Disk Brakes vs. V Brakes??

Hi,

I tried a bike with hydraulic disk brakes (Hayes Sole V6) yesterday
for the first time, and would appreciate your input on my impressions:

- On the first bike I tried, it was not possible to block the wheel
with the disk brake. I checked and found that the disk was oily. On
another bike (same brake) I was able to get the wheel to block, but
with application of extreme force to the brake handle, MUCH more than
required by any V brake I ever tried.

Question: Are Hydraulic Brakes really weaker than V brakes, or was this
bike just assembled by monkeys?

- I noticed that the hydraulic disc brakes have a much 'spongier' feel
than the cable actuated V brakes. This I guess was related to the
hydraulic hose / brake line expanding under pressure, because it was ok
on the front brake (1/2 of the brake lever way until full braking), and
not acceptable no the rear brake (had to pull the brake lever almost up
to the handle bar to get full breaking power)

Question: Is this again a problem of monkey assembly (not enough
fluid?, air in the lines?, what else? ...), or cheap brake lines, or
both? And are there better brake lines that expand less than the stock
ones?
Or ARE hydraulic disc brakes just spongier? If yes, that much
spongier??

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

Thanks a lot!

PS: All the monkey references are founded on an employee there telling
me that 'there are no electrical brakes' when I asked for differences
between hydraulic and cable actuated. When I asked her that about the
front fork maxing out, i.e. hitting the limit of it's travel hard, she
replied with 'many people like their forks soft'. (I found out how they
can be adjusted later.) When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

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wrote:
Hi,

I tried a bike with hydraulic disk brakes (Hayes Sole V6) yesterday
for the first time, and would appreciate your input on my impressions:

- On the first bike I tried, it was not possible to block the wheel
with the disk brake. I checked and found that the disk was oily. On
another bike (same brake) I was able to get the wheel to block, but
with application of extreme force to the brake handle, MUCH more than
required by any V brake I ever tried.

Question: Are Hydraulic Brakes really weaker than V brakes, or was this
bike just assembled by monkeys?

- I noticed that the hydraulic disc brakes have a much 'spongier' feel
than the cable actuated V brakes. This I guess was related to the
hydraulic hose / brake line expanding under pressure, because it was ok
on the front brake (1/2 of the brake lever way until full braking), and
not acceptable no the rear brake (had to pull the brake lever almost up
to the handle bar to get full breaking power)

Question: Is this again a problem of monkey assembly (not enough
fluid?, air in the lines?, what else? ...), or cheap brake lines, or
both? And are there better brake lines that expand less than the stock
ones?
Or ARE hydraulic disc brakes just spongier? If yes, that much
spongier??

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

Thanks a lot!

PS: All the monkey references are founded on an employee there telling
me that 'there are no electrical brakes' when I asked for differences
between hydraulic and cable actuated. When I asked her that about the
front fork maxing out, i.e. hitting the limit of it's travel hard, she
replied with 'many people like their forks soft'. (I found out how they
can be adjusted later.) When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

--
I haven't worked on any hydraulic bicycle disc brakes, but have
worked on many motorcycle ones and that sure sounds like there is some
air in the lines that needs to be bled out.

Smokey

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wrote:
Hi,

I tried a bike with hydraulic disk brakes (Hayes Sole V6) yesterday
for the first time, and would appreciate your input on my impressions:

- On the first bike I tried, it was not possible to block the wheel
with the disk brake. I checked and found that the disk was oily. On
another bike (same brake) I was able to get the wheel to block, but
with application of extreme force to the brake handle, MUCH more than
required by any V brake I ever tried.

Question: Are Hydraulic Brakes really weaker than V brakes, or was this
bike just assembled by monkeys?

Number 2..rotors and pads must be free of any contamination.

- I noticed that the hydraulic disc brakes have a much 'spongier' feel
than the cable actuated V brakes. This I guess was related to the
hydraulic hose / brake line expanding under pressure, because it was ok
on the front brake (1/2 of the brake lever way until full braking), and
not acceptable no the rear brake (had to pull the brake lever almost up
to the handle bar to get full breaking power)

Question: Is this again a problem of monkey assembly (not enough
fluid?, air in the lines?, what else? ...), or cheap brake lines, or
both? And are there better brake lines that expand less than the stock
ones?
Or ARE hydraulic disc brakes just spongier? If yes, that much
spongier??

Brakes need to be bled. Lines don't flex or expand, poor setup.

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

Temp no big deal.
Thanks a lot!

