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

[David Damerell]

Quoting Peter Clinch <[email protected]>:
>David Damerell 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.
>But rather less guesswork if they happen to have considerable experience
>of multiple brake systems.

And of being multiple people, if the guesswork is going to express more
than personal preference.

>How much time have you actually spent using hydraulic brake systems?

I think I'll spare myself the "I have more experience therefore my guess
is correct", thanks.
--
David Damerell <[email protected]> Kill the tomato!
Today is Leicesterday, August.

 

[David Damerell]

Quoting Peter Clinch <[email protected]>:
>David Damerell wrote:
>>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".
>Oh deary me, I have talked about *both* performance being better through
>better feel when maintained and being better in all respects when not
>maintained and left for some time.
>That's two things.

The second of which is then double accounting with "less maintenance".

>>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 opposed to "this is what I use and I think it's fine so obviously
>anyone else finding anuthing better is deluded"...

That's a perfectly reasonable thing to say when someone pretends their
personal prefence is universally applicable.

>>As I've just written in another article - too much sensitivity won't work,
>It isn't "too much" that hydraulics give you, it's more than cables, but
>less than too much. A better amount, in other words.

There must be a sweet spot not a region of equal utility because...
--
David Damerell <[email protected]> Kill the tomato!
Today is Leicesterday, August.

 

[Peter Clinch]

David Damerell wrote:

>> How much time have you actually spent using hydraulic brake systems?
>
> I think I'll spare myself the "I have more experience therefore my guess
> is correct", thanks.

That's a nice little sidestep to admitting "practically none at
all, so I'm working almost entirely from theory".

It isn't do I have more, it's do you have much to speak of
whatsoever? If you don't, and I suspect you don't, it's a bit like
Shaun Murray "proving" Alex Moulton hasn't got a clue about
designing road-going suspension based on his "technical mind" and a
trip around the block on an AM, or Nick Maclaren "proving" that
Bromptons are inherently unsafe for tall riders armed with nothing
but a measuring tape.

If I'm wrong about that then an apology is deserved and will be
supplied, but am I?

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/

 

[Roger Merriman]

David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>>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?
> >rear lift normally, hence the need to counter.
>
> So I was not saying you lock the wheels. You _made that up_.
>
> >>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.
> >with paniers you still have yours truely which is much heaver, far
> >higher, and forward. which more than makes up for the panniers.
>
> Well, no. Panniers weigh less; they're further from the normal centre of
> gravity. Works out about the same.

can you ladien the paniers so that on the flat with you on the bike, the
bike is at the tipping point? even with the big long hybrid i can make
the front lift by tipping my weight back.
>
> >>>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.
> >there is differnce between heat and power.
>
> Yes, and I'm talking about power. Tandems decelerate twice the load and
> can decelerate harder.
>
> >>As I've explained to you several times now, the steeper the road, the
> >>_less_ the maximum braking.
> >yes and as i've pointed out you can very effectvly counter that.
>
> Well, no, you've babbled aimlessly. A given bottom position can also be
> used on a shallower slope; once you do that, on the steeper slope, the
> maximum braking is... less.
>
it would be a very bad idea to shift one's weight that far as you can
make the bike tip up.

> >>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".
> >it wouldn't need to be as heavy weight, but bike brakes are light weight
> >things, look at the disks very thin, there is a middle ground.
>
> It would still be pointless for the reason above.

roger
--
www.rogermerriman.com

 

[Roger Merriman]

Jon <[email protected]> wrote:

> "Roger Merriman" <[email protected]> wrote
> >
> > what i do care about are brakes that will scrub off speed ie 40 to 50
> > range and allow one to decend with power left.
>
> Not sure what "decend with power left" means.
>
means to decend steep hills as in over 30% at speed with brakes that
will stop rather than just slow.

