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



 
 
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  #211  
Old October 30th 17, 05:51 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 2017-10-30 08:39, wrote:
On Monday, October 30, 2017 at 7:42:51 AM UTC-7, Joerg wrote:
On 2017-10-29 18:02, John B. wrote:
On Sun, 29 Oct 2017 07:59:34 -0700, Joerg
wrote:

On 2017-10-28 17:18, John B. wrote:
On Sat, 28 Oct 2017 08:09:28 -0700, Joerg
wrote:

On 2017-10-27 17:11, John B. wrote:
On Fri, 27 Oct 2017 06:58:27 -0700, Joerg
wrote:

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.

Well, the Blayleys state that the husband, John, has
ridden 10 - 17 thousand miles a year for the past 25
years and the wife, Pamela, has ridden from 10 - 14
thousand miles a year for the past 20 years, or another
way to put it might be that together they have ridden
from 20 - 30 thousand miles a year for the past 20
years.

Somehow I suspect that they may have encountered rain in
that period.


And grandpa has driven his cars without safety belts yet
survived ...


Well, since you mentioned it. My two grandfathers, neither of
whom ever had a road accident. One died at 92 and the other
at 87. My father never had a road accident although he did
get a speeding ticket once, died at 87. My mother had one
"accident", a guy ran a red light and tee-boned her car, no
speeding tickets, died at 86. All deaths were considered
"natural".

Do you really believe that safety belts would have benefited
them?


Counting on luck alone is not smart. The father of a friend's
wife died from the consequences of a minor fender bender at an
intersection because he didn't wear a belt. That accident was
100% survivable. Or would have been ...

So one of your friends died in a traffic accident and four of my
ancestors never had an accident at all. Thus safety belts are a
good idea?


Yes, they are. Ask any ER doctor who is old enough to remember the
days before safety belts and before motorcycle helmets. The folks
who do or did emergency surgery on traffic accident victims. My
wife used to work there so we know.


Before motorcycle safety helmets people would present in ER's with
lots of serious looking head wounds that would turn out to be mostly
superficial and the occasional skull fracture. Now they usually
present at the morgue with over-confidence caused fatal concussion
without skull fractures.

The number of motorcycle deaths before and after "safety" helmets has
not changed.

There were little to no head injuries on racing motorcycles simply
because they weren't generally involved in high speed collisions.

There doesn't seem to be any concern about the false claim that
helmets save lives. Instead helmets save minor head wounds in minor
accidents.


I worked in med-tech for a long time and so far all docs are of opposite
opinion.

Yes, some benefits of helmets will be offset by increase sisk taking.
Also, there were no Kawasaki Ninjas and such before the helmet law.

--
Regards, Joerg

http://www.analogconsultants.com/
Ads
  #212  
Old October 30th 17, 08:35 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 Monday, October 30, 2017 at 9:39:55 AM UTC-7, Joerg wrote:
On 2017-10-29 12:57, wrote:
On Sunday, October 29, 2017 at 10:02:12 AM UTC-7, Joerg wrote:
On 2017-10-29 09:45,
wrote:
On Saturday, October 28, 2017 at 8:09:18 AM UTC-7, Joerg wrote:

And grandpa has driven his cars without safety belts yet survived
...

For people who do not shy away from unpaved roads or use a lot of
singletrack and ride in the rain there is a much more extreme
issue: Wet mud.

There is NO brake the is proof against wet mud. In fact it is perhaps
worse on a disk since the additional pressure of the pads can turn
the silicon present in most muds into cutting instruments that on rim
brakes cuts into the rubber show rather than the hard and thin disk
pad.


Actually, no. I've had mud literally dripping from the calipers which
had become barely recognizable brownish blobs. The only thing that
happens is that they make an awful grinding noise just like muddy rim
brakes do. With the two major differences that they still come on full
force immediately and that this grinding does not eat up aluminum.
Aluminum as one of the braking surfaces plain does not make any sense,
certainly not in a muddy environment.