PS: All the monkey references are founded on an employee there telling
me that 'there are no electrical brakes' when I asked for differences
between hydraulic and cable actuated. When I asked her that about the
front fork maxing out, i.e. hitting the limit of it's travel hard, she
replied with 'many people like their forks soft'. (I found out how they
can be adjusted later.) When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

Typical of bike shop, USA..peopled by the untrained. Think that if they
ride a bike, they know something about them(no electric brakes, that is
amazing that she would say such a thing. I guess she has not heard of
'mechanical' disc brakes)

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wrote:
Hi,

I tried a bike with hydraulic disk brakes (Hayes Sole V6) yesterday
for the first time, and would appreciate your input on my impressions:

- On the first bike I tried, it was not possible to block the wheel
with the disk brake. I checked and found that the disk was oily. On
another bike (same brake) I was able to get the wheel to block, but
with application of extreme force to the brake handle, MUCH more than
required by any V brake I ever tried.

Question: Are Hydraulic Brakes really weaker than V brakes, or was this
bike just assembled by monkeys?

no, just assembled badly. hydraulic brakes are highly effective, more
so than rim brakes in off-road conditions.


- I noticed that the hydraulic disc brakes have a much 'spongier' feel
than the cable actuated V brakes. This I guess was related to the
hydraulic hose / brake line expanding under pressure, because it was ok
on the front brake (1/2 of the brake lever way until full braking), and
not acceptable no the rear brake (had to pull the brake lever almost up
to the handle bar to get full breaking power)

Question: Is this again a problem of monkey assembly (not enough
fluid?, air in the lines?, what else? ...), or cheap brake lines, or
both? And are there better brake lines that expand less than the stock
ones?
Or ARE hydraulic disc brakes just spongier? If yes, that much
spongier??

no, they're firm. sponginess means air in the line.


- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

they get warm because of the friction - that's what all brakes do.
you'll have no problem with heating issues on a disk braked bike - once
set up correctly, use with complete confidence.


Thanks a lot!

PS: All the monkey references are founded on an employee there telling
me that 'there are no electrical brakes' when I asked for differences
between hydraulic and cable actuated. When I asked her that about the
front fork maxing out, i.e. hitting the limit of it's travel hard, she
replied with 'many people like their forks soft'. (I found out how they
can be adjusted later.) When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

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posting problems, or contact the moderators, please see http://rbor.org/
Please read the charter before posting: http://rbor.org/rbor_charter.txt


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When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

I would strongly suggest you _run_ from a shop that is trying to sell a bike
with oiled braking surfaces. What else have they mis-assembled?

If you have to pay someone to get the bike to work, you're going to lose any
money you would save from their "sale" price. If you can do all the work
yourself, you don't need answers from rec.bicycles.tech.

-Dion


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jim beam wrote:
wrote:
Hi,

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

they get warm because of the friction - that's what all brakes do.
you'll have no problem with heating issues on a disk braked bike - once
set up correctly, use with complete confidence.


Regarding the heating issue, I came across a couple on a tandem who had
a hydraulic disk brake in back, instead of a drag brake. They said
that on long downhills the brake heating transfers heat to the fluid,
the fluid expands and they end up with the brake applied without any
lever action. They have to stop and let the fluid cool.

A tandem drag brake and a downhill ATB are not the exact same situation
but both can expect to sometimes apply the brake for 20-30 minutes on a
very long downhill. Does this ever occur on an ATB?

Tom

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On Tue, 10 Oct 2006 00:04:56 -0600, Chris_MdR wrote:

If they're working properly, either brake should be able to lock the rear
wheel or send you over the handlebars. Disk brakes offer more precise
modulation and better performance in wet conditions, but their extra power
is really unnecessary because other kinds of brakes are more than powerful
enough. Most mountain bikes with decent forks and other equipment come
with disk brakes anyway, so that's what you'll get. Just make sure the
disks are clean and nothing is leaking, and you'll be fine. The same
applies to rim brakes, whether V-brakes, traditional cantilever, or caliper.

Matt O.


Hi,

I tried a bike with hydraulic disk brakes (Hayes Sole V6) yesterday
for the first time, and would appreciate your input on my impressions:

- On the first bike I tried, it was not possible to block the wheel
with the disk brake. I checked and found that the disk was oily. On
another bike (same brake) I was able to get the wheel to block, but
with application of extreme force to the brake handle, MUCH more than
required by any V brake I ever tried.

Question: Are Hydraulic Brakes really weaker than V brakes, or was this
bike just assembled by monkeys?

