Difference in MA between traditional and aero levers?
Jim Rogers
newer aero levers have more mechanical advantage. Could someone please
provide the approximate ratio for aero levers? I'm interested in how
much difference there is between the two lever types.
Thanks,
--Jim
Tim McNamara
<93aa38be-3651-4192...@n33g2000pri.googlegroups.com>,
Jim Rogers <irene_...@yahoo.com> wrote:
These have been given in past discussions as (IIRC) 4:1 for non-aero
levers and 2.5:1 for aero levers. Jobst has done these measurements and
has posted on this; it might even be in the FAQ.
There are also differences in terms of the relationship of the cable to
the lever. In an aero lever, the cable is at nearly 90 degrees to the
brake lever blade; with a non-aero lever the cable is nearly in line
with the brake lever blade. I think this results in the aero brake
lever needing less force on the lever.
_
> There are also differences in terms of the relationship of the cable to
> the lever. In an aero lever, the cable is at nearly 90 degrees to the
> brake lever blade; with a non-aero lever the cable is nearly in line
> with the brake lever blade. I think this results in the aero brake
> lever needing less force on the lever.
No.
Absent any other factors, the angle between the cable and the lever makes
no difference - all that matters is the distance from the pivot to the
anchor.
JG
problem for V brakes is that their MA is well above 1:1. If aero
levers had half the MA as traditionals, they would be matched up with
V brakes. I do believe MA is now higher, because there is more
precision with modern cables, etc, so less need to have reserve travel
built in...
JG
A Muzi
Unless someone knows of a specific lever that's different, we commonly
add new DP calipers with 1960s levers and 1980s aero levers and set up
classic calipers of all styles with new aero or Ergo levers. No
significant or noticeable difference in any combination of road brake
equipment.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **
jobst....@stanfordalumni.org
I haven't seen any that visibly different lever ratios from the old
standard. These are readily assessable by comparing the distance of
the cable attachment to the lever pivot and that of the distance to
the crook in the lever where two fingers are intended to apply force.
What changed is the ME of calipers that brought on the dual pivot
design that was necessary to allow a higher overall ME because that
demands closer spacing between brake pad and rim. The dual pivot
mechanism prevents the caliper from going off center (brake drag).
Jobst Brandt
jobst....@stanfordalumni.org
Precision is not where it's at, its brake drag and pad wear that
requires operating with large clearance. The higher ME dual pivot
calipers readily run out of travel when descending in rain (where pad
wear is significant).
Campagnolo even scrapped rear dual pivot because one doesn't need high
ME in the rear and dual pivots, with their low pad clearance often
dragged on climbs when standing. The bad part of this is that
assessing break action in critical (poor traction) descents is
impossible with a different ME front and rear.
Jobst Brandt
JG
does cause that much drag), but cables have changed. I suspect people
like more MA because that is the only thing the really distinguishes
brake systems...
As for brake uniformity, you are assuming, perhaps incorrectly, that
humans can calibrate the relative force in their left and right hands.
jobst....@stanfordalumni.org
> Pad wear and wheel rub remain issues (although an unsprung brake pad
> does cause that much drag), but cables have changed. I suspect
> people like more MA because that is the only thing the really
> distinguishes brake systems...
What is an unsprung brake pad? At the risk of being repetitious, let
me repeat. I recall as the new wave of adult riders began, how they
complained about their Campagnolo brakes not stopping quickly enough
and the bicycle shop telling them that these are racing brakes and
racers only need to control speed, not stop.
That was a great line of BS because the faster one rides, the harder
one needs to brake. What they couldn't tell the customer was that
they were too weak to ride equipment made for young athletic racers.
They also could not shift gears worth a damn with friction levers and
couldn't pump a tire to reasonable pressure with the Silca Impero
frame fit pump. Not only that, they pumped while grasping the wheel
with the other hand instead of the pump head, so they often broke off
valve stems.
All these problems went away with Dual pivot brakes, CO2 cartridges,
and indexed shifting on the handlebar (brake lever). Skilled riders
can raise the rear wheel on hard braking even while sliding back on
the saddle while descending and not want for a higher MA.
> As for brake uniformity, you are assuming, perhaps incorrectly, that
> humans can calibrate the relative force in their left and right hands.
They do that to good accuracy if they are experienced riders, but to
do that with unknown differences in MA is not reasonably possible.
The point is that low clearance high MA brakes are a drag, so to
speak, especially for rear wheels.
Jobst Brandt
Jim Rogers
"Unless someone knows of a specific lever that's different, we
commonly
add new DP calipers with 1960s levers and 1980s aero levers and set up
classic calipers of all styles with new aero or Ergo levers. No
significant or noticeable difference in any combination of road brake
equipment. "
Jobst wrote (in part):
"I haven't seen any that visibly different lever ratios from the old
standard."
Jim replies: Sheldon Brown always said there was a difference in MA
between these two levers. For example, in his glossary he wrote:
"Æro brake levers usually have more mechanical advantage, which is
good in general, but may cause problems when they are used with
cantilever or drum brakes that require more cable than conventional
calipers."
http://sheldonbrown.com/gloss_a.html#aerobrake
In this newsgroup he has said many times that aero brakes greatly
increase stopping power, e.g.:
"Another big advantage of new style levers is the relocated pivot
point.
