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-   -   Why do some forks and frames have brake rotor size limits? (http://www.cyclebanter.com/showthread.php?t=254966)

John B.[_3_] October 28th 17 01:53 AM

Why do some forks and frames have brake rotor size limits?
 
On Fri, 27 Oct 2017 12:43:07 -0400, Frank Krygowski
wrote:

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.


In a more sober basis, of course it does.
--
Cheers,

John B.


Frank Krygowski[_4_] October 28th 17 01:55 AM

Why do some forks and frames have brake rotor size limits?
 
On 10/27/2017 5:40 PM, wrote:
On Friday, October 27, 2017 at 9:39:06 AM UTC-7, Frank Krygowski wrote:
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!


Exactly how do you plan ahead for someone opening their door?


I don't ride in a door zone. Ever.

--
- Frank Krygowski

John B.[_3_] October 28th 17 01:59 AM

Why do some forks and frames have brake rotor size limits?
 
On Fri, 27 Oct 2017 10:42:48 -0700, Jeff Liebermann
wrote:

On Fri, 27 Oct 2017 15:53:31 +0700, John B.
wrote:

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.


https://en.wikipedia.org/wiki/Compression_release_engine_brake
Ugh, don't remind me. I was going to college at Cal Poly, Pomona and
living in a dormitory located at the base of Kellogg Hill. Going over
the top of the hill was the San Bernardino Freeway. The slope was
steep enough that trucks had to use secondary braking to slow down. At
any hour of the day, a series of small explosions would be heard as
the trucks descended down Kellogg Hill:
https://archive.is/20130127022926/http://jake-brakes.com/about-us/noise-concerns.php
https://www.youtube.com/watch?v=a8PDO6tbVtw (first few seconds as
he slows the truck down).


Riding in one of the crew busses at the mine I don't remember the jake
brake being excessively loud, and as the alternate on most of that
road was "straight down a thousand feet" probably wouldn't have minded
anyway.
--
Cheers,

John B.


Frank Krygowski[_4_] October 28th 17 02:04 AM

Why do some forks and frames have brake rotor size limits?
 
On 10/27/2017 8:42 PM, John B. wrote:
On Fri, 27 Oct 2017 08:06:33 -0700 (PDT), wrote:

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.


If the choice is to run into a car door or be run over by a car then I
think I'd get off and walk.


In practice, at least in my experience, the actual choice is between the
_risk_ of getting hit by an opening door, and the _risk_ of a motorist
deliberately running me over from behind.

In my experience, the latter risk is almost zero. Consider, we're almost
certainly talking about a place where there are witnesses, because the
situation requires people parking, getting out of their cars, opposing
traffic that would prevent the guy behind from changing lanes, etc.
There just aren't that many psychopaths who would risk prison terms by
deliberately running you over, especially because it would slow them down.

On the other hand, the person doing the dooring doesn't have to be a
psychopath. He just has to be inattentive. There are lots and lots of
those people.

Now, for corroboration: I have definitely had situations where a door
popped open, and I would have been doored if I had been riding within
reach. But while I've occasionally (but rarely) had motorists honk or
yell when I claim a lane, I've never had one run me over.

And let's remember that dooring can be fatal. If the door snags your
right handlebar, the bike whips to the right and you are instantaneously
thrown to the left, directly into the path of the cars you were so
worried about.

--
- Frank Krygowski

Ralph Barone[_4_] October 28th 17 02:13 AM

Why do some forks and frames have brake rotor size limits?
 
John B. wrote:
On Fri, 27 Oct 2017 09:32:04 -0700, Joerg
wrote:

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.


Care to explain the mechanical difference? I mean a rotating surface
and two friction pads that are tightened against it....
--
Cheers,

John B.


As far as I can tell, the differences between a rim brake and a 622 mm disk
a

1) The disk doesn't have to provide tire clearance, so the pads can sit
closer, facilitating higher mechanical advantage.

2) The disk is not connected to the rim, so it doesn't bend and warp when
you hit a pothole. Again, the pads can sit closer and have higher MA.

3) The disk doesn't thermally couple to the tire, so no blowouts on long
descents.

4) The disk is solid, so there's less flexing when you squeeze it with the
pads.


Ralph Barone[_4_] October 28th 17 02:20 AM

Why do some forks and frames have brake rotor size limits?
 
Ralph Barone wrote:
John B. wrote:
On Fri, 27 Oct 2017 09:32:04 -0700, Joerg
wrote:

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.


Care to explain the mechanical difference? I mean a rotating surface
and two friction pads that are tightened against it....
--
Cheers,

John B.


As far as I can tell, the differences between a rim brake and a 622 mm disk
a

1) The disk doesn't have to provide tire clearance, so the pads can sit
closer, facilitating higher mechanical advantage.

2) The disk is not connected to the rim, so it doesn't bend and warp when
you hit a pothole. Again, the pads can sit closer and have higher MA.

3) The disk doesn't thermally couple to the tire, so no blowouts on long
descents.

4) The disk is solid, so there's less flexing when you squeeze it with the
pads.



Oops. Missed one.

5) The pads on the disk brake can be harder (because they're riding on a
harder material) and we care less about disk wear than rim wear. This
reduces slop in the system, which again allows tighter tolerances, which
begets higher MA.

Now the funny thing is that a 622 mm disk might end up having less
effective wet braking than a smaller disk because the increased lever arm
of the disk on the wheel would mean that the MA of the drive system would
have to be reduced in order to prevent you doing an endo on every stop.
Because of the lower pad pressure, water would not be displaced from the
disk as quickly and wet braking would then suffer.


John B.[_3_] October 28th 17 02:39 AM

Why do some forks and frames have brake rotor size limits?
 
