now retired, has
one entry in his blog about brakes - "centering side pull brakes".

Another blog from the long distance side of the bicycleing world, The
Blayleys, who are into Audex's and who apparently each ride in the
neighborhood of 10,000 miles annually, mentions Vee brakes in
reference to a Tandem while a photo of them on a tandem on their web
page shows disc brakes. On the other hand, when she discusses a "good
brevet bike she simply says that the "brakes must clear the fenders
and probably long reach caliper brakes will suffice".

In short, it seems that brakes just don't seem to be a hot subject in
much of the cycling fraternity.

To a large part that is because most cyclist will not ride in driving
rain. Some do and those know exactly how that delay with rim brakes
feels. Occasionally it is called "free fall" because that's how it feels
like.

I might comment that I've ridden coaster brakes, drum brakes, rod pull
brakes, cantilever brakes, side pull single pivot caliper brakes,
double pivot caliper, Vee brakes and for one short ride a cable disc
brake. and at the time I rode them I found all the brakes to give
acceptable service. Well with one exception, rim brakes and chrome
plated steel rims were sometimes a bit iffy :-)

Yes, those were the worst. It got a little better with aluminum rims but
not a lot. In the world of automotive such a brake "system" would not
stand the slightest change of being legal.

Finally after many decades the bicycle industry woke up and adopted what
the automotive guys had all along, disc brakes. Why should I accept an
inferior brake system on a new bike when there is a much better one?

--
Regards, Joerg

http://www.analogconsultants.com/

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

On 2017-10-26 17:16, John B. wrote:
On Thu, 26 Oct 2017 17:08:10 -0400, Radey Shouman
wrote:

jbeattie writes:

On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote:
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:

[ ... ]

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.

If you ride a lot in the rain and use a rim brake, you might go
through a front rim every 1-2 years -- at least based on the
experience of one of my commuter cohorts who just switched to discs.

And the slowly dying rims generate some really messy black sludge, at
least in my experience. I'm not sure why the "wax your chain to stay
clean" cohort hasn't noticed.

It is probably heresy to mention it, but some people wash their bikes,
particularly after riding in the rain. Amazing how easily all that
black sludge washes off with soap and water :-)

Oh yeah, now we have to wash out bikes after each rain ride. Standing
out there in the rain with sponge and shampoo. Great.

--
Regards, Joerg

http://www.analogconsultants.com/

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

On Friday, October 27, 2017 at 6:59:47 AM UTC-7, Joerg wrote:
On 2017-10-26 17:16, John B. wrote:
On Thu, 26 Oct 2017 17:08:10 -0400, Radey Shouman
wrote:

jbeattie writes:

On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote:
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:

[ ... ]

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.

If you ride a lot in the rain and use a rim brake, you might go
through a front rim every 1-2 years -- at least based on the
experience of one of my commuter cohorts who just switched to discs.

And the slowly dying rims generate some really messy black sludge, at
least in my experience. I'm not sure why the "wax your chain to stay
clean" cohort hasn't noticed.

It is probably heresy to mention it, but some people wash their bikes,
particularly after riding in the rain. Amazing how easily all that
black sludge washes off with soap and water :-)

Oh yeah, now we have to wash out bikes after each rain ride. Standing
out there in the rain with sponge and shampoo. Great.

The process can be pretty quick. Stand or lay the bike on the lawn and hose it off carefully. You don't even have to put it on a washstand. Do I do this? Rarely, but I was riding with my neighbor who does, and it takes him about three minutes. I even did it last weekend as kind of a bonding experience. He handed me the hose, so I gave the bike a rinse. The bike was also pretty clean before we left on our rain ride. If it were my commuter, a rinse would have just re-arranged the mud.

OT, I was riding my son's 29er up Emigration Canyon a while back and encountered a mud flow and sprayed crap all up the back of the seat tube. We didn't bother rinsing that off, and when I came to visit the next time, it was still there, hardened like cement. It was some sort of clay or adobe. Some mud is super-tough and should be rinsed off immediately.

-- Jay Beattie.

