Which Brakes? Avid Mechanical Disc? Magura Big or Marta HydraulicDisc?



A

Alan Braggins

Guest
In article <4lA*[email protected]>, David Damerell wrote:
>heat capacity. But the question asked was about brake fade - and, given
>that disc pads aren't made of anything magic, if anything they'll suffer
>_that_ first because they get hotter faster.


They might not be magic, but nor are they they same material as
rim brake pads, so they could still resist fade better.
 
P

Peter Clinch

Guest
David Damerell wrote:

> Well, no. There's a dodge going on here where the real advantage of not
> needing as much maintenance is twisted into better performance (because
> the performance is better when unmaintained). That's double accounting; if
> you're going to argue based on the unmaintained performance, you can't
> argue that they need less maintenance.


Two things:

1) maintenance is an improved feature

2) performance, via better control through more sensitivity, is an
improved feature.

It's in the books as two things because it's two things. The
maintenance angle is better, and the performance is better, quite
independently. But if you don't do all the maintenance on a mech cable
then the hydraulic performs much, much better, rather than merely a
(tangibly) bit better.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/
 
A

Alan Braggins

Guest
In article <[email protected]>, Artemisia wrote:
>Alan Braggins wrote:
>
>> Piled there with a digger on a beach for the express purpose of irritating
>> pedants who said it was impossible? Whether you could brake a bike down
>> such a slope no matter how precise your control is another question.
>> Maybe the OP measures slopes the other direction, with 0 being vertical
>> and 90 being flat.

>
>_This_ OP never spoke of degrees, just of steepness.


I meant original to the subthread about 60 degree slopes, not the
Which Brakes? question that started the main thread. Sorry.
 
D

Dave Larrington

Guest
In news:[email protected],
Ben C <[email protected]> tweaked the Babbage-Engine to tell us:

> I'm starting to wonder why disk overheating isn't a big problem with
> the lower heat capacity and probably lower dissipation rate to the
> air. Perhaps the operating temperature range of a disk is higher as I
> suggested earlier. I pulled this figure of 100C out of the air as
> "high" for a rim brake, but perhaps they don't really get that hot. A
> disk on the other hand can probably afford to get a bit hotter than
> that-- the fluid won't boil until perhaps 170C.


A bit of googling suggests that the boiling point of DOT5.1 brake fluid is
about 260 deg. C. The mineral oils used in Magura systems, and LHM used by
the parsimonious instead of the Magura stuff, seems to be in the same
region.

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Hoc ardur vincere docet.
 
R

Roger Merriman

Guest
David Damerell <[email protected]d.org.uk> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>V-brakes (alone) on a tandem have the difficulty that they will blow off
> >>tyres, so they are not without issue.

> >if they are not with out issue they why are tamdems being sold with
> >them? and very pricey ones at that?

>
> You will find those are not intended for anything like loaded touring
> or additionally have a drum or disc [1] brake intended for use as a
> drag brake. For example, a racing tandem doesn't have these issues.
>

maybe so but seems plenty about. which seems a odd saving when the
tamdem can be the price of a new car.

but yes from what you've said (and others) and just plain comman sence.
ie how well would those tamdems cope with two large men let alone their
gear...warm i guess at best.

i can see that Santana have spent a lot of time and effort into tamdem
brakes. consdering the possible weight, that still looks quite under
powered when you consider the weights.

> >>If you can't lift the rear wheel, adjust your brakes properly. Note that a
> >>downhill gradient makes this easier, not harder.

> >yes if don't shift my weight back, but shifting ones weight back, can be
> >very effective.

>
> Wrong again. Regardless of shifting weight, a downhill gradient makes it
> easier to lift the rear wheel.
>

if you don't shift your weight about yes, the greatest possiblity for a
endo is the emergency stop on the flat as you will be luckly to beable
to shift your weight fully, in the time it takes to stop.

decending a hill even a hill over 30% at least on a mountain bike you
can get a lot of weight over the rear, if fact going the other way i can
un weigh the rear enought to start to scrabble on the tarmack. i do
though acknowedge that one growing up in a steep sided gorge i'm used to
shifting one's weight around for hills, and that a mountain bike is
easyer to do that than on road bike.