> But it seems to me that there are perhaps some points of agreement:
>
> 1) for braking methods that rely on slowing wheel rotations [1],
> there is a maximum obtainable deceleration rate on a bicycle
> before the rear will lift and rotate around the front contact
> point.
>
> 2) changing weight distribution (or bicycle geometry) affects that
> maximum deceleration rate.
>
> 3) going down a hill implicitly shifts the bike and rider weight
> distribution forward.
>
> 4) the weight distribution downhill cannot be "further back" than
> it would be with the same rider position on flat ground, hence
> the maximum possible deceleration rate downhill is lower
> than on flat.
>
not entirely get your hanging off the back you can make the bike tip up,
ie endo.

if your used to shifting your weight, you can shift it so the bike will
tip on either end.

> 5) properly designed and adjusted disk and rim bicycle braking
> systems, cable and hydraulic, can produce braking force greater
> than the maximum possible deceleration rate.
>
> 6) braking power above that required to produce the maximum
> deceleration rate is irrelevant for how quickly one may stop.
>
> 7) [gratuitous ARBC content] long wheelbase recumbent
> bikes certainly have a greater maximum potential
> deceleration rate than upright bikes.
>
> This says nothing about which system is nicer, easier to use,
> maintain, modulate and control, or resists fading, or is better
> suited for wet and muddy conditions, etc... Or which one
> makes your bike look cool and your friends jealous! %^)
>
> There was recently a very good explanation of the limits
> of bicycle braking on the phred touring mailing list. Should
> be in the archives at:
>
> http://www.phred.org/mailman/listinfo/touring
>
> It was pointed why it's not a good idea to follow cars at
> high speeds too closely on a bicycle. Cars can stop at
> much higher deceleration rates than bicycles.
>
yes though worth noting they to suffer from weight transfure, even with
sporty set ups the rear's will unweight a fair bit under hard braking.

> Jon Meinecke
>
> [1] alternative braking methods could include dropping an anchor,
> deploying a drag parachute, firing retro-rockets, hitting a large
> rock face (with or without a tunnel entrance painted on it), etc...
>
> See Wiley Coyote field tests of Acme Products for examples...
> %^)

roger
--
www.rogermerriman.com

 

[Jon]

"Roger Merriman" <[email protected]> wrote
> Jon <[email protected]> wrote:
>
>> [ points 1-3]

Great! There seems to be some level of implicit agreement on
most points.

>> 4) the weight distribution downhill cannot be "further back" than
>> it would be with the same rider position on flat ground, hence
>> the maximum possible deceleration rate downhill is lower
>> than on flat.
>>
> not entirely get your hanging off the back you can make the bike tip up,
> ie endo.

Do you mean raising the front wheel by shifting weight back? Obviously
this would dramatically reduce front wheel braking effect! %^)

Equally obviously, this point of "wheelie" moves further back under
deceleration. And the fact that you can move further back on a slope
before the point of front wheel lift illustrates that there's less "room
left
to move" to counter decleration forces on a slope. That is, the point
of equalibrium starts further back on a slope. (For some slopes, there
may be enough "leeway" to correct to deceleration *and* slope, but
at no point can you obtain a greater effective weight shift on a slope
than on the flat. Proof is by simple trigonometry.)

>> [...] Cars can stop at
>> much higher deceleration rates than bicycles.
>>
> yes though worth noting they to suffer from weight transfure, even with
> sporty set ups the rear's will unweight a fair bit under hard braking.

Exactly. And the effect for cars is a tendency for the rear to pass the
front by rotating horizonatally (a sideways endo).

Here's a few excerpts from the posting by someone who seems to
have a lot of practical experience in braking and cites references:

George Hall wrote:

Cars and motorcycles can decelerate at a max rate
of about 0.7 - 0.9g.
...

If you only consider the coefficient of friction of tire
rubber on common pavement surfaces, you would
determine that about 0.7 - 0.8g of braking is possible
for a cyclist.

[for cyclists, a] practical limit of about 0.45 - 0.50g is
all that most folks will achieve before they experience
rear wheel liftoff.

[...] caliper brakes, cantilver brakes, V-brakes, or
disc brakes - all of these in normal circumstances can
produce a deceleration of 0.45g - 0.50g [...]

