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

  • Thread starter Tom \Johnny Sunset\ Sherman
  • Start date



T

Tom \Johnny Sunset\ Sherman

Guest
Artemisia wrote:
> I've been assuming all along that the brakes I would get on my new HPV
> Scorpion would be the Magura Big Hydraulic disc. I made this assumption
> because in the _Greenspeed_ customisation guide, these are given as the
> best choice for heavy riders in terms of max stopping power and subtlety
> of control. Greenspeed, unlike HPV, doesn't offer either the Martas or
> the Avids.
>
> Now I've been reading up on the competition, and have become confused.
> The Avid mechanical brakes are what come as standard. I've done some
> googling on these and have found the most incredibly consistent series
> of rave reviews. The consensus out there seems to be - people who fork
> out extra for hydraulic discs are plain stupid or misguided, the Avids
> are so good as to be unbeatable on function at a much lower price and
> much easier maintenance.
>
> I also learn that hydraulic brakes have brake fluid which can leak, and
> that they are a lot fiddlier to maintain, and a lot more delicate and
> likely to fail. Is this true?
>
> And does anyone know the difference between the Martas and the Bigs?
> What justifies the extra price on the Martas?
>
> I'm not quibbling on price. I will pay _whatever_is_necessary_ to get
> the product that is best for _me_. I will be using this trike to get
> down the very steep hills on my commute to work. I have never been able
> to bike these descents and have trouble even walking them, such is the
> angle. There is about a km of dizzying descent, crossed with traffic
> intersections. I _must_ be confident that I can stop.
>
> But simplicity of maintenance is as important as powerful stopping. The
> other vocation of the trike will be to come touring with me in places
> where support may not be easily found, and to be on and off planes and
> trains. If hydraulic disks are too delicate, and by failing immobilize
> the entire vehicle, then they may not justify their extra cost.
>
> Thanks for your experiences. Cheers,


I can lock up both from wheels on dry pavement with the Avid mechanical
disc brakes on my trike. The feel is mushy compared to a good hydraulic
system, however.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com
 
R

roger merriman

Guest
On 29 Aug, 05:03, "Tom \"Johnny Sunset\" Sherman"
<[email protected]> wrote:
> Artemisia wrote:
> > I've been assuming all along that the brakes I would get on my new HPV
> > Scorpion would be the Magura Big Hydraulic disc. I made this assumption
> > because in the _Greenspeed_ customisation guide, these are given as the
> > best choice for heavy riders in terms of max stopping power and subtlety
> > of control. Greenspeed, unlike HPV, doesn't offer either the Martas or
> > the Avids.

>
> > Now I've been reading up on the competition, and have become confused.
> > The Avid mechanical brakes are what come as standard. I've done some
> > googling on these and have found the most incredibly consistent series
> > of rave reviews. The consensus out there seems to be - people who fork
> > out extra for hydraulic discs are plain stupid or misguided, the Avids
> > are so good as to be unbeatable on function at a much lower price and
> > much easier maintenance.

>
> > I also learn that hydraulic brakes have brake fluid which can leak, and
> > that they are a lot fiddlier to maintain, and a lot more delicate and
> > likely to fail. Is this true?

>
> > And does anyone know the difference between the Martas and the Bigs?
> > What justifies the extra price on the Martas?

>
> > I'm not quibbling on price. I will pay _whatever_is_necessary_ to get
> > the product that is best for _me_. I will be using this trike to get
> > down the very steep hills on my commute to work. I have never been able
> > to bike these descents and have trouble even walking them, such is the
> > angle. There is about a km of dizzying descent, crossed with traffic
> > intersections. I _must_ be confident that I can stop.

>
> > But simplicity of maintenance is as important as powerful stopping. The
> > other vocation of the trike will be to come touring with me in places
> > where support may not be easily found, and to be on and off planes and
> > trains. If hydraulic disks are too delicate, and by failing immobilize
> > the entire vehicle, then they may not justify their extra cost.

