Centerpull brakes

[Gary Young]

Though I've been critical of Grant Peterson's effort to revive centerpull brakes, I have to admit
that the latest Rivendell Reader (#30) gave me reasons to pause.

First of all, in the letters section, a reader (Thomas Papetti) points out that dual-pivot sidepulls
won't track an out-of-true rim the way all other brake types will. I'm not sure how much that counts
in favor of centerpulls (Papetti doesn't discuss them at all). Even though most riders would
probably use long-reach dual pivots in lieu of centerpulls, long-reach single-pivot sidepulls and
cantilevers are still available if tracking is a significant worry.

Then in an article, Jan Heine makes several claims for the superiority of sidepulls.

He says, "The long lever on the cable side [above the pivot, if I understand him correctly] and the
short lever on the pad side [below the pivot] gives centerpulls a huge mechanical advantage over
sidepulls. Just like a bolt-cutter, where long arms and short jaws allow you to cut through thick
steel bolts." Later on, he adds that only with the advent of dual-pivot brakes did sidepulls catch
up to centerpulls in this respect.

That doesn't seem to jibe with Jobst's discussion in the FAQ, which seems to suggest that
single-pivot sidepulls and centerpulls had the same mechanical advantage.

He argues that only the part of the arm below the pivot needs to be beefy, because that's the only
place where flex matters. "As a result, the arms above the pivots can be incredibly skinny, as they
don't need to resist flex. That is where the weight savings of a centerpull originate." He doesn't
say what the weight savings is.

He writes, "And since the pivot on centerpull brakes is on the fork leg, adding reach does not
increase the flex or change the mechanical advantage. So there is not incentive to go to short-reach
brakes." I think he means that since the distance between the pad and the pivot point always remains
the same, adding lever length above the pivot doesn't effect the mechanical advantage. That sounds
dubious to me -- doesn't changing the length of a cantilever brake's straddle cable effect
mechanical advantage even if all else remains the same? Furthermore, from the photos of old
centerpulls in the Reader, it doesn't seem as if the distance from pivot to pad was always kept
constant (some long-reach brakes seem to achieve that reach in part by increasing the lever below
the pivot).

He notes that centerpulls don't stick out to the side like centerpulls. It seems to me that that
problem can be cured by using v-brakes, though that introduces problems of its own (e.g., mating
them to road levers).

He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
offered by Shimano don't leave much room for fenders. Is that true? Just how big a tire would you
have to run before you would crowd out the dual pivots? (Elsewhere in the Reader, Grant says that
centerpulls will clear a 40mm tire or a 38mm tire with fenders; what's the limit with the current
long-reach dual pivots?) Furthermore, why not long-reach single-pivots, which are still available?

Probably his most controversial claim is that single-pivot sidepulls "offered inferior performance"
and became widespread mostly because of Campagnolo's advertising and gruppo packaging. Contrast that
with Jobst's claim in the FAQ that, "The centerpull brake of the 1950's, was popular for nearly a
decade, in spite of being entirely without merit, being worse in all respects than the side pull
brake with which it competed."

In the past, I've been pretty fed up with Grant's talk of reviving centerpulls, because it so often
appeared side-by-side with complaints about Rivendell's financial straits and lack of popularity. I
do notice a more refreshing tone in this issue: he mentions a bike planned for next year that will
have braze-on pivots for centerpulls and adds, "But we don't expect anybody to follow that lead.,
and we fully expect to sell fewer bikes because of it. Centerpulls, for as much sense as they make,
will still scare off most customers."

 

[Simon Brooke]

[email protected] (Gary Young) writes:

> Though I've been critical of Grant Peterson's effort to revive centerpull brakes, I have to admit
> that the latest Rivendell Reader (#30) gave me reasons to pause.

Back in the eighties I was a great fan of centrepull brakes, partly because I believed them to be
greater in stopping power but mainly because I found them much more easy to adjust. That is, in my
opinion, a big benefit!

As you point out they give considerable and equal leverage to both blocks, acting symmetrically on
both sides of the rim. This certainly looks to me to be better leverage than the single pivot
calipers that were current at the time. However, cantilever brakes have at least equal leverage, are
lighter, are more securely mounted to the bike, and are even easier to adjust - for a very small
penalty in wind resistance. Where ultimate speed is not the issue they seem to me to be definitely
preferable over the older style crossed lever centrepulls. If ultimate low windage is a
consideration you're probably going to use dual pivot calipers these days anyway.

I know that V brakes have largely taken over from cantis, but personally I'm not yet persuaded that
they offer a real practical benefit for most uses - I think they're more of a style statement, and
the special levers mean that they're not so easy to interchange with other components. But I can't
now see any reason to prefer old-style crossed lever centrepulls to cantilevers.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

my other car is #<Subr-Car: #5d480> ;; This joke is not funny in emacs.

 

[Tim McNamara]

Simon Brooke <[email protected]> writes:

> I know that V brakes have largely taken over from cantis, but personally I'm not yet persuaded
> that they offer a real practical benefit for most uses - I think they're more of a style
> statement, and the special levers mean that they're not so easy to interchange with other
> components. But I can't now see any reason to prefer old-style crossed lever centrepulls to
> cantilevers.

I haven't used sidepulls since my mid-70s Schwinn Continental was stolen in 1976. As I recall they
were Dia-Compes. What I recall about them is that they stopped the bike fine. I've never seen weight
comparisons, which by rights ought to include all the relevant hardware such as hangers, straddle
wires, etc. Also, it's never seemed that there were cantilevers of the same quality as a Campy, Dura
Ace or Superbe sidepull.

From a design perspective, it seems to me that (1) centerpulls are much more complicated than either
single- or dual-pivot sidepulls; and
(2) centerpulls are more prone to flex under the force of the rim acting on the brake pads, mainly
due to flex in the hanger with the center bolt and pivots. I've never tried centerpulls mounted
on braze-ons, which might reduce or eliminate the flex problem. A number of people seem to claim
this is the case, including Tony Oliver, Jan Heine and Grant Petersen. They've used 'em and I
haven't, so at this point I have to take their word for it.

