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

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 http://www.dundee.ac.uk/~pjclinch/

Jon wrote:

"Roger Merriman" wrote
Jon 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.as...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

David Damerell wrote:

Quoting Roger Merriman :
David Damerell wrote:
Quoting Roger Merriman :
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

Quoting Roger Merriman :
David Damerell 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 flcl?
Today is Stilday, August - a weekend.