This improves the ergonomics greatly, making it possible to actually
_stop_ from the top-of-the-hoods position. "
and
"In my opinion, this was one of the major advances in
bicycle design. I don't claim that the aero aspect is a big deal, but
the improvement in braking is considerable."
http://groups.google.com/group/rec.bicycles.tech/msg/bd209956f09373a5?dmode=source
Obviously the difference is not big enough to rule out using a modern
lever with an older caliper, but it is enough to notice improved
braking with that combination, so it must be something. Maybe
something like 4.5:1?
--Jim
jim beam
> JG who? wrote:
>
>> Tim, I don't think those numbers can be at all correct. The big
>> problem for V brakes is that their MA is well above 1:1. If aero
>> levers had half the MA as traditionals, they would be matched up with V
>> brakes. I do believe MA is now higher, because there is more precision
>> with modern cables, etc, so less need to have reserve travel built
>> in...
>
> Precision is not where it's at, its brake drag and pad wear that
> requires operating with large clearance. The higher ME dual pivot
> calipers readily run out of travel when descending in rain (where pad
> wear is significant).
>
> Campagnolo even scrapped rear dual pivot because one doesn't need high
> ME in the rear and dual pivots, with their low pad clearance often
> dragged on climbs when standing.
no jobst. as you've been told many times, and as campy themselves admit,
they dropped dual pivot rears to save weight, nothing else.
> The bad part of this is that assessing
> break action in critical (poor traction) descents is impossible with a
> different ME front and rear.
then you've not ridden such brakes [no surprise]. i have. there's
absolutely no problem.
when is the great and mighty jobst brandt ever going to bother to check a
fact or bother to actually use equipment on which he's so quick to voice
[underinformed] opinion?
jim beam
absolute bullshit. you've never ridden this stuff jobst. put your money
where your mouth is, go ride, then get back with a real opinion, not this
presumptive drivel.
> The
> point is that low clearance high MA brakes are a drag, so to speak,
> especially for rear wheels.
>
rubbish.
jim beam
> Jim Rogers wrote:
>
>> My understanding is that traditional road levers were 4:1, and that
>> newer aero levers have more mechanical advantage. Could someone please
>> provide the approximate ratio for aero levers? I'm interested in how
>> much difference there is between the two lever types.
>
> I haven't seen any that visibly different lever ratios from the old
> standard. These are readily assessable by comparing the distance of the
> cable attachment to the lever pivot and that of the distance to the
> crook in the lever where two fingers are intended to apply force.
>
> What changed is the ME
"me"?
> of calipers that brought on the dual pivot design
> that was necessary to allow a higher overall ME
"me"?
> because that demands
> closer spacing between brake pad and rim. The dual pivot mechanism
> prevents the caliper from going off center (brake drag).
so, why exactly should we to pay attention to the ramblings of some guy
that apparently doesn't know about mechanical advantage ["ma"] and can't
be bothered to pay attention to manufacturer data?
jobst....@stanfordalumni.org
>>> Unless someone knows of a specific lever that's different, we
>>> commonly add new DP calipers with 1960s levers and 1980s aero
>>> levers and set up classic calipers of all styles with new aero or
>>> Ergo levers. No significant or noticeable difference in any
>>> combination of road brake equipment.
>> "I haven't seen any that visibly different lever ratios from the old
>> standard."
> Sheldon Brown always said there was a difference in MA between these
> two levers. For example, in his glossary he wrote:
http://sheldonbrown.com/gloss_a.html#aerobrake
# ÆRO BRAKE LEVERS
# Refers to brake levers made for drop handlebars. Older designs had
# the cables exit up from the front of the brake levers, arching over
# the handlebars. The newer style, where the cable exits out the back
# of the lever and runs under the handlebar tape is referred to as
# "æro" because it eliminates the wind drag of the exposed cables.
# Æro levers are generally an improvement over the older type. The
# pivots are located differently, making it possible to get fairly
# serious braking from the position where the rider's hand is on top
# of the lever hood. Non-æro levers would permit the use of this
# position for gentle deceleration only.
# Æro brake levers usually have more mechanical advantage, which is
# good in general, but may cause problems when they are used with
# cantilever or drum brakes that require more cable than conventional
# calipers.
> In this newsgroup he has said many times that aero brakes greatly
> increase stopping power, e.g.:
Unfortunately there are no diagrams or numbers with these qualitative
comments. Besides which, I disagree with the claim that braking over
the lever hoods is less effective. The levers are the same length and
their direction of motion is identical, only cable routing differs.
Therefore, there is no functional difference, and because I often
descend steep hills that way to enjoy scenery, I know that it works
well with both types.
# Another big advantage of new style levers is the relocated pivot
# point. This improves the ergonomics greatly, making it possible to
# actually _stop_ from the top-of-the-hoods position.
> and
http://groups.google.com/group/rec.bicycles.tech/msg/bd209956f09373a5?dmode=source
# In my opinion, this was one of the major advances in bicycle design.
# I don't claim that the aero aspect is a big deal, but the
# improvement in braking is considerable.
Again, this claim is not supported by the hardware and, as I said, old
type exposed cable levers work fin over the tops for me.
> Obviously the difference is not big enough to rule out using a
> modern lever with an older caliper, but it is enough to notice
> improved braking with that combination, so it must be something.
> Maybe something like 4.5:1?