V-brakes were created to benefit the mountain bike industry. The issue was cable routing and
simplifying basic setup, which created an economies-of-scale cost savings for manufacturers like
Giant, Cannondale, Trek, etc. The need for a cable hanger was problematic for rear suspension and,
to a lesser extent, front suspension. Plus they were new and different, and a less-than-astute bike
magazine industry mistakenly took V-brakes as a consumer-side improvement rather than a supply-side
improvement.

There may be some benefits for consumers, of course. It's harder to set up V-brakes wrongly than is
the case with cantilevers. The lever feel is different because there is less friction loss with the
longer cable pull. The mechanical advantage is slightly higher, trading off modulation for reduced
hand grip. There are downsides, including very close tolerances between the rim and the brake,
which is a problem if the wheel gets bent or a spoke breaks. And the pads are much thinner, wearing
out faster and needing to be replaced more often (also, the thinner pads are much less
compressible, which adds to the "power brake" feeling of V-brakes; this is mistakenly perceived as
"more stopping power").

Every decent brake- whether sidepull, centerpull, cantilever, V-brake, disc brake, drum brake, what
have you- provides enough stopping power to make the wheel skid. In that regard, none of these
brakes provide more stopping power than the others. The question of choice really rests on other
factors (lever feel, cable routing, clearance, etc).

 

[Gary Young]

[email protected] (Gary Young) wrote in message
news:<[email protected]>...
> Though I've been critical of Grant Peterson's effort to revive centerpull brakes, I have to admit
> that the latest Rivendell Reader (#30) gave me reasons to pause.
>
> First of all, in the letters section, a reader (Thomas Papetti) points out that dual-pivot
> sidepulls won't track an out-of-true rim the way all other brake types will. I'm not sure how much
> that counts in favor of centerpulls (Papetti doesn't discuss them at all). Even though most riders
> would probably use long-reach dual pivots in lieu of centerpulls, long-reach single-pivot
> sidepulls and cantilevers are still available if tracking is a significant worry.
>
> Then in an article, Jan Heine makes several claims for the superiority of sidepulls.

That should be "superiority of centerpulls."
>
> He says, "The long lever on the cable side [above the pivot, if I understand him correctly] and
> the short lever on the pad side [below the pivot] gives centerpulls a huge mechanical advantage
> over sidepulls. Just like a bolt-cutter, where long arms and short jaws allow you to cut through
> thick steel bolts." Later on, he adds that only with the advent of dual-pivot brakes did sidepulls
> catch up to centerpulls in this respect.
>
> That doesn't seem to jibe with Jobst's discussion in the FAQ, which seems to suggest that
> single-pivot sidepulls and centerpulls had the same mechanical advantage.
>
> He argues that only the part of the arm below the pivot needs to be beefy, because that's the only
> place where flex matters. "As a result, the arms above the pivots can be incredibly skinny, as
> they don't need to resist flex. That is where the weight savings of a centerpull originate." He
> doesn't say what the weight savings is.
>
> He writes, "And since the pivot on centerpull brakes is on the fork leg, adding reach does not
> increase the flex or change the mechanical advantage. So there is not incentive to go to
> short-reach brakes." I think he means that since the distance between the pad and the pivot point
> always remains the same, adding lever length above the pivot doesn't effect the mechanical
> advantage. That sounds dubious to me -- doesn't changing the length of a cantilever brake's
> straddle cable effect mechanical advantage even if all else remains the same? Furthermore, from
> the photos of old centerpulls in the Reader, it doesn't seem as if the distance from pivot to pad
> was always kept constant (some long-reach brakes seem to achieve that reach in part by increasing
> the lever below the pivot).
>
> He notes that centerpulls don't stick out to the side like centerpulls.

Should be "centerpulls don't stick out to the side like cantilevers."

> It seems to me that that problem can be cured by using v-brakes, though that introduces problems
> of its own (e.g., mating them to road levers).
>
> He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
> offered by Shimano don't leave much room for fenders. Is that true? Just how big a tire would you
> have to run before you would crowd out the dual pivots? (Elsewhere in the Reader, Grant says that
> centerpulls will clear a 40mm tire or a 38mm tire with fenders; what's the limit with the current
> long-reach dual pivots?) Furthermore, why not long-reach single-pivots, which are still available?
>
> Probably his most controversial claim is that single-pivot sidepulls "offered inferior
> performance" and became widespread mostly because of Campagnolo's advertising and gruppo
> packaging. Contrast that with Jobst's claim in the FAQ that, "The centerpull brake of the 1950's,
> was popular for nearly a decade, in spite of being entirely without merit, being worse in all
> respects than the side pull brake with which it competed."
>
> In the past, I've been pretty fed up with Grant's talk of reviving centerpulls, because it so
> often appeared side-by-side with complaints about Rivendell's financial straits and lack of
> popularity. I do notice a more refreshing tone in this issue: he mentions a bike planned for next
> year that will have braze-on pivots for centerpulls and adds, "But we don't expect anybody to
> follow that lead., and we fully expect to sell fewer bikes because of it. Centerpulls, for as much
> sense as they make, will still scare off most customers."

 

[Jobst Brandt]

Gary Young writes:

> Though I've been critical of Grant Peterson's effort to revive centerpull brakes, I have to admit
> that the latest Rivendell Reader (#30) gave me reasons to pause.

I think two things should be noted about all brakes before the dual pivot era, and that is they all
had a 1:1 ratio in the "caliper" and a
4:1 ratio in the hand lever, all brakes being interchangeable under any hand lever. This includes
sidepull, centerpull and cantilever.

The second feature is that sidepull brakes have the pad pivot above and only slightly (rim half
width) offset from the braking surface so that there is essentially no position change as the pad
sweeps through its wear life (cosine error). Centerpull and cantilever brakes approach the rim at
nearly a 45 degree angle and have large vertical change throughout pad wear life, so much so that
cantilever brakes have dived under the rim leaving the bicycle with no brake at all.

The cantilever dives under but had the advantage of endless mud or radial tire clearance, the
centerpull goes into the tire as it wears and offers no advantages whatsoever. I believe that is why
it died so quickly as it should have. It was sold on the premise that it had a higher mechanical
advantage, something that at first inspection it appears to have through its long levers. They are
twice as long as the pad arms... but there are two of them, each receiving half the force.

