Bike messengers take to track racing

Quoting :
wrote:
wrote:
I think the guy was probably sayng that a good messenger
on a track bike could stop faster than YOU on your
road bike, which is certainly possible.
Oh yeah, just like you, def. a superior attitude. Without knowing
anything about my abilities, of course..
Depending on you and depending on the messenger, it
is certainly possible. Do you deny it? Remember that some of
these guys/gals have logged over 300000 miles on no brakes
track bikes in crowded cities.

How does that move their centre of gravity relative to the front contact
patch?

There's a pretty fundamental piece of applied mathematics at work here.
You'd have done better to have confined yourself to the physically
possible.
--
David Damerell flcl?
Today is First Thursday, Presuary.

wrote:

ALL bikes are limited.

Some more than others. Like "track" bikes (fixed, no brakes), which are
harder to accelerate due to having to use some kind of gear that will
give *some* top speed, but then limits that speed to some extent; and
has to be ridden slower because backpedal braking is so completely
inferior to caliper braking.

When riding a track bike
you simply ride within the limitations of the machine
(which will be different for any given rider).

Translation: slower.

For some riders who are very skilled, they become
less limited on their track bikes in city traffic
than most road bike riders on their road bikes. This is
the fact that you seem so bunched up about.

Debunking: they could go even faster, and be safer, with brakes and
gears, especially if they ride in hills.

Harder to accelerate? ????!!

Big gears? Well, yeah, unless you're pointed downhill. Cumulative
effect, also. But then, that's one justification for running lights...

If you think stopping fast with hand brakes amounts to
squeezing a lever then you're in deep doo doo.

One thing for sure, if you don't squeeze the lever, you're not going to
stop. Yeah, I slid the front tire again a few weeks ago in a tight
maneuver and stayed up, only a few inches this time, my level of
expertise is *so* limited compared to yours (sarcasm drip off).

Nobody says it's [Houston] 'bike friendly.'
But veteran couriers who have worked
in several cities often cite Houston as the easiest city to work in.
Easier than Seattle, easier thanDenver traffic-wise. Not even
close to Boston or NYC.

Citation, please.

Dude it's in the appendix to the Messenger Ethos
Handbook, look it up.

Borrow yours? g

Seriously just about every messenger I've ever talked
to who's worked in Houston talks about how easy it is
to ride downtown compared to other cities. Rebecca
Reilly worked in about ten different cities before
she wrote a book about her experiences. Most couriers
would agree with her list from easiest to toughest:
Houston, Denver, Seattle, Chicago, San Fran, DC, Philly,
Boston, NYC (iirc). It's basically about space on the
streets.

Yes, there are sections in DT Houston where the streets are wide, and
it sure is flat. Otherwise, I very seldom rode alone in the Inner Loop,
as there is a percentage of drivers who know they can run you down and
not suffer much in the way of consequences. Further, about the only
place I noticed much give and take (aka respect) was in the short DT
area the Wed. night ride passed through. "Palpable difference", but not
to be relied on even there, and once we swung onto Memorial Drive,
jungle time. Having lived in Austin for years previous to our Houston
sojourn, it was a rude awakening to be honked, buzzed, and threatened
again. Oh yeah, the lights were synched, at least some of them, if not
always, and traffic could strangely be light on cross streets even when
some lanes were pretty busy.

Rec riders and "roadies" never run red lights right?

I just said that everyone breaks traffic rules. Personally, I tend to
be very conservative about "the rules". To the point that I've quit
riding with a group or two over the years, and never attended certain
rides famous for blasting signs and lights.

Give me a break. At least the messengers have a good reason for
doing it. People who actually live and work in cities
understand that.

I'll gladly give you a little on that. Certainly there are times that
it serves humanity, or business, to get "papers" to a destination
quickly. But there's a problem if you're riding a slower bike and
running reds as a matter of course to make up the difference.

Consider that the clients of these messengers demand
delivery times of 15 minutes or less from the time their
order is placed. Consider that 10 minutes out of that
15 is likely to be spent in elevators. Consider that
while you're sitting there waiting for a light to change,
I'm already 8 blocks away.