> [1] optimistically.


roger
--
www.rogermerriman.com
 
R

Roger Merriman

Guest
David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>No, there hasn't. With a well adjusted cable rim brake you can lift the
> >>rear wheel (or skid the front on a poor surface). How can a hydraulic disc
> >>offer more braking than that? It can't.

> >one at lower speeds it offers more control ie your not just janking on
> >the lever.

>
> If you're just "yanking on the lever" with a well-adjusted cable rim
> brake, that's your poor technique.
>

no it is easyer to make a controlled emergency stop if the lever
requires less force.

> >2nd at higher speeds you will have a job to lock the wheel, unless you
> >delbertly unweight a wheel etc.

>
> This one won't wash with anyone who has made emergency stops downhill on
> road. We might not brake as much, but the speeds are higher.


if your locking managing to lock the wheels at high speeds in the dry
etc then you either have tires with not enought grip or are not
countering with your weight. which a hill would help with.

i use my old mounatin bike on road, with road tires yes they have lot
more of footprint on the road, and i'm used to shifting weight. only the
other week i had to do a emergency stop down hill, no i didn't lock the
tires, i came close there was bit of slewing but not attaul locking.

roger
--
www.rogermerriman.com
 
B

Ben C

Guest
On 2007-09-06, Dave Larrington <[email protected]> wrote:
> In news:[email protected],
> Ben C <[email protected]> tweaked the Babbage-Engine to tell us:
>
>> I'm starting to wonder why disk overheating isn't a big problem with
>> the lower heat capacity and probably lower dissipation rate to the
>> air. Perhaps the operating temperature range of a disk is higher as I
>> suggested earlier. I pulled this figure of 100C out of the air as
>> "high" for a rim brake, but perhaps they don't really get that hot. A
>> disk on the other hand can probably afford to get a bit hotter than
>> that-- the fluid won't boil until perhaps 170C.

>
> A bit of googling suggests that the boiling point of DOT5.1 brake fluid is
> about 260 deg. C. The mineral oils used in Magura systems, and LHM used by
> the parsimonious instead of the Magura stuff, seems to be in the same
> region.


Yes, although I also got that "perhaps 170C" from a bit of googling. The
page I found made a distinction between "wet" and "dry" boiling points,
"wet" being what you get when your brake fluid has absorbed 3% of water.

Here it is: http://www.afcoracing.com/tech_pages/fluid.shtml

I went for the "wet" boiling point of DOT 4 since I heard somewhere else
that bicycle brake fluid boils much more easily than the car stuff
(although it strips the paint less).

Brake fluid should never boil in a car unless it's very old. You should
be able to get the pads practically on fire before the fluid boils. But
I have heard tell of fluid boiling occurring with MTB disks, implying to
me that the stuff people are putting in boils at a rather lower temp
than DOT4 or DOT5.1.

Dry for DOT5.1 is 288 deg C according to them.

Anyway you can get special paint for testing this. You get three or four
colour-coded paints with different, known melting points. You dab a
series of spots on the disk somewhere they won't get in the way, take
your favourite MTB route down Mont Blanc, and see which spots have
melted.
 
D

Dave Larrington

Guest
In news:[email protected],
Ben C <[email protected]> tweaked the Babbage-Engine to tell us:

> Yes, although I also got that "perhaps 170C" from a bit of googling.
> The page I found made a distinction between "wet" and "dry" boiling
> points, "wet" being what you get when your brake fluid has absorbed
> 3% of water.
>
> Here it is: http://www.afcoracing.com/tech_pages/fluid.shtml
>
> I went for the "wet" boiling point of DOT 4 since I heard somewhere
> else that bicycle brake fluid boils much more easily than the car
> stuff (although it strips the paint less).
>
> Brake fluid should never boil in a car unless it's very old. You
> should be able to get the pads practically on fire before the fluid
> boils. But I have heard tell of fluid boiling occurring with MTB
> disks, implying to me that the stuff people are putting in boils at a
> rather lower temp than DOT4 or DOT5.1.
>
> Dry for DOT5.1 is 288 deg C according to them.