You are guessing! Please make some ruler measurements: Cable anchor
to pivot and hand lever crook to pivot. Actually eyeballing it is
probably enough. It is obvious on old style levers where the three
points are visible externally.
Jobst Brandt
A Muzi
> Andy wrote:
>
> "Unless someone knows of a specific lever that's different, we
> commonly
> add new DP calipers with 1960s levers and 1980s aero levers and set up
> classic calipers of all styles with new aero or Ergo levers. No
> significant or noticeable difference in any combination of road brake
> equipment. "
>
> Jobst wrote (in part):
>
> "I haven't seen any that visibly different lever ratios from the old
> standard."
>
> Jim replies: Sheldon Brown always said there was a difference in MA
> between these two levers. For example, in his glossary he wrote:
>
> good in general, but may cause problems when they are used with
> cantilever or drum brakes that require more cable than conventional
> calipers."
>
> http://sheldonbrown.com/gloss_a.html#aerobrake
>
> In this newsgroup he has said many times that aero brakes greatly
> increase stopping power, e.g.:
>
> "Another big advantage of new style levers is the relocated pivot
> point.
> This improves the ergonomics greatly, making it possible to actually
> _stop_ from the top-of-the-hoods position. "
>
> and
>
> "In my opinion, this was one of the major advances in
> bicycle design. I don't claim that the aero aspect is a big deal, but
> the improvement in braking is considerable."
>
> http://groups.google.com/group/rec.bicycles.tech/msg/bd209956f09373a5?dmode=source
>
> Obviously the difference is not big enough to rule out using a modern
> lever with an older caliper, but it is enough to notice improved
> braking with that combination, so it must be something. Maybe
> something like 4.5:1?
You might easily measure that with a caliper (pivot points on centers)
for the specific levers which interest you. I bet there won't be much
variance.
jobst....@stanfordalumni.org
I haven't seen any that visibly different lever ratios from the old
standard. These are readily assessable by comparing the distance of
the cable attachment to the lever pivot and that of the distance to
the crook in the lever where two fingers are intended to apply force.
What changed is the MA of calipers that brought on the dual pivot
design that was necessary to allow a higher overall MA because that
demands closer spacing between brake pad and rim. The dual pivot
mechanism prevents the caliper from going off center (brake drag).
Jobst Brandt
A Muzi
Simple copy error.
It was "MA" in Jobst's original
On the same screen even! (just five lines up, 4:02pm and yours at 4:33
pm on a slow day)
Jim Rogers
> Unfortunately there are no diagrams or numbers with these qualitative
> comments. Besides which, I disagree with the claim that braking over
> the lever hoods is less effective. The levers are the same length and
> their direction of motion is identical, only cable routing differs.
> Therefore, there is no functional difference, and because I often
> descend steep hills that way to enjoy scenery, I know that it works
> well with both types.
> Again, this claim is not supported by the hardware and, as I said, old
> type exposed cable levers work fin over the tops for me.
A quick search of this newsgroup in Google Groups will show tens of
times that Sheldon said there is a very noticeable difference in the
braking power of aero levers. Here's another example:
"In addition, "aero" levers have a slighty different pivot location.
The
work approximately equally well when applied from the drops, but for
braking while riding on the hoods, "aero" levers are markedly
superior,
and I wouldn't recommend anything else."
http://groups.google.com/group/rec.bicycles.tech/msg/aee553490a4f3a04?dmode=source
It's hard to believe that Sheldon would be that wrong about something
like that.
> You are guessing! Please make some ruler measurements: Cable anchor
> to pivot and hand lever crook to pivot. Actually eyeballing it is
> probably enough. It is obvious on old style levers where the three
> points are visible externally.
Yes, I was providing a guess to indicate that I did not expect the
difference to be great. I could measure it myself, but I thought there
was a standard spec.
--Jim
Jim Rogers
> for the specific levers which interest you. I bet there won't be much
> variance.
I'll measure it. Since Sheldon said there was increased MA so many
times (with no disagreement) I assumed the ratio was a well-known
common spec that someone here could provide quicker than I could
measure.
--Jim
JG
millimeters for 36mm of lever travel...good luck, but I'd use a
calipers.
Sheldon's contention is that shape and pivot location of the newer
levers make for a better grip from the hoods. That is quite possible
and has nothing to do with cable direction, pull direction, lever
length, or MA. I certainly find that squeezing my Cobolto levers from
the top tends to throw my weight into my thumbs braced against the
hood cable ferrule. I can do it, but it's not a warm, fuzzy, secure
feeling...
An unsprung brake pad is one that's not sprung, i.e. one that's
resting on the rim.
JG
jobst....@stanfordalumni.org
>> Unfortunately there are no diagrams or numbers with these
>> qualitative comments. Besides which, I disagree with the claim
>> that braking over the lever hoods is less effective. The levers
>> are the same length and their direction of motion is identical,
>> only cable routing differs. Therefore, there is no functional
>> difference, and because I often descend steep hills that way to
>> enjoy scenery, I know that it works well with both types.
>> Again, this claim is not supported by the hardware and, as I said,
>> old type exposed cable levers work fine over the tops for me.