[...] Of course, there are a lot of other considerations
for your individual circumstances and preferences, I'm
only discussing this from the perspective of braking
ability.

http://search.bikelist.org/getmsg.asp?Filename=touring.10709.0118.eml

So points that disk brakes are better for some conditions, that
they feel better, are more responsive, or are easier to maintain,
or sexier, etc.. may all be good reasons for some to chose them!
Or not sufficient reasons for others... YMMV

Disk brakes do complicate some things, for instance, rear rack
mounting for loading touring upright bikes.

Jon

 

[David Damerell]

Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Well, no. Panniers weigh less; they're further from the normal centre of
>>gravity. Works out about the same.
>can you ladien the paniers so that on the flat with you on the bike, the
>bike is at the tipping point?

That's just fore-aft position of centre of gravity; height of centre of
gravity also affects maximum braking.

>>Well, no, you've babbled aimlessly. A given bottom position can also be
>>used on a shallower slope; once you do that, on the steeper slope, the
>>maximum braking is... less.
>it would be a very bad idea to shift one's weight that far as you can
>make the bike tip up.

Not under heavy braking!
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[David Damerell]

Quoting Peter Clinch <[email protected]>:
>David Damerell wrote:
>>>How much time have you actually spent using hydraulic brake systems?
>>I think I'll spare myself the "I have more experience therefore my guess
>>is correct", thanks.
>That's a nice little sidestep to admitting "practically none at
>all, so I'm working almost entirely from theory".

Well, imagine I do admit that. Let's imagine, not only have I never ridden
a bike with hydraulic discs, I've actually never seen one. When this
thread started, I didn't even know they existed, and I had to go and do a
little reading to find out what they were. In fact, I've only ever used
rod brakes and a little parachute for downhill work.

Let's imagine all that. Would that make your guesswork any less guesswork?
No.
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[Peter Clinch]

David Damerell wrote:
> Quoting Peter Clinch <[email protected]>:
>> David Damerell wrote:
>>>> How much time have you actually spent using hydraulic brake systems?
>>> I think I'll spare myself the "I have more experience therefore my guess
>>> is correct", thanks.
>> That's a nice little sidestep to admitting "practically none at
>> all, so I'm working almost entirely from theory".
>
> Well, imagine I do admit that. Let's imagine, not only have I never ridden
> a bike with hydraulic discs, I've actually never seen one. When this
> thread started, I didn't even know they existed, and I had to go and do a
> little reading to find out what they were. In fact, I've only ever used
> rod brakes and a little parachute for downhill work.
>
> Let's imagine all that. Would that make your guesswork any less guesswork?
> No.

A while ago you castigated Roger for just not coming out and saying he
was talking about steep and radical off-road. Why don't you just come
out and quantify the experience you have with hydraulic brakes so as to
inform other people reading the thread exactly what degree of experience
and what degree of conjecture and theory your comments are based on?

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/

 

[Roger Merriman]

David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>Well, no. Panniers weigh less; they're further from the normal centre of
> >>gravity. Works out about the same.
> >can you ladien the paniers so that on the flat with you on the bike, the
> >bike is at the tipping point?
>
> That's just fore-aft position of centre of gravity; height of centre of
> gravity also affects maximum braking.
>
on a bike with out paniers you can get low and rear, such as mountain
bike, you can make a lot of diffenance, you are far and away the
heaviest thing paniers even heavy loaded ones are light in comparison
and have less effect.

i grew up in a steep sided gorge, i'm prefectly aware it's possible to
endo and bike and aware that it's also possible not to, even under hard
braking.

> >>Well, no, you've babbled aimlessly. A given bottom position can also be
> >>used on a shallower slope; once you do that, on the steeper slope, the
> >>maximum braking is... less.
> >it would be a very bad idea to shift one's weight that far as you can
> >make the bike tip up.
>
> Not under heavy braking!

no but it does show that you can move a lot of weight about. down a
steep hill yes you might move a lot but on the flat even under hard
braking it will not be needed as much though some will be needed to
prevent a endo.

roger
--
www.rogermerriman.com

 

[David Damerell]

Quoting Peter Clinch <[email protected]>:
>>>David Damerell wrote:
>>>>I think I'll spare myself the "I have more experience therefore my guess
>>>>is correct", thanks.
>was talking about steep and radical off-road. Why don't you just come
>out and quantify the experience you have with hydraulic brakes so as to
>inform other people reading the thread exactly what degree of experience
>and what degree of conjecture and theory your comments are based on?