- I noticed that the hydraulic disc brakes have a much 'spongier' feel
than the cable actuated V brakes. This I guess was related to the
hydraulic hose / brake line expanding under pressure, because it was ok
on the front brake (1/2 of the brake lever way until full braking), and
not acceptable no the rear brake (had to pull the brake lever almost up
to the handle bar to get full breaking power)

Question: Is this again a problem of monkey assembly (not enough
fluid?, air in the lines?, what else? ...), or cheap brake lines, or
both? And are there better brake lines that expand less than the stock
ones?
Or ARE hydraulic disc brakes just spongier? If yes, that much
spongier??

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

Thanks a lot!

PS: All the monkey references are founded on an employee there telling
me that 'there are no electrical brakes' when I asked for differences
between hydraulic and cable actuated. When I asked her that about the
front fork maxing out, i.e. hitting the limit of it's travel hard, she
replied with 'many people like their forks soft'. (I found out how they
can be adjusted later.) When I showed her that the (later found to be
well oiled) disk didn't stop the bike, she said 'Oh. Eh? Uh?'
So monkeys or Neanderthals are definitely a possibility in that store.
But the bike is on sale, so I might still buy there. Uh. Uh. Uh. I

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posting problems, or contact the moderators, please see http://rbor.org/
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On Tue, 10 Oct 2006 12:46:37 -0600, wrote:

jim beam wrote:

wrote:

- After playing with the brakes for a few minutes, I noticed that
the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid
question, but they did get quite warm just by playing around on level
ground for about ten minutes.

they get warm because of the friction - that's what all brakes do.
you'll have no problem with heating issues on a disk braked bike - once
set up correctly, use with complete confidence.

Regarding the heating issue, I came across a couple on a tandem who had
a hydraulic disk brake in back, instead of a drag brake. They said that
on long downhills the brake heating transfers heat to the fluid, the
fluid expands and they end up with the brake applied without any lever
action. They have to stop and let the fluid cool.

I'm not surprised. Tandems have double the weight and therefore double
the energy to be dissipated while braking. If the brake components are
not upgraded to compensate it's likely they'll overheat. There are
tandem-specific disks for this reason. But because it's a smaller
market they may not be as well-developed as single MTB brakes -- which
also had overheating problems in their early days.

A tandem drag brake and a downhill ATB are not the exact same situation
but both can expect to sometimes apply the brake for 20-30 minutes on a
very long downhill. Does this ever occur on an ATB?

Yes. As I said, overheating was common with the first generation of
MTB disks.

The best "disk" is your rim, but overheating it can cause tires to blow
off, which is the reason for drag brakes at the hub on tandems.

Matt O.

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wrote:
jim beam wrote:
wrote:
Hi,

- After playing with the brakes for a few minutes, I noticed that the
discs get noticeably warm, around 170F. Are there ever heating issues
with disc brakes on longer downhill segments? Seems a stupid question,
but they did get quite warm just by playing around on level ground for
about ten minutes.

they get warm because of the friction - that's what all brakes do.
you'll have no problem with heating issues on a disk braked bike - once
set up correctly, use with complete confidence.


Regarding the heating issue, I came across a couple on a tandem who had
a hydraulic disk brake in back, instead of a drag brake. They said
that on long downhills the brake heating transfers heat to the fluid,
the fluid expands and they end up with the brake applied without any
lever action. They have to stop and let the fluid cool.

A tandem drag brake and a downhill ATB are not the exact same situation
but both can expect to sometimes apply the brake for 20-30 minutes on a
very long downhill. Does this ever occur on an ATB?


I've never had heat cause the brakes to apply through heat expansion.
What I do experience is dot4 brake fluid boiling (or the water in the
fluid boiling) and I loose all braking power. And I have to wait until
it cools before continuing down hill. On the same hill with v-brakes I
had a front tire blow because the rim got too hot.

My make of disk brake is not compatible with dot5 fluid, which if I
could use it, would help.

Here's a question, which action produces the most heat, keeping the
brakes on to control speed on a steep hill or letting the bike go and
then jamming on the brakes at the last second to kill the speed?
Laters,

Marz

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On Tue, 10 Oct 2006 13:45:38 -0600, Marz wrote:

Here's a question, which action produces the most heat, keeping the
brakes on to control speed on a steep hill or letting the bike go and
then jamming on the brakes at the last second to kill the speed?

Believe it or not it's the latter. The amount of energy to be dissipated
is a product of the mass of bike and rider and the height of the hill,
which remains the same whether you go fast or slow. But at higher speeds
there's more airflow over the rims or brake disks, so more heat is
transferred to the air.

Matt O.

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