> A quick search of this newsgroup in Google Groups will show tens of
> times that Sheldon said there is a very noticeable difference in the
> braking power of aero levers. Here's another example:
http://groups.google.com/group/rec.bicycles.tech/msg/aee553490a4f3a04?dmode=source
# In addition, "aero" levers have a slighty different pivot location.
# The work approximately equally well when applied from the drops, but
# for braking while riding on the hoods, "aero" levers are markedly
# superior, and I wouldn't recommend anything else."
> It's hard to believe that Sheldon would be that wrong about
> something like that.
Sheldon did not have the opportunity to make measurements and edit
this text before his health problems began taking most of his time. I
think, I'll defer to Andrew Muzi, who has these levers in his shop to
report back about the dimensions. I only recall that inspecting the
levers I found the cable routing feature cleverly done but not
different in lever ratios from external cables.
>> You are guessing! Please make some ruler measurements: Cable
>> anchor to pivot and hand lever crook to pivot. Actually eyeballing
>> it is probably enough. It is obvious on old style levers where the
>> three points are visible externally.
> Yes, I was providing a guess to indicate that I did not expect the
> difference to be great. I could measure it myself, but I thought
> there was a standard spec.
I have mentioned in the past, a feature of exposed (old style) cables,
is that most people who used them extensively can recall at least once
riding on the hoods when encountering a surprise divot in the road that
dropped the front end so fast, it left one hanging with thumbs in the
cables. Then the comment was how lucky the cables were still there to
catch instead of going over the bars. This was after the time when
aero levers were introduced.
Jobst Brandt
jobst....@stanfordalumni.org
> You are talking about eyeballing the difference between eight and
> nine millimeters for 36mm of lever travel... good luck, but I'd use
> a calipers. I use my fingers as a caliper so that the spread
> between thumbnail and index finger lie on the centers of the
> cable-to-pivot pins and then see how many of those distances fit
> the lever length.
> Sheldon's contention is that shape and pivot location of the newer
> levers make for a better grip from the hoods. That is quite
> possible and has nothing to do with cable direction, pull direction,
> lever length, or MA. I certainly find that squeezing my Cobolto
> levers from the top tends to throw my weight into my thumbs braced
> against the hood cable ferrule. I can do it, but it's not a warm,
> fuzzy, secure feeling...
It has worked well for me for many miles. I ride like that in city
traffic so I can see over cars.
> An unsprung brake pad is one that's not sprung, i.e. one that's
> resting on the rim.
I'm sorry, I'm still in the dark. I have never seen a spring on brake
pads. How do these work and what do they do. Can you direct me to a
URL where I can see such a beast, like for instance a manufacturer's
web site?
Jobst Brandt
Jim Rogers
> > It's hard to believe that Sheldon would be that wrong about
> > something like that.
>
> Sheldon did not have the opportunity to make measurements and edit
> this text before his health problems began taking most of his time.
No, the quote I provided was from this newsgroup in 1997-- well before
his illness.
> I
> think, I'll defer to Andrew Muzi, who has these levers in his shop to
> report back about the dimensions.
I agree. I could attempt to measure the ration of my aero levers, but
I have no non-aero levers to test as a control to verify method and
result. Andy can provide a more reliable result than I.
But I would expect there to be some measurable difference. Sheldon
claimed there was a difference in MA for nearly 10 years-- I can't
believe he would be that mistaken!
> I have mentioned in the past, a feature of exposed (old style) cables,
> is that most people who used them extensively can recall at least once
> riding on the hoods when encountering a surprise divot in the road that
> dropped the front end so fast, it left one hanging with thumbs in the
> cables. Then the comment was how lucky the cables were still there to
> catch instead of going over the bars. This was after the time when
> aero levers were introduced.
Interesting!
--Jim
JG
Authority...
You have certainly seen return springs on brake calipers, and because
the calipers are not independent, a displacement of one will be
resisted by the other, even though in general the spring act to
"return" the calipers away from the rim. If the caliper is "stuck",
the contact of the rim will move it away. It is certainly annoying
and to be avoided, it just doesn't cause all that much drag - but this
is all a paranthetical remark...
JG
jobst....@stanfordalumni.org
>>> It's hard to believe that Sheldon would be that wrong about
>>> something like that.
>> Sheldon did not have the opportunity to make measurements and edit
>> this text before his health problems began taking most of his time.
> No, the quote I provided was from this newsgroup in 1997-- well
> before his illness.
>> I think, I'll defer to Andrew Muzi, who has these levers in his
>> shop to report back about the dimensions.
> I agree. I could attempt to measure the ration of my aero levers,
> but I have no non-aero levers to test as a control to verify method
> and result. Andy can provide a more reliable result than I.
Not to worry, all non aero levers of the past of more than 75 years
were 4:1 and all calipers, including centerpull were 1:1. When Mafac
and others brought centepulls to market, it was generally accepted
that they had twice the MA, thier levers being twice as long. Of
course this was not correct because the cable force was divided in two
in the straddle cable.
Such mistakes are often made because the bicycle shop people are not
engineers familiar with mechanisms. At the time I wrote articles on
rec.bicycle explaining how this worked and measured most of the common
brakes. Ultimately measuring brake clearance and how much cable
motion it takes to move the pads to the rim (pad stroke vs cable
stroke) reveals that ration unambiguously. Hand levers follow the
bell crank principal and can be measures statically.
> But I would expect there to be some measurable difference. Sheldon
> claimed there was a difference in MA for nearly 10 years-- I can't
> believe he would be that mistaken!
