Disc brake failure in CX...

"Andre Jute" wrote in message
...

So it is probably indicative that an amazing number of the
available bikes with Rohloff rear ends use the Magura HS-11 or -33
hydraulic rim brakes, which cost half as much again as the cheaper
disc brakes from good-name manufacturers.

Maguras are great - but if considering them, don't bother with HS-11 - HS-33
sacrifices a bit of pad clearance for mechanical advantage, and since
there's more than enough to play with it's a worthwhile exchange.

With a ceramic (coated) rim, they will just need pad changes. But I still
got disks on the MTB. (ok, I had no choice, but I'd have got them anyway
even if I did)

I wonder if your observation has any basis in nationality - both Rohloff and
Magura are German, and the brakes could have a rather wider market
penetration over there. And of course Maguras don't require anything but
normal canti bosses, so are good choice for a "premium" quality brake on an
existing frameset.

On Nov 9, 3:15*pm, Andre Jute wrote:
On Nov 9, 9:53*pm, Ryan Cousineau wrote:





It turns out cheating at CX is harder than I thought.

I run Shimano cable-actuated discs on my cheater CX bike. It was
designed to be mud-proof.

Today, we finally had a race with epic rain and mud. It was great. The
first few laps, I confidently used my sweet brakes to go hard into some
pretty mucky terrain.

Then my brakes failed completely. Both ends. As in virtually zero
braking. I was able to demonstrate for people later that I could pull
the levers to the bar and roll the bike without serious resistance.

Considering this race had at least one steep and mucky descent, it got
pretty interesting!

So I get back to the pit, and it turns out a teammate, running Avid
cable discs, had exactly the same symptoms.

Anyone else seen this? I haven't taken the brakes apart yet to see what
happened to the pads. I'll let you know.

I think you'll find the pads just wore out, Ryan, and you'll also
find, if they're the pads that came with the brakes, that they're
"organic". Anyone with low-end (and some high-end "environmentally
aware") disc brakes knows the symptoms, and has had a scary experience
or two. The brakes just keep on going, and then suddenly, even if
brand new or apparently thick on the pre-race check, they get some mud
(or even just dust and a little water) on them and the wear rate
shoots up logarithmically. Sintered or metallic brakes do not display
this accelerated failure mode but they squeal and require more bedding-
in and are said to be less good in the wet than the organic kind. At
the mailorder discounters the two kinds of pad cost about the same, so
I suggest you try metallic pads if you're going to be riding in the
mud, and put up with the squeal when you ride in more civilized
surrounding.

The above is given from experience. I have also heard that sintered
pads are not as longlasting (under ideal conditions) as organic pads,
but have no experience as my disc brake pads all seem to last about a
thousand miles (no offroading, only clean rain).

I had one truly frightening experience. I check the pads about
monthly. I was riding this bike with half-worn pads when it started
raining. Maybe the pads were dusty from just standing; there was
certainly no mud on them. It started raining just as I reached the top
of one of my favourite hills and started the long downhill section,
which at the bottom has a couple of sharp blind turns and then a six-
way junction often with farm machinery on it; hard braking is required
even under ideal circumstances because the only runoff is an
impenetrable bramble hedge that'll chew you up and won't spit you out
again. When I braked, the bike slowed a little, and then there was
nothing, it just spurted forward again on the fall of the road. Just
like that. I took my chances with the road (I still had the rear
roller brake and could thus "lay the bike down" if necessary, spin it
out) and fortunately there wasn't a big tractor on it, but I can't
claim it is a day I remember fondly. I'm too old for gratuitous
adrenalin... I checked and found that the Shimano literature carries a
waning about this sort of behaviour of pads; I'd even read it before,
but missed the point that it could happen with dramatic suddenness.

HTH.

Andre Jutehttp://members.lycos.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html- Hide quoted text -

- Show quoted text -

When the pads wear on the BB7s, you just dial down the calipers, and
when they wear far enough, the spring clips hit the rotors, and you
get this annoying pinging sound -- so you know when your pads are
shot.

I just got back from a ride where 10-12 miles were spent on trails and
in mud and leaves in Forest Park on my CX bike -- and my brakes were a
little less powerful due to the crud, but they still stopped fine.
BUT, I was on 35mm slicks (thinking I was going to stay on the road),
and when the going got really tough, I got off -- because I had zero
traction. So my mud experience was less muddy than Ryan's.

Wash the rotors off and see if the bike stops. If so, then there was
probably mud packed into the space between the rotor and the pads, or
the rotors were packed with mud. If it doesn't work, then the cable
slipped or the pad needs to be adjusted. -- Jay Beattie.