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

On 2017-10-26 20:01, Jeff Liebermann wrote:
On Thu, 26 Oct 2017 13:40:21 -0400, Radey Shouman
wrote:

Surely the first step is just internal air passages in the brake disks,
as used in motor vehicles for years and years. Any other coolant is a
big step up in difficulty. Unfortunately that would be a major
modification.

Air is a lousy way to move heat.
https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html
Air 0.024 W/mK
Aluminum 205 W/mK
Cast iron 58 W/mK
Water 0.58 W/mK (ignores enthalpy from vaporization)

If the brake disk were red hot, it would take quite a bit of air blown
at the disk to cool it down. Water would drop the temperature far
quicker. I'm not certain, but my guess(tm) is that the holes in the
automobile brake disk were to reduce weight, not for air cooling.

Air does work if it's a lot of it:

https://www.youtube.com/watch?v=Ff-DHCWf-_8

Rather than transplant an automotive brake disk onto a bicycle, it
might be easier be a bit creative.

Automotive is, as usual, decades ahead in technology. Here is the
oil-cooled disc brake:

https://www.youtube.com/watch?v=dvCYBUOtKrk

... I could build a sandwich of two
disks, with copper or aluminum pipes in between. Getting water into
the pipe(s) will be a problem, but I have some ideas. As the brake
disk spins, hot water is ejected. One disk is larger diameter than
the other. The break shoes hit only the large diameter disk. The
small disk is just there to increase the surface area and support the
pipe(s). The axle length and dropout spacing will need to be tweaked
to accommodate the increased diameter.

Or, if you want something cheaper, make the brake disk hollow and out
of two solid disks. Essentially a can. Drill some tiny holes around
the circumference. Fill the can with water before every downhill run.
The spray of hot water will keep the disk cool.

Or, if you want something crude, and inverted water bottle dripping
water onto the brake disk.

A hose is all you really need. My MTB water bottle folder is on the
handlebar (fame has no space for it) so that would be easy.

... Aim the drip just ahead of the calipers so
that the disk will need to rotate a bit less than 360 degrees before
getting to the calipers. The water should have evaporated before it
can "lubricate" the brakes. Unfortunately, if you drip water on a
cold brake disk, it's likely to get the brake pads wet, which will
probably result in a regrettable incident. Maybe this isn't such a
great idea.

Ok, maybe a direct contact method. Clamp a wire brush onto the seat
stay and press the brush against the brake disk. Pump water through
the brush and onto the brake disk as needed. Hopefully, the red hot
brake disk will not melt the wire brush bristles. That should get the
water to where it's needed without worrying about it evaporating
before it makes contact.

Hmmmm... this tea tastes funny.

Or ... just get bigger rotors. That is what I am going to do.

--
Regards, Joerg

http://www.analogconsultants.com/

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

On Thursday, October 26, 2017 at 6:19:48 PM UTC-7, Tim McNamara wrote:
On Thu, 26 Oct 2017 13:22:07 -0400, Frank Krygowski
wrote:

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!

Careful, Frank! Someone will confuse you with a conservative.

Although these days even the "new conservatives" are no longer
conservative. They're just mad that their lives suck, looking for some
payback and usually blaming the wrong people. Principled actual
conservatives are sadly becoming rara aves.

A liberal is a conservative who wants everyone every to act in such a manner so as to sooth his own conscious. He wants laws passed to force everyone else to pay for charitable causes but in such a way that he himself need not.

I'm sure you read Frank's response to a woman buying a pound and a half of hamburger for $15. "I'd tell her to shop at a different store." The soft heart of liberalism.

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

Frank Krygowski writes:

On 10/26/2017 5:08 PM, Radey Shouman wrote:
jbeattie writes:

On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote:
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:

[ ... ]

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.

If you ride a lot in the rain and use a rim brake, you might go
through a front rim every 1-2 years -- at least based on the
experience of one of my commuter cohorts who just switched to discs.

And the slowly dying rims generate some really messy black sludge, at
least in my experience. I'm not sure why the "wax your chain to stay
clean" cohort hasn't noticed.

Oh, I've noticed! Somehow, I've never mustered the motivation to wax
my rims to prevent it. ;-)

Sounds like disk brakes ought to do the trick. If I ever buy a new bike
I'll seriously consider them.

--