As I said, such things occur often. When Sheldon began looking at
technical articles and gave these things more thought he was running
out of time. There was no time to make a retraction or correction.
>> I have mentioned in the past, a feature of exposed (old style)
>> cables, is that most people who used them extensively can recall at
>> least once riding on the hoods when encountering a surprise divot
>> in the road that dropped the front end so fast, it left one hanging
>> with thumbs in the cables. Then the comment was how lucky the
>> cables were still there to catch instead of going over the
>> bars. This was after the time when aero levers were introduced.
> Interesting!
I believe descending on rough roads (like our Page Mill Rd) on the
hoods without external cables is not a good idea, yet with my brakes I
do it often when not going max speed. I find Page Mill Rd. a great
descent because it is steep and has myriad odd curves while giving a
panorama of Santa Clara valley with the Diablo range as backdrop. A
bicyclist has almost the power of a motorcycle with that gradient.
It's fast! At several places going fast demands braking hard enough
to the raise the rear wheel.
http://home.mchsi.com/~lookoutvistas/DiabloHam.htm
Jobst Brandt
Jim Rogers
> Not to worry, all non aero levers of the past of more than 75 years
> were 4:1 and all calipers, including centerpull were 1:1.
Yes-- the fact that they are known to be 4:1 is why I would use them
as a control.
> When Mafac
> and others brought centepulls to market, it was generally accepted
> that they had twice the MA, thier levers being twice as long. Of
> course this was not correct because the cable force was divided in two
> in the straddle cable.
I understand, and find that interesting. One reason I'm thinking about
brakes is the current issue of Bicycle Quarterly is a special issue on
brakes. It discusses at length the development of brakes and brake
theory over the last hundred years.
Jan Heine is a big proponent of centerpulls for the reason of less arm
flex when the pivot points are nearer the rims. I've studied your
reasoning why single pivot side pulls are better (near zero cosine
error, ability to follow a rim with a broken spoke, good modulation,
and no problem locking the wheels unless you have unusually weak
hands).
I have found your point of view on this issue compelling, and I'm
probably going to engage Jan on this issue on the iBOB board.
> Such mistakes are often made because the bicycle shop people are not
> engineers familiar with mechanisms. At the time I wrote articles on
> rec.bicycle explaining how this worked and measured most of the common
> brakes.
Mostly because of your writing, I use single pivot side pulls on my
bikes. Based on Andy Muzi's high opinion of them, I use the Dia Compe
G and Weinmann 500 and 730's that originally came with the bikes.
They have the springs with the coils on each side of the pivot, but,
as you suggested, I just occasionally clean the sliding point (I use a
pipe cleaner), put a drop of lubricant, and they center perfectly. I
use Kool-Stop salmon pads and use aero levers and they work great.
Chalo Colina has expressed a preference for non-side pulls because, at
his extreme weight, he observes unacceptable flex. However, I
regularly use my 730's (80mm reach), I weigh 200 lbs., and routinely
brake hard (I live in a very hilly town). I never have any problem
(that I know of) with brake arm flex.
So they work for me, and I can enjoy their benefits.
> As I said, such things occur often. When Sheldon began looking at
> technical articles and gave these things more thought he was running
> out of time. There was no time to make a retraction or correction.
OK-- I did not know he had revised his opinion.
> http://home.mchsi.com/~lookoutvistas/DiabloHam.htm
You have beautiful country out there. Here in Nebraska I'm currently
commuting in six inches of snow, now mostly packed into icy ruts. I
have an old mountain bike dedicated for snow use with strong lights
and studded tires.
By spring I'm glad to see the snow disappear, but for the first few
months it's a challenge and quite fun!
--Jim
Bill Sornson
> Anecdotal evidence is of immense Value, but only when voiced by
> Authority...
Dude (?), please quote that to which you are replying. Your posts are
rendered nearly meaningless with no context.
JG
>> technical articles and gave these things more thought he was running
>> out of time. There was no time to make a retraction or correction.
>OK-- I did not know he had revised his opinion.
We don't know that he is wrong to begin with. Not until someone goes
and measures aero levers. And you can't eyeball 8 versus 9 mm...
Besides, he said "usually" - it has little to do with his argument
that the newer levers are more effective.
JG
Jim Rogers
(mentioned above), I see that there is an explanation by Jan Heine on
the increased MA of aero brake levers. Somehow I missed that on my
first reading.
Jan says that the increased MA of aero levers is a result of the fact
that, in those levers, the pivot point is moved forward. In non-aero
levers the pivot point is much further back, i.e., under your palms
when you're in the hoods.
So with aero levers, the fact that the pivot point is ahead of your
hand means you have much more MA when in the hoods. He says the MA in
the drops is the same for both levers.
This implies that the increased MA is not a result of differential
cable pull (as I had thought), but due to increased MA of the hand
itself while in the hoods.
Perhaps that's what Sheldon meant all along.
--Jim
jobst....@stanfordalumni.org
The pivot was moved because unlike exposed cable brake levers that
pulled down on the brake cable, aero levers pull forward (90°) from
that or as the fingers move rearward the cable moves forward on a
teeter totter lever system. Location of the pivot is immaterial while
lever lengths from the pivot are what defines MA.