A downside of bicycle disc brakes is that in contrast to most motor
vehicles the rotors have "vent holes" and weight weenie spiders. This
results in rather fast heat-up and in "brake mousse" when you plow
through thick vegetation on an overgrown trail. Mashed star-thistle and
other weeds get shredded and a sort of pulp develops which cakes up in
the holes of the rotor. It doesn't diminish the brake force but lets of
a bad stench. One of the reasons why I carry a Swiss Army knife in a
pocket. Not in a pannier, so I can whip it out in seconds. This also
helps in poking out the giant mud clump that forms behind the BB and can
prevent the rear wheel from turning.


Joerg - that additional noise is wear.


Sure. However, the rotors last thousands of miles, cost around $20 and
take only minutes to change. The pads cost $2/pair for ceramic-based
material (like motorcycles have) and last around 1000mi depending on
turf and weather. That is way more hassle than with a motor vehicle but
way less hassle than swapping out a shot rim.

I started riding again in fall 2013, using an older model MTB with
almost zero miles on it. By the end of 2013 it had around 1000mi on it
and the front rim looks horrible.

The problem in our area is this: Mud contains granules of decomposed
granite. Rubber pads need water diverter grooves and the granules lodge
in these grooves. They also pierce the rubber itself and lodge in there.
When pulling the lever that lets of a horrid grinding noise. Coming down
a hill you have to keep the brake engaged and you can literally hear the
rim being tortured all the way to the bottom of the hill. On flat
surfaces you have to stop and pry out the granules. On a rainy day that
means stopping every few miles. I stand by my opinion that rim brakes
are inadequate for any serious MTB riding.


Well, perhaps it was from older parts but I saw a significant number of MTB riders walking their bikes back off of hills. Those were the older cable pull brakes so that might have been when they were still developing the proper compounds.

https://www.youtube.com/watch?v=Wdb7KEc7xJI

This is comparing an 11 speed Ghost with an aluminum el-cheapo Raleigh. This was a highly unfair test to begin with: On the climbing test the Raleigh had an eight speed compact that simply didn't have the correct gearing. And the bicycle size and set-up was entirely wrong.

On the braking test it was hydraulic disks against what appeared to the the old-fashioned long throw brakes. There was so much bend in the brakes that you could bottom out the lever.

On the TT again the problem was that there simply wasn't the proper gearing.. And since the Raleigh wasn't sized correctly it was nearly impossible to get into an aero position.

Personally in the brake test I believe my Skeleton brakes would have finished not exactly with the disks but really close. There is no flex to speak of in my brakes and while I think I could lock the front wheel and allow the rear wheel to rise off of the ground there is absolutely no day I would do such a thing.

My bikes are set up similar seating position to the Raleigh. But I could merely change the stem to gain a position such as the Ghost. I personally don't give much credit to the aerodynamics of a frame.
  #214  
Old October 30th 17, 08:44 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 Monday, October 30, 2017 at 9:51:06 AM UTC-7, Joerg wrote:

I worked in med-tech for a long time and so far all docs are of opposite
opinion.

Yes, some benefits of helmets will be offset by increase sisk taking.
Also, there were no Kawasaki Ninjas and such before the helmet law.


I know and that is why it is dangerous to listen to doctors.

http://www.vehicularcyclist.com/kunich.html

There is no change since 2002 because the only way of improving a helmet is via increasing the size. And helmets are already of bothersome size to people.

Remember that I was the safety director of the American Federation of Motorcyclists after I gave up racing. I was also a professional mechanic with the American Motorcycle Association.

So when I speak about helmets it is from a position of study as well as painful experience.
  #215  
Old October 30th 17, 08:50 PM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 5,870
Default Why do some forks and frames have brake rotor size limits?

