Wheel (not tire) sizing

JeffWills said:

Solvang Cyclist said:

Ben C <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

(I'm not of the belief that
gyroscopic effects have anything to do with the stability of a bike).

You are joking, right?

Think about it for a moment: You can remain upright if you are on rollers,
so forward momentum is obviously not a factor. Also, if you hold a wheel in
your hands and spin it, then try to change the plane it's spinning in, you
will find it difficult, yet it's not hard to do if the wheel is not
spinning. These facts would seem to point to the angular momentum of the
wheels being a huge factor in bicycle stability.

If you don't think that gyroscopic forces are involved in stability, I'm
curious to know what you believe does keep the bike upright when riding?

If gyroscopic forces are involved in stability, explain how this:
http://mnhpva.org/ice/2004/pages/RayBio2.htm
is rideable.

Poorly.

Ron

Artoi said:

In article <[email hidden]>,

JeffWills said:

If gyroscopic forces are involved in stability, explain how this:
http://mnhpva.org/ice/2004/pages/RayBio2.htm
is rideable.

On the face of it, the guy is standing and holding a ski bike. Nothing
to say it is rideable, until we see additional evidence. 😉

Perhaps the following photographs were submitted to Darwin Awards / Jackass /
litigation against the manufacturer?

Ron

In article <[email hidden]>,

Solvang Cyclist said:

Ben C <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

(I'm not of the belief that gyroscopic effects have anything to do
with the stability of a bike).

You are joking, right?

Think about it for a moment: You can remain upright if you are on
rollers, so forward momentum is obviously not a factor. Also, if you
hold a wheel in your hands and spin it, then try to change the plane
it's spinning in, you will find it difficult, yet it's not hard to do
if the wheel is not spinning. These facts would seem to point to the
angular momentum of the wheels being a huge factor in bicycle
stability.

As you will find out in this thread, this has been researched quite
thoroughly. Gyroscopic forces in bicycles are relatively weak and are
only a minor contributor to keeping a bike upright, as Jones showed by
canceling the front wheel's gyroscopic force. He reported that the bike
felt a little odd but was quite rideable.

The gyroscopic force you feel when holding a spinning wheel in your
hands is misleading, because when you ride a bike there is a long lever.
Spin that wheel in the fork with the front wheel in the air, and then
turn it using the handlebars- it takes trivial effort.

Quoted message said:

If you don't think that gyroscopic forces are involved in stability,
I'm curious to know what you believe does keep the bike upright when
riding?

Constant correction keeping the wheels centered beneath the bike's
center of gravity. When we first learn to ride, those corrections are
large and we ride- as H.G. Wells put it- opulently. As we get more
skilled, we learn to anticipate and to make smaller corrections,
eventually riding in pretty straight line. With most cyclists, if you
have them ride over unmarked dirt and then examine the tracks, you will
find that the front wheel crosses back and forth over the path of the
rear wheel. The better skilled the cyclist, the smaller those
deviations are. That's what keeps a bicycle upright, even on rollers.

What keeps a bicycle upright during a trackstand are adjustments both of
the bicycle under the rider- rocking back and forth slightly with the
front wheel cocked to one side- and also the rider shifting his or her
weight over the bicycle. No gyroscopic forces are needed. Good
trackstanders can go on for a long time, and really good ones can
trackstand no handed and with one foot off the pedals.

In article <[email hidden]>,

bill said:

In fact gyroscopic action [censored] steering. The only time I have
noticed this is when travelling in excess of 50 MPH. The handling
gets rather heavy, though the speed makes quick handling uneccessary
for balance, as it is easy to generate angular acceleration with the
slightest steering angle displacement, when travelling that fast.

I'm not sure that the phenomenon you notice is due to gyroscopic action,
although I am not confident in saying that it is not. What I think is
happening is that you are riding a racing type road bike which usually
has a fairly large amount of trail- about 60 mm typically. Trail is a
lever arm between the road and the steering axis (I don't remember who
on this newsgroup pointed that out to me; I do remember disbelieving it
at first). High trail bikes are very responsive to steering by leaning
and have a tendency to oversteer, which is why bike racers like them (up
to a point at least). High trail bikes have a tendency to steer in
decreasing radius, a useful trait when racing through a turn in a pack,
as it naturally counteracts the tendency to drift to the outside. (You
can readily demonstrate this tendency for yourself by walking the bike
and steering it from the saddle).