Jobst Brandt
JG
> The pivot was moved because unlike exposed cable brake levers that
> pulled down on the brake cable, aero levers pull forward (90°) from
> that or as the fingers move rearward the cable moves forward on a
> teeter totter lever system. Location of the pivot is immaterial while
> lever lengths from the pivot are what defines MA.
Which, of course, means the MA is improved when pulling the lever
against the hood from above...
jobst....@stanfordalumni.org
No it doesn't... or it would mean that, with hands in the hooks, the
MA is worse, which it isn't, since that is the primary mode of use.
Cur off the nose to spite the face!
Jobst Brandt
pm
It is not the simple lever length, but the projection of the lever
perpendicular to the applied force which determines the torque around
the pivot.
-pm
Michael Press
<dc4dbf12-d140-4787...@a26g2000prf.googlegroups.com>,
JG <jc...@cox.net> wrote:
You did not put in any quoted text.
--
Michael Press
Michael Press
<b205cb3f-28e0-49c3...@m12g2000vbp.googlegroups.com>,
Jim Rogers <irene_...@yahoo.com> wrote:
I replaced old Dia Comp exposed cable levers with
Tektro aero levers. Both lever sets are 21 mm from
lever pivot to cable anchor.
The difference is that the old levers have the
lever pivot further aft, while the aero levers
have the lever pivot in a vertical line with the lever.
With the old style when one actuates the lever from the
hoods the rotation of the lever moves the lever downward,
taking the initial point of contact between the fingers
and lever further up the lever, giving our grip less
leverage.
--
Michael Press
Michael Press
jobst....@stanfordalumni.org wrote:
Not so. With the pivot point behind the lever,
the rotation of the lever gives a downward component
of motion to the lever. When in the hoods, this motion
moves our finger contact up the lever, decreasing the
mechanical advantage of our grip.
--
Michael Press
jobst....@stanfordalumni.org
>>> Upon further reading of the Bicycle Quarterly issue on brakes
>>> (mentioned above), I see that there is an explanation by Jan Heine
>>> on the increased MA of aero brake levers. Somehow I missed that
>>> on my first reading.
>>> Jan says that the increased MA of aero levers is a result of the
>>> fact that, in those levers, the pivot point is moved forward. In
>>> non-aero levers the pivot point is much further back, i.e., under
>>> your palms when you're in the hoods.
>>> So with aero levers, the fact that the pivot point is ahead of
>>> your hand means you have much more MA when in the hoods. He says
>>> the MA in the drops is the same for both levers.
>>> This implies that the increased MA is not a result of differential
>>> cable pull (as I had thought), but due to increased MA of the hand
>>> itself while in the hoods.
>>> Perhaps that's what Sheldon meant all along.
>> The pivot was moved because unlike exposed cable brake levers that
>> pulled down on the brake cable, aero levers pull forward (90?) from
>> that or as the fingers move rearward the cable moves forward on a
>> teeter totter lever system. Location of the pivot is immaterial
>> while lever lengths from the pivot are what defines MA.
> Not so. With the pivot point behind the lever, the rotation of the
> lever gives a downward component of motion to the lever. When in the
> hoods, this motion moves our finger contact up the lever, decreasing
> the mechanical advantage of our grip.
I'm not sure I understand what you believe is "not so". The hand
lever is in either design is intended to be pulled toward the
handlebar by a hand on the crook of the bar. That means it is
designed to move rearward... the same as exposed cable levers. It is
the attachment position of the cable that changed, it needing to be
pulled forward instead of down. That doesn't interest the user
because the hand lever still moves the same as before relative to the
bar and hood.
Jobst Brandt
Michael Press
jobst....@stanfordalumni.org wrote:
On the old style exposed cable levers, the lever
pivot is two or three centimeters behind the
lever axis. When the lever rotates, the lever
motion has a downward component (as well as
a component of motion toward the hooks.
When the hands are in the hoods this motion
of the lever moves the finger to lever contact
point along the lever toward the pivot, decreasing
the mechanical advantage of the grip.
--
Michael Press
jobst....@stanfordalumni.org
No doubt there is cosine error in any lever and that doesn't change
the MA of these levers. This sound much like Cino Cinelli believing
that smaller wheels will allow TT riders to spin more than riders with
larger wheels. This is all leverage and rotation. To make up for the
higher mechanical advantage of dual pivot brakes, pad clearance has
been reduced. If this were not don, nothing would have been gained by
the higher MA of dual pivot calipers.
No one messed with the hand lever ration. I don't have such brakes
available to me now, but I recall measuring them to discover what all
the talk about brakes was truly about. Most of it was marketing,
claiming things that aren't there.
If you are sure of your contention, pleas measure the radial distance
from the lever crook to pivot and that of the cable anchor to that
pivot. If that becomes involved, measure the change in distance
between brake pads with released hand lever and when the lever is
pulled to the bar.
Jobst Brandt
Michael Press
jobst....@stanfordalumni.org wrote:
This is not cosine error. Do the math.
Better yet, get an old style and an
aero style lever. Put your hand in on
the hood of the old style, squeeze,
and feel your grip slide up the lever.
Observe: Not cosine error.
The instantaneous motion of the lever as it rotates
has a considerable vertical component. Not ~= cos(0 degree).