I use DOT 5.1 from Halfrauds in all my hydraulic discs and can't recall any
problems which might have been caused by boiling fluid. This is 99.9%
on-road, admittedly, but even try to keep a recumbent down to a sane speed
on a steep wet twisty downhill in the middle of the night using only the
rear brake[1] it's been OK.

1 - the front one decided to lose interest after a minor off - no sign of a
fluid leak and rebleeding seems to have restored normal functionality.
Colour me baffled.

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Apparently Guy has now got a Brompton. I'd never have guessed.
 
B

Ben C

Guest
On 2007-09-06, Dave Larrington <[email protected]> wrote:
> In news:[email protected],
> Ben C <[email protected]> tweaked the Babbage-Engine to tell us:
>
>> Yes, although I also got that "perhaps 170C" from a bit of googling.
>> The page I found made a distinction between "wet" and "dry" boiling
>> points, "wet" being what you get when your brake fluid has absorbed
>> 3% of water.
>>
>> Here it is: http://www.afcoracing.com/tech_pages/fluid.shtml
>>
>> I went for the "wet" boiling point of DOT 4 since I heard somewhere
>> else that bicycle brake fluid boils much more easily than the car
>> stuff (although it strips the paint less).
>>
>> Brake fluid should never boil in a car unless it's very old. You
>> should be able to get the pads practically on fire before the fluid
>> boils. But I have heard tell of fluid boiling occurring with MTB
>> disks, implying to me that the stuff people are putting in boils at a
>> rather lower temp than DOT4 or DOT5.1.
>>
>> Dry for DOT5.1 is 288 deg C according to them.

>
>
> I use DOT 5.1 from Halfrauds in all my hydraulic discs and can't recall any
> problems which might have been caused by boiling fluid. This is 99.9%
> on-road, admittedly, but even try to keep a recumbent down to a sane speed
> on a steep wet twisty downhill in the middle of the night using only the
> rear brake[1] it's been OK.


Yes I think you'd have a hard time boiling DOT 5.1 in anything, which is
as it should be. Boiling brake fluid is not something you file under
"acceptable".

> 1 - the front one decided to lose interest after a minor off - no sign of a
> fluid leak and rebleeding seems to have restored normal functionality.
> Colour me baffled.


Perhaps it got a gulp of air into the lines when it was upside down.
 
D

David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>You will find those are not intended for anything like loaded touring
>>or additionally have a drum or disc [1] brake intended for use as a
>>drag brake. For example, a racing tandem doesn't have these issues.

>maybe so but seems plenty about. which seems a odd saving when the
>tamdem can be the price of a new car.


It's also a large weight saving. The Arai brake, which is the only really
effective solution for long descents, weighs a ton because it's a giant
heatsink.

>i can see that Santana have spent a lot of time and effort into tamdem
>brakes. consdering the possible weight, that still looks quite under
>powered when you consider the weights.


But your perceptions of brake "power" are worthless because every decent
design of brake has exactly the same stopping power on a solo.

>>Wrong again. Regardless of shifting weight, a downhill gradient makes it
>>easier to lift the rear wheel.

>if you don't shift your weight about yes,


What I say remains accurate. It's elementary mechanics.
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D

David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>If you're just "yanking on the lever" with a well-adjusted cable rim
>>brake, that's your poor technique.

>no it is easyer to make a controlled emergency stop if the lever
>requires less force.


This is not necessarily true. If the brake could be put completely on with
the touch of a feather, it would be impossible to make a controlled
emergency stop; if the brake required your absolute maximum hand strength
to put on, it would also be impossible. Therefore it is nonsense to say
that less (or more) force always makes it easier.

Somewhere between those two points is a spot or region where it is
easiest, but to say that that's a spot not a region and that that spot
happens to be the amount of force required by the brakes you have _and_
that that will be true for any user is pure guesswork.

