Closed-System Brakes: An observation...

(PeteCresswell) · May 24, 2005

Was slowly going down some fairly steep terrain yesterday when I noticed my
front brake's travel getting less and less.

In my experience, this is normal behavior as a closed-system brake heats up.

So I reach over and go to spin the adjustment knob back a little. Oops, can't
turn it. "Oh well, I'll just keep going until I get to that flat spot down
there...."

Never made the flat spot. Without any pressure on the lever that sucker just
got tigheter and tighter - finally stopping me completely.

Had to dismount and walk the bike on it's rear wheel. Took about ten minutes
for it to cool down enough to adjust.

Now I'm wondering what happens if that little feedback loop kicks in while
somebody's descending at speed.

Endo time?
--
PeteCresswell

(PeteCresswell) · May 24, 2005

Per (PeteCresswell):
>Now I'm wondering what happens if that little feedback loop kicks in while
>somebody's descending at speed.

.... and is too dumb to stop when they see it starting...
--
PeteCresswell

Dean A. Stepper · May 24, 2005

"(PeteCresswell)" <[email protected]> wrote in message
news:[email protected]...
> Was slowly going down some fairly steep terrain yesterday when I noticed
> my
> front brake's travel getting less and less.
>
> In my experience, this is normal behavior as a closed-system brake heats
> up.
>
> So I reach over and go to spin the adjustment knob back a little. Oops,
> can't
> turn it. "Oh well, I'll just keep going until I get to that flat spot
> down
> there...."
>
> Never made the flat spot. Without any pressure on the lever that sucker
> just
> got tigheter and tighter - finally stopping me completely.
>
> Had to dismount and walk the bike on it's rear wheel. Took about ten
> minutes
> for it to cool down enough to adjust.
>
> Now I'm wondering what happens if that little feedback loop kicks in while
> somebody's descending at speed.
>
> Endo time?
> --
> PeteCresswell

Pete what brakes are you using?

Santiago Peak in Orange County, Ca; 4000 ft elevation drop in 12 miles...40
minutes of constant brake pressure. Hayes Mags...no fad, nothing like you
are experiencing.

(PeteCresswell) · May 25, 2005

Per Dean A. Stepper:
>Pete what brakes are you using?
>
>Santiago Peak in Orange County, Ca; 4000 ft elevation drop in 12 miles...40
>minutes of constant brake pressure. Hayes Mags...no fad, nothing like you
>are experiencing.

Hope C2s.

It was the first time for me.

Had some noticible fade once on a long steep descent into Jim Thorpe Penna, but
that was the only time I experienced fade.

The lever travel thing, though is SOP - part of the deal with closed systems I
think. It's just that it never got to the point of locking up except for
this one time. What was different about this was that it was very steep and I
was going very slowly - as in walking pace or slower (and I weigh about 220...)
--
PeteCresswell

doki · May 25, 2005

(PeteCresswell) wrote:
> Per Dean A. Stepper:
>> Pete what brakes are you using?
>>
>> Santiago Peak in Orange County, Ca; 4000 ft elevation drop in 12
>> miles...40 minutes of constant brake pressure. Hayes Mags...no fad,
>> nothing like you are experiencing.
>
> Hope C2s.
>
> It was the first time for me.
>
> Had some noticible fade once on a long steep descent into Jim Thorpe
> Penna, but that was the only time I experienced fade.
>
> The lever travel thing, though is SOP - part of the deal with closed
> systems I think. It's just that it never got to the point of
> locking up except for this one time. What was different about this
> was that it was very steep and I was going very slowly - as in
> walking pace or slower (and I weigh about 220...)

Hope are known here for working fine until people go to the Alps on holiday,
and then they die. Shimano are universally liked, despite the lack of a
bling name.