> First of all, in the letters section, a reader (Thomas Papetti) points out that dual-pivot
> sidepulls won't track an out-of-true rim the way all other brake types will. I'm not sure how much
> that counts in favor of centerpulls (Papetti doesn't discuss them at all). Even though most riders
> would probably use long-reach dual pivots in lieu of centerpulls, long-reach single-pivot
> sidepulls and cantilevers are still available if tracking is a significant worry.

> Then in an article, Jan Heine makes several claims for the superiority of sidepulls.

> He says, "The long lever on the cable side [above the pivot, if I understand him correctly] and
> the short lever on the pad side [below the pivot] gives centerpulls a huge mechanical advantage
> over sidepulls. Just like a bolt-cutter, where long arms and short jaws allow you to cut through
> thick steel bolts." Later on, he adds that only with the advent of dual-pivot brakes did sidepulls
> catch up to centerpulls in this respect.

> That doesn't seem to jibe with Jobst's discussion in the FAQ, which seems to suggest that
> single-pivot sidepulls and centerpulls had the same mechanical advantage.

They had to have the same ME or you couldn't operate them with the same pad clearance. The purpose
of the dual pivot is to allow half the pad clearance of former brakes and this required accurate
centering. This is necessary to offer the higher mechanical advantage today's avocational riders
need to stop their bicycles.

Just recall the story bicycle shops had to come up with to explain why riders could not stop their
Campagnolo Record equipped bicycles... "These are racing brakes. Racers only need to modulate speed,
not stop." and the like. If you believe that you deserve to be led around by the nose. The faster
you go the harder you must brake. Descending a mountain pass with straights and hairpin turns
requires standing the bicycle on its front wheel into every turn. This is done with two fingers by
racers using 4:1 brakes.

> He argues that only the part of the arm below the pivot needs to be beefy, because that's the only
> place where flex matters. "As a result, the arms above the pivots can be incredibly skinny, as
> they don't need to resist flex. That is where the weight savings of a centerpull originate." He
> doesn't say what the weight savings is.

Flex in any part of the system eats up hand lever stroke. Who invents this **** and bull stuff
anyway? The lower arm must be stronger because it is loaded in torsion from brake pad drag.

> He writes, "And since the pivot on centerpull brakes is on the fork leg, adding reach does not
> increase the flex or change the mechanical advantage. So there is not incentive to go to
> short-reach brakes." I think he means that since the distance between the pad and the pivot point
> always remains the same, adding lever length above the pivot doesn't effect the mechanical
> advantage. That sounds dubious to me -- doesn't changing the length of a cantilever brake's
> straddle cable effect mechanical advantage even if all else remains the same? Furthermore, from
> the photos of old centerpulls in the Reader, it doesn't seem as if the distance from pivot to pad
> was always kept constant (some long-reach brakes seem to achieve that reach in part by increasing
> the lever below the pivot).

These are not people to be believed. They have no idea what they are talking about and do it
profusely. It reminds me of the kooks I see at InterBike every year with a new crank mechanism that
will make you go faster, not to mention how much mechanism and weight it adds to the bicycle.

> He notes that centerpulls don't stick out to the side like sidepulls. It seems to me that that
> problem can be cured by using v-brakes, though that introduces problems of its own (e.g., mating
> them to road levers).

How far??? What is the issue here anyway. Is it perhaps streamlining or just someone who suffers
from the "loose ends" syndrome (things that protrude, as in toilet paper rolls that pay off the
front instead of the back [hidden ends])?

> He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
> offered by Shimano don't leave much room for fenders. Is that true?

NO.

> Just how big a tire would you have to run before you would crowd out the dual pivots? (Elsewhere
> in the Reader, Grant says that centerpulls will clear a 40mm tire or a 38mm tire with fenders;
> what's the limit with the current long-reach dual pivots?) Furthermore, why not long-reach
> single-pivots, which are still available?

> Probably his most controversial claim is that single-pivot sidepulls "offered inferior
> performance" and became widespread mostly because of Campagnolo's advertising and gruppo
> packaging. Contrast that with Jobst's claim in the FAQ that, "The centerpull brake of the 1950's,
> was popular for nearly a decade, in spite of being entirely without merit, being worse in all
> respects than the side pull brake with which it competed."

A conspiracy! The sidepull brake is the obvious mechanism for road bicycles to all who understand
mechanical design. All this other stuff is amateur thinking guided by misunderstanding of the
concept. Even places like Campagnolo are not immune. After Tullio died the place was run by
incompetents who made the Delta brake, a non linear response brake with huge cosine error. It was an
Ide? fixe of someone with "loose end" syndrome, externally clean but a mess inside.

http://draco.acs.uci.edu/rbfaq/FAQ/8f.15.html

> In the past, I've been pretty fed up with Grant's talk of reviving centerpulls, because it so
> often appeared side-by-side with complaints about Rivendell's financial straits and lack of
> popularity. I do notice a more refreshing tone in this issue: he mentions a bike planned for next
> year that will have braze-on pivots for centerpulls and adds, "But we don't expect anybody to
> follow that lead., and we fully expect to sell fewer bikes because of it. Centerpulls, for as much
> sense as they make, will still scare off most customers."

... and they should. Now let's hear it again concisely. What are the advantages?

Jobst Brandt [email protected]

 

[Jobst Brandt]

Tim McNamara writes:

> Every decent brake- whether sidepull, centerpull, cantilever, V-brake, disc brake, drum brake,
> what have you- provides enough stopping power to make the wheel skid. In that regard, none of
> these brakes provide more stopping power than the others. The question of choice really rests on
> other factors (lever feel, cable routing, clearance, etc).

That may be true today but for the older brakes, before dual pivot, it was not. 4:1 leverage was
more than a non athletic rider could handle, especially with two fingers.

The different ratio hand levers caused problems for which people found solutions. One of these was
the Travel Agent, a clever and appropriate name that we don't hear much about now that the dust
has settled.

http://tinyurl.com/r6la

Jobst Brandt [email protected]

 

[Donald Gillies]

[email protected] (Gary Young) writes:

>In the past, I've been pretty fed up with Grant's talk of reviving centerpulls, because it so often
>appeared side-by-side with complaints about Rivendell's financial straits and lack of popularity. I
>do notice a more refreshing tone in this issue: he mentions a bike planned for next year that will
>have braze-on pivots for centerpulls and adds, "But we don't expect anybody to follow that lead.,
>and we fully expect to sell fewer bikes because of it.