>>>2nd at higher speeds you will have a job to lock the wheel, unless you
>>>delbertly unweight a wheel etc.

>>This one won't wash with anyone who has made emergency stops downhill on
>>road. We might not brake as much, but the speeds are higher.

>if your locking managing to lock the wheels at high speeds in the dry
>etc then you either have tires with not enought grip or are not
>countering with your weight. which a hill would help with.


Did I say I'd locked the wheels? No.

But - more than once - descending at speed, with heavy panniers (so with
the overall centre of gravity already lower and to the rear) - I've
had to brake so hard it's finished with the thump of the rear wheel
regaining contact with the road.

Bog ordinary cantilevers. You don't need hydraulic discs to make a
controller emergency stop at high speeds.
--
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D

David Damerell

Guest
Quoting Peter Clinch <[email protected]>:
>David Damerell wrote:
>>Well, no. There's a dodge going on here where the real advantage of not
>>needing as much maintenance is twisted into better performance (because
>>the performance is better when unmaintained). That's double accounting; if
>>you're going to argue based on the unmaintained performance, you can't
>>argue that they need less maintenance.

>Two things:
>1) maintenance is an improved feature
>2) performance, via better control through more sensitivity, is an
>improved feature.


But that's a dodge. What you were talking about was performance via not
degrading as badly when unmaintained, and that's double accounting with
"less maintenance".

Performance via better control through more sensitivity is something
that's basically been made up here. It's the usual confusion - "this
_feels_ better so it must _be_ better" (combined with "this feels better
_to me_ so it must be better _for everyone_").

As I've just written in another article - too much sensitivity won't work,
too much force won't work. Somewhere between there's a sweet spot or
region; when you say you know that's a spot and it happens to be where
your brake setup is - for every user, no less - you're just speculating.
--
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R

Roger Merriman

Guest
David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>If you're just "yanking on the lever" with a well-adjusted cable rim
> >>brake, that's your poor technique.

> >no it is easyer to make a controlled emergency stop if the lever
> >requires less force.

>
> This is not necessarily true. If the brake could be put completely on with
> the touch of a feather, it would be impossible to make a controlled
> emergency stop; if the brake required your absolute maximum hand strength
> to put on, it would also be impossible. Therefore it is nonsense to say
> that less (or more) force always makes it easier.
>
> Somewhere between those two points is a spot or region where it is
> easiest, but to say that that's a spot not a region and that that spot
> happens to be the amount of force required by the brakes you have _and_
> that that will be true for any user is pure guesswork.
>

yes still needs to be some resistance, or it would be too easy to be a
system that was on/off

> >>>2nd at higher speeds you will have a job to lock the wheel, unless you
> >>>delbertly unweight a wheel etc.
> >>This one won't wash with anyone who has made emergency stops downhill on
> >>road. We might not brake as much, but the speeds are higher.

> >if your locking managing to lock the wheels at high speeds in the dry
> >etc then you either have tires with not enought grip or are not
> >countering with your weight. which a hill would help with.

>
> Did I say I'd locked the wheels? No.


look back at your post not the snippage here, you pritty much did if not
in actualality.
>
> But - more than once - descending at speed, with heavy panniers (so with
> the overall centre of gravity already lower and to the rear) - I've
> had to brake so hard it's finished with the thump of the rear wheel
> regaining contact with the road.


yes, but it's very unlikely the paniers are close to your weight, you
can make a much more impact moving your body, assuming the bike allows
it, that is.
>
> Bog ordinary cantilevers. You don't need hydraulic discs to make a
> controller emergency stop at high speeds.


no you don't but all things being equal they should make a better job of
it. it's a over used line but power is nothing with out control.

look do you really think that it's a big con and that brakes haven't
improved over the years? motor vehicals have been useing disks and
hydraulic at that for years, that some companies put some that where
simply not up for the job says more about those companies than what
hydraulic disks can and can't do.

roger
--
www.rogermerriman.com
 
R

Roger Merriman

Guest
David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>You will find those are not intended for anything like loaded touring
> >>or additionally have a drum or disc [1] brake intended for use as a
> >>drag brake. For example, a racing tandem doesn't have these issues.