Ride-A-Lot · May 25, 2005

(PeteCresswell) wrote:
> Per Dean A. Stepper:
>
>>Pete what brakes are you using?
>>
>>Santiago Peak in Orange County, Ca; 4000 ft elevation drop in 12 miles...40
>>minutes of constant brake pressure. Hayes Mags...no fad, nothing like you
>>are experiencing.
>
>
> Hope C2s.
>
> It was the first time for me.
>
> Had some noticible fade once on a long steep descent into Jim Thorpe Penna, but
> that was the only time I experienced fade.
>
> The lever travel thing, though is SOP - part of the deal with closed systems I
> think. It's just that it never got to the point of locking up except for
> this one time. What was different about this was that it was very steep and I
> was going very slowly - as in walking pace or slower (and I weigh about 220...)

Pete,

I come down the Wagon Trail at JT on a 30# Ellsworth ID with Hayes HFX
hydros. I have never had a fade or lockup. Same with intermediate DH
at Vail on the same bike. Seven miles at a fair incline with no fade or
lockup. It might be the fluid you are using. It may be heating up too
fast. I use DOT-4 brake fluid (regular automotive fluid you buy in Pep
Boys) and have never had a problem.

--
o-o-o-o Ride-A-Lot o-o-o-o
www.schnauzers.ws

Michael Dart · May 25, 2005

(PeteCresswell) wrote:
> Per (PeteCresswell):
>> The lever travel thing, though is SOP - part of the deal with closed
>> systems I think.
>
> Can anybody comment on open systems? i.e. are they subject to having
> the brakes tighten up upon heating?

An open system has a reservoir to hold the expanding fluid so the volume in
the system between the master cylinder and the caliper remains constant
(more or less). In a closed system it has no where to go except the
caliper pushing out the pistons.

With Hayes it's easy to make them into a closed system by "nursing" the
levers. It doesn't take much pull to close off the hole leading to the
reservior. You have to remember to completely release the lever
occaisionally.

Mike

(PeteCresswell) · May 25, 2005

Per (PeteCresswell):
>The lever travel thing, though is SOP - part of the deal with closed systems I
>think.

Can anybody comment on open systems? i.e. are they subject to having the brakes
tighten up upon heating?
--
PeteCresswell

Michael Dart · May 26, 2005

Ride-A-Lot wrote:
> (PeteCresswell) wrote:
>> Per Dean A. Stepper:
>>
>>> Pete what brakes are you using?
>>>
>>> Santiago Peak in Orange County, Ca; 4000 ft elevation drop in 12
>>> miles...40 minutes of constant brake pressure. Hayes Mags...no
>>> fad, nothing like you are experiencing.
>>
>>
>> Hope C2s.
>>
>> It was the first time for me.
>>
>> Had some noticible fade once on a long steep descent into Jim Thorpe
>> Penna, but that was the only time I experienced fade.
>>
>> The lever travel thing, though is SOP - part of the deal with closed
>> systems I think. It's just that it never got to the point of
>> locking up except for this one time. What was different about this
>> was that it was very steep and I was going very slowly - as in
>> walking pace or slower (and I weigh about 220...)
>
> Pete,
>
> I come down the Wagon Trail at JT on a 30# Ellsworth ID with Hayes HFX
> hydros. I have never had a fade or lockup. Same with intermediate DH
> at Vail on the same bike. Seven miles at a fair incline with no fade
> or lockup. It might be the fluid you are using. It may be heating
> up too fast. I use DOT-4 brake fluid (regular automotive fluid you
> buy in Pep Boys) and have never had a problem.

Hayes HFX hydros are an open hydraulic system. The reservoir (bladder) is
hidden in the lever.

Mike

MattB · May 26, 2005

(PeteCresswell) wrote:
> Per (PeteCresswell):
>
>>The lever travel thing, though is SOP - part of the deal with closed systems I
>>think.
>
>
> Can anybody comment on open systems? i.e. are they subject to having the brakes
> tighten up upon heating?

My Magura Marta SLs (open, I believe) have faded a little on long
downhills. I just find the lever moving closer to the bars on the couple
of occasions it's happened (on 2-3000 Ft. DH runs). If I pump it a
couple of times it seems to go away. Never been a problem for me.

Matt

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Closed-System Brakes: An observation...

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