I have owned 2 bikes with centerpulls (raleigh grand prix, dawes low-end), and 3 bikes with
sidepulls (schwinn paramount, trek 500, alan), and 1 bike with dual-pivot sidepulls (trek 2300) and
one bike with U-brakes (schwinn moab). I currently live on a very steep hill in san diego, present.
In terms of stopping power, this is where I think that things stack up.

sidepulls (campy) - worst dual-pivots (shimano) - better centerpulls - best

U-brakes - hard to gauge since these are on a totally different kind of (mountain) bike.

It is worth pointing out that when i recently got the Alan bike with campy sidepulls, I immediately
removed the campy pads and put new low-end pads on it, since the campy pads weren't working. I then
took off the low end pads and bought premium oversized shimano pads, since the low-end pads weren't
working. the premium (ultegra) pads just barely work. I am still very unhappy with the campy gran
sport sidepull performance, and I feel jeopardized every time i go down the hill.

Campy and Shimano marketing hype aside, i think you can easily determine the most powerful brakes by
looking historically at what got installed on tandem bicycles in the past. In the late 1960's and
1970's and 1980's, the choices were :

cantilevers - best centerpulls - second best

no sidepulls installed on tandems. even today, nobody puts dual-pivots on tandems.

i like the higher braking precision in centerpulls. The lever travel is farther on centerpulls and
so you know there is more mechanical advantage. you can see it just by placing a set of weinmann
levers next to some campy levers.

that's all i need to know.

- Don Gillies San Diego, CA

 

[Tim McNamara]

[email protected] (Donald Gillies) writes:

> I have owned 2 bikes with centerpulls (raleigh grand prix, dawes low-end), and 3 bikes with
> sidepulls (schwinn paramount, trek 500, alan), and 1 bike with dual-pivot sidepulls (trek 2300)
> and one bike with U-brakes (schwinn moab). I currently live on a very steep hill in san diego,
> present. In terms of stopping power, this is where I think that things stack up.
>
> sidepulls (campy) - worst dual-pivots (shimano) - better centerpulls - best
>
> U-brakes - hard to gauge since these are on a totally different kind of (mountain) bike.

Actually, U-brakes were just a new name for an old design" centerpulls. Take a close look, they are
just centerpull brakes with a slightly different arm shape.

> It is worth pointing out that when i recently got the Alan bike with campy sidepulls, I
> immediately removed the campy pads and put new low-end pads on it, since the campy pads weren't
> working. I then took off the low end pads and bought premium oversized shimano pads, since the
> low-end pads weren't working. the premium (ultegra) pads just barely work. I am still very
> unhappy with the campy gran sport sidepull performance, and I feel jeopardized every time i go
> down the hill.

Try Mathauser or KoolStop Continental slamon colored pads. They work better than any other pad on
the market IMHO.

 

[Tim McNamara]

[email protected] writes:

> Tim McNamara writes:
>
> > Every decent brake- whether sidepull, centerpull, cantilever, V-brake, disc brake, drum brake,
> > what have you- provides enough stopping power to make the wheel skid. In that regard, none of
> > these brakes provide more stopping power than the others. The question of choice really rests on
> > other factors (lever feel, cable routing, clearance, etc).
>
> That may be true today but for the older brakes, before dual pivot, it was not. 4:1 leverage was
> more than a non athletic rider could handle, especially with two fingers.

I'll concede that and excuse myself by admitting a limited point of viewq. Having always been an
"athletic" rider, I never have had trouble with being able to squeeze any brake lever hard enough to
make the brake work. Being 6'4" and having commensurately sized hands, I have tended to find brake
lever bodies too small and uncomfortable (only the 1998 and later Campy Ergo lever bodies feel
really comfortable to me).

Certainly my sidepulls with non-aero levers take more effort to use than my dual pivot Campy Ergo
brakes/levers. I don't remember what the centerpull lever feel was like. I will agree that all
brakes are not equal from the practical, ergonomic perspective.

 

[Chalo]

Tim McNamara <[email protected]> wrote:

> From a design perspective, it seems to me that (1) centerpulls are much more complicated than
> either single- or dual-pivot sidepulls;

More so than single-pivot, less so than dual-pivot as the pivots are symmetrical and there is no
proportioning mechanism.

> and (2) centerpulls are more prone to flex under the force of the rim acting on the brake pads,
> mainly due to flex in the hanger with the center bolt and pivots.

If you have developed such an impression, it was probably due to the reach length of any centerpull
brakes you have tried being well in excess of whichever sidepull you were using for comparison.

Centerpulls locate the mechanical pivots, and their accompanying play, further down the lever arm,
for less effect on overall pad deflection at the rim. The "bridge" element containing the pivot
studs is typically stouter than the analogous portion of sidepull arm.

> I've never tried centerpulls mounted on braze-ons, which might reduce or eliminate the flex
> problem. A number of people seem to claim this is the case, including Tony Oliver, Jan Heine and
> Grant Petersen. They've used 'em and I haven't, so at this point I have to take their word for it.

Brazed-on pivots work. That is the definitive difference between the road bike centerpull as used
during the bike boom, and the U-brake as used during the 80s MTB craze. The stopping power of a
U-brake dwarfs that of any road bike brake ever made, and U-brakes were no more difficult to set up
than a road caliper.

Brazing centerpull pivots to the frame usually reduces the overhung length by more than half, and it
usually anchors the brake to a stiffer piece of the frame than a centerbolt does. What flex remains
can be attenuated by a booster plate, unlike flex that occurs at a centerbolt.

> Every decent brake- whether sidepull, centerpull, cantilever, V-brake, disc brake, drum brake,
> what have you- provides enough stopping power to make the wheel skid.

--in the rear, if you are a single lightweight rider on a short-wheelbase upright bike without a
heavy load. The incapacity of the road caliper brake as furnished to provide more stopping power
when appropriate is its most serious shortcoming.

The ability of cantilever brakes, U-brakes (and other stud-mounted centerpulls), v-brakes, and
hydraulic rim brakes to be set up to deliver more stopping power than most riders require is what
makes them versatile and valuable, even if it is of no benefit to most sport riders.