On Saturday, October 28, 2017 at 8:13:26 PM UTC-7, Frank Krygowski wrote:
On 10/28/2017 9:11 PM, John B. wrote:
On Sat, 28 Oct 2017 16:59:47 -0700 (PDT), jbeattie
wrote:

On Saturday, October 28, 2017 at 3:40:36 PM UTC-7, AMuzi wrote:
On 10/28/2017 4:27 PM, jbeattie wrote:
On Saturday, October 28, 2017 at 12:08:44 PM UTC-7, Sir Ridesalot wrote:
On Saturday, October 28, 2017 at 11:09:18 AM UTC-4, Joerg wrote:
On 2017-10-27 17:11, John B. wrote:
On Fri, 27 Oct 2017 06:58:27 -0700, Joerg
wrote:

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.

Well, the Blayleys state that the husband, John, has ridden 10 - 17
thousand miles a year for the past 25 years and the wife, Pamela, has
ridden from 10 - 14 thousand miles a year for the past 20 years, or
another way to put it might be that together they have ridden from 20
- 30 thousand miles a year for the past 20 years.

Somehow I suspect that they may have encountered rain in that period.


And grandpa has driven his cars without safety belts yet survived ....

For people who do not shy away from unpaved roads or use a lot of
singletrack and ride in the rain there is a much more extreme issue: Wet
mud. You may have never encountered it but I have many times. You reach
in and, after a second or two of nothing, the rim brakes come on but let
off an awful grinding noise. You can literally hear the rim being
tortured but because of a rapidly approaching curve you can't let go. As
I have mentioned before the rims on my old MTB are only 1000mi old but
the front rim is almost shot from all that. Deep grooves.

I stand by my opinion that rim brakes are fair weather brakes. Then they
are fine but not when the going gets tough. Like this kind of weather:

https://www.youtube.com/watch?v=mX_EKybzK4Y


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?

Well, when I worked on airplanes I remember that the F-4 had multi
plate disc brakes which provided a tremendous amount of stopping power
in a very small package.


Some tandems have that as well, and of course motorcycles: Two discs up
front. But not stacks of discs.


One supposes that will be next big improvement in bicycle brakes. Or
perhaps a drag chute for those long downhill's to keep the rims from
melting?


I've thought about it :-)

--
Regards, Joerg

http://www.analogconsultants.com/

Oh ****! I've ridden many hundreds of miles off road in dry and wet sand, mud, heavy rain, rutted roads/trails and did so on an MTB with cantilever brakes and NEVER had trouble stopping either when I needed to or when I wanted too. I've ridden on ice and in 4 inches+ deep snowand also never had trouble stopping.

Perhaps you ride too fast for the conditions/sight lines or you don't keep your brakes adjusted properly.

Really? I have trouble standing up on ice. There is a point at which you don't want super-strong brakes.

-- Jay Beattie.


Yeah me too.
Snow is one thing - I'm used to that- but ice is quite
another. Depending on the recent weather, a frozen slick
patch of ice under snow will dump me right on my ass. We
mere humans would have some trouble with Jobst's famous tour
down a frozen Swiss river.

I live at a whopping 400 feet (about) elevation. The garage in my building is probably 0 feet. That minor elevation change sometimes means the difference between ice and no ice -- so I walk outside in the morning and say f*** this! And then I jump in the car and half-way to work, creeping along in traffic, there is no ice -- and then I regret not riding. So, in order to avoid that regret, I have done some pretty stupid sh** spinning around on ice or hoofing it in my SPDs to get out of my neighborhood and then being freaked out riding over the slick bridges and viaducts into town. I met up with another guy on a bike who was fish-tailing down the road on one of those mornings, and we looked at each other and shook our heads -- "we're a couple of idiots." So, now I'm working on not feeling regret or guilt if I drive. And don't get me going about the dopes who jump into their Malibus with no-season/no-tread tires and crash on the ice and/or snow. I'll slap on the snow tires in
November. I really miss studs, but I'm doing penance with studless.

-- Jay Beattie.


Are studded auto tires legal? I seem to remember that back in the
1960's when I was in Maine that it was illegal to drive studded tires
on bare roads. It was a long time ago and memory is always
questionable but I'm sure that I remember people getting a ticket for
using studded tires under certain conditions.


