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

[Peter Clinch]

David Damerell wrote:

> Yes, an unmaintained brake can be dangerous. Not a new fact.

You've gloriously and spectacularly missed the fact that Clive's
hydraulic brakes haven't been maintained for the precise reason that
they haven't /needed/ maintaining in order not to degrade unacceptably,
as manifestly doesn't happen with "just as good" mechanical brakes.

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/

 

[Peter Clinch]

David Damerell 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.

*** isn't the *more* it offers you from locking, it's the fine control
of /ever so slightly less/ than locking which is easier with the more
sensitive feel of a hydraulic.

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/

 

[Marz]

On Sep 4, 9:09 am, 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.
> --
> David Damerell <[email protected]> Kill the tomato!
> Today is Second Saturday, August - a weekend.

Not always true. A disk brake will offer more braking in wet, muddy
conditions than a rim brake and hence why us mtbers love 'em.

 

[Peter Clinch]

Marz wrote:

> Not always true. A disk brake will offer more braking in wet, muddy
> conditions than a rim brake and hence why us mtbers love 'em.

Though true, that doesn't cover the qualitative difference between
hydraulic and cable systems. It seems that the better MTBs have
hydraulics, and I think that's probably about feel and consequently fine
control, possibly the difference between locking and optimum braking.

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/

 

[Ben C]

On 2007-09-04, David Damerell <[email protected]> wrote:
> Quoting Roger Merriman <[email protected]>:
>>David Damerell <[email protected]> wrote:
>>>Because mountain bikes can't actually use any more braking than any other
>>>solo bike.
>>really? funny the jump though various cable rim brakes to hydraulic
>>disks has been a steady improvement in braking.
>
> 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?

Easily, it might have better power dissipation and therefore not
overheat and become useless after prolonged and/or repeated use.

Think about car brakes. Just about any car will do an emergency stop
from 30mph without the brakes overheating; but drive fast for 30 miles
on twisty roads and many cars will start to suffer brake fade as things
get too hot.

Any brake that's merely half-decent should be able to lift the back
wheel on demand. It doesn't end there.

 

[Roger Merriman]

David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>Or the disc warping, the hydraulic fluid boiling, plastic bits catching on
> >>fire... yes, Santana produced all these failure modes in disc brakes.
> >still a disk failing has to be safer than a tire blowing off?
>
> Neither is an acceptable outcome.

true.
>
> >which then begs the question why the standard v brakes with out issue
> >then?
>
> Please look up "begs the question" to find out what it means.
>
> 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?
>
> >>The real answer is that what people think of as "strong" brakes aren't.
> >>_Any_ sensible design of brake can lift the rear wheel (or skid the front
> >>wheel on a poor surface). For solo bikes there is no difference in brake
> >>strength from one design to another.
> >that is not my experance at least given enought, speed and/or gradiant.
>
> 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. you can get a lot of braking out of the rear by doing
that well.

roger
--
www.rogermerriman.com

 

[Roger Merriman]

CoyoteBoy <[email protected]> wrote:

> On 4 Sep, 13:16, [email protected] (Roger Merriman) wrote:
>
> > that as maybe certinaly at slower speeds, but ramp the speed up to and
> > disks do seem to stop one faster and cleaner then rim brakes, the rim
> > did stop the bike and safely, but at higher speeds they don't at least
> > in my experiance attaully stop as fast.
>
> I suspect this is down to heat buildup - a rim brake has a much higher
> contact speed than a disk brake so the pads will suffer from the
> effects of heat much faster. Oh and dont forget the rim pads have to
> be fairly soft rubbery stuff so as not to eat the soft rims, which
> doesnt help with heat dissipation and pad life.

that would make sence yes, if you ever get the chance to ride on **** it
quite apart from making the sort of mud that all but the most clean
running mud tires clog up in, also eats pads,

roger
--
www.rogermerriman.com

 

[Roger Merriman]

David Damerell <[email protected]> wrote:

> Quoting Roger Merriman <[email protected]>:
> >David Damerell <[email protected]> wrote:
> >>Because mountain bikes can't actually use any more braking than any other
> >>solo bike.
> >really? funny the jump though various cable rim brakes to hydraulic
> >disks has been a steady improvement in braking.
>
> 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.

