Re: Slime, any good?

PBridge130 said:

Among many things, [email hidden] states:

Quoted message said:

Quoted message said:

Meditate, as you put it, on rotating mass some more. It does
make a difference in acceleration, but not in steady speed.

Quoted message said:

Carl, you apparently have a lot more invested in this than I do. I have
confidence in my own conclusions, and in "my kind of experience", and I
certainly don't ask you or anyone else to ride my wheels.

However, since you're working so hard at proving that you're right, let me
point out a little problem in your logic. How many rides are "steady speed"?
Is there any need to say any more?

Quoted message said:

Quoted message said:

And the difference in acceleration is so small that lighter
wheels usually work out on to less than a bike length in a
professional sprint.

Oh, so there is a difference? I wonder how said difference might affect, say,
75 miles of roller coaster hills? Mightn't one experience speeds that are not
exactly steady on such a ride, and on many rides?

The speed will not be steady on such a ride, but the effect of a little
extra weight in the tire will still be just as small. Consider that you
add a bit of energy into getting the wheel turning each time you
accelerate, but then you get that energy back as you start to slow down
and the flywheel effect of the heavier wheel helps to keep your speed
up. The only rotational energy that's lost is if you have to apply the
brakes to deliberately slow down and the bit of energy you first put in
to get the wheels up to speed. So for rolling hills where no brakes are
applied the overall effect is negligible.

However, there could certainly be an effect on how the bike feels in
response to your pedal and steering inputs. The extra rotational
inertia could make it feel a bit less responsive even if no
significant extra energy is needed and the greater gyroscopic
stability of the front wheel could reduce the steering responsiveness.

But if Slime slows you down significantly I'd guess the cause to be
related to increased rolling resistance rather than from rotational
weight. Consider the part of the tire at the contact patch with the
ground. The tire and tube at that point are deformed and some energy is
lost to heat as the materials aren't perfectly compliant (that's why we
use rather thin tubes, flexible tire sidewalls, and little or no tread).
Adding a viscous liquid means that a bit more energy is lost in changing
the shape of that material in the contact patch area and therefore
increases the rolling resistance. Note that this will be the case even
if the Slime stays in place within the tube rather than flowing to
the bottom.

On 13 Dec 2004 05:56:19 GMT, [email hidden] (PBridge130)

Quoted message said:

Among many things, [email hidden] states:

Quoted message said:

Meditate, as you put it, on rotating mass some more. It does
make a difference in acceleration, but not in steady speed.

Carl, you apparently have a lot more invested in this than I do. I have
confidence in my own conclusions, and in "my kind of experience", and I
certainly don't ask you or anyone else to ride my wheels.

However, since you're working so hard at proving that you're right, let me
point out a little problem in your logic. How many rides are "steady speed"?
Is there any need to say any more?

Quoted message said:

And the difference in acceleration is so small that lighter
wheels usually work out on to less than a bike length in a
professional sprint.

Oh, so there is a difference? I wonder how said difference might affect, say,
75 miles of roller coaster hills? Mightn't one experience speeds that are not
exactly steady on such a ride, and on many rides?

I'm done. See Mark Twain's quote on statistics for any further debate.

Dear PB,

Think about "blind testing."

Now think about a claim that someone else's lively bike felt
dead, that slime tubes had been installed, that the tubes
were replaced in hopes of fixing things--and the expectation
was fulfilled, even only 5 ounces have been added to a total
weight of over 2,500 ounces.

It's not dishonesty or lying or myth and lore--but it does
look like the kind of thing that physics and blind testing
suggest is a common psychological misperception.

A fairly common comment on rec.bicycles.tech is that almost
any change intended to improve the bike will work at first.
But far fewer changes improve things for more than a week or
two--the new toy effect wears off.

The acceleration on a bicycle is typically absurdly slow and
a fairly steady speed is usually achieved when wind drag,
grade, and the rider's normal effort match. Do a little
checking of your idea and let us know how well you can tell
the difference just riding between normal and slime tubes.