In the situation you describe, what I think is happening is that you are
going fast, leaned over, and there is a lot of force on that lever
(trail) from your weight and the centripetal forces of turning through
the plane of the bicycle. I suspect there tends to be a weight transfer
to the front wheel when turning, as well. So the upshot is that the
front wheel in particular is much more highly loaded than when you are
riding in a straight line with the bike upright. The increased effort
you notice is overcoming those forces coming through the lever of trail
between the contact patch and the steering axis. I'm not sure I
described that very well.

Low trail designs- say 55 mm and all the way down to 35 mm or so- have a
light steering feel and are not very responsive to leaning. This makes
them good for things like carrying large amounts of weight on a front
rack (delivery bikes, loaded tourers, randonneuses, etc.). These bikes
are less responsive when walking them and trying to steer by the saddle
because they do not respond as much to leaning. This is good with 50
pounds of stuff on the front, in the case of a delivery bike, or maybe
10 pounds of stuff in the case of a randonneur with a handlebar bag.
The rider must steer with the bars more and by leaning less. This is a
benefit for randonneurs who are often riding when they are very tired;
the bike is less likely to weave around on the road.

I checked this out for myself with my Ritchey and my Rivendell
All-Rounder. The Ritchey is a wonderfully handling racing bike,
seemingly telepathic in its responsiveness to steering inputs. Of all
the race bikes I ever had, this one was by far the best and is the only
one I have kept now that I don't race. But on very long rides (10-12
hours or more) as I get tired, there is more of a tendency to weave
about on the road- sometimes quite abruptly. My Rivendell, with less
trail and also wider tires, tends to run very straight down the road
even when I am quite tired. It also has 26" wheels of very similar
weight as the Ritchey's wheels, so the gyroscopic factor ought to be
less. Even with a handlebar bag, the Rivendell's steering feel is
lighter than the Ritchey's.

Tandems also tend to have low trail, or should- if they have a large
amount of trail, they are overly sensitive to the movements of the
stoker and are easily steered from the back, which is frustrating and
tiring for the captain. I speak from experience here.

Tim McNamara said:

In article <[email hidden]>,

bill said:

In fact gyroscopic action [censored] steering. The only time I have
noticed this is when travelling in excess of 50 MPH. The handling
gets rather heavy, though the speed makes quick handling uneccessary
for balance, as it is easy to generate angular acceleration with the
slightest steering angle displacement, when travelling that fast.

I'm not sure that the phenomenon you notice is due to gyroscopic action,
although I am not confident in saying that it is not. What I think is
happening is that you are riding a racing type road bike which usually
has a fairly large amount of trail- about 60 mm typically. Trail is a
lever arm between the road and the steering axis (I don't remember who
on this newsgroup pointed that out to me; I do remember disbelieving it
at first). High trail bikes are very responsive to steering by leaning
and have a tendency to oversteer, which is why bike racers like them (up
to a point at least). High trail bikes have a tendency to steer in
decreasing radius, a useful trait when racing through a turn in a pack,
as it naturally counteracts the tendency to drift to the outside. (You
can readily demonstrate this tendency for yourself by walking the bike
and steering it from the saddle).

In the situation you describe, what I think is happening is that you are
going fast, leaned over, and there is a lot of force on that lever
(trail) from your weight and the centripetal forces of turning through
the plane of the bicycle. I suspect there tends to be a weight transfer
to the front wheel when turning, as well. So the upshot is that the
front wheel in particular is much more highly loaded than when you are
riding in a straight line with the bike upright. The increased effort
you notice is overcoming those forces coming through the lever of trail
between the contact patch and the steering axis. I'm not sure I
described that very well.

Low trail designs- say 55 mm and all the way down to 35 mm or so- have a
light steering feel and are not very responsive to leaning. This makes
them good for things like carrying large amounts of weight on a front
rack (delivery bikes, loaded tourers, randonneuses, etc.). These bikes
are less responsive when walking them and trying to steer by the saddle
because they do not respond as much to leaning. This is good with 50
pounds of stuff on the front, in the case of a delivery bike, or maybe
10 pounds of stuff in the case of a randonneur with a handlebar bag.
The rider must steer with the bars more and by leaning less. This is a
benefit for randonneurs who are often riding when they are very tired;
the bike is less likely to weave around on the road.

I checked this out for myself with my Ritchey and my Rivendell
All-Rounder. The Ritchey is a wonderfully handling racing bike,
seemingly telepathic in its responsiveness to steering inputs. Of all
the race bikes I ever had, this one was by far the best and is the only
one I have kept now that I don't race. But on very long rides (10-12
hours or more) as I get tired, there is more of a tendency to weave
about on the road- sometimes quite abruptly. My Rivendell, with less
trail and also wider tires, tends to run very straight down the road
even when I am quite tired. It also has 26" wheels of very similar
weight as the Ritchey's wheels, so the gyroscopic factor ought to be
less. Even with a handlebar bag, the Rivendell's steering feel is
lighter than the Ritchey's.