>
> > Thanks for your experiences. Cheers,

>
> I can lock up both from wheels on dry pavement with the Avid mechanical
> disc brakes on my trike. The feel is mushy compared to a good hydraulic
> system, however.
>
> --
> Tom Sherman - Holstein-Friesland Bovinia
> A Real Cyclist [TM] keeps at least one bicycle in the bedroom.
>


Thing is though that locking the wheels is one thing, stopping fast
and safely is another, my cheap hybrid can lock it's wheels, but i
would regard is brakes as poor, in that it wouldn't stop in hurry at
speed, while my moutain bikes will, which considering the rubber on
the road i'd probably struggle to lock wheels up.

like the other day had to do a emergency stop, squeeling of tires on
hot road but not locking.

roger
 
P

Peter Clinch

Guest
roger merriman wrote:

> Thing is though that locking the wheels is one thing, stopping fast
> and safely is another, my cheap hybrid can lock it's wheels, but i
> would regard is brakes as poor, in that it wouldn't stop in hurry at
> speed, while my moutain bikes will, which considering the rubber on
> the road i'd probably struggle to lock wheels up.


Indeed. And this is where hydraulics are better IMHO, as they let you
have high power combined with very sensitive fingertip control.

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/
 
C

CoyoteBoy

Guest
On 29 Aug, 09:57, Peter Clinch <[email protected]> wrote:
> roger merriman wrote:
> > Thing is though that locking the wheels is one thing, stopping fast
> > and safely is another, my cheap hybrid can lock it's wheels, but i
> > would regard is brakes as poor, in that it wouldn't stop in hurry at
> > speed, while my moutain bikes will, which considering the rubber on
> > the road i'd probably struggle to lock wheels up.

>
> Indeed. And this is where hydraulics are better IMHO, as they let you
> have high power combined with very sensitive fingertip control.


I'm fairly sure its the cable stretch and binding alone that causes it
- with hydro it just releases the pressure and hence force, with
cables you have to overcome friction and stretch as well.
 
P

Peter Clinch

Guest
CoyoteBoy wrote:

> I'm fairly sure its the cable stretch and binding alone that causes it
> - with hydro it just releases the pressure and hence force, with
> cables you have to overcome friction and stretch as well.


I agree. Having recently re-cabled my Brompton's brakes and changed it
from potential death trap to bike with fair brakes I'm very aware of
just how much cables can degrade. But the hydrualics on the 'bent are
still beautifully responsive 3 years after putting them 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/
 
C

Clive George

Guest
"Peter Clinch" <[email protected]> wrote in message
news:[email protected]
> CoyoteBoy wrote:
>
>> I'm fairly sure its the cable stretch and binding alone that causes it
>> - with hydro it just releases the pressure and hence force, with
>> cables you have to overcome friction and stretch as well.

>
> I agree. Having recently re-cabled my Brompton's brakes and changed it
> from potential death trap to bike with fair brakes I'm very aware of
> just how much cables can degrade. But the hydrualics on the 'bent are
> still beautifully responsive 3 years after putting them on


If they behave as well as those on our tandem, they'll still be good 10
years after fitting.

But the magura rim brakes are closed, and the tolerances can be much
greater - there's loads of room for eg pad movement. With an open disc
system, you introduce the joy of eg bleeding the damn things, and there's
less margin for error. When I manage to let the smoke out of the hydraulic
discs on the MTB tandem, they work very well - but the rim brakes are
fit-and-forget in the way the discs distinctly aren't :-(

(still probably wouldn't have cables though)

cheers,
clive
 
C

CoyoteBoy

Guest
On 29 Aug, 15:16, "Clive George" <[email protected]> wrote:
> "Peter Clinch" <[email protected]> wrote in message
>
> news:[email protected]
>
> > CoyoteBoy wrote:

>
> >> I'm fairly sure its the cable stretch and binding alone that causes it
> >> - with hydro it just releases the pressure and hence force, with
> >> cables you have to overcome friction and stretch as well.