When a call comes in from your biggest client at 4:54
and the dispatcher asks you if you can pick the package
and make it to the court before they close, the correct
answer is NOT "depends on the lights."

Yielding to some extent on your points.

Even the police, for the most part, are tolerant of
"scofflaw" messengers, because they understand, through
familiarity over time, that the messengers are just doing
their jobs. They dont want to needlessly harrass some
guy who they've seen day in day out doing no harm to
anyone except to the sensitivities of some fragile souls.
Some of my favorite acquaintances downtown are in fact
U.S. Marshalls who have a clear unobstructed front row
seat of me carving up traffic in front of their building
all day long, red lights and all. If they thought I was
a "scofflaw" they wouldn't let me come near their
federal court, understand?

Again, yielding to some extent.

You had better be someone who NEVER runs a red light
to be giving me this lecture. You're not, of course,
so stuff it. I don't come to your
cubicle and tell you how to shuffle your papers
around. Running red lights by messengers may in fact
be not OK, that may be true, but it IS part of the job,
and it's not going to change any time soon. So you
can begin to come to terms with it or continue
****ing up a rope.

I'm retired (no cubicle). But there you go again, trying to pin me with
that "inferior" button. Just to tell you, I worked in the service biz
(res/commercial plumbing repair) so I know something about hauling
through traffic to make money. Five years, one ticket and one BS
"collision" BTW. Lots of saves...

On the bike? I suffer the slings and arrows-- "Why did you stop at that
stop sign (snort)?" Nope, not "perfect" but very aware of motorist
attitudes. IOW, other than following groups through on a changing light
red (leader catching a yellow), no, I don't run lights, and I don't
blast SS's. Bad PR, plus sometimes those cars sneak up on you...

I cant remember the last time I went through a
red light with a 'FU attitude.' Of course I
can't speak for the commuters and 'roadies' and all the
other non-messengers out there who are responsible for
99% of all light runnings and other 'scofflaw' cycling,
but messengers are usually just doing their jobs.
Considering YOUR obvious prejudicial attitude against
all messengers, however, it's possible
that the 'FU attitude' you sense from them is directed at
you, and only at you.

Actually, I was talking about the no-brakes guys, who seem to commonly
regard the "messengers" as demi-gods who are above the laws of man and
physics. You can talk about your own attitude; that doesn't whitewash
what others do. The fixed/no brakes thing is an ethos; there is a
scofflaw subculture which includes messengers, for all your
protestations about compulsory speed on which, remember, I yielded to
you, to an extent.

Dang, it's Wednesday, last real ride I had was Friday's 71.xx miler.
Broken cars/computer, kids at home, crazy work sched. Time for b-fast
out with the other half, then maybe repeat one of a couple of last
week's 40-50 miles with a Triangle (Austin training loop, some nice
little hills) after on the 50/15 fixer (one powerful, well-adjusted
front brake, road fork in track frame).

Have a safe and productive day. Thanks. --TP

wrote:

The typical messenger is of course already a much better
"bike handler" than the typical Cat IV or V.

I live in Seattle and belong to a bike club that includes a bunch of
cycle messengers. Since the business is in decline and its numbers
diminishing, those who still do this for a living are quite good at
what they do.

In my observation, bike messengers are capable, fast riders. They put
in a lot of miles, and they are as fit as you'd expect for the mileage
they ride. But they are generally neither faster nor more capable than
folks who ride similar mileages for sport-- if they enjoy any
categorical superiority to other riders, it is only in traffic-specific
skills. More to the point in question, those messengers who use fixies
pay a performance penalty to do so.

Among my messenger friends who use fixies for work, there seem to be
two major reaszons for their choice of bikes. First, and probably
foremost, fixies are seen as "badass" and are a fashionable type of
bike at the moment (though there is obviously some recursive element at
work here, since bike messengers define a certain kind of urban chic).
Second, many of the riders who use them are mechanically disinclined,
and the simplicity, overall reliability, durability, and fault
tolerance of a fixie appeal to them.