Tandems also tend to have low trail, or should- if they have a large
amount of trail, they are overly sensitive to the movements of the
stoker and are easily steered from the back, which is frustrating and
tiring for the captain. I speak from experience here.

This is a nice dissertation, but I'm afraid it doesn't address my
poorly delineated post. In terms of heavier steering at speed, I am
not speaking of cornering; rather I am speaking of the feel of the bike
in a straight line at high speed. It just feels heavier than it does at
lower speed. This may be an odd sort of kinesthetic sensation though.
It may be illusory.

Now back to the trail business. Yes, high trail is quicker steering,
for the reasons you point out--the bars "flop" more for a given lean.
My favorite party trick is the bike with reverse trail--in other words
lead. This is easily demonstrated with an old Huffy clunker where you
have purposely bent the forks forward excessively. This arrangement
will steer the wrong way with lean! You have to push the steering when
you lean. It is an odd sensation.

Interestingly, even with the lead instead of trail, it is entirely
ridable: it is just that you have to actively "oversteer" the
handlebars to turn, whereas on a bike with great trail, you have to
actively "understeer" the bars.

My Gios Compact Pro must have more trail than some of my earlier bikes.
I find it difficult to tie a shoelace while I am coasting. Conversely
my brother's vintage Team Raleigh Record is extremly stable and yet
maneuverable too.

Donga said:

[email hidden] wrote:

[snip]

Quoted message said:

I swapped from a heavy-ish front wheel (DT champs, Ambrosio Excellence,
brass nipples) to a lighter one (DT Revs, Velocity AeroHead, alloy
nipples) with the same tires and noticed considerably better handling,
i.e. it was easier to steer. Why would this be? I'm presuming the
momentum of the wheel is reduced and hence the vector can be changed
more readily. In the reverse, the momentum would assist in keeping the
bike upright and moving forwards?

Donga

Dear Donga,

Yes, a different mass will behave differently.

But I suspect that this is not the explanation for any perceived
handling difference in a bicycle's front wheel at normal speeds.

Bicyclists are notorious for noticing that X becomes better or worse
after they replace parts, even when the equipment turns out to have no
connection to whatever felt as if it changed.

The classic case is the tremendous improvement in acceleration and
climbing speed often noticed by riders whose new bicycles are two
pounds lighter. While the reduced mass does indeed mean that they must
speed up and climb a little faster, it's unlikely that they notice the
roughly 1% improvement that actually shows up when their 200 pound
load drops to 198 pounds.

If you work out the weight reduction on the front wheel, I think that
you'll find that the change in mass due to new spokes, nipples, and
rims is trivial, particularly when you remember that you turn at
normal bicycling speeds by leaning the weight of your body to one side
and letting gravity do the work--you can probably make gentle turns
while riding no-hands.

A quick Google shows that Velocity lists their front Aerohead at 760
grams, while the first front Ambrosio Excellence that I found was
listed at 896 grams--with skewer.

Add around 300 grams for a tire and tube, and you have somewhere
around 1,060 verus 1,200 grams.

Consider just how small an angle the front wheel actually moves
through when you turn at normal speeds.

Now remember that at normal speeds, you actually push the wheel the
other way, opposite the turn.

Add the non-rotating mass of the fork and handlebars, which still has
to be turned the opposite way, and--

Well, you get the idea. It's possible that what you felt was more the
pride of those detailed parts replacements and their effect on your
wallet than an actual difference in handling.

You can test things by standing a bike on its rear wheel. Spin the
front tire with your hand and then see how hard it is to tilt the
wheel an inch or so to either side, which is about all that you do at
20 mph. It's very unlikely that you can feel any difference in
resistance due to minor weight changes.

Cheers,

Carl Fogel

In article <[email hidden]>,

Quoted message said:

That's why the tall bikes, twice as high as ordinary bikes, are so
surprisingly easy to ride, even though you'd think at first that
they'd be horribly difficult and dangerous.

I guess you are suggesting the penny farthing here.

Thanks for the explanation. I'll try it when I have the tools together
to convince myself. 🙂
--

In article <[email hidden]>,

bill said:

This is a nice dissertation, but I'm afraid it doesn't address my
poorly delineated post. In terms of heavier steering at speed, I am
not speaking of cornering; rather I am speaking of the feel of the
bike in a straight line at high speed. It just feels heavier than it
does at lower speed. This may be an odd sort of kinesthetic sensation
though. It may be illusory.