>
> > I agree. Having recently re-cabled my Brompton's brakes and changed it
> > from potential death trap to bike with fair brakes I'm very aware of
> > just how much cables can degrade. But the hydrualics on the 'bent are
> > still beautifully responsive 3 years after putting them on

>
> If they behave as well as those on our tandem, they'll still be good 10
> years after fitting.
>
> But the magura rim brakes are closed, and the tolerances can be much
> greater - there's loads of room for eg pad movement. With an open disc
> system, you introduce the joy of eg bleeding the damn things, and there's
> less margin for error. When I manage to let the smoke out of the hydraulic
> discs on the MTB tandem, they work very well - but the rim brakes are
> fit-and-forget in the way the discs distinctly aren't :-(
>
> (still probably wouldn't have cables though)
>
> cheers,
> clive


What the hell have you been doing to your discs? Why would you need to
bleed you discs unless you've damaged them? What error do you need
margin for? I found HS33s lose their bite when you run low on pad and
have to adjust them out to meet the rim. Plus they are a pain in the
**** when you buckle a rim which is far more frequent than buckling a
rotor?
 
P

Paul Boyd

Guest
Clive George said the following on 29/08/2007 15:16:

> but the rim
> brakes are fit-and-forget in the way the discs distinctly aren't :-(


Nothing against your opinion personally, but I've seen this sort of view
expressed before and I'm a bit puzzled by it. I fitted my hydraulic
disc brakes ages ago, and I've forgotten about them ever since. With
hydraulic disc brakes there's far less to go wrong than with any cable
brakes (can you even still get open systems?), and they just keep
working. They may need to be bled once every so often, but cables need
maintenance more than once every so often. All brakes need pads/blocks
replaced periodically, so I'm genuinely interested in why you think
discs aren't "fit and forget".

> (still probably wouldn't have cables though)


Agreed. I have had cables, then hydraulics, and the "feel" of the two
is worlds apart.

--
Paul Boyd
http://www.paul-boyd.co.uk/
 
C

Clive George

Guest
"Paul Boyd" <[email protected]> wrote in message
news:[email protected]
> Clive George said the following on 29/08/2007 15:16:
>
>> but the rim brakes are fit-and-forget in the way the discs distinctly
>> aren't :-(

>
> Nothing against your opinion personally, but I've seen this sort of view
> expressed before and I'm a bit puzzled by it.


That's because you carefully snipped the bit where I said "magura rim
brakes". You do know that magura don't make cable brakes, don't you? Their
hydraulic rim brakes have been around for ages now.

> I fitted my hydraulic disc brakes ages ago, and I've forgotten about them
> ever since.

....
> They may need to be bled once every so often


That isn't "forgotten about them". I've never opened the rim brake
internals - and they are 10 years old now.

> All brakes need pads/blocks replaced periodically, so I'm genuinely
> interested in why you think discs aren't "fit and forget".


Compared to the magura rim brakes, they aren't IME. That's it.

cheers,
clive
 
P

Paul Boyd

Guest
On 29/08/2007 18:18, Clive George said,

> That's because you carefully snipped the bit where I said "magura rim
> brakes". You do know that magura don't make cable brakes, don't you?
> Their hydraulic rim brakes have been around for ages now.


Are we talking at crossed purposes here? You said "but the rim brakes
are fit-and-forget in the way the discs distinctly aren't". I know you
were talking about the Magura rim brakes as being fit and forget - that
wasn't in question, but you said that disc brakes aren't. I was just
curious as to why you thought disc brakes weren't fit and forget - if
you haven't had to touch them in 10 years (apart from pads, presumably)
then you've now partly explained it.

However, I haven't had hydraulic disc brakes for 10 years, so I can't
comment on whether I would actually need to bleed them every so often or
not - I haven't had to in 12 months. I've just heard that they should
be bled every couple of years. Like Magura though, Shimano use a closed
system filled with mineral oil, so in theory they should never need
bleeding, and my POV is that I'll only bleed them if they get spongy.
To me, that is fit and forget, but I'll let you know in 9 years time :)

--
Paul Boyd
http://www.paul-boyd.co.uk/
 
C

Clive George

Guest
"coyoteboy" <[email protected]> wrote in message
news:[email protected]
> Paul Boyd wrote:
>>(can you even still get open systems?), and they just keep

>
> Lots of the top end systems are open - its how they get automatic pad wear
> adjustment. Certainly most of the systems I've seen on the trail have been
> open - closed just makes no sense - need to adjust pad on the fly and back
> it off if you heat the caliper up.


