Brake pad question



"daveornee" <[email protected]> wrote in message
news:[email protected]...
> It is nearly impossible to guess from here, but I have had
> a cable housing end come out of the frame "braze-on" and
> re-seat itself on the edge of the braze-on, thus pulling
> the cable tighter. This happened on our tandem, which has
> lots of rear cable and a few extra frame fittings to
> check. I have also come up on other riders who were
> experiencing similar brake rub issues (wouldn't have
> caught them without their handicap) and seen the housing
> end problem... and even one time when they put the
> slightly wider rimmed wheel on an alternate bicycle....
> the regular rim was 19 mm outside width, but the
> substitute was 20 mm wide.

Thanks for the suggestion, I hadn't checked this. I'll take
a look in the morning.
--
Mark South: World Citizen, Net Denizen
 
" S o r n i" <[email protected]> wrote in message
news:[email protected]...
> Mark South wrote:
>
> > OK, can we change the terms of the question now? Can we
> > assume, just for one moment, that it wasn't some twit
> > thing that I did, could there be anything else that woud
> > produce this effect? Has anyone else ever seen or heard
> > of this?
> >
> > One-line shots are more than acceptable, but best when
> > they are funny.
>
> I think a bike fairy injected the pads with some fat
> surreptitiously sucked from your left butt cheek.

Line allowance exceeded!

> Bill "look to the turkey baster" S.

C'mere, I'll give you a close look at my turkey
baster. :) :)
--
"...and his pants appeared to have exploded," police said.
 
"jdc" <[email protected]> wrote in message news:[email protected]...

> Did you take the pads off (out of the cartridge) and
> examine them? perhaps they have come apart or split.

Worth double checking, but the pads are almost new and
braking function is good.
--
Mark South: World Citizen, Net Denizen
 
"Jeff Wills" <[email protected]> wrote in message
news:[email protected]...
> "Mark South" <[email protected]> wrote in message
news:<[email protected]>...
> > The brakes were binding, both sides clamped down on the
> > (true) rim.
> >
> > > Check to see if your dual-pivot brakes need a bit of
> > > lube on the pivots.
> >
> > They worked fine after a bit of cable was fed through
> > the binder bolt.
> >
> > > The rubber wouldn't expand that much before melting...
> >
> > I have started wondering if the cables suddenly bedded
> > in in some mysterious
way
> > due to hard braking, not that I had to do a lot of that
> > on a gentle ride in
the
> > country.
>
> This is a possible explanation. Somehow the cable housing
> slipped out of the adjuster and then caught in the
> compressed position. This is *extremely* unlikely though.

Well, I know they didn't come out of the adjuster barrel,
which is pretty deep anyway, because I checked that that
hadn't backed up and I would have noticed.

> Was the bike left parked or unattended for some period?
> Some vandal may have come along and used the cable
> adjuster to clamp the brakes shut. Since the brakes are in
> otherwise perfect working order, I'd suspect this first.

No, the brakes were fine, I rode 20km and they were binding.
The change happened with me on the bike and probably while I
was moving.
--
"I would recommend Iowa or North Dakota for your dip
into reality."
- Ed Dolan in alt.rec.bicycles.recumbent
 
"Mark South" <[email protected]> wrote in message news:<[email protected]>...
>
> No, the brakes were fine, I rode 20km and they were
> binding. The change happened with me on the bike and
> probably while I was moving.

OK... unlikely explanation #3: how old are the rims? Could
they be worn to the point where they are bulging outward and
meeting the brake pads? This would require that the rims be
quite worn *and* that they bulge evenly around their
circumference. Also, the adjustment would have to be very
close to begin with.

What kind of rim is it? Are the rim walls parallel or do
they taper somewhat, like this: \__/ ?? I'm thinking that
the center bolt of the caliper could have bent upwards
somehow, binding the brake pads against the rim.

Could one or both of the brake pads have come slightly
loose, allowing them to rotate in the caliper? I've had this
happen- and the pads remain pretty tight afterwards.