There are some other contributing reasons that messengers choose fixies
(low cost, the cult of skill surrounding them, light weight, good
looks, their resistance to some kinds of casual theft), but I have
never once heard a messenger here in Seattle suggest that he was faster
point-to-point on a fixie than on a road bike.

Chalo Colina

David Damerell wrote:
Quoting :
wrote:
wrote:
I think the guy was probably sayng that a good messenger
on a track bike could stop faster than YOU on your
road bike, which is certainly possible.
Oh yeah, just like you, def. a superior attitude. Without knowing
anything about my abilities, of course..
Depending on you and depending on the messenger, it
is certainly possible. Do you deny it? Remember that some of
these guys/gals have logged over 300000 miles on no brakes
track bikes in crowded cities.

How does that move their centre of gravity relative to the front contact
patch?

Skill level has everything to do with how their
center of gravity moves relative to the contact patch.


There's a pretty fundamental piece of applied mathematics at work here....

Not as fundamental as most people seem to think.

Even with a handbrake, stopping distance is highly
variable depending primarily on the timing and magnitude
of the rider's body movement. Yes
it is a 'simple formula,' but only after the acceleration/
deceleration of the body mass has been accounted for,
which is not simple. All the formulae I've seen on this
(Bicycling Science, Forester) assume that all bodies
remain completely static under heavy braking, and that
seems pretty silly, although convenient for formula-
makers. But it nonetheless explains why
skilled rders can stop quicker than the .6-.7g that
has been cited as the shortest possible stop for a
cyclist based on the static-body formula.

messengers on track bikes. I have seen messengers
on track bikes with no brakes perform .6-.7g stops.
They do it by stopping the wheel and throwing it violently
to the side, perhaps even ending up on the ground, feet
first. While there are certainly many cyclists with
hand brakes who can perform .6-.7g stops., I'm sure there
are many who can not. And when they end up on the ground
it aint feet first.

Robert

On 29 Jun 2005 19:39:40 -0700, wrote:

David Damerell wrote:
Quoting :
wrote:
wrote:
I think the guy was probably sayng that a good messenger
on a track bike could stop faster than YOU on your
road bike, which is certainly possible.
Oh yeah, just like you, def. a superior attitude. Without knowing
anything about my abilities, of course..
Depending on you and depending on the messenger, it
is certainly possible. Do you deny it? Remember that some of
these guys/gals have logged over 300000 miles on no brakes
track bikes in crowded cities.

How does that move their centre of gravity relative to the front contact
patch?

Skill level has everything to do with how their
center of gravity moves relative to the contact patch.


There's a pretty fundamental piece of applied mathematics at work here....

Not as fundamental as most people seem to think.

Even with a handbrake, stopping distance is highly
variable depending primarily on the timing and magnitude
of the rider's body movement. Yes
it is a 'simple formula,' but only after the acceleration/
deceleration of the body mass has been accounted for,
which is not simple. All the formulae I've seen on this
(Bicycling Science, Forester) assume that all bodies
remain completely static under heavy braking, and that
seems pretty silly, although convenient for formula-
makers. But it nonetheless explains why
skilled rders can stop quicker than the .6-.7g that
has been cited as the shortest possible stop for a
cyclist based on the static-body formula.

messengers on track bikes. I have seen messengers
on track bikes with no brakes perform .6-.7g stops.
They do it by stopping the wheel and throwing it violently
to the side, perhaps even ending up on the ground, feet
first. While there are certainly many cyclists with
hand brakes who can perform .6-.7g stops., I'm sure there
are many who can not. And when they end up on the ground
it aint feet first.

Robert

Dear Robert,

Wouldn't stopping the rear wheel and throwing the bike
sideways involve an instant rear wheel slide?

And isn't the sliding coefficient of friction of rubber
tires on pavement considerably inferior to their rolling
coefficient?

Any actual speeds and distances for this interesting braking
scheme?

Curiously,

Carl Fogel

carl fogeled:

Dear Robert,

Wouldn't stopping the rear wheel and throwing the bike
sideways involve an instant rear wheel slide?