Indeed. If you get your brakes hot, closed doesn't work. And I got that on
hardly any hill at all. But then this was on a tandem.

>> working. They may need to be bled once every so often, but cables need
>> maintenance more than once every so often. All brakes need pads/blocks
>> replaced periodically, so I'm genuinely interested in why you think discs
>> aren't "fit and forget".

>
> And if you want to bleed them, which isnt really needed for a decade at a
> time, you just lob a piece of hose on the nipple, take the top off the
> caliper and squeeze, undo, tighten, release a few times and its done - not
> even as complex as replacing a cable!


Hmm. I'm guessing you've never bled a set of Hopes then. I've done one end
of ours, and it was a right pain, even with the bleeding kit.

One problem is them using DOT brake fluid. I _hate_ DOT brake fluid. (My car
doesn't use it either...). It needs changing in a way that the mineral oil
doesn't - 2 years, not 10.

I guess if I had Magura disks, some of my complaints may go away. (Shimano's
a no-no based on the use we give them).

The reason I say the discs aren't fit and forget in the same way as the
magura rims is that I have had to do this sort of **** on them, whereas the
rims have been sealed since I fitted them 10 years ago, and have never given
any problems.

There is another question though : is it worth the hassle? And the answer
for the MTB tandem is definitely yes. Can't tell for the road tandem since
nobody makes suitable hydraulic discs...

(Paul - does this answer your question too?)

cheers,
clive
 
P

Paul Boyd

Guest
On 29/08/2007 19:58, coyoteboy said,

> Lots of the top end systems are open - its how they get automatic pad
> wear adjustment. Certainly most of the systems I've seen on the trail
> have been open - closed just makes no sense - need to adjust pad on the
> fly and back it off if you heat the caliper up.


OK - I didn't realise the first bit, but the second bit? That's why
Shimano have the bladder in the lever - so that as the fluid expands the
air in the bladder compresses to compensate. Perhaps I'm
misunderstanding what is meant by a closed system.

> And if you want to bleed them, which isnt really needed for a decade at
> a time, you just lob a piece of hose on the nipple, take the top off the
> caliper and squeeze, undo, tighten, release a few times and its done -
> not even as complex as replacing a cable!


Surely that's the same for any system, except I assume you mean take the
top off the lever?

--
Paul Boyd
http://www.paul-boyd.co.uk/
 
C

Clive George

Guest
"coyoteboy" <[email protected]> wrote in message
news:[email protected]

> Many disc manufacturers use mineral oil like maggies so it doesnt absorb
> water, but even so the DOT based fluids never reach the sort of heat
> required to "wet boil" in anything other than extreme downhill conditions.


Remember I'm using ours on a tandem...

> I just dont understand where this idea that hydro discs are "high
> maintenance" comes from.


I'm not sure where you get it from either. I'm talking about relative to the
rim brakes.

But if you consider this experience -

Rim brakes : Worked out of the box, zero maintenance required of the
internals in 10 years

Discs : Need bedding in, needed bleeding to make the back brake work,
pistons misbehaving a little in 2 years. And of course there's the way the
disc pads can't cope with oil on them :-( (got sintered now, so you just
need to let the smoke out to fix this - but the rims don't suffer in this
way)

them you might understand where I'm coming from.

cheers,
clive
 
C

coyoteboy

Guest
Paul Boyd wrote:
>(can you even still get open systems?), and they just keep


Lots of the top end systems are open - its how they get automatic pad
wear adjustment. Certainly most of the systems I've seen on the trail
have been open - closed just makes no sense - need to adjust pad on the
fly and back it off if you heat the caliper up.

> working. They may need to be bled once every so often, but cables need
> maintenance more than once every so often. All brakes need pads/blocks
> replaced periodically, so I'm genuinely interested in why you think
> discs aren't "fit and forget".


And if you want to bleed them, which isnt really needed for a decade at
a time, you just lob a piece of hose on the nipple, take the top off the
caliper and squeeze, undo, tighten, release a few times and its done -
not even as complex as replacing a cable!
 