Chalo Colina

 

[David L. Johnso]

On Thu, 16 Oct 2003 00:40:31 +0000, Gary Young wrote:

> Though I've been critical of Grant Peterson's effort to revive centerpull brakes, I have to admit
> that the latest Rivendell Reader (#30) gave me reasons to pause.

My memories of center-pull brakes were not all that pleasant. I remember when most racing bikes had
them, in the late '60s. The competition, then, were usually poorly-designed sidepulls, which would
tend to rotate so that one pad would drag on the rim. Campy sidepulls changed all that, and everyone
went for them despite the outrageous cost. They could be properly centered fairly easily, and stayed
where you put them.

Centerpulls depended on the balance of their springs to center them. Use and dirt would make them
one-sided as easily as old sidepulls. They also were mushy, so that it was easy to bottom out the
lever in a hard stop, especially in wet weather.

Modern dual-pivot sidepulls, and probably the Campy single-pivot rear brake, are much easier to
adjust, stay where they are adjusted, and do an excellent job. I also think that V brakes work quite
well, and have the advantage of huge tire clearance. The angle problem mentioned by Jobst has not
been a difficulty for me, but would be if you were not attentive to pad wear. I know that modern
cantilever brakes also are easy to adjust, but they still have the variable-pull characteristic of
old center-pulls.

> dual-pivot sidepulls won't track an out-of-true rim the way all other brake types will.

Why would that be the case? I don't see how the mechanism would be that different. Of course,
dual-pivot brakes have short reach and so small possible "tracking" distance, but they would have
some capability.

> He says, "The long lever on the cable side [above the pivot, if I understand him correctly] and
> the short lever on the pad side [below the pivot] gives centerpulls a huge mechanical advantage
> over sidepulls.

The problem with this is that any increased mechanical advantage means more cable pull for an
equivalent motion of the pad, so the lever has to have less mechanical advantage as a result. Net
advantage, 0. You have to be able to exert maximum force on the system before the lever bottoms out,
and you need the same open pad clearance on any brake. There isn't enough room to increase the
mechanical advantage and still have a usable lever. You can decrease, slightly, pad clearance when
the brake is open, but that means the wheels have to be kept true. A broken spoke makes the bike
impossible to ride, not the best for a tour.

The only other factor that comes into play is arm flex, which centerpulls had in spades.

--

David L. Johnson

__o | Let's not escape into mathematics. Let's stay with reality. -- _`\(,_ | Michael Crichton
(_)/ (_) |

 

[Simon Brooke]

Tim McNamara <[email protected]> writes:

> Certainly my sidepulls with non-aero levers take more effort to use than my dual pivot Campy Ergo
> brakes/levers. I don't remember what the centerpull lever feel was like. I will agree that all
> brakes are not equal from the practical, ergonomic perspective.

If you mean the classic 1970s style centrepull - the things Weinnman made in such huge numbers - the
answer has to be 'worryingly spongy', presumably because of flex in the system. Still, they worked
well enough when all the competition was single-pivot calipers, and those, in their turn, were
infinitely superior to the roller-lever brakes they superceded.

When I was a kid bicycle brakes that we had access to did not match the sort of performance we could
get out of our bikes downhill. We certainly could not have locked wheels at speed. Forty years of
development really have achieved something.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/ ;; gif ye hes forget our auld
plane Scottis quhilk your mother lerit you, ;; in tymes cuming I sall wryte to you my mind in Latin,
for I am nocht ;; acquyntit with your Southeron ;; Letter frae Ninian Winyet tae John Knox datit 27t
October 1563

 

[Gary Young]

[email protected] (Donald Gillies) wrote in message news:<[email protected]>... <snip>
> I have owned 2 bikes with centerpulls (raleigh grand prix, dawes low-end), and 3 bikes with
> sidepulls (schwinn paramount, trek 500, alan), and 1 bike with dual-pivot sidepulls (trek 2300)
> and one bike with U-brakes (schwinn moab). I currently live on a very steep hill in san diego,
> present. In terms of stopping power, this is where I think that things stack up.
>
> sidepulls (campy) - worst dual-pivots (shimano) - better centerpulls - best
>
> U-brakes - hard to gauge since these are on a totally different kind of (mountain) bike.
>
> It is worth pointing out that when i recently got the Alan bike with campy sidepulls, I
> immediately removed the campy pads and put new low-end pads on it, since the campy pads weren't
> working. I then took off the low end pads and bought premium oversized shimano pads, since the
> low-end pads weren't working. the premium (ultegra) pads just barely work. I am still very
> unhappy with the campy gran sport sidepull performance, and I feel jeopardized every time i go
> down the hill.

Have you compared all three brakes using the same pad? Or at least the same make of pad?
>
> Campy and Shimano marketing hype aside, i think you can easily determine the most powerful brakes
> by looking historically at what got installed on tandem bicycles in the past. In the late 1960's
> and 1970's and 1980's, the choices were :
>
> cantilevers - best centerpulls - second best
>
> no sidepulls installed on tandems. even today, nobody puts dual-pivots on tandems.

Sheldon has a different take on that:

"Few tandems come equipped with caliper brakes these days, because it is widely believed that
caliper brakes don't have sufficient stopping power for tandem service. This belief is incorrect.
Tandems set up for racing can get perfectly adequate braking from good quality caliper brakes....

In the 1970's, center-pull caliper brakes were common, which did provide reasonable tire clearance,
but these have gone out of fashion and are not provided on new bikes."

Source: http://www.sheldonbrown.com/tandem-brakes.html.

 

[Chalo]

[email protected] wrote:

> ...sidepull brakes have the pad pivot above and only slightly (rim half width) offset from the
> braking surface so that there is essentially no position change as the pad sweeps through its wear
> life (cosine error). Centerpull and cantilever brakes approach the rim at nearly a 45 degree angle
> and have large vertical change throughout pad wear life,

This trait of stud-mounted brakes can be accomodated by adusting the pad height as it wears. The pad
rub on tire sidewalls exhibited by single-pivot sidepulls, however, is due to the extreme
fore-to-aft flex these brakes display and can not reliably be adjusted away.

This horrible characteristic of single-pivot sidepull brakes is IMO one of the reasons for the
annoying move to "short reach" road calipers-- because the stubby arms of those brakes are somewhat
resistant to allowing sidewall rub for most average-sized riders.

