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

On Friday, October 27, 2017 at 1:24:49 AM UTC-7, John B. wrote:
On Thu, 26 Oct 2017 13:37:00 -0400, Radey Shouman
wrote:

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.

I suspect that may be the secret. I've never been "doored", perhaps
because if I have to ride past a line of parked cars where a door
might be opened I either slow down or ride further enough away that a
door wouldn't hit me.

Here the bike lane can be so narrow that the car door on a two-door totally covers the lane and there's no place to dodge because passing cars will spot that and not let you out.

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

John B. writes:

On Thu, 26 Oct 2017 16:50:42 -0700, Joerg
wrote:

On 2017-10-26 10:43, wrote:
On Thursday, October 26, 2017 at 10:37:02 AM UTC-7, Radey Shouman wrote:
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.


Sometimes one has to reach a destination on schedule and slowing down to
little old lady speed isn't always in the cards. That's why I prefer my
MTB on rainy days. It is slightly slower than the road bike but the
brakes are unfazed by rain. They are noisy in the rain though.


You remind me of a young Indonesian chap I had working for me. We were
driving over some country roads in North Sumatra to get to the Medan
airport to meet "the boss" and he was driving like a crazy man. "Slow
Down!", I said. He replied that we had to drive fast or we'd be late
in picking up the Manager and I said, "but, if we crash we'll never
get there"...

Exactly.

--

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

On Friday, October 27, 2017 at 1:37:19 AM UTC-7, John B. wrote:
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 :-)

They are saying that FOAM broke a hole in the wing? What sort of foam was it - titanium?

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

Jeff Liebermann writes:

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 is a great way to move heat, the supply is free, the flow rate is
much higher than the practical water flow rate. I'm thinking of the
vents that run parallel to the braking surface, so the disk acts as a
centrifugal air pump while the wheel is turning. I thought that most
cars used these for the front brakes nowadays.

Ventilation does add to both thickness and weight.

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

--

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

On 10/27/2017 10:10 AM, wrote:
On Friday, October 27, 2017 at 1:37:19 AM UTC-7, John B. wrote:
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 :-)

They are saying that FOAM broke a hole in the wing? What sort of foam was it - titanium?


Alien invasion with their killer reflector weapons:

http://www.yellowjersey.org/photosfr...t/trekaggr.jpg

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

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

On 10/27/2017 9:58 AM, Joerg wrote:

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?

sigh There are advantages and disadvantages to this equipment choice,
just as with other equipment choices. The disadvantages of discs have
been discussed. If they don't matter or apply to you, fine; but they
matter to others.

But I'll note that you're currently in a project to increase your disc's
diameter from something like 160mm or 180mm up to 200mm or more. You
seem to feel bigger diameter is better.

Well, even "better," why not go up to roughly 622mm? That's what lots
of us prefer, with cable actuation.

--
- Frank Krygowski

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

On 2017-10-27 07:11, jbeattie wrote:
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:

[...]

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.


Same here, my road bike is never particularly clean because of unpaved
road sections. Rinsing would just smear the dirt around.

I can't understand the fuss of many riders about their bikes. Almost
before every ride they have to pump up, Saturdays they spend cleaning
their various machines. I just like to ... ride. Thanks to thick tubes I
don't have to pump before a ride, I can just stash my water bottles and
food, replenish the bike wallet for a brewsky on the way home and go.
When I get home I park my bike in the garage, take the empty bottles and
walk into the house. Why should a bicycle require more pre- and
post-ride effort than a car?


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.


Dirt on an MTB is a badge of honor. So far I've never cleaned my MTB
because it'll be dirty again 10 miles later.

http://www.analogconsultants.com/ng/bike/Muddy3.JPG

After a free bike wash due to rain:

http://www.analogconsultants.com/ng/bike/Muddy3.JPG

The remainder is caked in so hard that the soft side of a green-yellow
kitchen sponge won't get it off. The scrub pad of it might but then the
paint job is going to be scuffed and it'll collect dirt like a magnet.

Urban dwellers can buy spray-on dirt so their ride looks more manly. No
kidding.

https://www.theguardian.com/science/2005/jun/14/uknews

--
Regards, Joerg

http://www.analogconsultants.com/

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

On 2017-10-27 09:25, Frank Krygowski wrote:
On 10/27/2017 9:58 AM, Joerg wrote:

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?

sigh There are advantages and disadvantages to this equipment choice,
just as with other equipment choices. The disadvantages of discs have
been discussed. If they don't matter or apply to you, fine; but they
matter to others.


Many others just don't know any better. I have witnessed several people
riding a bike with hydraulic disc brakes for the first time and the
reaction was usually "WHOA!". Same with me, it almost sent me over the bar.


But I'll note that you're currently in a project to increase your disc's
diameter from something like 160mm or 180mm up to 200mm or more. You
seem to feel bigger diameter is better.


Because bigger is better here.


Well, even "better," why not go up to roughly 622mm? That's what lots
of us prefer, with cable actuation.


The disadvantages have been discussed ad nauseam. A rim brake is not a
disc brake. Not even close.

--
Regards, Joerg

http://www.analogconsultants.com/

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

On 10/27/2017 11:06 AM, wrote:
On Friday, October 27, 2017 at 1:24:49 AM UTC-7, John B. wrote:
I've never been "doored", perhaps
because if I have to ride past a line of parked cars where a door
might be opened I either slow down or ride further enough away that a
door wouldn't hit me.

Here the bike lane can be so narrow that the car door on a two-door totally covers the lane and there's no place to dodge because passing cars will spot that and not let you out.

In my experience, the trick is to plan ahead. If I've got to move left
to avoid parked cars, etc. I tend to do it earlier rather than later.

And it may be different in other places, I suppose. (Over the years,
we've heard lots of "But the drivers HERE are really mean!") But the
shopping trip I make almost daily by bike has me leaving the store on a
street that's wide enough to share for about one block; then it gets
narrow. I stay to the right for the first part, but move left for the
narrow part. It sometimes involves looking over my shoulder at the next
motorist and signaling left to sort of negotiate; but I can't recall a
time when I wasn't allowed to merge left.

Sometimes I have to be a bit pushy. Riding in downtown Pittsburgh a few
weeks ago I came to an oddball intersection. (Pittsburgh has many.) I
had to turn right then immediately move into a left turn lane at a
traffic light.

A woman driving an SUV from the opposite direction wanted to turn left
into the same space I was using, and she tried to intimidate me into
staying at the curb. I just looked at her and kept my path, and she
stayed back.

Of course, when the light finally turned green and our ways parted, she
blared her horn. Because, you know, it was SO frustrating to have to sit
behind a bicycle, instead of being ten feet further ahead at the traffic
light!

--
- Frank Krygowski

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

On 10/27/2017 4:34 AM, John B. wrote:
On Wed, 25 Oct 2017 08:59:46 -0700 (PDT), wrote:

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.

Well, "cause I want 'em" is, I guess, a valid reason.

But not necessarily proof of superiority :-)

"I want 'em" is the ultimate decision point for lots and lots of
consumer goods.

Of course, people learn to "want them" after consuming tons of
advertising bull****.

I guess it keeps our economy going.

--
- Frank Krygowski