C

coyoteboy

Guest
Clive George wrote:

> That isn't "forgotten about them". I've never opened the rim brake
> internals - and they are 10 years old now.


I've replaced the magura blood after 4 years (just because I got some
for free) and it makes definite difference to pad movement feel. But
then my other HS33s had their oil replaced with chip oil when i ripped
the hose out of them on holiday and that works just as well to this day.
I think the point is that there is no need to bleed a disc, as there
isnt with a HS33. Many disc manufacturers use mineral oil like maggies
so it doesnt absorb water, but even so the DOT based fluids never reach
the sort of heat required to "wet boil" in anything other than extreme
downhill conditions. People often bleed hydro discs because they assume
they "should" - there is no need.

>> All brakes need pads/blocks replaced periodically, so I'm genuinely
>> interested in why you think discs aren't "fit and forget".

>
> Compared to the magura rim brakes, they aren't IME. That's it.


IME (I "maintain" 2 sets of HS33s - one pair of Raceline D and one
newer, 2 hope DH4s, 1 hope mini, 1 hope mini mono, a pair of louise FRs
and have direct contact with owners of cheapo cable and shimano XT discs
and have plain old Vs on the old machine that gets no use these days)
they are comparable to maggies - in fact less effort required, and less
problems with rim damage effecting them. The worst thing is the
occasional bouts of squeel, but then the HS33s get that with the wet
weather pads from time to time too. I managed to melt a set of HS33 pads
to the rim in the alps (DH course) and have blue'd the rotors on the
DH4s and mini several times. I just dont understand where this idea that
hydro discs are "high maintenance" comes from. I'd not replace my
maguras on my trials bike because the discs just dont bite as
aggressively at low speed, but then the maggies dont control as well at
high speed so I wouldnt use them on my MTB anymore - even with the
maggies I've run into the back of my brother (DH4s) on numerous
occasions due to the poorer high-speed braking (which is still
blisteringly good IMO).
 
C

CoyoteBoy

Guest
On 29 Aug, 19:13, "Clive George" <[email protected]> wrote:
> "coyoteboy" <[email protected]> wrote in message
> Indeed. If you get your brakes hot, closed doesn't work. And I got that on
> hardly any hill at all. But then this was on a tandem.


Tandems are a tad of an issue being essentially twice the energy being
dissipated as the brake was designed for. Must say I've never worked
on them but I cant see any reason why the mechanics of the work is any
different.

> Hmm. I'm guessing you've never bled a set of Hopes then. I've done one end
> of ours, and it was a right pain, even with the bleeding kit.


Yup, hopes were my first ever disc, never had a problem, never had the
bleed kit. I've shortened hoses on them a few times between frame/fork
changes on other peoples bikes and I didnt find bleeding them an issue
at all? Certainly easier than magura HS33s. But then I'm used to
bleeding the brakes on my car - maybe that helps? I didnt think it
could possibly be considered a difficult task?

> One problem is them using DOT brake fluid. I _hate_ DOT brake fluid. (My car
> doesn't use it either...). It needs changing in a way that the mineral oil
> doesn't - 2 years, not 10.


No it doesnt - this is where you are mistaken. It requires changing
only if you are going to overheat it - recommendations of 2 years are
set by car standards (which were thought up decades ago when brake
systems were considerably more agricultural and allowed moisture
absorbtion easily) and our brakes do not reach the heat of a car
caliper (though, of course, a tandem may get closer). Even on a DH run
in the alps myDH4 /calipers/ rarely got hot enough to burn with me
(15stone, the bike at 40lbs and speeds of 40mph). The wet boil temp of
DOT4 is 155 degrees C - if you get your calipers to anywhere near 155C
i bow down to your superior braking! (or pass you on the way down :),
most braking is un-necessary if you pick the right lines) I've yet to
hear of anyone boiling fluid in a bike brake - fading organic pads due
to outgassing, yes (solved by choosing a correct pad material from the
start). On a car - yes. The primary reason for bleeding DOT fluids is
to remove the fluid which has absorbed water (hence the wet boil
temps) and return "dry" fluid which boils at 240C. I actually change
out my fluid for DOT5.1 if I change the cable routing etc and have to
bleed, much the same as I'd change the cables on a cable brake or
change the fluid on the maggies.