> the centerpull goes into the tire as it wears and offers no advantages whatsoever.

When mounted on frame studs, it offers vastly superior maximum stopping power to any caliper brake.
I know this because I have bent many forks under the braking forces generated by U-brakes. Before
applying stopping power like that, caliper brakes become so twisted out of shape that applying more
cable tension does not result in more braking.

> Flex in any part of the system eats up hand lever stroke.

Insufficient stroke length can be addressed by using levers that pull more cable, and pulling them
harder. However, the swinging flex endemic to all centerbolt-mounted brakes, and the torsional flex
that is particularly pronounced in single-pivot brakes, act disproportionately to diminish the
braking that can be applied regardless of how hard or how far the cable is pulled.

The "ceiling" on stopping force resulting from flex-related distortion of the brake mechanism is
lower, and more abrupt, with single-pivot calipers than with any other type of brake.

> > He notes that centerpulls don't stick out to the side like sidepulls.
>
> How far??? What is the issue here anyway.

I have seen enough bikes damaged by the sidepull brake arm bashing into the downtube to think of
that design characteristic as a liability.

> > He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
> > offered by Shimano don't leave much room for fenders. Is that true?
>
> NO.

It is true if you wish to run decent-sized tires and fenders at the same time. Even the most
careful brake placement will not allow "standard reach" dual-pivot calipers to encompass 38mm tires
with fenders.

> The sidepull brake is the obvious mechanism for road bicycles to all who understand mechanical
> design. All this other stuff is amateur thinking guided by misunderstanding of the concept.

Sorry, but that's just not true. It might be "the obvious mechanism" if one is unconcerned about
generating the most stopping force from a given amount of brake, and if one disregards the benefits
of voluminous tires, and if one happily tolerates pad rub due to a brake design that can not be
centered accurately. But most "who understand mechanical design" demand (or at least desire) better
performance than that!

Getting the brake pivot as close as practiceable to the pads pays huge dividends in turning lever
force into stopping force. That very translation is exactly where single-pivot calipers are so weak.
They only provide an approximately linear relationship between lever force and braking force up to a
point-- a point easily exceeded by many riders in many circumstances.

Add to this the inherent characteristic of them being impossible to center consistently, and
it's not at all obvious that they are superior to the worst of other brake designs, let alone
the best of them.

> Now let's hear it again concisely. What are the advantages?

Concisely? Stopping. Centering.

Chalo Colina

 

[Simon Brooke]

Tim McNamara <[email protected]> writes:

> [email protected] (Donald Gillies) writes:
>
> > I have owned 2 bikes with centerpulls (raleigh grand prix, dawes low-end), and 3 bikes with
> > sidepulls (schwinn paramount, trek 500, alan), and 1 bike with dual-pivot sidepulls (trek 2300)
> > and one bike with U-brakes (schwinn moab). I currently live on a very steep hill in san diego,
> > present. In terms of stopping power, this is where I think that things stack up.
> >
> > sidepulls (campy) - worst dual-pivots (shimano) - better centerpulls - best
> >
> > U-brakes - hard to gauge since these are on a totally different kind of (mountain) bike.
>
> Actually, U-brakes were just a new name for an old design" centerpulls. Take a close look, they
> are just centerpull brakes with a slightly different arm shape.

To be fair, the U brakes mount to bosses on the forks rather than to a saddle which mounts to a bolt
in the classic 'brake bolt' position. This must make them rather stronger and less flexible (and
also probably lighter) than old-design centrepulls.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/ ;; gif ye hes forget our auld
plane Scottis quhilk your mother lerit you, ;; in tymes cuming I sall wryte to you my mind in Latin,
for I am nocht ;; acquyntit with your Southeron ;; Letter frae Ninian Winyet tae John Knox datit 27t
October 1563

 

[Bfd]

"Gary Young" <[email protected]> wrote in message
news:[email protected]...
> [email protected] (Donald Gillies) wrote in message
news:<[email protected]>...
> <snip>
> > I have owned 2 bikes with centerpulls (raleigh grand prix, dawes low-end), and 3 bikes with
> > sidepulls (schwinn paramount, trek 500, alan), and 1 bike with dual-pivot sidepulls (trek 2300)
> > and one bike with U-brakes (schwinn moab). I currently live on a very steep hill in san diego,
> > present. In terms of stopping power, this is where I think that things stack up.
> >
> > sidepulls (campy) - worst dual-pivots (shimano) - better centerpulls - best
> >
> > U-brakes - hard to gauge since these are on a totally different kind of (mountain) bike.
> >
> > It is worth pointing out that when i recently got the Alan bike with campy sidepulls, I
> > immediately removed the campy pads and put new low-end pads on it, since the campy pads weren't
> > working. I then took off the low end pads and bought premium oversized shimano pads, since the
> > low-end pads weren't working. the premium (ultegra) pads just barely work. I am still very
> > unhappy with the campy gran sport sidepull performance, and I feel jeopardized every time i go
> > down the hill.
>
> Have you compared all three brakes using the same pad? Or at least the same make of pad?
> >
> > Campy and Shimano marketing hype aside, i think you can easily determine the most powerful
> > brakes by looking historically at what got installed on tandem bicycles in the past. In the late
> > 1960's and 1970's and 1980's, the choices were :
> >
> > cantilevers - best centerpulls - second best
> >
> > no sidepulls installed on tandems. even today, nobody puts dual-pivots on tandems.
>
> Sheldon has a different take on that:
>
> "Few tandems come equipped with caliper brakes these days, because it is widely believed that
> caliper brakes don't have sufficient stopping power for tandem service. This belief is incorrect.
> Tandems set up for racing can get perfectly adequate braking from good quality caliper brakes....
>
> In the 1970's, center-pull caliper brakes were common, which did provide reasonable tire
> clearance, but these have gone out of fashion and are not provided on new bikes."
>
> Source: http://www.sheldonbrown.com/tandem-brakes.html.

Agree, Calfee's 28.5 lb *racing* tandem also uses sidepull caliper brakes too:

http://www.calfeedesign.com/tandem.shtml

Of course, a "standard" Calfee tandem frame starts at $5300 and if you want the deluxe Dragonfly
Custom tandem frame, 6 lb tandem frame, it will cost you $7400.....