The above is given from experience. I have also heard that sintered
pads are not as longlasting (under ideal conditions) as organic pads,
but have no experience as my disc brake pads all seem to last about a
thousand miles (no offroading, only clean rain).

Organic pads wear faster, sometimes much faster, than the metallic
versions. But they generally bed in more quickly and make less noise.

How this plays into the CX brake failure I don't know. I suspect it's
more likely they became contaminated by something in the muck, which
might be a more-likely source of trouble with a longer-lasting brake
pad, because the contamination wouldn't wear away as quickly. Maybe. No
personal experience on this one; my last CX race was 35 years ago, and
I'm not chomping at the bit to try it again. Way too clumsy off the
bike.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com


"Andre Jute" wrote in message
...
On Nov 9, 9:53 pm, Ryan Cousineau wrote:
It turns out cheating at CX is harder than I thought.

I run Shimano cable-actuated discs on my cheater CX bike. It was
designed to be mud-proof.

Today, we finally had a race with epic rain and mud. It was great. The
first few laps, I confidently used my sweet brakes to go hard into
some
pretty mucky terrain.

Then my brakes failed completely. Both ends. As in virtually zero
braking. I was able to demonstrate for people later that I could pull
the levers to the bar and roll the bike without serious resistance.

Considering this race had at least one steep and mucky descent, it got
pretty interesting!

So I get back to the pit, and it turns out a teammate, running Avid
cable discs, had exactly the same symptoms.

Anyone else seen this? I haven't taken the brakes apart yet to see
what
happened to the pads. I'll let you know.

I think you'll find the pads just wore out, Ryan, and you'll also
find, if they're the pads that came with the brakes, that they're
"organic". Anyone with low-end (and some high-end "environmentally
aware") disc brakes knows the symptoms, and has had a scary experience
or two. The brakes just keep on going, and then suddenly, even if
brand new or apparently thick on the pre-race check, they get some mud
(or even just dust and a little water) on them and the wear rate
shoots up logarithmically. Sintered or metallic brakes do not display
this accelerated failure mode but they squeal and require more bedding-
in and are said to be less good in the wet than the organic kind. At
the mailorder discounters the two kinds of pad cost about the same, so
I suggest you try metallic pads if you're going to be riding in the
mud, and put up with the squeal when you ride in more civilized
surrounding.

The above is given from experience. I have also heard that sintered
pads are not as longlasting (under ideal conditions) as organic pads,
but have no experience as my disc brake pads all seem to last about a
thousand miles (no offroading, only clean rain).

I had one truly frightening experience. I check the pads about
monthly. I was riding this bike with half-worn pads when it started
raining. Maybe the pads were dusty from just standing; there was
certainly no mud on them. It started raining just as I reached the top
of one of my favourite hills and started the long downhill section,
which at the bottom has a couple of sharp blind turns and then a six-
way junction often with farm machinery on it; hard braking is required
even under ideal circumstances because the only runoff is an
impenetrable bramble hedge that'll chew you up and won't spit you out
again. When I braked, the bike slowed a little, and then there was
nothing, it just spurted forward again on the fall of the road. Just
like that. I took my chances with the road (I still had the rear
roller brake and could thus "lay the bike down" if necessary, spin it
out) and fortunately there wasn't a big tractor on it, but I can't
claim it is a day I remember fondly. I'm too old for gratuitous
adrenalin... I checked and found that the Shimano literature carries a
waning about this sort of behaviour of pads; I'd even read it before,
but missed the point that it could happen with dramatic suddenness.

HTH.

Andre Jute
http://members.lycos.co.uk/fiultra/B...20CYCLING.html

Jay Beattie wrote:
I just got back from a ride where 10-12 miles were spent on trails and
in mud and leaves in Forest Park on my CX bike -- and my brakes were a
little less powerful due to the crud, but they still stopped fine.
BUT, I was on 35mm slicks (thinking I was going to stay on the road),
and when the going got really tough, I got off -- because I had zero
traction. So my mud experience was less muddy than Ryan's.

Do you just stay on Leif Erikson when you go out there?

--
Paul M. Hobson
..:change the f to ph to reply:.

On Nov 9, 5:05*pm, "Paul M. Hobson" wrote:
Jay Beattie wrote:
I just got back from a ride where 10-12 miles were spent on trails and
in mud and leaves in Forest Park on my CX bike -- and my brakes were a
little less powerful due to the crud, but they still stopped fine.
BUT, I was on 35mm slicks (thinking I was going to stay on the road),
and when the going got really tough, I got off -- because I had zero
traction. *So my mud experience was less muddy than Ryan's.

Do you just stay on Leif Erikson when you go out there?

