Brakes

"David Scheidt" wrote in message
...
Frank Krygowski wrote:

:Personally, I prefer brakes that require a bit more hand pressure. I
:still remember the power brakes on my dad's 1959 Pontiac. It seemed you
:could lock the four wheels with a light touch - not very controllable.

Probably had drum brakes. Drums have shoes that, in one direction,
tend to pull themselves into the drums, reducing the force needed to
apply them.

Drum brakes can be regular or twin-leading.

Twin leading has a separate cam (or piston) for each shoe, the shoes are
arranged so both are drawn harder on by the drum rotation.

Regular pushes one shoe further on and the other tending to push off.

My last drum brake motorcycle had twin leading front, it did brilliant
stoppies - but "ground handling" while pointing up a hill took some pressure
on the lever to stop it rolling backwards.

On Tue, 08 Dec 2015 07:53:16 -0600, AMuzi wrote:

On 12/7/2015 7:03 PM, John B. wrote:

I am presently assembling the new (old) bike and find that I need
"special" brakes for it as it is old enough to have ~55mm brakes and
the ones that were on the bike when I bought the bike are in very poor
condition.

In looking for replacement brakes I find quite a number that will work
and am wondering whether there is really a difference between single
and double pivot caliper brakes, as I have found some Dia-Comp single
pivot brakes that are in almost new condition and fit the period in
which the bike was made.

comments?
--
cheers,

John B.


Both work. Classic sidepulls are simple, cheap and will stop
a bicycle. Dual pivot calipers are heavier with a small
increase in braking power. Neither is 'wrong'.

That was my assumption, but I thought it best to ask... as sometimes
assumptions aren't correct :-)
--
cheers,

John B.

Phil W Lee wrote:
avid Scheidt considered Tue, 8 Dec 2015 18:46:16
:+0000 (UTC) the perfect time to write:

:Frank Krygowski wrote:
:
::Personally, I prefer brakes that require a bit more hand pressure. I
::still remember the power brakes on my dad's 1959 Pontiac. It seemed you
::could lock the four wheels with a light touch - not very controllable.
:
:Probably had drum brakes. Drums have shoes that, in one direction,
:tend to pull themselves into the drums, reducing the force needed to
:apply them. With power brakes, it's very easy to apply too much
:intial force and lock a wheel.

:With most drum brakes, it's equally true in both directions, because
:there's only one pivot with both shoes bearing on it. So in the other
:direction, the other shoe becomes the leading one, and the one that
:was the leading shoe becomes the trailing one.
:A few motorcycles and probably some cars had twin leading shoe drum
:brakes (including one motorcycle I once owned), which have two cams
or cylinders if hydraulic) so that both shoes are applied from the
:leading edge. Setting up twin leading shoe brakes is pretty critical,

Twin (or triple!) leading shoes on the front, and a single leading
shoe in the back (which don't do much, so save the money. Plus better
brakes in reverse.) was the common american set up in the 60s. 50s
stuff is probably single leading shoes. 50s american cars are ****,
out of the high end stuff, which was nice for the time, but **** by
modern standards. 60s stuff isn't much better. There's a reason the
japanese eat their lunch.


--
sig 51

On Tue, 8 Dec 2015 12:42:49 -0500, Frank Krygowski
wrote:

On 12/7/2015 10:35 PM, John B. wrote:
On Mon, 7 Dec 2015 20:28:40 -0500, Frank Krygowski wrote:


Dual pivot brakes will probably have a significantly higher mechanical
advantage. With single pivot brakes, you'll have to squeeze harder for
the same deceleration. OTOH, they'll provide more lateral clearance
when open, so less chance of rubbing if your wheel's a bit out of true,
providing they're well centered.

There's this: http://sheldonbrown.com/brandt/brakes.html
and this: http://sheldonbrown.com/calipers.html

But, is the higher mechanical advantage significant, in the sense that
one type actually stops better, or faster, then the other. Or perhaps
"is one safer then the other?" to appease those with broken straddle
cables :-)

I don't think the higher mechanical advantage causes faster stops. With
decent brake blocks, either brake type delivers stops that are fast
enough to throw you over the bars, which is the practical limit. You
just have to squeeze a bit harder with single pivot brakes.