I don't know if they're legal in Oregon now (Jay can tell us) but I've
driven out there in the summer and experienced the weirdness of a
freeway with two troughs worn in it by thousands of studded tires.

Our cars track (i.e. left to right wheel span) didn't quite match the
trough widths, and our car had a disturbing tendency to "hunt" back and
forth as I drove.


Studs are still legal. https://www.tripcheck.com/Pages/Chain-Law#

-- Jay Beattie.
  #216  
Old October 30th 17, 09:17 PM posted to rec.bicycles.tech
Doug Landau
external usenet poster
 
Posts: 1,424
Default Why do some forks and frames have brake rotor size limits?

On Monday, October 30, 2017 at 9:39:55 AM UTC-7, Joerg wrote:
On 2017-10-29 12:57, wrote:
On Sunday, October 29, 2017 at 10:02:12 AM UTC-7, Joerg wrote:
On 2017-10-29 09:45,
wrote:
On Saturday, October 28, 2017 at 8:09:18 AM UTC-7, Joerg wrote:

And grandpa has driven his cars without safety belts yet survived
...

For people who do not shy away from unpaved roads or use a lot of
singletrack and ride in the rain there is a much more extreme
issue: Wet mud.

There is NO brake the is proof against wet mud. In fact it is perhaps
worse on a disk since the additional pressure of the pads can turn
the silicon present in most muds into cutting instruments that on rim
brakes cuts into the rubber show rather than the hard and thin disk
pad.


Actually, no. I've had mud literally dripping from the calipers which
had become barely recognizable brownish blobs. The only thing that
happens is that they make an awful grinding noise just like muddy rim
brakes do. With the two major differences that they still come on full
force immediately and that this grinding does not eat up aluminum.
Aluminum as one of the braking surfaces plain does not make any sense,
certainly not in a muddy environment.

A downside of bicycle disc brakes is that in contrast to most motor
vehicles the rotors have "vent holes" and weight weenie spiders. This
results in rather fast heat-up and in "brake mousse" when you plow
through thick vegetation on an overgrown trail. Mashed star-thistle and
other weeds get shredded and a sort of pulp develops which cakes up in
the holes of the rotor. It doesn't diminish the brake force but lets of
a bad stench. One of the reasons why I carry a Swiss Army knife in a
pocket. Not in a pannier, so I can whip it out in seconds. This also
helps in poking out the giant mud clump that forms behind the BB and can
prevent the rear wheel from turning.


Joerg - that additional noise is wear.


Sure. However, the rotors last thousands of miles, cost around $20 and
take only minutes to change. The pads cost $2/pair for ceramic-based
material (like motorcycles have) and last around 1000mi depending on
turf and weather. That is way more hassle than with a motor vehicle but
way less hassle than swapping out a shot rim.

I started riding again in fall 2013, using an older model MTB with
almost zero miles on it. By the end of 2013 it had around 1000mi on it
and the front rim looks horrible.

The problem in our area is this: Mud contains granules of decomposed
granite. Rubber pads need water diverter grooves and the granules lodge
in these grooves. They also pierce the rubber itself and lodge in there.
When pulling the lever that lets of a horrid grinding noise. Coming down
a hill you have to keep the brake engaged and you can literally hear the
rim being tortured all the way to the bottom of the hill. On flat
surfaces you have to stop and pry out the granules. On a rainy day that
means stopping every few miles. I stand by my opinion that rim brakes
are inadequate for any serious MTB riding.


That is the reason to use Kool-stop Salmons. The compound will not let granules lodge.

  #217  
Old October 30th 17, 09:20 PM posted to rec.bicycles.tech
Doug Landau
external usenet poster
 
Posts: 1,424
Default Why do some forks and frames have brake rotor size limits?


Well, it certainly doesn't help to be wearing all black in the evening without lights. That was so popular for several years that it's almost unbelievable.