> I guess if I had Magura disks, some of my complaints may go away. (Shimano's
> a no-no based on the use we give them).


Yes, I agree you wouldnt want shimano discs on a tandem - too
lightweight IME.

> The reason I say the discs aren't fit and forget in the same way as the
> magura rims is that I have had to do this sort of **** on them, whereas the
> rims have been sealed since I fitted them 10 years ago, and have never given
> any problems.


Why did you have to bleed it? It just isnt necessary. And as
mentioned, it couldnt be an easier task to blow through new fluid, not
like when you get really bad bubbles in and have to get shut of them
too. I'll do a youtube vid soon, maybe I have some magic technique I
didnt know was magic?

> There is another question though : is it worth the hassle? And the answer
> for the MTB tandem is definitely yes. Can't tell for the road tandem since
> nobody makes suitable hydraulic discs...


I'm missing where the hassle comes in TBH - which was my point from
the start - hydros are the most fit and forget items on any bike I've
owned or maintained!
 
P

Paul Boyd

Guest
On 29/08/2007 20:12, CoyoteBoy said,

> Yup, i think thats where the confusion comes in - a closed system is
> one where the entire volume of the fluid is under pressure when the
> lever is squozed :) An open system has a reservoir (be it a bladder or
> a cup etc).


I was totally confused, wasn't I? :)

--
Paul Boyd
http://www.paul-boyd.co.uk/
 
C

CoyoteBoy

Guest
On 29 Aug, 19:24, "Clive George" <[email protected]> wrote:
> "coyoteboy" <[email protected]> wrote in message
>
> news:[email protected]
>
> > Many disc manufacturers use mineral oil like maggies so it doesnt absorb
> > water, but even so the DOT based fluids never reach the sort of heat
> > required to "wet boil" in anything other than extreme downhill conditions.

>
> Remember I'm using ours on a tandem...
>
> > I just dont understand where this idea that hydro discs are "high
> > maintenance" comes from.

>
> I'm not sure where you get it from either. I'm talking about relative to the
> rim brakes.


You are suggesting that hydro discs need frequent maintenance and are
more complex than the rims - im suggesting they arent.

> But if you consider this experience -
>
> Rim brakes : Worked out of the box, zero maintenance required of the
> internals in 10 years
>
> Discs : Need bedding in, needed bleeding to make the back brake work,
> pistons misbehaving a little in 2 years. And of course there's the way the
> disc pads can't cope with oil on them :-( (got sintered now, so you just
> need to let the smoke out to fix this - but the rims don't suffer in this
> way)


It takes a short ride to bed a disc - 10-20 miles - if it takes longer
you have the caliper mis-aligned. Maggies also need you to carefully
align the pads or you get squeeks and the pads wearing unevenly. Why
would you have to bleed the rear? Presumably to fit to the frame- the
same with any hydro brake such as HS33? Why (and how) are the pistons
misbehaving - this again suggests you have the caliper misaligned to
start with - the pads pushing at odd angles tend to get jammed and not
retract well? This is totally contrary to my experience with well set
up discs, but i did get to practice on a few customers bikes before I
could afford my own! No, pads cant cope with oil on them, but then
maggie pads cant cope well in mud and ice. If you get oil on them then
thats carelessness, not the brake at fault - at least when out on the
trail a disc will work when drowned in mud and ice (better in most
cases) while maggies tend to tail off a little, especially at speed
again. If you ride in any real snow you'll find maggies get a nice
smooth layer of snow-ice packed onto the rim eventually - this isnt
fun - discs remain hot and prevent this.
 
C

Clive George

Guest
"CoyoteBoy" <[email protected]> wrote in message
news:[email protected]
> On 29 Aug, 19:13, "Clive George" <[email protected]> wrote:
>> "coyoteboy" <[email protected]> wrote in message
>> Indeed. If you get your brakes hot, closed doesn't work. And I got that
>> on
>> hardly any hill at all. But then this was on a tandem.

>
> Tandems are a tad of an issue being essentially twice the energy being
> dissipated as the brake was designed for. Must say I've never worked
> on them but I cant see any reason why the mechanics of the work is any
> different.