> >maybe so but seems plenty about. which seems a odd saving when the
> >tamdem can be the price of a new car.

>
> It's also a large weight saving. The Arai brake, which is the only really
> effective solution for long descents, weighs a ton because it's a giant
> heatsink.
>

consdering that the weight of a tamdem can be fairly impressive ie in
the folks, thus two big men + gear and thats a whole lot of trouble.

> >i can see that Santana have spent a lot of time and effort into tamdem
> >brakes. consdering the possible weight, that still looks quite under
> >powered when you consider the weights.

>
> But your perceptions of brake "power" are worthless because every decent
> design of brake has exactly the same stopping power on a solo.
>

maybe in paper, but taking my old cant bike away from the rolling downs
and to the beacons shows that while it's brakes can cope with the soft
lumps of the south east. proper hills it lacks the power, compared with
a newer bike with disks.


> >>Wrong again. Regardless of shifting weight, a downhill gradient makes it
> >>easier to lift the rear wheel.

> >if you don't shift your weight about yes,

>
> What I say remains accurate. It's elementary mechanics.


within a very tight artifial peramitors yes. if you shift your postion
and weight the rear is quite useable. even down very steep gradient's

roger
--
www.rogermerriman.com
 
D

David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>But your perceptions of brake "power" are worthless because every decent
>>design of brake has exactly the same stopping power on a solo.

>maybe in paper,


And in elementary mechanics.

>but taking my old cant bike away from the rolling downs
>and to the beacons shows that while it's brakes can cope with the soft
>lumps of the south east. proper hills it lacks the power, compared with
>a newer bike with disks.


Which is still rubbish because an increasing downhill gradient _reduces_
the maximum deceleration.

>>>>Wrong again. Regardless of shifting weight, a downhill gradient makes it
>>>>easier to lift the rear wheel.
>>>if you don't shift your weight about yes,

>>What I say remains accurate. It's elementary mechanics.

>within a very tight artifial peramitors yes. if you shift your postion
>and weight the rear is quite useable. even down very steep gradient's


Which is also still rubbish as anyone can determine with heavy panniers.
30kg in panniers shifts the centre of gravity more than you can by moving
your bottom; and with 30kg in panniers you can still lift the rear wheel
under braking; and a downhill gradient still reduces the maximum
deceleration before that happens.

You're just clinging to purely psychosomatic ideas of brake power. It
won't wash; and particularly it won't wash with anyone familiar with
tandem applications, where you actually _can_ produce differences in brake
power.
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D

David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Somewhere between those two points is a spot or region where it is
>>easiest, but to say that that's a spot not a region and that that spot
>>happens to be the amount of force required by the brakes you have _and_
>>that that will be true for any user is pure guesswork.

>yes still needs to be some resistance, or it would be too easy to be a
>system that was on/off


Reducing your guesswork to what it is.

>>>if your locking managing to lock the wheels at high speeds in the dry
>>>etc then you either have tires with not enought grip or are not
>>>countering with your weight. which a hill would help with.

>>id I say I'd locked the wheels? No.

>look back at your post not the snippage here, you pritty much did if not
>in actualality.


Let's see a quote from you that shows it, then. Hint; you can't.

>>But - more than once - descending at speed, with heavy panniers (so with
>>the overall centre of gravity already lower and to the rear) - I've
>>had to brake so hard it's finished with the thump of the rear wheel
>>regaining contact with the road.

>yes, but it's very unlikely the paniers are close to your weight, you
>can make a much more impact moving your body,


That's also not true. The panniers don't weigh what a body does, true -
but you can easily have 20 or 30kg there - and they are also much further
from the centre of gravity of a normal bike/rider system than a moved
bottom is, so they affect the CoG proportionately more. It's definitely in
the same ballpark.

>>Bog ordinary cantilevers. You don't need hydraulic discs to make a
>>controller emergency stop at high speeds.

>no you don't but all things being equal they should make a better job of
>it.