A friend in Oregon had a nasty crash with injuries when he rear-ended a black cow with no taillights standing in the middle of the road
  #218  
Old October 30th 17, 09:38 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 2017-10-30 12:38, wrote:
On Monday, October 30, 2017 at 9:48:34 AM UTC-7, Joerg wrote:
On 2017-10-30 08:33,
wrote:

Joerg, heroics can also be described as riding a really heavy
bike such as yours at any pace above mild.


That's not heroic because it doesn't come with additional risk.
Over time you just build up a lot of leg muscle. This also helps
for rides with the road bike like yesterday. I rode along a canal
bike path purely for exercise. It's otherwise a boring ride but ...
no speed limit ... woohoo! The path sometimes tunnels underneath
roads and such but for some obstacles it runs above, steep
sections. With enough leg muscle you don't have to shift, just
leave it in high gear, put on the coals so you reach 25mph or more
at the bottom, keep the torque on until it crests and then let it
coast back down. I didn't shift at all until I reached the Cosumnes
River where I had my snack break. Four years ago I couldn't have
done that.


I have to differ with you there. Climbing is only half of it.
Descending is the other half and a heavy bike under any conditions is
a dangerous downhill bike if you do not know the trail intimately.


It's a canal bike trail, long straight shot, very wide. Almost like a
midwest freeway. You could go 50mph and be totally safe.

https://cdn-assets.alltrails.com/upl...31324781d8.jpg

The only real danger there is falling asleep and veering off the side.
Probably happens, sometimes a soft curve like this comes and you see
screech marks:

https://cloudfront.traillink.com/pho...l_27481_lb.jpg

At 29:15min you can see a small hump, the ones on the sides are a bit
higher:

https://www.youtube.com/watch?v=A-3gnLIUum0

--
Regards, Joerg

http://www.analogconsultants.com/
  #219  
Old October 30th 17, 09:48 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 2017-10-30 12:44, wrote:
On Monday, October 30, 2017 at 9:51:06 AM UTC-7, Joerg wrote:

I worked in med-tech for a long time and so far all docs are of
opposite opinion.

Yes, some benefits of helmets will be offset by increase sisk
taking. Also, there were no Kawasaki Ninjas and such before the
helmet law.


I know and that is why it is dangerous to listen to doctors.

http://www.vehicularcyclist.com/kunich.html


With all due respect, quote

"... that no area receives more than a single blow. While it is plain
why this is done, it most assuredly does not mimic the real world where
a person falling off a bicycle may have his head bounce down the road
several times before stopping ..."

doesn't apply to many serious accidents. Most that I know of were one
big smack into something hard. A tree, a rock, a car. You might roll off
and hit something else or the pavement but not at full brunt anymore.
Others have had such crashes where they came away alright but the
styrofoam inside the helmet had clearly absorbed a lot of the impact
energy and was crushed. That's when the helmet must be replaced.

This is why you find styrofoam in or behind the bumber of many cars.


There is no change since 2002 because the only way of improving a
helmet is via increasing the size. And helmets are already of
bothersome size to people.

Remember that I was the safety director of the American Federation of
Motorcyclists after I gave up racing. I was also a professional
mechanic with the American Motorcycle Association.

So when I speak about helmets it is from a position of study as well
as painful experience.


Ok, everybody has their opinion. The docs I spoke to were very much
convinced of the benefits of helmets. Some accidents remained the same
in terms of force despite advances in motorcycle engines. For example in
cities where traffic is slow it doesn't matter much whether you ride a
Ninja or a 250. That's one area where they saw a noticable drop in the
severity of head injuries.

--
Regards, Joerg

http://www.analogconsultants.com/
  #220  
Old October 30th 17, 09:54 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 2017-10-30 12:35, wrote:
On Monday, October 30, 2017 at 9:39:55 AM UTC-7, Joerg wrote:
On 2017-10-29 12:57,
wrote:
On Sunday, October 29, 2017 at 10:02:12 AM UTC-7, Joerg wrote:
On 2017-10-29 09:45,
wrote:
On Saturday, October 28, 2017 at 8:09:18 AM UTC-7, Joerg
wrote:

And grandpa has driven his cars without safety belts yet
survived ...