 

[Jobst Brandt]

David L. Johnson writes:

> My memories of center-pull brakes were not all that pleasant. I remember when most racing bikes
> had them, in the late '60s. The competition, then, were usually poorly-designed sidepulls, which
> would tend to rotate so that one pad would drag on the rim. Campy sidepulls changed all that, and
> everyone went for them despite the outrageous cost. They could be properly centered fairly easily,
> and stayed where you put them.

I use those brakes today and find that they are as prone to going off center as well as any sliding
return spring brake. That is one thing Campagnolo did not address but used the same return spring
shape that was the downfall of all other sidepull brakes. This is the dual "ram's horn" shape, whose
ends rotate about the center of the "ram's horn" instead of the pivot bolt.

I was glad to see that the new Mavic side pull brake that I saw at InterBike has solved this problem
and has a no-slide return spring. If you want to see how bad others are, note that Campagnolo and
Shimano have a special sleeve in which the spring slides like a piston. This gets full of fine grit
and changes the return force, the problem with non-dual pivot brakes.

> Centerpulls depended on the balance of their springs to center them. Use and dirt would make them
> one-sided as easily as old sidepulls. They also were mushy, so that it was easy to bottom out the
> lever in a hard stop, especially in wet weather.

That is the reason for having dual pivots.

Their reasonably good centering may be the only sliver of benefit of the centerpull configuration.
It arises from its use of "torsion" springs around the pivot bolts, and the short straddle cable
that puts a strong bias on returning to center almost as if it were made of a rigid two bar linkage.
To go off center the straddle cable would need to slide in the cable yoke.

> Modern dual-pivot sidepulls, and probably the Campy single-pivot rear brake, are much easier to
> adjust, stay where they are adjusted, and do an excellent job. I also think that V brakes work
> quite well, and have the advantage of huge tire clearance. The angle problem mentioned by Jobst
> has not been a difficulty for me, but would be if you were not attentive to pad wear. I know that
> modern cantilever brakes also are easy to adjust, but they still have the variable-pull
> characteristic of old center-pulls.

No current single pivot brake centers well because they all use the traditional "ram's horn" coil
return spring.

>> dual-pivot sidepulls won't track an out-of-true rim the way all other brake types will.

> Why would that be the case? I don't see how the mechanism would be that different. Of course,
> dual-pivot brakes have short reach and so small possible "tracking" distance, but they would have
> some capability.

It's not whether it should or not. The brake pads cannot move independently of the other. That is
the reason for these brakes... to always remain centered. If you doubt it, try pushing the wheel
sideways with the brake applied. Open the QR so the wheel can move if it wants to.

>> He says, "The long lever on the cable side [above the pivot, if I understand him correctly] and
>> the short lever on the pad side [below the pivot] gives centerpulls a huge mechanical advantage
>> over sidepulls.

You'll notice that this ratio is 2:1 and that half the force goes to each side resulting in a
caliper ratio of 1:1. I wrote an article about that in the 1970's for Bike World.

> The problem with this is that any increased mechanical advantage means more cable pull for an
> equivalent motion of the pad, so the lever has to have less mechanical advantage as a result. Net
> advantage, 0. You have to be able to exert maximum force on the system before the lever bottoms
> out, and you need the same open pad clearance on any brake. There isn't enough room to increase
> the mechanical advantage and still have a usable lever. You can decrease, slightly, pad clearance
> when the brake is open, but that means the wheels have to be kept true. A broken spoke makes the
> bike impossible to ride, not the best for a tour.

Today's road bicycles are dead in the water with a broken spoke, tire clearance in the frame or fork
being almost that of brake pad clearance. This plays to the short bike, fast cornering aficionados.
Everything has got to be as tightly packed as possible.

> The only other factor that comes into play is arm flex, which centerpulls had in spades.

... to make up for all the positive features they didn't have.

Jobst Brandt [email protected]

 

[Jobst Brandt]

Chalo Colina writes:

>> ...sidepull brakes have the pad pivot above and only slightly (rim half width) offset from the
>> braking surface so that there is essentially no position change as the pad sweeps through its
>> wear life (cosine error). Centerpull and cantilever brakes approach the rim at nearly a 45 degree
>> angle and have large vertical change throughout pad wear life,

> This trait of stud-mounted brakes can be accommodated by adjusting the pad height as it wears. The
> pad rub on tire sidewalls exhibited by single-pivot sidepulls, however, is due to the extreme
> fore-to-aft flex these brakes display and can not reliably be adjusted away.

> This horrible characteristic of single-pivot sidepull brakes is IMO one of the reasons for the
> annoying move to "short reach" road calipers-- because the stubby arms of those brakes are
> somewhat resistant to allowing sidewall rub for most average-sized riders.

Wait a minute, this is a geometric given, there is nothing you can do to the motion of the pad
because it sweeps around its pivot and that pivot lies in the wrong place. Therefore when descending
in bad weather, pads wear and sweep upward if the pivot point is above and outside of the tire.
Cantilevers do the opposite and sweep downward, the angle of attack of both being roughly 45 degrees
instead of near zero of a good sidepull.

>> the centerpull goes into the tire as it wears and offers no advantages whatsoever.

> When mounted on frame studs, it offers vastly superior maximum stopping power to any caliper
> brake. I know this because I have bent many forks under the braking forces generated by U-brakes.
> Before applying stopping power like that, caliper brakes become so twisted out of shape that
> applying more cable tension does not result in more braking.

OK, if you say so but you'll have to do some measurements to convince
me. Regardless of where they are mounted, the mechanical advantage cannot be higher than the
average human reach allows. You seem to be using hyperbole in that description. A brake that
operates at the yield point will break off in short order. I have never seen a caliper that was
bent from braking and I don't expect to see one.

>> Flex in any part of the system eats up hand lever stroke.

> Insufficient stroke length can be addressed by using levers that pull more cable, and pulling them
> harder. However, the swinging flex endemic to all center bolt-mounted brakes, and the torsional
> flex that is particularly pronounced in single-pivot brakes, act disproportionately to diminish
> the braking that can be applied regardless of how hard or how far the cable is pulled.