I think I've already answered that one, just above. No matter how much or
how little experience I have, your guesswork remains guesswork. I'm sure
you'd love to produce a spurious justification of it on those grounds; too
bad (except inasmuch as you will now say something like "obviously you
don't really have any experience" and use that to justify your pure
guesswork, which will still be nonsense.)
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[David Damerell]

Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Quoting Roger Merriman <[email protected]>:
>>>can you ladien the paniers so that on the flat with you on the bike, the
>>>bike is at the tipping point?
>>That's just fore-aft position of centre of gravity; height of centre of
>>gravity also affects maximum braking.
>on a bike with out paniers you can get low and rear

Maybe you can; but lifting the front wheel doesn't measure "low", just
"rear".

>bike, you can make a lot of diffenance, you are far and away the
>heaviest thing paniers even heavy loaded ones are light in comparison
>and have less effect.

But - as mentioned to you about a million times now - although they are
lighter (but not far and away lighter if heavily laden) - they can be
further from the CoG of the unladen normal-position system.

>>>it would be a very bad idea to shift one's weight that far as you can
>>>make the bike tip up.
>>Not under heavy braking!
>no but it does show that you can move a lot of weight about.

Which is not being disputed. You've lost track of the point in your
semiliterate gibberish.
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[Peter Clinch]

David Damerell wrote:

> I think I've already answered that one, just above.

What you've done is come up with a precious excuse for not actually
letting on whether you know what you're talking about from
experience or just from theory (guesswork, in other words, even if
educated guesswork).

> No matter how much or
> how little experience I have, your guesswork remains guesswork.

I specifically pointed out I didn't know what experience you
actually had, and asked for clarification. Which you rather
pathetically persist in avoiding giving.

If someone is reading the thread wanting advice it is to their
advantage if the basis of any advice they get is known.

So why not just stop with the precious justifications of not
actually saying whether your opinions are based on experience or
just theory, and let people know? Do you actually want to provide
useful information, or just pour scorn on people?

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/

 

[Roger Merriman]

Jon <[email protected]> wrote:

> "Roger Merriman" <[email protected]> wrote
> > Jon <[email protected]> wrote:
> >
> >> [ points 1-3]
>
> Great! There seems to be some level of implicit agreement on
> most points.

yup.
>
> >> 4) the weight distribution downhill cannot be "further back" than
> >> it would be with the same rider position on flat ground, hence
> >> the maximum possible deceleration rate downhill is lower
> >> than on flat.
> >>
> > not entirely get your hanging off the back you can make the bike tip up,
> > ie endo.
>
> Do you mean raising the front wheel by shifting weight back? Obviously
> this would dramatically reduce front wheel braking effect! %^)
>
quite the point being that you can achive a fairly radical weight shift.
if needed.

> Equally obviously, this point of "wheelie" moves further back under
> deceleration. And the fact that you can move further back on a slope
> before the point of front wheel lift illustrates that there's less "room
> left
> to move" to counter decleration forces on a slope. That is, the point
> of equalibrium starts further back on a slope. (For some slopes, there
> may be enough "leeway" to correct to deceleration *and* slope, but
> at no point can you obtain a greater effective weight shift on a slope
> than on the flat. Proof is by simple trigonometry.)
>
true, that is less room to move, though in pratice even a very steep
road you can get enought weight to prevent endo. off road some slopes
are steep enought you probably can't but thats a mute point as
attempting to brake would probably be foolish.

> >> [...] Cars can stop at
> >> much higher deceleration rates than bicycles.
> >>
> > yes though worth noting they to suffer from weight transfure, even with
> > sporty set ups the rear's will unweight a fair bit under hard braking.
>
> Exactly. And the effect for cars is a tendency for the rear to pass the
> front by rotating horizonatally (a sideways endo).
>
yes can be done though mostly just a slide forward locking the brakes.