No, the mechanics are the same.

>> Hmm. I'm guessing you've never bled a set of Hopes then. I've done one
>> end
>> of ours, and it was a right pain, even with the bleeding kit.

>
> Yup, hopes were my first ever disc, never had a problem, never had the
> bleed kit. I've shortened hoses on them a few times between frame/fork
> changes on other peoples bikes and I didnt find bleeding them an issue
> at all? Certainly easier than magura HS33s. But then I'm used to
> bleeding the brakes on my car - maybe that helps? I didnt think it
> could possibly be considered a difficult task?


Maybe the mono levers are more of a pain then. Certainly the bits which are
similar to a car were no problem whatsoever - but the reserviour is
significantly more hassle, being all tiny and fiddly and having no spare
capacity.

>> One problem is them using DOT brake fluid. I _hate_ DOT brake fluid. (My
>> car
>> doesn't use it either...). It needs changing in a way that the mineral
>> oil
>> doesn't - 2 years, not 10.

>
> No it doesnt - this is where you are mistaken. It requires changing
> only if you are going to overheat it


Or if it gets wet. The mineral oil I have sitting around won't suffer this -
but the container of DOT fluid may well do :-(

> The wet boil temp of
> DOT4 is 155 degrees C - if you get your calipers to anywhere near 155C
> i bow down to your superior braking! (or pass you on the way down :),


Probably both. I'm not a fantastically confident descender, so will use the
brakes, and as you noticed I can put twice the energy into them. (Actually
it's potentially more than that, since I can't endo...)

>> The reason I say the discs aren't fit and forget in the same way as the
>> magura rims is that I have had to do this sort of **** on them, whereas
>> the
>> rims have been sealed since I fitted them 10 years ago, and have never
>> given
>> any problems.

>
> Why did you have to bleed it?


Because there was air in it. I think the people who put the tandem-length
pipe on it got it wrong - that was Hope BTW.

> It just isnt necessary.


Except it was...

> And as
> mentioned, it couldnt be an easier task to blow through new fluid, not
> like when you get really bad bubbles in and have to get shut of them
> too.


Like I did?

>> There is another question though : is it worth the hassle? And the answer
>> for the MTB tandem is definitely yes. Can't tell for the road tandem
>> since
>> nobody makes suitable hydraulic discs...

>
> I'm missing where the hassle comes in TBH - which was my point from
> the start - hydros are the most fit and forget items on any bike I've
> owned or maintained!


> If you get oil on them then thats carelessness, not the brake at fault


Actually, it's the fork air seal failing and dumping the oil on the brakes.

The sensitivity of the brakes to oil is a definite downside - with care, the
problem can be avoided, but I'm sure you'd agree the it would be better if
it wasn't there in the first place.

I think my discs are set up fairly well - they're definitely straight (I
spent a while getting that right when first installing them, and I'm not
completely mechanically inept.)

cheers,
clive
 
T

Tom \Johnny Sunset\ Sherman

Guest
roger merriman wrote:
> On 29 Aug, 05:03, "Tom \"Johnny Sunset\" Sherman"
> <[email protected]> wrote:
>>
>> I can lock up both from wheels on dry pavement with the Avid mechanical
>> disc brakes on my trike. The feel is mushy compared to a good hydraulic
>> system, however.
>>

> Thing is though that locking the wheels is one thing, stopping fast
> and safely is another, my cheap hybrid can lock it's wheels, but i
> would regard is brakes as poor, in that it wouldn't stop in hurry at
> speed, while my moutain bikes will, which considering the rubber on
> the road i'd probably struggle to lock wheels up.
>
> like the other day had to do a emergency stop, squeeling of tires on
> hot road but not locking.


Can you lock the front wheel on your hybrid? An upright bicycle will
"pitch over" before the front wheel will lock on dry pavement.
Conversely, due to weight transfer, the rear wheel can be locked with
quite weak brakes (or almost no brake at the point where the wheel is
about to be unloaded).

On a tadpole trike with a low seat, braking is limited by tire traction
only. The available braking force is generally about 40% more than could
be produced on an upright.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
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