Jeff (grasping at straws now)
 
ZeeExSixAre wrote:

> Mark South wrote:
>
>>Today I exeperienced something new to me.
>>
>>About 20 km into my Sunday morning ride, I was coming up a
>>gentle hill into a tiny village and thinking "Hell, I must
>>be getting weaker every day, why is this incline so hard?"
>>
>>So, I stopped for a breather and hopped of the bike. When
>>I was about to get on I noticed that the bike didn't roll
>>easily. Lifting the front wheel and spinning it showed the
>>front brake was binding hard, which explained the
>>difficulty up the gentle hill.
>>
>>Now the question: how did this happen? Before you answer,
>>some facts:
>>
>>A. The rim was and is true to within better than 1mm.
>>B. The wheel spun freely at the start of the ride (I
>> always check).
>>C. The brake adjuster had not moved - it was locked onto
>> the locknut.
>>D. I adjusted these brakes 6 weeks ago and they have been
>> perfect since then, until today.
>>E. Ambient conditions were blue sky, sun, steady cool
>> breeze, temps about 25 Celsius with wind cooling,
>> hotter out of the wind.
>>F. I hadn't done any heavy braking on the ride so far.
>>G. These are dual pivots on a road bike, with plain black
>> stock Shimano pads. H. The pads were running just
>> clear of the rim all round.
>>
>>So, could the pads have absorbed enough sun to heat and
>>expand and bind on the rim?
>>
>>Has anyone else ever seen this happen?
>>
>>Or is there another explanation?
>
>
>
> Although it's probably not the problem here, many often
> don't put the wheel all the way into the dropouts after
> taking the wheels off. Check to see if it's askew,
> especially if the brakes rub on one side. Check to see if
> your dual-pivot brakes need a bit of lube on the pivots.
>
> The rubber wouldn't expand that much before melting...
>
A brake shoe adjusted low will wear to a ridge that can
catch below the rim. Trim it away with a blade and raise the
shoe if that's the problem

--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971
 
"Jeff Wills" <[email protected]> wrote in message
news:[email protected]...
> "Mark South" <[email protected]> wrote in message
news:<[email protected]>...
> >
> > No, the brakes were fine, I rode 20km and they were
> > binding. The change happened with me on the bike and
> > probably while I was moving.
>
> OK... unlikely explanation #3: how old are the rims? Could
> they be worn to the point where they are bulging outward
> and meeting the brake pads? This would require that the
> rims be quite worn *and* that they bulge evenly around
> their circumference. Also, the adjustment would have to be
> very close to begin with.

The rims only have about 1200km on them, with very little
heavy braking. They are non-machine, non-anodized 32-spoke
Ambrosio semi-aero rims.

> What kind of rim is it? Are the rim walls parallel or do
> they taper somewhat, like this: \__/ ?? I'm thinking that
> the center bolt of the caliper could have bent upwards
> somehow, binding the brake pads against the rim.

Very close to parallel.

> Could one or both of the brake pads have come slightly
> loose, allowing them to rotate in the caliper? I've had
> this happen- and the pads remain pretty tight afterwards.

I'm going to treble-check that next time I have a moment to
look at the bike carefully.

Thanks for all the responses, BTW. I'm appreciative of all
the suggestions everyone has made.
--
"I would recommend Iowa or North Dakota for your dip
into reality."
- Ed Dolan in alt.rec.bicycles.recumbent
 
"A Muzi" <[email protected]> wrote in message
news:[email protected]...
>
> A brake shoe adjusted low will wear to a ridge that can
> catch below the rim.

Good point.

> Trim it away with a blade and raise the shoe if that's
> the problem

The rim is semi-aero, so doesn't have an edge to the brake
track, it just curves gently round to the spoke bed.

Thanks for the suggestion.
--
Mark South: World Citizen, Net Denizen
 
you need a centering tool.

http://www.parktool.com/repair_help/sidepull.shtml

so far you have not said if you actually tried centering
them or not.

did you say if the friction was on one side or equally
distributed?

i know someone asked..

wle.

In article <[email protected]>,
[email protected] says...
>
>"daveornee" <[email protected]> wrote in
>message news:[email protected]...
>> It is nearly impossible to guess from here, but I have
>> had a cable housing end come out of the frame "braze-on"
>> and re-seat itself on the edge of the braze-on, thus
>> pulling the cable tighter. This happened on our tandem,
>> which has lots of rear cable and a few extra frame
>> fittings to check. I have also come up on other riders
>> who were experiencing similar brake rub issues (wouldn't
>> have caught them without their handicap) and seen the
>> housing end problem... and even one time when they put
>> the slightly wider rimmed wheel on an alternate
>> bicycle.... the regular rim was 19 mm outside width, but
>> the substitute was 20 mm wide.
>
>Thanks for the suggestion, I hadn't checked this. I'll take
>a look in the morning.
>--
>Mark South: World Citizen, Net Denizen
 
my brakes go off center quite a lot. as someone said, center
them using a centering tool.

heat and humidity changes seem to cause this. possibly also
your calipers are loose.

or the centering adjustment is loose [this can be a separate
nut inside the calipers. hard to explain]

what i think is they are not meant to stay centered closer
than a mm or so.

it;s all friction, in standard road bike brakes.

also, the centering is usually not changed if someone came
along and tried to rotate the calipers around their pivot.
they will stay like that only til the brakes are applied and
then go right back to where they were.

center pull brakes are different but can also go off center.

wle.