I usually take Saltzman as my slacker route up to Skyline. That's what
I did today because I have a cold. For non-PDXers, Saltzman is a three
or so mile packed dirt fire road that ascends the West Hills and is
more or less part of the Forest Park trail system. I road up to
Skyline but decided to go back down and go south on Leif Erikson.
When I hit Thurman, I decided not to go home through town but to stay
in the hills and foolishly took the trail at the end of Aspen -- which
goes straight up and is muddy and covered in thick leaves. I couldn't
get traction on my 35mm slicks and ended up trudging through the mud
-- probably half the trail. That put me at the park on 53rd -- I
climbed up 53rd to Thompson, and then climbed up Thompson to Skyline
and road south over the various hills (Greenleaf) back to South
Burlingame. All of the numbered fire lanes are steep, narrow and
muddy. You need knobbies for those this time of the year. Here are
some maps of the trails. http://www.artofgeography.com/maps/p...n-saltzman.pdf

The real CXers, including my usual riding buddy, were out at PIR for
the SS CX Nationals. My buddy is an engineer for Yakima and when he
wasn't racing, he was manning a giant windmill obstacle he and his
cohorts had created and a giant bubble machine. The single speed scene
is like Belgium meets Wayne's World. -- Jay Beattie.

On Nov 10, 12:14*am, "Clive George" wrote:
"Andre Jute" wrote in message

...

So it is probably indicative that an amazing number of the
available bikes with Rohloff rear ends use the Magura HS-11 or -33
hydraulic rim brakes, which cost half as much again as the cheaper
disc brakes from good-name manufacturers.

Maguras are great - but if considering them, don't bother with HS-11 - HS-33
sacrifices a bit of pad clearance for mechanical advantage, and since
there's more than enough to play with it's a worthwhile exchange.

With a ceramic (coated) rim, they will just need pad changes. But I still
got disks on the MTB. (ok, I had no choice, but I'd have got them anyway
even if I did)

I wonder if your observation has any basis in nationality - both Rohloff and
Magura are German, and the brakes could have a rather wider market
penetration over there. And of course Maguras don't require anything but
normal canti bosses, so are good choice for a "premium" quality brake on an
existing frameset.

I wondered about that, but the Magura rim hydraulics are also on
custom-framed bikes where the makers could have fitted anything,
including disc braze-ons. In any event, with a Rohloff bike with a
sliding frame end, the disc brake fitting sits on the bit that bolts
on to the disc, which costs a few bucks to change. Getting a disc-
capable fork isn't a big deal. I think there's probably real value
beyond a "national" choice there.

All the same, now that I cycle so much, I think I'll stick to disc
brakes. I don't fancy rebuilding wheels when the rims wear through.
Mind you, that took about ten years on my last bike with rim brakes, a
bit into the past now. If I ride twice as much, the rims could last
five years before the nuisance arises of having the wheels rebuilt.

Andre Jute
Our legislators managed to criminalize fox-hunting and smoking; when
will they get off their collective fat backside and criminalize
negative feedback? It is clearly consumed only by thickoes.

On Nov 10, 2:13*am, Jay Beattie wrote:

I usually take Saltzman as my slacker route up to Skyline. That's what
I did today because I have a cold. For non-PDXers, Saltzman is a three
or so mile packed dirt fire road that ascends the West Hills and is
more or less part of the Forest Park trail system. I road up to
Skyline but decided to go back down and go south on Leif Erikson.
When I hit Thurman, I decided not to go home through town but to stay
in the hills and foolishly took the trail at the end of Aspen -- which
goes straight up and is muddy and covered in thick leaves. *I couldn't
get traction on my 35mm slicks and ended up trudging through the mud
-- probably half the trail. *That put me at the park on 53rd -- I
climbed up 53rd to Thompson, and then climbed up Thompson to Skyline
and road south over the various hills (Greenleaf) back to South
Burlingame. *All of the numbered fire lanes are steep, narrow and
muddy. You need knobbies for those this time of the year. * Here are
some maps of the trails.http://www.artofgeography.com/maps/p...n-saltzman.pdf

Gee, Jay, are you sure you want the whole of RBT to come live in your
backyard? I live in the countryside and I don't have that many lanes,
though mine are admittedly all blacktop in very nice condition (even
the real farm lanes are easily passable on 35-37mm tyres). Publishing
a map like that is like an invitation to the less fortunate. -- Andre
Jute

On Nov 10, 12:13*am, "Tom Kunich" cyclintom@yahoo. com wrote:
"Andre Jute" wrote in message

...



Did you see Chalo's very interesting post about the advantages of rim
brakes a few days ago?