I'll note, though, that there's a compounding effect that's not widely
recognized. If the cable tension at the brake is less by (say) 30%, the
force at the lever is reduced an even greater amount. This is because
friction is always present around every bend in the cable, which sort of
amplifies any difference. T1/T2 = e^(mu*theta)
http://www.answers.com/Q/How_to_find..._around_circle

Personally, I prefer brakes that require a bit more hand pressure. I
still remember the power brakes on my dad's 1959 Pontiac. It seemed you
could lock the four wheels with a light touch - not very controllable.

In one cycling class I taught, a not-very-bright beginner showed up with
the bike her boyfriend had just lent to her. It had dual pivot brakes,
and she definitely was not used to the lower hand force. On her first
excursion across the parking lot, she locked up the front wheel and went
over the bars.

Perhaps because of those sorts of incidents, Shimano has put brake
limiting spring devices into the front brake cables of some comfort
bikes with V-brakes. Seems a bit weird to build a super-strong brake,
then sort of cripple it, but I guess there are reasons.

I find that I tend to associate hand pressure with actual stopping.
I've got a knock about bike with vee brakes that will, with very light
hand pressure, lock either wheel coasting down hill at ~ 30 KPH. I
have no problems riding it, without constantly admonishing myself
mentally, "light brakes, light brakes". I do note though that the
final halt and put the foot down is a bit more abrupt :-)

--
cheers,

John B.

On Tue, 8 Dec 2015 11:34:12 -0800, sms
wrote:

On 12/8/2015 11:16 AM, Tosspot wrote:
On 08/12/15 18:42, Frank Krygowski wrote:

snip

Perhaps because of those sorts of incidents, Shimano has put brake
limiting spring devices into the front brake cables of some comfort
bikes with V-brakes. Seems a bit weird to build a super-strong brake,
then sort of cripple it, but I guess there are reasons.

These are the work of Stan. If you don't want to go over the
handlebars, use less fingers or more sense.

Who is Stan?

But it makes sense to prevent cyclist from serious injuries by reducing
the likelihood of locking up a wheel and being thrown over the handlebars.

And of course, putting lumps on the front fork dropout to prevent the
fools from losing the front wheel if they set off without locking the
front skewer.

One can only speculate on why and when cyclists became so incompetent.
--
cheers,

John B.

On 12/8/2015 4:31 PM, Ian Field wrote:

Drum brakes can be regular or twin-leading.

Twin leading has a separate cam (or piston) for each shoe, the shoes are
arranged so both are drawn harder on by the drum rotation.

Regular pushes one shoe further on and the other tending to push off.

My last drum brake motorcycle had twin leading front, it did brilliant
stoppies - but "ground handling" while pointing up a hill took some
pressure on the lever to stop it rolling backwards.

Same for my 1972 BMW. It's still that way.

--
- Frank Krygowski

On 12/8/2015 7:11 PM, John B. wrote:
On Tue, 8 Dec 2015 12:42:49 -0500, Frank Krygowski
wrote:

On 12/7/2015 10:35 PM, John B. wrote:
On Mon, 7 Dec 2015 20:28:40 -0500, Frank Krygowski wrote:


Dual pivot brakes will probably have a significantly higher mechanical
advantage. With single pivot brakes, you'll have to squeeze harder for
the same deceleration. OTOH, they'll provide more lateral clearance
when open, so less chance of rubbing if your wheel's a bit out of true,
providing they're well centered.

There's this: http://sheldonbrown.com/brandt/brakes.html
and this: http://sheldonbrown.com/calipers.html

But, is the higher mechanical advantage significant, in the sense that
one type actually stops better, or faster, then the other. Or perhaps
"is one safer then the other?" to appease those with broken straddle
cables :-)

I don't think the higher mechanical advantage causes faster stops. With
decent brake blocks, either brake type delivers stops that are fast
enough to throw you over the bars, which is the practical limit. You
just have to squeeze a bit harder with single pivot brakes.

I'll note, though, that there's a compounding effect that's not widely
recognized. If the cable tension at the brake is less by (say) 30%, the
force at the lever is reduced an even greater amount. This is because
friction is always present around every bend in the cable, which sort of
amplifies any difference. T1/T2 = e^(mu*theta)
http://www.answers.com/Q/How_to_find..._around_circle

Personally, I prefer brakes that require a bit more hand pressure. I
still remember the power brakes on my dad's 1959 Pontiac. It seemed you
could lock the four wheels with a light touch - not very controllable.