Hmm. I've missed the boat again...

Quoted message said:

Now back to the trail business. Yes, high trail is quicker steering,
for the reasons you point out--the bars "flop" more for a given lean.
My favorite party trick is the bike with reverse trail--in other
words lead. This is easily demonstrated with an old Huffy clunker
where you have purposely bent the forks forward excessively. This
arrangement will steer the wrong way with lean! You have to push the
steering when you lean. It is an odd sensation.

Wow, that's really bending the forks a lot.

Quoted message said:

Interestingly, even with the lead instead of trail, it is entirely
ridable: it is just that you have to actively "oversteer" the
handlebars to turn, whereas on a bike with great trail, you have to
actively "understeer" the bars.

I suspect that a lot of steering geometries are fine once you get used
to them.

Quoted message said:

My Gios Compact Pro must have more trail than some of my earlier
bikes. I find it difficult to tie a shoelace while I am coasting.
Conversely my brother's vintage Team Raleigh Record is extremly
stable and yet maneuverable too.

Probably a little less trail and a much longer wheelbase. Possibly
wider tires, too.

Solvang Cyclist said:

Ben C <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

(I'm not of the belief that
gyroscopic effects have anything to do with the stability of a bike).

You are joking, right?

Not at all.

Quoted message said:

Think about it for a moment: You can remain upright if you are on rollers,
so forward momentum is obviously not a factor.

Interesting point. But does it make any difference?-- the relative
movement of bike and "road" is the same.

Quoted message said:

Also, if you hold a wheel in your hands and spin it, then try to
change the plane it's spinning in, you will find it difficult, yet
it's not hard to do if the wheel is not spinning. These facts would
seem to point to the angular momentum of the wheels being a huge
factor in bicycle stability.

If you don't think that gyroscopic forces are involved in stability,
I'm curious to know what you believe does keep the bike upright when
riding?

I think it's because the bike has negative caster, which gives it
directional instability, but keeps it upright.

If you lean a bike to the left while wheeling it slowly along holding
onto the saddle, you will see that the front wheel steers to the left.
This is because the contact patch is in front of the steering pivot
(negative caster). Uncorrected, the bike goes further and further off
course. This is what I mean by "directional instability". Cars have
postive caster (contact patch behind steering pivot) which is why their
steering self-corrects-- you can turn the car, and let go of the
steering wheel, and it winds back to the centre position by itself.

Back to bikes. If a bike is going round a left-hand bend, its centre of
mass is naturally thrown out to the right. This effect is commonly
called "centrifugal force".

So, bike leans to the left, that makes it steer left, which makes it
lean right again, correcting the original left-lean. That's the basis of
the stability.

If you ride a bike through a puddle, and then continue slowly, and then
look at the wet trail made by the tyres, you see a straight footprint
made by the rear tyre, and usually a sort of sinusoidal one crossing
backwards and forwards over it made by the front tyre. These are the
small left-to-right corrections of the steering that are keeping the bike
upright.

I have also heard that bikes have been built with counter-rotating
flywheels attached to the wheels. The flywheels are smaller in diameter
but have the same moment of inertia as the wheels. They should
counteract any gyroscopic effects. The conclusion of the experiment was
that the bikes were no harder to ride than normal.

I do not have a link to this experiment though.

Artoi said:

In article <[email hidden]>,

Quoted message said:

That's why the tall bikes, twice as high as ordinary bikes, are so
surprisingly easy to ride, even though you'd think at first that
they'd be horribly difficult and dangerous.

I guess you are suggesting the penny farthing here.

Thanks for the explanation. I'll try it when I have the tools together
to convince myself. 🙂

Dear Artoi,

No, I'm suggesting tall bikes:

http://home.comcast.net/~carlfogel/download/tallride4.jpg

Chalo Colina, the rider, is about 6'8", so it's even more giraffe-like
than you'd think. Chalo is just cruising gently around his machine
shop, obviously not worried about falling over into his lathes and
drill presses. He's probably moving at about walking speed.

Cheers,

Carl Fogel

Quoted message said:

...
As a sidelight, the small-wheel Moulton bicycles with full-size frames
may look like something a clown would ride in a circus, but no one
ever complains that the reduced gyroscopic effect of their itty-bitty
wheels makes them harder to balance at any speeds.

On the other hand, a low-racer recumbent, with a much lower center of
gravity and much lower polar moment of inertia than a traditional
diamond-frame bike, will wobble and tend to tip over at very low
speeds.