> Here's a few excerpts from the posting by someone who seems to
> have a lot of practical experience in braking and cites references:
>
> George Hall wrote:
>
> Cars and motorcycles can decelerate at a max rate
> of about 0.7 - 0.9g.
> ...
>
> If you only consider the coefficient of friction of tire
> rubber on common pavement surfaces, you would
> determine that about 0.7 - 0.8g of braking is possible
> for a cyclist.
>
> [for cyclists, a] practical limit of about 0.45 - 0.50g is
> all that most folks will achieve before they experience
> rear wheel liftoff.
>
> [...] caliper brakes, cantilver brakes, V-brakes, or
> disc brakes - all of these in normal circumstances can
> produce a deceleration of 0.45g - 0.50g [...]
>
> [...] Of course, there are a lot of other considerations
> for your individual circumstances and preferences, I'm
> only discussing this from the perspective of braking
> ability.
>
> http://search.bikelist.org/getmsg.asp?Filename=touring.10709.0118.eml
>
> So points that disk brakes are better for some conditions, that
> they feel better, are more responsive, or are easier to maintain,
> or sexier, etc.. may all be good reasons for some to chose them!
> Or not sufficient reasons for others... YMMV
>
> Disk brakes do complicate some things, for instance, rear rack
> mounting for loading touring upright bikes.
>
> Jon

roger
--
www.rogermerriman.com

 

[Roger Merriman]

David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>Quoting Roger Merriman <[email protected]>:
> >>>can you ladien the paniers so that on the flat with you on the bike, the
> >>>bike is at the tipping point?
> >>That's just fore-aft position of centre of gravity; height of centre of
> >>gravity also affects maximum braking.
> >on a bike with out paniers you can get low and rear
>
> Maybe you can; but lifting the front wheel doesn't measure "low", just
> "rear".
>
the point is the endo, if heavy braking will cause a bike to endo, i'm
pointing out it's possible (upto a point) to counter.

> >bike, you can make a lot of diffenance, you are far and away the
> >heaviest thing paniers even heavy loaded ones are light in comparison
> >and have less effect.
>
> But - as mentioned to you about a million times now - although they are
> lighter (but not far and away lighter if heavily laden) - they can be
> further from the CoG of the unladen normal-position system.

i didn't think the rear rack would take anything like 80KG? most seem to
20/30KG range. which is a long way from even a light person.
>
> >>>it would be a very bad idea to shift one's weight that far as you can
> >>>make the bike tip up.
> >>Not under heavy braking!
> >no but it does show that you can move a lot of weight about.
>
> Which is not being disputed. You've lost track of the point in your
> semiliterate gibberish.

one it is you are disputing at least in your belief that strong brakes
don't matter you'll endo before there any use on a solo.

roger
--
www.rogermerriman.com

 

[David Damerell]

Quoting Roger Merriman <[email protected]>:
>David Damerell <[email protected]> wrote:
>>Maybe you can; but lifting the front wheel doesn't measure "low", just
>>"rear".
>the point is the endo, if heavy braking will cause a bike to endo, i'm
>pointing out it's possible (upto a point) to counter.

Thank you, Captain Obvious! Perhaps you would like to tell me fire is hot
next?

>>But - as mentioned to you about a million times now - although they are
>>lighter (but not far and away lighter if heavily laden) - they can be
>>further from the CoG of the unladen normal-position system.
>i didn't think the rear rack would take anything like 80KG? most seem to
>20/30KG range. which is a long way from even a light person.

Mine's a Tortec Expedition steel, which is rated to 45kg, and yes, I fill
them full of heavy stuff sometimes. Given that the panniers are also
lower than anyone's getting with bottom contortions, and bottom contortions
don't move your full weight the full distance the bottom moves...

>one it is you are disputing at least in your belief that strong brakes
>don't matter you'll endo before there any use on a solo.

Try again in English.
--
David Damerell <[email protected]> flcl?
Today is Stilday, August - a weekend.