On Sat, 28 Oct 2017 01:13:54 +0000 (UTC), Ralph Barone
wrote:

John B. wrote:
On Fri, 27 Oct 2017 09:32:04 -0700, Joerg
wrote:

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.


Care to explain the mechanical difference? I mean a rotating surface
and two friction pads that are tightened against it....
--
Cheers,

John B.


As far as I can tell, the differences between a rim brake and a 622 mm disk
a

1) The disk doesn't have to provide tire clearance, so the pads can sit
closer, facilitating higher mechanical advantage.

I'm not sure that is correct. After all some old Greek guy was
supposed to have said, "Give me a lever and a place to stand and I
will move the earth". Nothing about being close.


2) The disk is not connected to the rim, so it doesn't bend and warp when
you hit a pothole. Again, the pads can sit closer and have higher MA.

3) The disk doesn't thermally couple to the tire, so no blowouts on long
descents.

4) The disk is solid, so there's less flexing when you squeeze it with the
pads.

--
Cheers,

John B.


John B.[_3_] October 28th 17 02:46 AM

Why do some forks and frames have brake rotor size limits?
 
On Sat, 28 Oct 2017 01:20:37 +0000 (UTC), Ralph Barone
wrote:

Ralph Barone wrote:
John B. wrote:
On Fri, 27 Oct 2017 09:32:04 -0700, Joerg
wrote:

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.

Care to explain the mechanical difference? I mean a rotating surface
and two friction pads that are tightened against it....
--
Cheers,

John B.


As far as I can tell, the differences between a rim brake and a 622 mm disk
a

1) The disk doesn't have to provide tire clearance, so the pads can sit
closer, facilitating higher mechanical advantage.

2) The disk is not connected to the rim, so it doesn't bend and warp when
you hit a pothole. Again, the pads can sit closer and have higher MA.

3) The disk doesn't thermally couple to the tire, so no blowouts on long
descents.

4) The disk is solid, so there's less flexing when you squeeze it with the
pads.



Oops. Missed one.

5) The pads on the disk brake can be harder (because they're riding on a
harder material) and we care less about disk wear than rim wear. This
reduces slop in the system, which again allows tighter tolerances, which
begets higher MA.


Ahem, but aluminum rims are a relatively recent innovation. Before
that rims were steel.


Now the funny thing is that a 622 mm disk might end up having less
effective wet braking than a smaller disk because the increased lever arm
of the disk on the wheel would mean that the MA of the drive system would
have to be reduced in order to prevent you doing an endo on every stop.
Because of the lower pad pressure, water would not be displaced from the
disk as quickly and wet braking would then suffer.


As I've written in the past. My utility bike with conventional Vee
brakes has sufficient braking force to lock the front wheel on either
wet or dry blacktop pavement. Can a disc brake provide more braking
force?
--
Cheers,

John B.


Joy Beeson October 28th 17 03:17 AM

Why do some forks and frames have brake rotor size limits?
 
On Fri, 27 Oct 2017 06:59:56 -0700, Joerg
wrote:

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


You don't have a garden hose?

Back when I could ride after the outside faucets had been turned off
for the winter, I used to hose salt and ice off my bike by filling my
water bottles with hot tap water, reserving the first squirt from each
bottle to get under the fenders. I don't think I ever had to make
more than two trips into the house for more water.

Come to think of it, I don't think I ever hosed it in the summer
(except when cleaning the braking surfaces, of course), because I rode
only on pavement. There was one mile of gravel road in an adjacent
county, but the grader wore out and it was cheaper to pave the road
than to buy a new grader.


--
Joy Beeson
joy beeson at comcast dot net
http://wlweather.net/PAGEJOY/

Ralph Barone[_4_] October 28th 17 04:54 AM

Why do some forks and frames have brake rotor size limits?
 
John B. wrote:
On Sat, 28 Oct 2017 01:20:37 +0000 (UTC), Ralph Barone
wrote:

Ralph Barone wrote:
John B. wrote:
On Fri, 27 Oct 2017 09:32:04 -0700, Joerg
wrote:

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.

Care to explain the mechanical difference? I mean a rotating surface
and two friction pads that are tightened against it....
--
Cheers,

John B.

As far as I can tell, the differences between a rim brake and a 622 mm disk
a

1) The disk doesn't have to provide tire clearance, so the pads can sit
closer, facilitating higher mechanical advantage.

2) The disk is not connected to the rim, so it doesn't bend and warp when
you hit a pothole. Again, the pads can sit closer and have higher MA.

3) The disk doesn't thermally couple to the tire, so no blowouts on long
descents.

4) The disk is solid, so there's less flexing when you squeeze it with the
pads.



Oops. Missed one.

5) The pads on the disk brake can be harder (because they're riding on a
harder material) and we care less about disk wear than rim wear. This
reduces slop in the system, which again allows tighter tolerances, which
begets higher MA.


Ahem, but aluminum rims are a relatively recent innovation. Before
that rims were steel.


True, but I also mentioned rim wear. Even back in the steel rim days, brake
pads were pretty soft, and until ceramic coated rims came out, there was
nothing nearing the hardness of disk brake pads.

Now the funny thing is that a 622 mm disk might end up having less
effective wet braking than a smaller disk because the increased lever arm
of the disk on the wheel would mean that the MA of the drive system would
have to be reduced in order to prevent you doing an endo on every stop.
Because of the lower pad pressure, water would not be displaced from the
disk as quickly and wet braking would then suffer.


As I've written in the past. My utility bike with conventional Vee
brakes has sufficient braking force to lock the front wheel on either
wet or dry blacktop pavement. Can a disc brake provide more braking
force?
--
Cheers,

John B.







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