Hope to see you in a new thread--I spent an hour having fun
timing the same wheel's deceleration with a normal and then
a slime tube.

Carl Fogel

Quoted message said:

Think about "blind testing."

Now think about a claim that someone else's lively bike felt
dead, that slime tubes had been installed,

By "feeling dead", I understood the original poster to mean steering,
not speed.

In my experience, adding a few ounces at the rim of the front wheel
makes many lively bikes feel more dead. Just like installing your race
day lightweight wheels makes the bike feel less stable. By feel I mean
steering response, handling.

PBridge130 said:

Among many things, [email hidden] states:

Quoted message said:

Meditate, as you put it, on rotating mass some more. It does
make a difference in acceleration, but not in steady speed.

However, since you're working so hard at proving that you're right, let me
point out a little problem in your logic. How many rides are "steady speed"?

The point is not about some hypothetical completely steady speed ride, but
that on any ride much of your power output is going to maintain your
speed, and that activity is not affected at all by extra weight.

Quoted message said:

Oh, so there is a difference? I wonder how said difference might affect, say,
75 miles of roller coaster hills?

A particularly poor example, since on a hilly ride most acceleration is
done by gravity, not by the rider's muscles.

Quoted message said:

I'm done. See Mark Twain's quote on statistics for any further debate.

Unfortunately Twain had little to say about ignorance of basic mechanics.
--
David Damerell <[email hidden]> flcl?

Peter said:

But if Slime slows you down significantly I'd guess the cause to be
related to increased rolling resistance rather than from rotational
weight.

I'm sure this is the correct answer.
--
David Damerell <[email hidden]> flcl?

dianne_1234 said:

Quoted message said:

Think about "blind testing."

Now think about a claim that someone else's lively bike felt
dead, that slime tubes had been installed,

By "feeling dead", I understood the original poster to mean steering,
not speed.

In my experience, adding a few ounces at the rim of the front wheel
makes many lively bikes feel more dead. Just like installing your race
day lightweight wheels makes the bike feel less stable. By feel I mean
steering response, handling.

Dear Dianne,

I can see your interpretation about the original comment as
possibly meaning handling.

But the original poster went on to talk about "rotating
mass" and "8 or 9 thousand vertical feet" and the "rider's
times" without mentioning steering or vibration.

So I think that he's talking about acceleration and speed
being noticeably impaired by eight ounces or less of Slime
in two tires.

Whether he meant speed or handling, I still wonder how much
difference is due to physical change and how much is due to
the natural human expectation of an effect--and I wonder the
same about the common claims that race wheels make a huge
difference.

When we know that we're switching to the really light,
fragile, expensive stuff, we can't help expecting to notice
how light, fragile, and different it feels--even when some
wicked psychologist secretly reinstalls the original heavy,
sturdy, cheap stuff.

The effect has little (if anything) to do with intelligence
or experience or character or honesty. The annals of science
and medicine are littered with long-forgotten wonders that
fooled extremely sharp people, but which failed to survive
double-blind testing.

This morning, several people at a client's front desk
thanked me for coming in over the weekend. They assured me
that their computers were running much better and faster
because of my wonderful work.

I had to explain that I hadn't touched their computers. I
worked on some unrelated computers in the back room and an
ultrasound machine's printer.

Most motorcycle mechanics have similar stories about racers
getting excited over the difference that the new engine or
suspension parts made--the ones that weren't yet installed.

The Slime tubes lend themselves nicely to blind testing. If
you're curious, arrange for a friend to swap (or not swap)
some Slime and some regular tubes in and out of your bike
over a week or two (taping the valve stems to conceal the
difference) and see if you notice the extra ounces.

It would be interesting to find out if an experienced and
skillful rider really can tell the difference. Obviously,
adding even a slight weight should make a bike slightly
slower and should have a slight effect on handling. The
question is how small a difference can someone actually
detect blindly.

Carl Fogel