You can't make a better job of stopping than stopping with the rear wheel
on the edge of lifting.

>look do you really think that it's a big con and that brakes haven't
>improved over the years?


I certainly think it's partly marketing, but I think the advantages of
discs aren't what you think they are. "Power" is a red herring on solos,
and tandems have not found discs exceptionally powerful.

We've had real advantages of hydraulic disc systems listed. Immunity to
wet muddy conditions; low maintenance (especially no rim wear). And, of
course, if a rider has very weak hands they will get a real benefit from
the reduced application force. But "power"? Not a chance.

>motor vehicals have been useing disks and hydraulic at that for years,


So what? Are you going to put a five-speed gearbox on your bike next?
Just because it fits motorised applications doesn't mean it fits bikes.
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R

Roger Merriman

Guest
David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>But your perceptions of brake "power" are worthless because every decent
> >>design of brake has exactly the same stopping power on a solo.

> >maybe in paper,

>
> And in elementary mechanics.


i'm sure it terms of heat they are much of a muchness. and yes if you
don't move at point X the bike will endo.
>
> >but taking my old cant bike away from the rolling downs
> >and to the beacons shows that while it's brakes can cope with the soft
> >lumps of the south east. proper hills it lacks the power, compared with
> >a newer bike with disks.

>
> Which is still rubbish because an increasing downhill gradient _reduces_
> the maximum deceleration.
>

yes if i sit on the saddle and just jank the brake, but most will learn
to get out of the saddle and use that weight.

> >>>>Wrong again. Regardless of shifting weight, a downhill gradient makes it
> >>>>easier to lift the rear wheel.
> >>>if you don't shift your weight about yes,
> >>What I say remains accurate. It's elementary mechanics.

> >within a very tight artifial peramitors yes. if you shift your postion
> >and weight the rear is quite useable. even down very steep gradient's

>
> Which is also still rubbish as anyone can determine with heavy panniers.
> 30kg in panniers shifts the centre of gravity more than you can by moving
> your bottom; and with 30kg in panniers you can still lift the rear wheel
> under braking; and a downhill gradient still reduces the maximum
> deceleration before that happens.


yes of coarse a hill will increase a heavly laden bikes endo point, but
you weigh a lot more than 30KG and on some bikes you can move that
weight around a lot, not just a minor shift, that is one reason Mountain
bikes don't allways have the sadle up high so that weight can be
shifted. you can get suprisingly low and far back, the limit is the
sadle and the rear tire.
>
> You're just clinging to purely psychosomatic ideas of brake power. It
> won't wash; and particularly it won't wash with anyone familiar with
> tandem applications, where you actually _can_ produce differences in brake
> power.


try taking a bike up and down steep hills good 30% shift your weight
around by that i don't mean your bottom as you put it, but bodly get
right back as far as you can go and as far forward. you may be suprised.

roger
--
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R

Roger Merriman

Guest
David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]demon.co.uk>:
> >David Damerell <[email protected]> wrote:
> >>Somewhere between those two points is a spot or region where it is
> >>easiest, but to say that that's a spot not a region and that that spot
> >>happens to be the amount of force required by the brakes you have _and_
> >>that that will be true for any user is pure guesswork.

> >yes still needs to be some resistance, or it would be too easy to be a
> >system that was on/off

>
> Reducing your guesswork to what it is.


brakes that can be feathered with out having to use any force proper
will be easyer to control, most things requiring fine control try not to
require too much effort.
>
> >>>if your locking managing to lock the wheels at high speeds in the dry
> >>>etc then you either have tires with not enought grip or are not
> >>>countering with your weight. which a hill would help with.
> >>id I say I'd locked the wheels? No.

> >look back at your post not the snippage here, you pritty much did if not
> >in actualality.

>
> Let's see a quote from you that shows it, then. Hint; you can't.


fine

">2nd at higher speeds you will have a job to lock the wheel, unless you
delbertly unweight a wheel etc."

>This one won't wash with anyone who has made emergency stops downhill
>on
>road. We might not brake as much, but the speeds are higher.
>

if your not saying you lock your wheels at speed then what are you
saying?