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

on loose surfaces point one will help one get to but not over the point
the tires skid.

roger
--
www.rogermerriman.com

 

[Tony Raven]

[email protected] (Alan Braggins) wrote in
news:[email protected]:

>>>
>>> Less likely on a
>>> tandem, but on an MTB pointing down a 60 degree loose slope you need
>>> very precise braking control
>>
>><pedant>
>>You can't have a 60 degree loose slope - its beyond the maximum angle of
>>repose for loose material.
>></pedant>
>
> I think you might reasonably consider damp sand to be a loose slope for
> the purpose of riding a bike down it, even though it obviously isn't as
> loose as dry sand (which is why it has a much higher angle of repose).
>

It would have to never dry out to stay there and how it got there in that
state in the first place would be an interesting story.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

 

[Tony Raven]

Marz <[email protected]> wrote in
news:[email protected]:

> On Sep 4, 3:01 am, Tony Raven <[email protected]> wrote:
>> Paul Boyd <usenet.is.worse@plusnet> wrote
>> innews:[email protected]:
>>
>>
>>
>> > Less likely on a
>> > tandem, but on an MTB pointing down a 60 degree loose slope you
>> > need very precise braking control
>>
>> <pedant>
>>
>> You can't have a 60 degree loose slope - its beyond the maximum angle
>> of repose for loose material.
>>
>> </pedant>
>>
>> --
>> Tony
>>
>> " I would never die for my beliefs because I might be wrong."
>> Bertrand Russell
>
> You can very easily have a 60 degree slope, rock face, rooty sections,
> washed out river banks, but it's not something you're ever going to
> attempt to brake on. When things get that steep all you're hoping to
> do is roll it out without crashing.
>
>

But it can't be a loose slope - the loose material will just roll off it
if the slope is steeper than the maximum angle of repose which is
typically IIRC around 30-40 degrees.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

 

[Peter Clinch]

Tony Raven wrote:

> It would have to never dry out to stay there and how it got there in that
> state in the first place would be an interesting story.

I direct m'lud's attention to the nearest sand dunes for plenty of sand
cliff-ettes which are loose enough to be easily pulled away with hands
but are steep enough that kids much enjoy sailing over them to the nice
soft landings beyond.

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/

 

[Tony Raven]

Peter Clinch <[email protected]> wrote in
news:[email protected]:

> Tony Raven wrote:
>
>> It would have to never dry out to stay there and how it got there in
>> that state in the first place would be an interesting story.
>
> I direct m'lud's attention to the nearest sand dunes for plenty of
> sand cliff-ettes which are loose enough to be easily pulled away with
> hands but are steep enough that kids much enjoy sailing over them to
> the nice soft landings beyond.
>

I would refer my honourable friend to Exhibits 1 on the geology of sand
dunes where the maximum angle is 30-34 degrees on the steep side.
Exhibit 1: http://www2.nature.nps.gov/geology/usgsnps/dune/dune.html



--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

 

[Peter Clinch]

Tony Raven wrote:

> I would refer my honourable friend to Exhibits 1 on the geology of sand
> dunes where the maximum angle is 30-34 degrees on the steep side.
> Exhibit 1: http://www2.nature.nps.gov/geology/usgsnps/dune/dune.html

Having a geology degree I am well aware of that, /but/ that's a free
dune with no vegetation, and the "no vegetation" bit is most important
(as any Dutch flood engineer will tell you, and why they tend their
coastal dunes very carefully!). I'm quite sure you've been to dunes by
the UK sea-side with practically vertical small sections, and a walk
along many river banks will often reveal similar structures well over 34
degrees that will easily fall to pieces with a little encouragement.

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/

 

[Tony Raven]

Peter Clinch <[email protected]> wrote in news:5k74puF2eca8U1
@mid.individual.net:

> Tony Raven wrote:
>
>> I would refer my honourable friend to Exhibits 1 on the geology of sand
>> dunes where the maximum angle is 30-34 degrees on the steep side.
>> Exhibit 1: http://www2.nature.nps.gov/geology/usgsnps/dune/dune.html
>
> Having a geology degree I am well aware of that, /but/ that's a free
> dune with no vegetation, and the "no vegetation" bit is most important
> (as any Dutch flood engineer will tell you, and why they tend their
> coastal dunes very carefully!). I'm quite sure you've been to dunes by
> the UK sea-side with practically vertical small sections, and a walk
> along many river banks will often reveal similar structures well over 34
> degrees that will easily fall to pieces with a little encouragement.
>

I stand corrected then but going back to the OP, do you think the situation
of "on an MTB pointing down a 60 degree loose slope you need very precise
braking control" is realistic. I recognise there are 60 degree slopes but
there is unlikely to be any loose material on them and I somehow doubt the
rear wheel would stay down if you tried to brake.


--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

 

[Peter Clinch]

Tony Raven wrote:

> I stand corrected then but going back to the OP, do you think the situation
> of "on an MTB pointing down a 60 degree loose slope you need very precise
> braking control" is realistic. I recognise there are 60 degree slopes but
> there is unlikely to be any loose material on them and I somehow doubt the
> rear wheel would stay down if you tried to brake.