_________________________________________________
|
|
|
| Lever pivot
| _________________________________
| | |
| | O |
| | _________________________|
| | |
| | |
| | |
| | |
|__|______|______________________________________
| |
| L |
| e |
| v |
| e |
| r |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
|______|
--
Michael Press
Tom Sherman
mechanical advantage of both conventional drop bar brake levers and
"aero" levers is the same. However, the pivot point location of the
conventional lever means as the lever is squeezed, the fingers of the
rider move up the lever, reducing the multiplier of the force applied by
the rider's fingers. With the aero levers, the rider's finger can grip
nearer the bottom of the lever while braking from the hoods, resulting
in a greater force multiplier.
The above is born out by anecdotal evidence that aero levers require
less squeezing force for a given braking when the rider is "on the hoods".
--
Tom Sherman - 42.435731,-83.985007
LOCAL CACTUS EATS CYCLIST - datakoll
pm
wrote:
> jobst.bra...@stanfordalumni.org aka Jobst Brandt wrote:
>
> > No one messed with the hand lever ration. I don't have such brakes
> > available to me now, but I recall measuring them to discover what all
> > the talk about brakes was truly about. Most of it was marketing,
> > claiming things that aren't there.
>
> > If you are sure of your contention, pleas measure the radial distance
> > from the lever crook to pivot and that of the cable anchor to that
> > pivot. If that becomes involved, measure the change in distance
> > between brake pads with released hand lever and when the lever is
> > pulled to the bar.
>
> I believe that Jobst misunderstands Michael's contention here. The
> mechanical advantage of both conventional drop bar brake levers and
> "aero" levers is the same.
Indeed. It should be obvious that the mechanical advantage of the
pedal on the rotation of the wheel is constant around the pedal's
revolution. Yet everyone experiences the fact that one cannot effect
nearly as much wheel torque when the pedals are vertical as when the
pedals are horizontal. 'Mechanical advantage' does not nearly tell the
story.
A similar situation applies to the amount of tension one can impart on
the brake cable, dependent on hand and pivot position. Try analyzing
the torque around the pivot. It is the cross product of (1) the moment
arm, in this case from the pivot to the locus of applied force, and
(2) the applied force itself. The latter is a vector. The hand
squeezes from fingers to thumb.
-pm
pm
Here is an experiment that anyone can do, given a bike with an exposed
rear brake cable run along the top tube, and a relatively musical ear.
Stuff two hard metal objects between the rear brake cable and the top
tube--I used some wrench sockets. These are to act as frets.
Then squeeze the brake with one hand, and pluck the cable with the
other. The pitch that is sounded directly reflects the cable tension
you are able to effect with your lever squeeze.
Shifting your hand from the hooks to the hoods, squeeze with the same
effort and pluck again. The pitch will be lower, as you cannot effect
as much braking force from the hoods. The musical interval between the
pitch sounded while squeezing from the hooks and that sounded
squeezing from the hoods relates to the ratio of the cable tension in
the two conditions. I tried two bikes, one with STI brake/shifters and
one with aero levers -- the interval was about a musical fifth in both
cases, corresponding to roughly a halving of cable tension. (a fifth
being a ratio of 3/2 in frequency, and frequency scaling as the square
root of tension.)
I don't have bikes on hand with non-aero levers to try, but I hope
someone on the group can do this and report whether the interval
produced is wider of not.
-pm
jobst....@stanfordalumni.org
That is an invalid example, brake levers make about 20° max angle
whereas pedals turn 360°. Bell cranks only work through moderate
angles and brake levers are typical bell crank applications.
Jobst Brandt
jim beam
no jobst, it's an extreme example, not an invalid one.
> Bell cranks only work through moderate angles
> and brake levers are typical bell crank applications.
>
> http://tinyurl.com/856t3d
that either a deliberately irrelevant red herring, or a gross case of non-
comprehension.
pm
It is a valid example for demonstrating that torque is a cross
product, one factor of which is the vector of the applied force.
However if you wish for an example with fewer irrelevant differences,
observe that the cable tension given by squeezing the brake lever from
the hoods is significantly less than that given by squeezing it from
the drops. A procedure for demonstrating this given minimal equipment
was posted in this thread.
-pm
Michael Press
I did measure the lever pivot to cable anchor pivot,
and published the figures in this very thread. It's
around here ... [riffle riffle riffle riffle snap]
ah, here you go:
------------------------------
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From: Michael Press <rub...@pacbell.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Difference in MA between traditional and aero levers-- Update
Organization: Possum Lodge
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I replaced old Dia Comp exposed cable levers with
Tektro aero levers. Both lever sets are 21 mm from
lever pivot to cable anchor.
The difference is that the old levers have the
lever pivot further aft, while the aero levers
have the lever pivot in a vertical line with the lever.
With the old style when one actuates the lever from the
hoods the rotation of the lever moves the lever downward,
taking the initial point of contact between the fingers
and lever further up the lever, giving our grip less
leverage.
------------------------------
--
Michael Press
Frank Krygowski
>
>
> ...Shifting your hand from the hooks to the hoods, squeeze with the same
> effort and pluck again. The pitch will be lower, as you cannot effect
> as much braking force from the hoods. The musical interval between the
> pitch sounded while squeezing from the hooks and that sounded
> squeezing from the hoods relates to the ratio of the cable tension in
> the two conditions. I tried two bikes, one with STI brake/shifters and
> one with aero levers -- the interval was about a musical fifth in both
> cases, corresponding to roughly a halving of cable tension. (a fifth
> being a ratio of 3/2 in frequency, and frequency scaling as the square
> root of tension.)