> >>But - more than once - descending at speed, with heavy panniers (so with
> >>the overall centre of gravity already lower and to the rear) - I've
> >>had to brake so hard it's finished with the thump of the rear wheel
> >>regaining contact with the road.

> >yes, but it's very unlikely the paniers are close to your weight, you
> >can make a much more impact moving your body,

>
> That's also not true. The panniers don't weigh what a body does, true -
> but you can easily have 20 or 30kg there - and they are also much further
> from the centre of gravity of a normal bike/rider system than a moved
> bottom is, so they affect the CoG proportionately more. It's definitely in
> the same ballpark.


the only limit to how far back and low is rear tire, and saddle more
than enought to be more than 30KG of panniers. particulally as with 30KG
of panniers the possiblt of shifting ones weight much is limited.
>
> >>Bog ordinary cantilevers. You don't need hydraulic discs to make a
> >>controller emergency stop at high speeds.

> >no you don't but all things being equal they should make a better job of
> >it.

>
> You can't make a better job of stopping than stopping with the rear wheel
> on the edge of lifting.
>

correct which is why you need to shift ones' weight back and push that
point to a higher point.

not needed on a tamdem but is on a solo.

> >look do you really think that it's a big con and that brakes haven't
> >improved over the years?

>
> I certainly think it's partly marketing, but I think the advantages of
> discs aren't what you think they are. "Power" is a red herring on solos,
> and tandems have not found discs exceptionally powerful.
>

considering the weight that a tamdem could be, they really should be
useing something a with a lot more bite. even the big disks you like are
still rather light weight.

power isn't a red herring, while it is possible to endo it is also
possible to counter, up to a point, which disks are not at so far.

> We've had real advantages of hydraulic disc systems listed. Immunity to
> wet muddy conditions; low maintenance (especially no rim wear). And, of
> course, if a rider has very weak hands they will get a real benefit from
> the reduced application force. But "power"? Not a chance.


reduced application force is certinaly a real plus in some situations,
very few roads are steep enought to be a issue though tamdems might make
more. but certinaly off road, the differnace from decending down a long
steep hill on cant's or disks can be felt.

and also mean that one doesn't need to put whole hand on lever when you
really should be worring about that rock...
>
> >motor vehicals have been useing disks and hydraulic at that for years,

>
> So what? Are you going to put a five-speed gearbox on your bike next?
> Just because it fits motorised applications doesn't mean it fits bikes.


it means just becuase x number of companies made a balls up of it
doesn't mean there is anything wrong with the underlying idea.

it works else where and very well. on faster heaver vehicals than a
tamdem.

roger
--
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D

David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Quoting Roger Merriman <[email protected]>:
>>>David Damerell <[email protected]> wrote:
>>>>But your perceptions of brake "power" are worthless because every decent
>>>>design of brake has exactly the same stopping power on a solo.
>>>maybe in paper,

>>And in elementary mechanics.

>i'm sure it terms of heat they are much of a muchness. and yes if you
>don't move at point X the bike will endo.


And for a given bottom position, every design of brake has the same
stopping power.

>>>but taking my old cant bike away from the rolling downs
>>>and to the beacons shows that while it's brakes can cope with the soft
>>>lumps of the south east. proper hills it lacks the power, compared with
>>>a newer bike with disks.

>>Which is still rubbish because an increasing downhill gradient _reduces_
>>the maximum deceleration.

>yes if i sit on the saddle and just jank the brake, but most will learn
>to get out of the saddle and use that weight.


Doesn't matter. If you can brake on the those soft lumps, you can manage
the deceleration possible on proper hills because it _is less_.

>>Which is also still rubbish as anyone can determine with heavy panniers.
>>30kg in panniers shifts the centre of gravity more than you can by moving
>>your bottom; and with 30kg in panniers you can still lift the rear wheel
>>under braking; and a downhill gradient still reduces the maximum
>>deceleration before that happens.