Yes, but you can catch yourself with your hand before you go over. 😉

I find low speed balance easy on my small wheel lowracer [1] down to
about 4 mph/6-7 kph.

[1] <http://www.ihpva.org/incoming/2002/sunset/Sunset001.jpg>.

--
Tom Sherman - Here, not there.

Ben C <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

Quoted message said:

Quoted message said:

(I'm not of the belief that
gyroscopic effects have anything to do with the stability of a bike).

You are joking, right?

Not at all.

Okay, guys, I've never been one to stubbornly hold on to an argument in
the face of reasonable evidence to the contrary.

Let's say I've learned something new and interesting here.

Just don't try to convince me that helmets cause more head injuries than
they prevent. <grin, dodge and RUN!>

Cheers!
David

Quoted message said:

Quoted message said:

My Gios Compact Pro must have more trail than some of my earlier
bikes. I find it difficult to tie a shoelace while I am coasting.
Conversely my brother's vintage Team Raleigh Record is extremly
stable and yet maneuverable too.

Probably a little less trail and a much longer wheelbase. Possibly
wider tires, too.

Wheelbases are a whole inch apart. Raleigh is 39-1/2". Gios 38-1/2",
even though the Raleigh is a smaller frame (22-1/2" vs 59 cm). Tires
are of course the same. They are both racing machines with tubulars.

But the length is all in the chainstays. The Raleigh could take
fenders! and my toeclips hit the front wheel more on the Raleigh than
on the Gios.

Trail is harder to measure and so I don't know what either one is.
Someday I should take the Raleigh in to a framebuilder and have it
copied:-)

In article
<[email hidden]>,

JeffWills said:

Solvang Cyclist said:

Ben C <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

(I'm not of the belief that
gyroscopic effects have anything to do with the stability of a bike).

You are joking, right?

Think about it for a moment: You can remain upright if you are on rollers,
so forward momentum is obviously not a factor. Also, if you hold a wheel in
your hands and spin it, then try to change the plane it's spinning in, you
will find it difficult, yet it's not hard to do if the wheel is not
spinning. These facts would seem to point to the angular momentum of the
wheels being a huge factor in bicycle stability.

If you don't think that gyroscopic forces are involved in stability, I'm
curious to know what you believe does keep the bike upright when riding?

If gyroscopic forces are involved in stability, explain how this:
http://mnhpva.org/ice/2004/pages/RayBio2.htm
is rideable.

Another foolhardy fashion victim riding a fixed gear
without a front brake. When will they learn?

--
Michael Press

In article
<[email hidden]>
,
"Johnny Sunset aka Tom Sherman"

Quoted message said:

Quoted message said:

...
As a sidelight, the small-wheel Moulton bicycles with full-size frames
may look like something a clown would ride in a circus, but no one
ever complains that the reduced gyroscopic effect of their itty-bitty
wheels makes them harder to balance at any speeds.

On the other hand, a low-racer recumbent, with a much lower center of
gravity and much lower polar moment of inertia than a traditional
diamond-frame bike, will wobble and tend to tip over at very low
speeds.

Yes, but you can catch yourself with your hand before you go over. 😉

I find low speed balance easy on my small wheel lowracer [1] down to
about 4 mph/6-7 kph.

And I can ride at 4 kph in a straight line. That's
slower than foot traffic on a city sidewalk.

<630 mm x 28 mm tires, free hub gears>

--
Michael Press

Michael Press said:

In article
<[email hidden]>
,
"Johnny Sunset aka Tom Sherman"

Quoted message said:

Quoted message said:

...
As a sidelight, the small-wheel Moulton bicycles with full-size frames
may look like something a clown would ride in a circus, but no one
ever complains that the reduced gyroscopic effect of their itty-bitty
wheels makes them harder to balance at any speeds.

On the other hand, a low-racer recumbent, with a much lower center of
gravity and much lower polar moment of inertia than a traditional
diamond-frame bike, will wobble and tend to tip over at very low
speeds.

Yes, but you can catch yourself with your hand before you go over. 😉

I find low speed balance easy on my small wheel lowracer [1] down to
about 4 mph/6-7 kph.

And I can ride at 4 kph in a straight line. That's
slower than foot traffic on a city sidewalk.

Why bother to ride if walking is faster? 😉

--
Tom Sherman - Here, not there.

Johnny Sunset aka Tom Sherman said:

Why bother to ride if walking is faster? 😉

Riding a bike (and this thread) is not about speed - is it?? ;-)

Ken, Canada