To put it mildly. The rear end is coming around in this
kind of stop. It is angled in and scraped sideways across
the surface, not a garden variety slide. Streets are not
smooth, they are made of rocks, glued together. In
these situations there is generally enough friction
that the danger is more from high side than not stopping
soon enough. This is bad for tires and wheels and
rear triangles.

And isn't the sliding coefficient of friction of rubber
tires on pavement considerably inferior to their rolling
coefficient?

I dont think there is a pair of legs out there that
could stop a fixed gear in that range of gforce without
the kind of jackknife/powerslide maneuver I described.
Perhaps I'm wrong but I don't think normal human
muscles are up to that. I would be amazed to see it.


Any actual speeds and distances for this interesting braking
scheme?

I said .6-.7g. Plug it in for any speed you want.

Curiously,

Really?

With suspicion,

Robert

On 29 Jun 2005 20:31:06 -0700, wrote:

carl fogeled:

Dear Robert,

Wouldn't stopping the rear wheel and throwing the bike
sideways involve an instant rear wheel slide?

To put it mildly. The rear end is coming around in this
kind of stop. It is angled in and scraped sideways across
the surface, not a garden variety slide. Streets are not
smooth, they are made of rocks, glued together. In
these situations there is generally enough friction
that the danger is more from high side than not stopping
soon enough. This is bad for tires and wheels and
rear triangles.

And isn't the sliding coefficient of friction of rubber
tires on pavement considerably inferior to their rolling
coefficient?

I dont think there is a pair of legs out there that
could stop a fixed gear in that range of gforce without
the kind of jackknife/powerslide maneuver I described.
Perhaps I'm wrong but I don't think normal human
muscles are up to that. I would be amazed to see it.


Any actual speeds and distances for this interesting braking
scheme?

I said .6-.7g. Plug it in for any speed you want.

Curiously,

Really?

With suspicion,

Robert

Dear Robert,

Where does the extra friction come from?

That is, how does sliding sideways help traction versus
sliding in a straight line? If the contact patch is larger,
then the pressure is less, isn't it?

I really am curious--I don't see how it works, so I stand to
to learn something darned interesting.

Just in case I'm missing something (d'oh!), the idea as I
understand it is that a fixed-gear bicycle with no front
brake can be stopped just as quickly on dry pavement as a
bike with a front brake by resisting the pedals and pitching
the bike sideways, causing the rear tire to stop rotating
and skid--right?

Presumably the rider has much of his weight "back" toward
the rear wheel (sort of sideways in terms of general motion,
but closer to the rear wheel than the front, if you see what
I mean).

And presumably his feet are clipped to the pedals, with the
foot near the ground in the high position of the pedal
cycle. Or does he unclip in time to plant the trailing foot
on the pavement?

What kind of speed would be usual on pavement for this sort
of maneuver?

Curiously,

Carl Fogel

fogeled:

Dear Robert,

Where does the extra friction come from?

That is, how does sliding sideways help traction versus
sliding in a straight line? If the contact patch is larger,
then the pressure is less, isn't it?

Wow that's a completely useless way to think about
this, but while we're on the subject, why would the
contact patch be larger?

Let me answer your question about the extra friction
with a question: how well would a boat get through
the water if you took the propeller off the back and
stuck it on the side?

You are thinking of the mythical completely featureless
smooth surface and therefore only of the two dimensional
contact patch. But, relative to the scale of the
tire it's like a little mountain range down there on the
surface. Imagine your sliding rear tire, when it is
sliding forward in the normal position, as a boat skimming
across a rough and intractable sea. The shape of the
bottom of the boat allows it to slide right over the chop.
Turn that boat sideways, and all bets are off, it wants
to capsize or at least stop.

I really am curious--I don't see how it works, so I stand to
to learn something darned interesting.

Just in case I'm missing something (d'oh!), the idea as I
understand it is that a fixed-gear bicycle with no front
brake can be stopped just as quickly on dry pavement as a
bike with a front brake

Not in my opinion. It is my contention that some
riders can stop their track bikes in about .6-.7g,
but that not all road bike riders can stop their bikes
that quickly. OTOH, I believe hand-braked bikes can
be stopped faster than .8g by some.