Levers that pull more cable are ones that have a lower mechanical advantage. You can't have both or
we wouldn't use power brakes on cars. I don't know what torsional flex you are referring to but it
isn't large. The toe-in of brake pads arises from pad rotation due to clearance and flex. That
isn't much.

> The "ceiling" on stopping force resulting from flex-related distortion of the brake mechanism is
> lower, and more abrupt, with single-pivot calipers than with any other type of brake.

To what do you attribute this claim. I'm not sure what you mean by the ceiling anyway. Could you
expand on that.

>>> He notes that centerpulls don't stick out to the side like sidepulls.

>> How far??? What is the issue here anyway.

> I have seen enough bikes damaged by the sidepull brake arm bashing into the downtube to think of
> that design characteristic as a liability.

I guess we'll have to live with that as we do with drinking glasses being brittle. I've been riding
sidepull brakes a long time and have not had one damaged. Neither mine or those of my riding
companions.

>>> He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
>>> offered by Shimano don't leave much room for fenders. Is that true?

>> NO.

> It is true if you wish to run decent-sized tires and fenders at the same time. Even the most
> careful brake placement will not allow "standard reach" dual-pivot calipers to encompass 38mm
> tires with fenders.

OK, I recall even back when brakes had far more clearance, split fenders that went to the back of
the fork and continued from the brake bolt forward were the rave it you had to have racing brakes.

>> The sidepull brake is the obvious mechanism for road bicycles to all who understand mechanical
>> design. All this other stuff is amateur thinking guided by misunderstanding of the concept.

> Sorry, but that's just not true. It might be "the obvious mechanism" if one is unconcerned about
> generating the most stopping force from a given amount of brake, and if one disregards the
> benefits of voluminous tires, and if one happily tolerates pad rub due to a brake design that can
> not be centered accurately. But most "who understand mechanical design" demand (or at least
> desire) better performance than that!

I qualified that with road bicycle, but I probably should have said 28mm tires or smaller. Even
then, larger calipers are available from people other than Campagnolo or Shimano. The point is that
the side pull, or more accurately, the center pivot-bolt brake offers the best mechanism for
bringing brake pads into contact with the rim.

> Getting the brake pivot as close as practiceable to the pads pays huge dividends in turning lever
> force into stopping force. That very translation is exactly where single-pivot calipers are so
> weak. They only provide an approximately linear relationship between lever force and braking force
> up to a point-- a point easily exceeded by many riders in many circumstances.

That is not the place where leverage needs to be gained. Besides tire size demands that centerpull
and cantilever (and their derivatives) have their mounts far enough away so the wheel can be removed
without letting the air out. This puts the pivot point at an undesirable location that makes the pad
move at a steep angle across the braking surface.

> Add to this the inherent characteristic of them being impossible to center consistently, and it's
> not at all obvious that they are superior to the worst of other brake designs, let alone the best
> of them.

Ah, but they can be centered as you can see on the new Mavic brake that uses a spring that doesn't
slide and suffer from friction variation, the cause of off center brakes.

>> Now let's hear it again concisely. What are the advantages?

> Concisely? Stopping. Centering.

Somehow the stopping part is a mystery to me. I and the many riders with whom I have ridden have
taken a lot of steep and long descents over many years and have not had a problem with that, yet
you say they stop better. Better than what? I can raise the rear wheel on descents. I don't need
more leverage.

Jobst Brandt [email protected]

 

[Marcus Coles]

Gary Young wrote:
>
> He says that even the standard-reach (what would be called long-reach by most) dual-pivot brakes
> offered by Shimano don't leave much room for fenders. Is that true? Just how big a tire would you
> have to run before you would crowd out the dual pivots? (Elsewhere in the Reader, Grant says that
> centerpulls will clear a 40mm tire or a 38mm tire with fenders; what's the limit with the current
> long-reach dual pivots?) Furthermore, why not long-reach single-pivots, which are still available?
>

While I have no doubt that mast centre-pulls will clear a 38mm or 40mm tire and fender, one might
have one heck of a time getting said tire past the brake pads on some traditional centre-pulls.
Unless the tire was deflated or possibly V-brake pads were used.

Surely some of us can remember barely squeezing a fat 27 x 1 1/4" tire past the pads in the good old
days even with the QR or straddle released.

In my book the biggest selling points for centre-pull brakes when they were popular were the
aethetic symmetry and the fact that the village idiot assembling bikes at the local
hardware/sports/department store could centre the brakes. Prior to that point most people had only
be exposed to coaster brakes or poorly installed sidepull brakes that were forever rubbing one side
of the rim.

In my experience with the exception of rod brakes with leather pads. Any bicycle brake I have tried
can be set up to stop well in the dry for at least a few stops. Including the stamped steel
sidepulls that want to rub the one side of the rim ;-)

IMHO the most important things become the ease of modulation and repeatability.

Marcus

 

[Donald Gillies]

[email protected] writes:

>You'll notice that this ratio is 2:1 and that half the force goes to each side resulting in a
>caliper ratio of 1:1. I wrote an article about that in the 1970's for Bike World.

This just shows that you can get anything published at all. Such generalizations are clearly
unwarranted, which is easily seen just by looking at the variation in calipers within one brand such
as weinmann. The weinmann 750 had more mechanical advantage than the weinmann 610. The earlier 610's
had less mechanical advantage than the later 610's, by virtue of the shorter upper arms in the
calipers, and a straddle wire and carrier that was designed to rest higher above the caliper than
the later straddle carriers.

The mechanical advantage varies _more_ over the stroke of the centerpull brake, and the ideal brake
has a high mechanical advantage early in the stroke, and a low mechanical advantage late in the
stroke. This gets the pad to the rim quickly, then allows you to easily modulate stopping force once
you touch the rim. This is how centerpulls and cantilevers work, and its why they are easier to
control and were the most popular brakes in the 1970's.

http://www.sheldonbrown.com/cantilever-geometry.html#vbrake

In my opinion, campy did everyone a disservice by popularizing the lightweight short reach sidepull
caliper, and it has taken almost a generation to twist the centerpull caliper over to the side of
the brake (e.g. dual pivot) and produce a brake with almost the same modulation in mechanical
advantage and therefore to undo the damage that campagnolo had wrought in the 1970's.

- Don Gillies San Diego, CA