>
> I don't have bikes on hand with non-aero levers to try, but I hope
> someone on the group can do this and report whether the interval
> produced is wider of not.
Interesting test method. Maybe I'll try it later.
I just grabbed some calipers and a bunch of brake levers (junk box and
some current bikes) and took measurements. It's not perfectly easy,
because a) judging where ones fingers would apply force is difficult
on a gently curving brake lever; and b) what's really needed is the
distance perpendicular to the force direction, not necessarily to the
cable anchor.
That last dimension was so difficult to judge with STI levers, that
for those I switched to measuring lever travel divided by measured
cable pull. Even so these aren't up to the usual accuracy standards
of Fogel Labs. But it's late; I'm tired.
I also noticed another possible complication: one aero lever had the
cable anchor above and _behind_ the pivot. As the lever squeezed,
that would lengthen the perpendicular distance from the cable force
vector to the pivot, giving a "progressive" braking action. I didn't
bother to try to measure that.
Still, here are the numbers in mm: finger lever length/cable lever
length (with the ratio, MA, parenthesized). Models of most brakes
isn't known, and in some cases, I don't even know the manufacturer.
STI are different ratios, but same MA, as described.
NON-AERO
Shimano 90/21 (4.3)
Weinmann 96/23 (4.2)
Dia Compe 100/22 (4.5)
No name 92/21 (4.4)
all the above are "ordinary" drop bar levers.
Mafac dual-cable (for tandems) 95/21 (4.5)
Weinmann for straight bars, non-ATB 96/24 (4.0)
Nashbar interrupters 61/22 (2.8)
AERO
Dia Compe 80/15 (5.3)
No name 78/18 (4.3)
Dia Compe Compact (womens) 73/18 (4.1)
Dia Compe 82/19 (4.3)
Dia Compe 287 (for use with Vee brakes) 80/32 (2.5)
Shimano Tiagra STI 24/5.6 (4.3)
Shimano Sora 18/4.1 (4.4)
The drop bar outliers are, of course, the Dia Compe 287s, by design;
and that one Dia Compe with very high MA. Otherwise, MAs don't vary
much. Averages for the two groups, excluding outliers, are quite
close.
Now, my opinion: I'm noticeably stronger braking from the hoods using
aero levers, because of the pivot position and direction of lever
rotation. The action of my hand is more squeezing, less trying to
pivot about my thumbs. The mechanical advantage may not be greater,
but I think the ergonomics are simply better with the aero levers.
- Frank Krygowski
bjwe...@gmail.com
Should you be interested in more detail, most
Dia Compe levers have a date code like "0784"
stamped inside the lever blade - you have to press
the lever open to see it. Shimanos have a date code
as two tiny stamped or stickered letters somewhere
on each part. The vintage-Trek website has a key.
I mention this in case it helped investigate the origin
of the oddball Dia Compe lever.
Ben
jobst....@stanfordalumni.org
> ------------------------------
Oops! Where's the math? I didn't see the MA calculated or compared.
We are talking Mechanical Advantage after all. Whether your hand
likes the feel of the grip or not was not the question.
Jobst Brandt
Michael Press
jobst....@stanfordalumni.org wrote:
The math is that the distance from lever pivot to cable anchor pivot
is the same for old and new styles.
But,
the further away from the lever pivot your hands are, the greater
your Mechanical Advantage. Actuating the old style levers from
the hoods means that the finger to lever contact patch moves
along the lever, bringing it closer to the lever pivot, decreasing
the Mechanical Advantage. Furthermore the crossproduct of
finger force and contact patch to lever pivot vector decreases
not only with the decreased distance of contact patch to pivot,
but with the decreased angle.
--
Michael Press
jim beam
no "but". you should measure distance from pivot to finger/cable anchor,
not any circuitous distance via the lever layout. both lever styles.
Alan Hoyle
>> Perhaps that's what Sheldon meant all along.
> The pivot was moved because unlike exposed cable brake levers that
> pulled down on the brake cable, aero levers pull forward (90??) from
> that or as the fingers move rearward the cable moves forward on a
> teeter totter lever system. Location of the pivot is immaterial while
> lever lengths from the pivot are what defines MA.
I recently swapped the brake levers from an 80's Nishiki from the
original non-aero levers to a pair of cheap aero levers while leaving
the original single-pivots brakes. I did this primarily so I would
have a more comfortable riding position from the hoods. In addition
to the more comfortable hand position, I also found that I was able to
apply much more braking force with my hands one the hoods.
It's not that the MA/cable pull changed when measured from the tip of
the lever (i.e. what you grab when you're in the drops); the MA from
the drops is the same. However, when riding on the hoods, the moved
pivot point on aero-brake levers gives a relatively longer lever from
that hand position. This allows riders to apply more braking force
with less effort than on non-aero levers when riding on the hoods.
I don't have any levers at hand, but it's pretty obvious. Measure the
lever length from the pivot point to where you actually grab the
lever. When grabbed from the hoods, non-aero have a shorter lever
than aero levers.
If you only apply your brakes from the drops, there is no advantage in
to aero levers. But if you ever want to apply your brakes from the
hoods, aero levers are significantly better. In both cases, you get
better MA from the drops.
-alan
--
Alan Hoyle - al...@unc.edu - http://www.alanhoyle.com/