Presumably the rider has much of his weight "back" toward
the rear wheel (sort of sideways in terms of general motion,
but closer to the rear wheel than the front, if you see what
I mean).

And presumably his feet are clipped to the pedals, with the
foot near the ground in the high position of the pedal
cycle. Or does he unclip in time to plant the trailing foot
on the pavement?

Depending on the severity of the stop the foot may
come out in automatic preparation for
meeting pavement. I have seen a guy do a stop like
this, end up turned completely opposite direction, and
ride out of it without ever putting a foot down.


What kind of speed would be usual on pavement for this sort
of maneuver?

Let's go with 20 mph!

R

wrote:
It is my contention that some
riders can stop their track bikes in about .6-.7g,
but that not all road bike riders can stop their bikes
that quickly. OTOH, I believe hand-braked bikes can
be stopped faster than .8g by some.

Where do you get these numbers?

--
Dave
dvt at psu dot edu

wrote:

I'll gladly give you a little on that. Certainly there are times that
it serves humanity, or business, to get "papers" to a destination
quickly.

I'm not going to sit here and pretend messengers
provide some lofty service for the good of the world.
The world would probably be better off if most of that
stuff never got delivered at all. Attorneys and para-
legals, primarily, have grown to rely on messengers
to pull their balls out of the fire on a daily basis.
They know they have that safety net and thus tend to
use it, putting everything off until the very last
minute. Messengers are essentially Procrastination
Facilitators.

But the point is that highly visible 'scofflaw'
behavior of messengers is driven by market forces
that are larger than the messengers themselves.
It's not like a bunch of messengers got together in
some dude's basment and cooked up a scheme to
say FU to the world by running red lights.

But there's a problem if you're riding a slower bike and
running reds as a matter of course to make up the difference.

That would be a problem. It's not like that though.

All messengers run lights, no matter what kind of bike
they're on. Again, it's the running of the lights that
provides the speed of delivery, and differences in bikes
or in rider strength have very small meaning in the
grand scheme.



I'm retired (no cubicle). But there you go again, trying to pin me with
that "inferior" button.

Sorry about the cubicle crack. Uncalled for.

Actually, I was talking about the no-brakes guys, who seem to commonly
regard the "messengers" as demi-gods who are above the laws of man and
physics. You can talk about your own attitude; that doesn't whitewash
what others do. The fixed/no brakes thing is an ethos; there is a
scofflaw subculture which includes messengers, for all your
protestations about compulsory speed on which, remember, I yielded to
you, to an extent.

I think it's entirely possible that your problem is
not really with messengers but with this whole new
school trendy thing out there with the coffee shop
people and students and critical massers etc who now
choose fixed gears. Most of the track bike riders you
see are going to fall into that crowd. They may try to
look like messengers, they may even wish they were
messengers, but they are not, I repeat they are not actual
bike messengers. Most of them do seem like pretty
nice folks though, I have to say, thoughtful people
relatively, who are willing to at least dabble in a
car-free lifestyle. To these people, bikes are cool
and riding bikes is cool, and that's...cool.

Whatever, I'll take your word for it on the ethos
thing. I'm old and out of the loop. Strangely, most of
my messenger friends are also old and out of the loop.

Dang, it's Wednesday, last real ride I had was Friday's 71.xx miler.
Broken cars/computer, kids at home, crazy work sched. Time for b-fast
out with the other half, then maybe repeat one of a couple of last
week's 40-50 miles with a Triangle (Austin training loop, some nice
little hills) after on the 50/15 fixer (one powerful, well-adjusted
front brake, road fork in track frame).

That's a HUGE massive gear for riding in traffic.
No wonder you can't stop! I ride a 48x16 (3-to-1)
when I ride the fixed gear and that
is about as big a gear as a normal sized individual
like myself can ride without brakes, I would have
a much easier time with a smaller gear. I guess you
know what you're doing.

R