For people who do not shy away from unpaved roads or use a
lot of singletrack and ride in the rain there is a much
more extreme issue: Wet mud.

There is NO brake the is proof against wet mud. In fact it is
perhaps worse on a disk since the additional pressure of the
pads can turn the silicon present in most muds into cutting
instruments that on rim brakes cuts into the rubber show
rather than the hard and thin disk pad.


Actually, no. I've had mud literally dripping from the calipers
which had become barely recognizable brownish blobs. The only
thing that happens is that they make an awful grinding noise
just like muddy rim brakes do. With the two major differences
that they still come on full force immediately and that this
grinding does not eat up aluminum. Aluminum as one of the
braking surfaces plain does not make any sense, certainly not
in a muddy environment.

A downside of bicycle disc brakes is that in contrast to most
motor vehicles the rotors have "vent holes" and weight weenie
spiders. This results in rather fast heat-up and in "brake
mousse" when you plow through thick vegetation on an overgrown
trail. Mashed star-thistle and other weeds get shredded and a
sort of pulp develops which cakes up in the holes of the rotor.
It doesn't diminish the brake force but lets of a bad stench.
One of the reasons why I carry a Swiss Army knife in a pocket.
Not in a pannier, so I can whip it out in seconds. This also
helps in poking out the giant mud clump that forms behind the
BB and can prevent the rear wheel from turning.

Joerg - that additional noise is wear.


Sure. However, the rotors last thousands of miles, cost around $20
and take only minutes to change. The pads cost $2/pair for
ceramic-based material (like motorcycles have) and last around
1000mi depending on turf and weather. That is way more hassle than
with a motor vehicle but way less hassle than swapping out a shot
rim.

I started riding again in fall 2013, using an older model MTB with
almost zero miles on it. By the end of 2013 it had around 1000mi on
it and the front rim looks horrible.

The problem in our area is this: Mud contains granules of
decomposed granite. Rubber pads need water diverter grooves and the
granules lodge in these grooves. They also pierce the rubber itself
and lodge in there. When pulling the lever that lets of a horrid
grinding noise. Coming down a hill you have to keep the brake
engaged and you can literally hear the rim being tortured all the
way to the bottom of the hill. On flat surfaces you have to stop
and pry out the granules. On a rainy day that means stopping every
few miles. I stand by my opinion that rim brakes are inadequate for
any serious MTB riding.


Well, perhaps it was from older parts but I saw a significant number
of MTB riders walking their bikes back off of hills. Those were the
older cable pull brakes so that might have been when they were still
developing the proper compounds.

https://www.youtube.com/watch?v=Wdb7KEc7xJI


Wow, 2x the stopping distance for the rim brakes. I wouldn't have
imagined it could be that much worse.


This is comparing an 11 speed Ghost with an aluminum el-cheapo
Raleigh. This was a highly unfair test to begin with: On the climbing
test the Raleigh had an eight speed compact that simply didn't have
the correct gearing. And the bicycle size and set-up was entirely
wrong.

On the braking test it was hydraulic disks against what appeared to
the the old-fashioned long throw brakes. There was so much bend in
the brakes that you could bottom out the lever.


I don't think he bottomed out the levers.


On the TT again the problem was that there simply wasn't the proper
gearing. And since the Raleigh wasn't sized correctly it was nearly
impossible to get into an aero position.

Personally in the brake test I believe my Skeleton brakes would have
finished not exactly with the disks but really close. There is no
flex to speak of in my brakes and while I think I could lock the
front wheel and allow the rear wheel to rise off of the ground there
is absolutely no day I would do such a thing.

My bikes are set up similar seating position to the Raleigh. But I
could merely change the stem to gain a position such as the Ghost. I
personally don't give much credit to the aerodynamics of a frame.


Gearing and such are a different matter but brakes are safety-relevant.
I wouldn't want to compromise there.

--
Regards, Joerg

http://www.analogconsultants.com/
 




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