In article <[email protected]>,
[email protected] says...
>
>"Jeff Wills" <[email protected]> wrote in message
>news:[email protected]...
>> "Mark South" <[email protected]> wrote in message
>news:<[email protected]>...
>> >
>> > No, the brakes were fine, I rode 20km and they were
>> > binding. The change happened with me on the bike and
>> > probably while I was moving.
>>
>> OK... unlikely explanation #3: how old are the rims?
>> Could they be worn to the point where they are bulging
>> outward and meeting the brake pads? This would require
>> that the rims be quite worn *and* that they bulge evenly
>> around their circumference. Also, the adjustment would
>> have to be very close to begin with.
>
>The rims only have about 1200km on them, with very little
>heavy braking. They are non-machine, non-anodized 32-spoke
>Ambrosio semi-aero rims.
>
>> What kind of rim is it? Are the rim walls parallel or do
>> they taper somewhat, like this: \__/ ?? I'm thinking that
>> the center bolt of the caliper could have bent upwards
>> somehow, binding the brake pads against the rim.
>
>Very close to parallel.
>
>> Could one or both of the brake pads have come slightly
>> loose, allowing them to rotate in the caliper? I've had
>> this happen- and the pads remain pretty tight afterwards.
>
>I'm going to treble-check that next time I have a moment to
>look at the bike carefully.
>
>Thanks for all the responses, BTW. I'm appreciative of all
>the suggestions everyone has made.
>--
>"I would recommend Iowa or North Dakota for your dip into
>reality."
>- Ed Dolan in alt.rec.bicycles.recumbent
 
w l e @ h o t m a i l . c o m (wle - no address harvesting!!) top-posted:

> you need a centering tool.

Or thumbs.

Bill "not even opposable, necessarily" S.
 
w l e @ h o t m a i l . c o m (wle - no address harvesting!!) wrote in message news:<[email protected]>...
> my brakes go off center quite a lot. as someone said,
> center them using a centering tool.
>
<much snipped>

wle-

Go back through the thread- you'll find that centering the
caliper *was not* the problem. We've eliminated the common
causes, plus a bunch of unlikely causes. What remains,
*however unlikely*, is probably the truth. (Thank you,
Sherlock Holmes.)

And *please* find the "shift" key!

Jeff
 
"Jeff Wills" <[email protected]> wrote in message
news:[email protected]...
> w l e @ h o t m a i l . c o m (wle - no address
> harvesting!!) wrote in message
news:<[email protected]>...
> > my brakes go off center quite a lot. as someone said,
> > center them using a centering tool.
> >
> <much snipped>

Sorry, none of the above.

> Go back through the thread- you'll find that centering the
> caliper *was not* the problem. We've eliminated the common
> causes, plus a bunch of unlikely causes. What remains,
> *however unlikely*, is probably the truth. (Thank you,
> Sherlock Holmes.)

I had a look at the bike and checked over the other
suggestions I hadn't thought of. None of them apply, notably
the barrel adjuster is not implicated.

Recall that I said I unbound the brakes by feeding a little
more cable (couple of mm) through the cable binder nut? Well
today, in a cool garage, the front brake is now running
notably wider than on Sunday, and the brake lever comes
nearer the handlebar. So I'm beginning to think that the
pads must have expanded some in the heat and contracted back
slightly in the cool.
--
Mark South: World Citizen, Net Denizen
 
"Mark South" <[email protected]> wrote in message news:<[email protected]>...

> > >I noticed that the bike didn't roll easily. Lifting the
> > >front wheel and spinning it showed the front brake was
> > >binding hard, which explained the difficulty up the
> > >gentle hill.
> > >
>
> OK, can we change the terms of the question now? Can we
> assume, just for one moment, that it wasn't some twit
> thing that I did, could there be anything else that woud
> produce this effect? Has anyone else ever seen or heard
> of this?
>

You still haven't told us what "this" is. The answer will be
found visually, and since we cannot see your bike, well, ...
it will be found by you.

> One-line shots are more than acceptable, but best when
> they are funny.

Look harder, homer. Something changed. Keep looking until
you see what is.

Doug
 
"Mark South" <[email protected]> wrote in message news:<[email protected]>...