No, and it isn't on my list either. Hmmm, what group did he post in?

This one. The thread was " Which brakes are strongest". Here's
Chalo's contribution:

************
There are at least two relevant measures of brake "strength": braking
force per lever force, and gross braking force available irrespective
of what that takes at the lever.

By the first measure, hydraulic discs are very good, as are hydraulic
rim brakes, dual-pivot short reach calipers, and properly adjusted
linear-pull brakes with adjustable-gain levers. Drums are among the
worst in this regard.

What matters most to me is a brake that will keep delivering more
braking power as I demand more, especially one that will dish it out
at a linear or better-than-linear rate. Most of the above brakes that
have strong lever response give less and less additional braking power
as more lever effort is applied. That's not a big deal if your hand
strength and the amount of braking torque you can actually use are
normal. I can use a lot more braking power than normal, thus total
system stiffness and instantaneous heat capacity come into play. Drum
brakes are some of the best in their ability to keep braking harder as
the lever is pulled harder (until they overheat); their limitation is
related to the travel and MA of the lever and the amount of mush in
the cable.

A linear-pull brake with monolithic arms, stiff pads, and a stiff
booster, applied to a sturdy rim, can deliver as much gross braking
force and power as anything else you or I have named. Magura
hydraulic rim brakes are just as strong _if_ a booster is used, and I
understand that trials bike manufacturers now provide soft pads that
have much better feel and friction coefficient than the rock-hard grey
pads I used way back when. Discs-- even big hydraulic ones-- in my
observation display a falling rate of lever response, coupled with
fade at high sustained loads.

Shimano Rollerbrakes have not worked well for me. They have good
initial bite compared to normal drum brakes, but like discs they have
a falling rate as forces rise. They fade sooner and more dramatically
than any other bicycle brakes I have experienced. They require more
frequent service (greasing) than normal drums, though it's still far
less maintenance than rim or disc brakes. I'll use one as a rear
brake, but not on the front. A respectable front disc brake with
sintered metal pads would be a fine companion for a rear Rollerbrake.
I would use a cable-actuated one like the Avid BB7 so that I could use
matched Speed Dial or similar levers for both front and rear.

Chalo

*************

On Nov 9, 7:12*pm, Andre Jute wrote:
On Nov 10, 2:13*am, Jay Beattie wrote:

I usually take Saltzman as my slacker route up to Skyline. That's what
I did today because I have a cold. For non-PDXers, Saltzman is a three
or so mile packed dirt fire road that ascends the West Hills and is
more or less part of the Forest Park trail system. I road up to
Skyline but decided to go back down and go south on Leif Erikson.
When I hit Thurman, I decided not to go home through town but to stay
in the hills and foolishly took the trail at the end of Aspen -- which
goes straight up and is muddy and covered in thick leaves. *I couldn't
get traction on my 35mm slicks and ended up trudging through the mud
-- probably half the trail. *That put me at the park on 53rd -- I
climbed up 53rd to Thompson, and then climbed up Thompson to Skyline
and road south over the various hills (Greenleaf) back to South
Burlingame. *All of the numbered fire lanes are steep, narrow and
muddy. You need knobbies for those this time of the year. * Here are
some maps of the trails.http://www.artofgeography.com/maps/p...n-saltzman.pdf

Gee, Jay, are you sure you want the whole of RBT to come live in your
backyard? I live in the countryside and I don't have that many lanes,
though mine are admittedly all blacktop in very nice condition (even
the real farm lanes are easily passable on 35-37mm tyres). Publishing
a map like that is like an invitation to the less fortunate. -- Andre
Jute

You know, Andre, that link was a mistake and only showed one panel of
the Forest Park trail system. Here is the right link with all the
panels. http://www.artofgeography.com/maps/fp/index.html The trails
are pretty spectacular this time of year with the leaves changing
color. There are a few old and (mostly) second growth fir with lots
of maple species -- probably introduced a hundred or more years ago.
It's not the Emerald Isle, but its a nice place to ride so close to
downtown. -- Jay Beattie.

"Andre Jute" wrote in message
...

All the same, now that I cycle so much, I think I'll stick to disc
brakes. I don't fancy rebuilding wheels when the rims wear through.
Mind you, that took about ten years on my last bike with rim brakes, a
bit into the past now. If I ride twice as much, the rims could last
five years before the nuisance arises of having the wheels rebuilt.

Get ceramic coated rims and you won't have that nuisance.

(That said, any road bike here just has plain ally rims - I'm only really
concerned about rim wear on the MTBs. I can and have rebuilt when rims have
worn out - last one lasted about 15,000 mi IIRC).