>yes of coarse a hill will increase a heavly laden bikes endo point, but
>you weigh a lot more than 30KG and on some bikes you can move that
>weight around a lot,


You can move _some_ of that weight around a lot; your arms and legs don't
move so much for a given bottom shift. And when we say "a lot", it's not a
lot compared to the distance that rear panniers are below and to the rear
of the saddle.

>>You're just clinging to purely psychosomatic ideas of brake power. It
>>won't wash; and particularly it won't wash with anyone familiar with
>>tandem applications, where you actually _can_ produce differences in brake
>>power.

>try taking a bike up and down steep hills good 30%


When the gradient gets steep enough, the available braking before endo is
small regardless of bottom position. That's one reason it's so blindingly
obvious you're taking rubbish; you're picking the worse case for a brake
to demonstrate supposedly superior power.

>shift your weight around by that i don't mean your bottom as you put it


Yes, you do. Your hands won't move; your shoulders won't get any further
from the handlebars than they are with straight arms, although they will
drop a bit. Your feet aren't going anywhere. The bottom is exactly the
part that moves a lot.
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David Damerell

Guest
Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Quoting Roger Merriman <[email protected]>:
>>>yes still needs to be some resistance, or it would be too easy to be a
>>>system that was on/off

>>Reducing your guesswork to what it is.

>brakes that can be feathered with out having to use any force proper
>will be easyer to control, most things requiring fine control try not to
>require too much effort.


This is just restating the guesswork. Yes, there's a sweet spot or region
- but you've failed to show that the brakes you personally prefer are in
it or that other designs are outside it - for all possible rider hand
strengths.

>>>look back at your post not the snippage here, you pritty much did if not
>>>in actualality.

>>Let's see a quote from you that shows it, then. Hint; you can't.

>fine


Coo, you're literally minded. But let's see a quote from _me_ that shows I
said it?

>>This one won't wash with anyone who has made emergency stops downhill
>>on road. We might not brake as much, but the speeds are higher.

>if your not saying you lock your wheels at speed then what are you
>saying?


On a good surface what happens first with the front brake - front lock or
rear lift?

>the only limit to how far back and low is rear tire, and saddle more
>than enought to be more than 30KG of panniers.


No. Atop the rear tyre, the very bottom of the weight you shifted is at
the top of where panniers would be.

>particulally as with 30KG
>of panniers the possiblt of shifting ones weight much is limited.


Try reading comprehension; it's either/or. The point is, a rider with
heavy panniers has an overall centre of gravity just as low and rearward
without shifting his weight.

>>You can't make a better job of stopping than stopping with the rear wheel
>>on the edge of lifting.

>correct which is why you need to shift ones' weight back and push that
>point to a higher point.


Try reading comprehension.

>>I certainly think it's partly marketing, but I think the advantages of
>>discs aren't what you think they are. "Power" is a red herring on solos,
>>and tandems have not found discs exceptionally powerful.

>considering the weight that a tamdem could be, they really should be
>useing something a with a lot more bite.


That's sort of the point. There's actually some chance of discovering
which brakes are powerful.

>>We've had real advantages of hydraulic disc systems listed. Immunity to
>>wet muddy conditions; low maintenance (especially no rim wear). And, of
>>course, if a rider has very weak hands they will get a real benefit from
>>the reduced application force. But "power"? Not a chance.

>reduced application force is certinaly a real plus in some situations,
>very few roads are steep enought to be a issue


As I've explained to you several times now, the steeper the road, the
_less_ the maximum braking.

>and also mean that one doesn't need to put whole hand on lever when you
>really should be worring about that rock...


Yes, I worry about rocks with my fingers. Not.

>>So what? Are you going to put a five-speed gearbox on your bike next?
>>Just because it fits motorised applications doesn't mean it fits bikes.

>it works else where and very well. on faster heaver vehicals than a
>tamdem.


I've no doubt a disc system as heavy-duty as those on a motor car would
make a fine brake, if you didn't mind it weighing as much as your bike
did before you fitted it. Of course, it would still be pointless on a solo
because the limit on a solo still isn't braking "power".
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