>
> I had a look at the bike and checked over the other
> suggestions I hadn't thought of. None of them apply,
> notably the barrel adjuster is not implicated.
>
> Recall that I said I unbound the brakes by feeding a
> little more cable (couple of mm) through the cable binder
> nut? Well today, in a cool garage, the front brake is now
> running notably wider than on Sunday, and the brake lever
> comes nearer the handlebar. So I'm beginning to think that
> the pads must have expanded some in the heat and
> contracted back slightly in the cool.

Are you sure that the brake pads are contacting the rims
when the binding occurs? I'm guessing that the sidewall is
shot and the tire is changing shape and is what's contacting
the brake.

Doug
 
"Douglas Landau" <[email protected]> wrote in message
news:[email protected]...
> "Mark South" <[email protected]> wrote in message
news:<[email protected]>...
>
> > I had a look at the bike and checked over the other
> > suggestions I hadn't
thought
> > of. None of them apply, notably the barrel adjuster is
> > not implicated.
> >
> > Recall that I said I unbound the brakes by feeding a
> > little more cable
(couple
> > of mm) through the cable binder nut? Well today, in a
> > cool garage, the
front
> > brake is now running notably wider than on Sunday, and
> > the brake lever comes nearer the handlebar. So I'm
> > beginning to think that the pads must have expanded some
> > in the heat and contracted back slightly in the cool.
>
> Are you sure that the brake pads are contacting the rims
> when the binding occurs? I'm guessing that the sidewall is
> shot and the tire is changing shape and is what's
> contacting the brake.

New rims, no sidewall flex.
--
Mark South: World Citizen, Net Denizen
 
Mark South wrote:

> ... No, the brakes were fine, I rode 20km and they were
> binding. The change happened with me on the bike and
> probably while I was moving.
> --
> "I would recommend Iowa or North Dakota for your dip into
> reality."
> - Ed Dolan in alt.rec.bicycles.recumbent

The Usenet Gods made your brakes drag as punishment for
quoting Ed Dolan. ;)

--
Tom Sherman – Quad City Area
 
"Tom Sherman" <[email protected]> wrote in message
news:[email protected]...
> Mark South wrote:
>
> > ... No, the brakes were fine, I rode 20km and they were
> > binding. The change happened with me on the bike and
> > probably while I was moving.
> > --
> > "I would recommend Iowa or North Dakota for your dip
> > into reality."
> > - Ed Dolan in alt.rec.bicycles.recumbent
>
> The Usenet Gods made your brakes drag as punishment for
> quoting Ed Dolan. ;)

That's the most plausible explanation so far :)

But I'm pretty sure that I only started using that quote
after Sunday....However, the idea of Ed Dolan directing
someone else toward reality is too funny!
--
"To ... just not care that there are naked triathletes
running across your lawn, that's just a waste of
exhibitionism."
- Kibo, in alt.religion.kibology
 
[email protected] (Jeff Wills) wrote in message news:<[email protected]>...
> w l e @ h o t m a i l . c o m (wle - no address
> harvesting!!) wrote in message
> news:<[email protected]>...
> > my brakes go off center quite a lot. as someone said,
> > center them using a centering tool.
> >
> <much snipped>
>
> wle-
>
> Go back through the thread- you'll find that centering the
> caliper *was not* the problem. We've eliminated the common
> causes, plus a bunch of unlikely causes. What remains,
> *however unlikely*, is probably the truth. (Thank you,
> Sherlock Holmes.)
>
> And *please* find the "shift" key!
>
> Jeff

I had this very problem w/the front brake every time I made
a fast decent. The brakes are a pr. of Avid Arch Rival Mag
Linear brakes. At the bottom I would have to detach the
noodle until cool. I completely overhauled the frt. brake.
New noodle, pads, cable, housing, bellows. Cleaned & greased
every friction surface. New pads were Kool stop brick
colored (Scott-M) Thinlines. (Thinlines are the ones w/o a
metal backing. It's possible that the metal backing
transfered more heat to the mag arms from the pads.) Also
tightened the allen set screws @ the bushings. All this has
reduced the problem. As the new pads have worn in, it has
improved even more. (And I now have plenty of lever pull,
which I didn't before). I believe the problem was a
combination of the mag arms, the original black pads. I
think the mag arms are more prone to heat distortion. But
the main cause was the bushing setscrews becoming loose over
time. As a further precaution, I'm going to blue Loctite
them. I realize that you have dbl. pivot road brakes, but
perhaps you might be able to glean some small morsel of info
that could help. Good luck John
 
"Mark South" <[email protected]> wrote in message news:<[email protected]>...
> Today I exeperienced something new to me.
>
> About 20 km into my Sunday morning ride, I was coming up a
> gentle hill into a tiny village and thinking "Hell, I must
> be getting weaker every day, why is this incline so hard?"

well, after all that, what was it?

wle.