In one cycling class I taught, a not-very-bright beginner showed up with
the bike her boyfriend had just lent to her. It had dual pivot brakes,
and she definitely was not used to the lower hand force. On her first
excursion across the parking lot, she locked up the front wheel and went
over the bars.

Perhaps because of those sorts of incidents, Shimano has put brake
limiting spring devices into the front brake cables of some comfort
bikes with V-brakes. Seems a bit weird to build a super-strong brake,
then sort of cripple it, but I guess there are reasons.

I find that I tend to associate hand pressure with actual stopping.
I've got a knock about bike with vee brakes that will, with very light
hand pressure, lock either wheel coasting down hill at ~ 30 KPH. I
have no problems riding it, without constantly admonishing myself
mentally, "light brakes, light brakes". I do note though that the
final halt and put the foot down is a bit more abrupt :-)

I wonder how many riders here have actually practiced maximum
deceleration stops on their bikes? Those who haven't might learn a lot.

This autumn, I had the closest call I've ever had regarding braking. I
was at about 30 mph on a downhill when a young deer ran out in front of
me. I had never braked anywhere near that hard at anywhere near that
speed.

So many people focus on equipment, when there are far bigger
opportunities for improvement in their own skills.

--
- Frank Krygowski

On 09/12/15 01:18, John B. wrote:
On Tue, 8 Dec 2015 11:34:12 -0800, sms
wrote:

On 12/8/2015 11:16 AM, Tosspot wrote:
On 08/12/15 18:42, Frank Krygowski wrote:

snip

Perhaps because of those sorts of incidents, Shimano has put brake
limiting spring devices into the front brake cables of some comfort
bikes with V-brakes. Seems a bit weird to build a super-strong brake,
then sort of cripple it, but I guess there are reasons.

These are the work of Stan. If you don't want to go over the
handlebars, use less fingers or more sense.

Who is Stan?

But it makes sense to prevent cyclist from serious injuries by reducing
the likelihood of locking up a wheel and being thrown over the handlebars.

And of course, putting lumps on the front fork dropout to prevent the
fools from losing the front wheel if they set off without locking the
front skewer.

One can only speculate on why and when cyclists became so incompetent.

Perzackerly. How many people actually go over the handlebars or have
front wheels fall off?

Am 08.12.2015 um 20:28 schrieb sms:
On 12/8/2015 10:46 AM, David Scheidt wrote:
Frank Krygowski wrote:

:Personally, I prefer brakes that require a bit more hand pressure. I
:still remember the power brakes on my dad's 1959 Pontiac. It seemed you
:could lock the four wheels with a light touch - not very controllable.

Probably had drum brakes. Drums have shoes that, in one direction,
tend to pull themselves into the drums, reducing the force needed to
apply them. With power brakes, it's very easy to apply too much
intial force and lock a wheel.

Yes, early power brakes were all drum brakes. They were really touchy.

Nowadays, the only drum brakes on new cars are the parking brakes,
though there may be some low end vehicles that still do front discs and
rear drums.

The reason for this being that drum brakes cannot be made as heat
resistant as disc brakes; drum brakes tend to fade unter massive
braking. In terms of braking power and controllability, there is not
that much difference between well-designed drum brakes and well-designed
disc brakes.

On Wed, 09 Dec 2015 07:18:22 +0700, John B.
wrote:

On Tue, 8 Dec 2015 11:34:12 -0800, sms
wrote:

On 12/8/2015 11:16 AM, Tosspot wrote:
On 08/12/15 18:42, Frank Krygowski wrote:

snip

Perhaps because of those sorts of incidents, Shimano has put brake
limiting spring devices into the front brake cables of some comfort
bikes with V-brakes. Seems a bit weird to build a super-strong brake,
then sort of cripple it, but I guess there are reasons.

These are the work of Stan. If you don't want to go over the
handlebars, use less fingers or more sense.

Who is Stan?

But it makes sense to prevent cyclist from serious injuries by reducing
the likelihood of locking up a wheel and being thrown over the handlebars.

And of course, putting lumps on the front fork dropout to prevent the
fools from losing the front wheel if they set off without locking the
front skewer.

One can only speculate on why and when cyclists became so incompetent.

Gee Frank, if you had only had disk brakes you'd have had no problems.
even in the rain :-)
--
cheers,

John B.