I can see such a slope existing if one takes "loose" as "stuck on... but
not at all well, and not enough to stay put when a bike hits it", but
I'd agree that anyone going down 60 degree slopes on a bike is pretty
much wasting their time with the brakes! 60 degrees is actually typical
of lower grade rock climbing, and IME people very often over-estimate
true steepness of steep slopes (where "steep" starts at about 20 degrees).

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/

 

On 5 Sep,
Peter Clinch <[email protected]> wrote:

> Tony Raven wrote:
>
> > I stand corrected then but going back to the OP, do you think the
> > situation of "on an MTB pointing down a 60 degree loose slope you need
> > very precise braking control" is realistic. I recognise there are 60
> > degree slopes but there is unlikely to be any loose material on them and
> > I somehow doubt the rear wheel would stay down if you tried to brake.
>
> I can see such a slope existing if one takes "loose" as "stuck on... but
> not at all well, and not enough to stay put when a bike hits it", but I'd
> agree that anyone going down 60 degree slopes on a bike is pretty much
> wasting their time with the brakes! 60 degrees is actually typical of
> lower grade rock climbing, and IME people very often over-estimate true
> steepness of steep slopes (where "steep" starts at about 20 degrees).

A slope of 45 degrees would require a coefficient of friction of one just to
stay on it. Coefficients higher than one are unusual, perhaps limiting at
about 1.1 with sticky tyres. It would be impossible to stay put, nevermind
brake to a halt, on a 60 degree slope, unless there was an interlocking rack
and pinion arrangement.


--
BD
Change lycos to yahoo to reply

 

[Ace]

On Wed, 05 Sep 2007 09:18:13 +0100, Peter Clinch
<[email protected]> wrote:

>I'd agree that anyone going down 60 degree slopes on a bike is pretty
>much wasting their time with the brakes! 60 degrees is actually typical
>of lower grade rock climbing, and IME people very often over-estimate
>true steepness of steep slopes (where "steep" starts at about 20 degrees).

Same happens in skiing - many people will overestimate the angle of
slope they've just skied, and the main reason isn't one of boasting,
but just that it _feels_ like that. In practice, marked runs over
40degrees are very rare, although I know a couple that I have
personally measured at 42=43deg. I have a clinometer needle on my
compass which can amuse or embarrass folk who will insist that the
slope's steeper than it really is.

As for 'loose' material on such a steep slope - we're taught in
avalanche training that slopes above 55deg are outside the danger
angles, as it's not possible for enough snow to accumulate on them.

38deg is normally accepted as the most dangerous angle, as this is the
maximum slope that a truly granular substance will stick to.

--
Ace in Alsace - brucedotrogers a.t rochedotcom

 

[Peter Clinch]

Ace wrote:

> As for 'loose' material on such a steep slope - we're taught in
> avalanche training that slopes above 55deg are outside the danger
> angles, as it's not possible for enough snow to accumulate on them.

You need to be careful about qualifying assumptions like that... how
about a convex slope where the bottom is too steep for accumulation, but
the top isn't?

Friends of mine have been caught in a cornice collapse in a gully where
loose snow wasn't accumulating, but was unfortunately passing through at
some speed :-(

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/

 

[Ace]

On Wed, 05 Sep 2007 11:01:46 +0100, Peter Clinch
<[email protected]> wrote:

>Ace wrote:
>
>> As for 'loose' material on such a steep slope - we're taught in
>> avalanche training that slopes above 55deg are outside the danger
>> angles, as it's not possible for enough snow to accumulate on them.
>
>You need to be careful about qualifying assumptions like that... how
>about a convex slope where the bottom is too steep for accumulation, but
>the top isn't?

Oh yes, you're quite right - clearly one needs to be looking at the
slope above you as well as the bit you're planning to ski on.

>Friends of mine have been caught in a cornice collapse in a gully where
>loose snow wasn't accumulating, but was unfortunately passing through at
>some speed :-(

Known as a "terrain trap". Hope they weren't hurt.

--
Ace in Alsace - brucedotrogers a.t rochedotcom

 

[Tony Raven]

Ace <[email protected]> wrote in news:8ktsd35r1us5kqm3b8rgbc2gtllb1uimi5@
4ax.com:

> On Wed, 05 Sep 2007 09:18:13 +0100, Peter Clinch
> <[email protected]> wrote:
>
>> [...]
>
> Same happens in skiing - many people will overestimate the angle of
> slope they've just skied, and the main reason isn't one of boasting,
> but just that it _feels_ like that. In practice, marked runs over
> 40degrees are very rare, although I know a couple that I have
> personally measured at 42=43deg. I have a clinometer needle on my
> compass which can amuse or embarrass folk who will insist that the
> slope's steeper than it really is.

Saudan's Couloir/Couloir Extreme in Blackcomb is reputedly 50 degrees and a
marked double diamond run. It feels vertical but they run an annual GS
race down it.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell