Wheel (not tire) sizing

ihccab said:

Is there an advantage of one size wheel over another?

Yes and no.

Quoted message said:

For a road bike
there are two size wheels I'm aware of, 650mm and 700mm.

You are really talking *rim* sizes, not wheel sizes.

There's much mroe than that. 650 A B etc 700C, B etc.

In the US we really have 28", 27", 700C, tubular 28" (700c diameter),
26" balloon tire (MTB) 26 x 1-3/8 (three speed), a different Schwinn
26" size, and there are more I haven't thought of.

It is easier to be sure by looking at the actual rim size that a given
tire is supposed to go on:
28" = 635
27" = 630
700C = 622

Quoted message said:

Is one size
used for us short folks, and a larger size for tall?

Yes, and no. There are bikes built for women that use 26" or even 24"
wheels, either both front and rear or front only. Anyone over 5'-2"
really doesn't qualify for this.

Quoted message said:

Does it take more
work, watts, to spin a larger wheel if the gear set is equal?

Well, you can use your H.S. physics to ponder this.

Quoted message said:

Is there
any relationship between wheel size and crank length?

Not directly in terms of compatibility. But the frame needs to be
designed to accept wheels and cranks.

Quoted message said:

I'll stop now. Thanks.

You are welcome.

Go to Sheldon Brown's website for the whole complete unabridged
discussion of rim sizes, tire sizes etc.

ihccab said:

Is there an advantage of one size wheel over another? For a road bike
there are two size wheels I'm aware of, 650mm and 700mm. Is one size
used for us short folks, and a larger size for tall? Does it take more
work, watts, to spin a larger wheel if the gear set is equal? Is there
any relationship between wheel size and crank length?

They both contribute to overall "gain" in the gearing-- bigger wheels
and shorter cranks both mean higher gearing if all other variables are
equal.

But that doesn't matter, because whatever size wheels, the bike should
have the right number of teeth on the gears to give you a useful range.
If you had very small wheels, you could just use a bigger chainring and
it would all work out.

This is why the Penny Farthing has a huge front wheel-- to give you a
reasonably high gear in the absence of any other gearing.

I have heard it claimed that bikes with small wheels are harder to
balance, but I can't think of any reason why (I'm not of the belief that
gyroscopic effects have anything to do with the stability of a bike).

ihccab said:

Is there an advantage of one size wheel over another? For a road bike
there are two size wheels I'm aware of, 650mm and 700mm. Is one size
used for us short folks, and a larger size for tall? Does it take more
work, watts, to spin a larger wheel if the gear set is equal? Is there
any relationship between wheel size and crank length?

I'll stop now. Thanks.

Dear I.,

A smaller wheel will spin up faster because it has less mass in a
smaller circle, an advantage often mentioned by Moulton enthusiasts,
who dream of wild acceleration.

They forget that the wheels amount to less than 5% of the entire mass
that is being accelerated, that the less than 5% doesn't vanish, and
that the reduced rotating mass means that they won't coast quite as
far up the other side of the gully before having to pedal.

The smaller wheel can improve wind drag.

On the other hand, it's going to wear the same tread thickness out
faster.

The small-wheel Moulton also boasts suspension, which Jobst has
pointed out is more a necessity than a luxury. The smaller the wheel,
the rougher the ride over the same surface.

As for gearing, if the crank and sprockets are the same, the smaller
wheel lowers gearing. This is why you'll find chain rings over 53
teeth on truly small wheels and special rear cogs as small as 9 teeth.

For a 650cx1" versus a 700x25, Cateye suggests calibrating the tires
at 1952 and 2105 mm. At 25 mph, that works out to about 79 versus 73
rpm for a 52x12. The smaller wheel would drop to about 72 rpm with a
52x11.

The lower 650c is favored by shorter riders (women's bikes are more
likely to use 650c tires) and by riders who hope that the lower front
wheel will let them tuck down even farther to reduce wind drag.

Cheers,

Carl Fogel

ihccab said:

Is there an advantage of one size wheel over another?

In many cases, the principal advantage is in the range of selections
available for a popular size vs some other size.

Quoted message said:

For a road bike
there are two size wheels I'm aware of, 650mm and 700mm.

Although your designations are imprecise, the actual assertion is
true, with 700c taking most of the field.

Quoted message said:

Is one size
used for us short folks, and a larger size for tall?

Some builders take that approach, while others think 650c is suitable
for any size of rider, but more use 700c for all.

Quoted message said:

Does it take more
work, watts, to spin a larger wheel if the gear set is equal?

Moment of rotation goes up with mass and diameter; a very light but
large wheel may have a smaller acceleration energy requirement than a
heavier but smaller one. Once accelerated, the only relevant factors
are aerodynamic drag and rolling resistance, which must be evaluated
on a case-by-case basis since most bike racing wheels are very light
and most bike racing tires have low rolling resistance already.

Quoted message said:

Is there
any relationship between wheel size and crank length?

No, and one should not be made. If anything is used as a determinant
of crank length, it should be the rider's leg length and riding style.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Quoted message said:

A smaller wheel will spin up faster because it has less mass in a
smaller circle, an advantage often mentioned by Moulton enthusiasts,
who dream of wild acceleration.

Not only Moultonites, else why boutique wheels?

Quoted message said:

The small-wheel Moulton also boasts suspension, which Jobst has
pointed out is more a necessity than a luxury. The smaller the wheel,
the rougher the ride over the same surface.

As for gearing, if the crank and sprockets are the same, the smaller
wheel lowers gearing. This is why you'll find chain rings over 53
teeth on truly small wheels and special rear cogs as small as 9 teeth.

64x13 on Nexus-7, 16x1.75 tyres (305mm bead seat).

ihccab said:

Is there an advantage of one size wheel over another? For a road bike
there are two size wheels I'm aware of, 650mm and 700mm. Is one size
used for us short folks, and a larger size for tall? Does it take more
work, watts, to spin a larger wheel if the gear set is equal? Is there
any relationship between wheel size and crank length?

650c and 700c (not millimeters) are the most popular road wheel sizes,
although there are many other sizes as well.

Small frames are often designed to use 650c wheels to get a more
conventional frame geometry and better fit. While slight performance
differences can be claimed, the effect is small. For medium to large
road frames, 700c wheels make the most sense, and give a greater choice
of rims and tires.

For more info see:
http://sheldonbrown.com/tire-sizing.html#french

and

http://sheldonbrown.com/650b.html

Art Harris

"Werehatrack" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

ihccab said:

Is there an advantage of one size wheel over another?

In many cases, the principal advantage is in the range of selections
available for a popular size vs some other size.

Quoted message said:

For a road bike
there are two size wheels I'm aware of, 650mm and 700mm.

Although your designations are imprecise, the actual assertion is
true, with 700c taking most of the field.

Quoted message said:

Is one size
used for us short folks, and a larger size for tall?

Some builders take that approach, while others think 650c is suitable
for any size of rider, but more use 700c for all.

Quoted message said:

Does it take more
work, watts, to spin a larger wheel if the gear set is equal?

Moment of rotation goes up with mass and diameter; a very light but
large wheel may have a smaller acceleration energy requirement than a
heavier but smaller one. Once accelerated, the only relevant factors
are aerodynamic drag and rolling resistance, which must be evaluated
on a case-by-case basis since most bike racing wheels are very light
and most bike racing tires have low rolling resistance already.

Quoted message said:

Is there
any relationship between wheel size and crank length?

No, and one should not be made. If anything is used as a determinant
of crank length, it should be the rider's leg length and riding style.

Before the late 1970's, 700c tires and rims were very scarce in the US.
Most of those that were available were intended to replace 700c sewups
so they had a fairly small cross section.

The US standard for most 10 speed bikes was 27 x 1 1/4". A few 27 x 1
1/8' "high performance" tires were available

650c was a later development for smaller riders and triathlon bikes.

Today, there is a far wider selection of tires and rims available for
700c than any of the smaller sizes (or 27"😉.

Chas.

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?

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.

Jeff

"JeffWills" <[email hidden]> wrote in
news:[email hidden]:

Quoted message 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.

Jeff

First, I notice that the ice bike has a rear wheel and quite a large
gear. I assume that this wheel does turn when riding?

Second, I don't claim that you can't stay upright without the wheels
spinning. Certanly many riders can balance while stopped at a traffic
light (or on a track bike). But there's no doubt that it's harder than if
the wheels are spinning. Again, as I pointed out - it's easy to stay
upright while on rollers while the bike is not moving forward, but it's
much harder to do so while stopped without the wheels turning.

Finally, as I asked in my first post: if you don't think gyroscopic
forces are involved in stability, I'd like to know what you think *IS*
involved? Please be sure to factor in what you think is keeping a rider
upright on rollers.

Cheers!
David

On 17 Oct 2006 22:19:00 -0700, "JeffWills" <[email hidden]>
wrote:

[snip]

Dear Jeff,

http://mnhpva.org/ice/2004/pages/RayBio2.htm

I suppose that the intended icy surface is supposed to be an excuse,
but is that another dangerous no-front-brake fixie?

Is it even a fixie? Or is it a freewheel with no braking at all?

For shame!

Cheers,

Carl Fogel

[email hidden] wrote in news:41ebj2dqol5fbsan5s90v4fc5ogm1h4221@
4ax.com:

Quoted message said:

So how do we balance on bicycles?

Mostly by constantly steering the contact patch back and forth under
the center of gravity, which turns out to be easier with a long pole.

Thanks for the reasonable explaination Carl.

However, this still doesn't explain why it's easier to balance on rollers
than while stopped at a traffic light. Certainly gyroscopic action must be
a part of the equation, although not the only part.

Solvang Cyclist said:

"JeffWills" <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

Solvang Cyclist said:

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

> (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.

Jeff

First, I notice that the ice bike has a rear wheel and quite a large
gear. I assume that this wheel does turn when riding?

Second, I don't claim that you can't stay upright without the wheels
spinning. Certanly many riders can balance while stopped at a traffic
light (or on a track bike). But there's no doubt that it's harder than if
the wheels are spinning. Again, as I pointed out - it's easy to stay
upright while on rollers while the bike is not moving forward, but it's
much harder to do so while stopped without the wheels turning.

Finally, as I asked in my first post: if you don't think gyroscopic
forces are involved in stability, I'd like to know what you think *IS*
involved? Please be sure to factor in what you think is keeping a rider
upright on rollers.

Cheers!
David

Dear David,

The gyro effect helps, but what really allows balancing on rollers is
the freedom of the wheels to move from side to side almost as smoothly
as they do when rolling normally.

Again, it's the ability to keep moving the contact patch back and
forth under your center of gravity that allows you to balance easily
on a bicycle.

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.

Cheers,

Carl Fogel

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. 😉
--

[email hidden] wrote in news:ncgbj2tviql7164mq4cpk3v3tk4upkb56k@
4ax.com:

Quoted message said:

The gyro effect helps, but what really allows balancing on rollers is
the freedom of the wheels to move from side to side almost as smoothly
as they do when rolling normally.

So you are saying that it's as easy to balance on rollers while not
peddling as when the rear wheel is turning?

It's easy to see that a very slow rotation of a bike wheel in your hands
will give a strong force of angular momentum.

I don't discount the role of balance and center of gravity. But
gyroscopic forces are a huge factor.

Quoted message said:

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.

Note also that when a rider a diamond-frame is moving at higher speeds,
they are able to lower their center of gravity and remain upright. If
anything, this would show that both actions are at play and their
significance in balance appear to be inversely related to speed.

Balancing the higher center of gravity could be the overwhelming factor
at low speeds, while gyroscopic effects are significant at higher speeds.
However, I have no idea where the cross over points would be.

And regardless of years of riding with toeclips and tight straps, I'm not
one that ever mastered the stop light balancing act (thank god for
clipless pedals). So I'm sure I'm more dependant on gyroscopic action
than some other riders. <grin>

Cheers,
David

Solvang Cyclist said:

[email hidden] wrote in news:41ebj2dqol5fbsan5s90v4fc5ogm1h4221@
4ax.com:

Quoted message said:

So how do we balance on bicycles?

Mostly by constantly steering the contact patch back and forth under
the center of gravity, which turns out to be easier with a long pole.

Thanks for the reasonable explaination Carl.

However, this still doesn't explain why it's easier to balance on rollers
than while stopped at a traffic light. Certainly gyroscopic action must be
a part of the equation, although not the only part.

Because you can easily move the bike under you on rollers but not at a
standstill.

Friday

Solvang Cyclist said:

[email hidden] wrote in news:41ebj2dqol5fbsan5s90v4fc5ogm1h4221@
4ax.com:

Quoted message said:

So how do we balance on bicycles?

Mostly by constantly steering the contact patch back and forth under
the center of gravity, which turns out to be easier with a long pole.

Thanks for the reasonable explaination Carl.

However, this still doesn't explain why it's easier to balance on rollers
than while stopped at a traffic light. Certainly gyroscopic action must be
a part of the equation, although not the only part.

Dear Dave,

Actually, it does explain why rollers are easier than trackstands. The
secret is that the tires are free to move sideways on the rollers.

Stopped at a traffic light, you can't steer the contact patch from
side to side under the center of gravity. The tires are stuck against
the pavement by the tremendous friction of your weight pressing the
rubber against the motionless pavement.

On the rollers, there's plenty of friction, but the rolling action
unsticks the tire. You don't skid from side to side any more on
rollers than you do when rolling on pavement, but you can easily move
the tire sideways in both cases, something that you can't do while
stopped at the traffic light.

Ordinary riders perform trackstands by cheating slightly. We usually
[censored] the front wheel to one side. This helps in two ways.

First, the long contact patch on the front is placed at an angle to
the long contact patch at the rear to make a much better tripod:

-- / is much easier to balance than -- --

There are people who can balance no-hands just sitting on the seat
with the wheels straight, but we can safely ignore those miserable
sons-of--

Never mind. I get worked up about evil Chinese acrobats, who can do
handstands on bicycles standing motionless on just the rear wheel.

Second, with the front wheel cocked to one side, you can roll back and
forth ever so slightly over the front contact patch, rocking the
contact patch from side to side. Here's an exaggerated diagram:
/
-- / is really wavering from -- to --
/
It's even easier if the bike is heading slightly uphill, so that you
can rock even further back and forth. (Lower tire pressure is another
trick--it broadens the contact patches.)

Take away that little sneaky sideways movement of the front tire in a
trackstand, and most of us topple over.

Cheers,

Carl Fogel

Quoted message said:

Solvang Cyclist said:

[email hidden] wrote in news:41ebj2dqol5fbsan5s90v4fc5ogm1h4221@
4ax.com:

Quoted message said:

So how do we balance on bicycles?

Mostly by constantly steering the contact patch back and forth under
the center of gravity, which turns out to be easier with a long pole.

Thanks for the reasonable explaination Carl.

However, this still doesn't explain why it's easier to balance on rollers
than while stopped at a traffic light. Certainly gyroscopic action must be
a part of the equation, although not the only part.

Dear Dave,

Actually, it does explain why rollers are easier than trackstands. The
secret is that the tires are free to move sideways on the rollers.

Stopped at a traffic light, you can't steer the contact patch from
side to side under the center of gravity. The tires are stuck against
the pavement by the tremendous friction of your weight pressing the
rubber against the motionless pavement.

On the rollers, there's plenty of friction, but the rolling action
unsticks the tire. You don't skid from side to side any more on
rollers than you do when rolling on pavement, but you can easily move
the tire sideways in both cases, something that you can't do while
stopped at the traffic light.

Ordinary riders perform trackstands by cheating slightly. We usually
[censored] the front wheel to one side. This helps in two ways.

First, the long contact patch on the front is placed at an angle to
the long contact patch at the rear to make a much better tripod:

-- / is much easier to balance than -- --

There are people who can balance no-hands just sitting on the seat
with the wheels straight, but we can safely ignore those miserable
sons-of--

Never mind. I get worked up about evil Chinese acrobats, who can do
handstands on bicycles standing motionless on just the rear wheel.

Second, with the front wheel cocked to one side, you can roll back and
forth ever so slightly over the front contact patch, rocking the
contact patch from side to side. Here's an exaggerated diagram:
/
-- / is really wavering from -- to --
/
It's even easier if the bike is heading slightly uphill, so that you
can rock even further back and forth. (Lower tire pressure is another
trick--it broadens the contact patches.)

Take away that little sneaky sideways movement of the front tire in a
trackstand, and most of us topple over.

Cheers,

Carl Fogel

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

Solvang Cyclist said:

[email hidden] wrote in news:ncgbj2tviql7164mq4cpk3v3tk4upkb56k@
4ax.com:

Quoted message said:

The gyro effect helps, but what really allows balancing on rollers is
the freedom of the wheels to move from side to side almost as smoothly
as they do when rolling normally.

So you are saying that it's as easy to balance on rollers while not
peddling as when the rear wheel is turning?

It's easy to see that a very slow rotation of a bike wheel in your hands
will give a strong force of angular momentum.

I don't discount the role of balance and center of gravity. But
gyroscopic forces are a huge factor.

Haha. You can discount anything you want. That doesn't make you
correct.

Quoted message said:

Quoted message said:

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.

Note also that when a rider a diamond-frame is moving at higher speeds,
they are able to lower their center of gravity and remain upright. If
anything, this would show that both actions are at play and their
significance in balance appear to be inversely related to speed.

Balancing the higher center of gravity could be the overwhelming factor
at low speeds, while gyroscopic effects are significant at higher speeds.
However, I have no idea where the cross over points would be.

And regardless of years of riding with toeclips and tight straps, I'm not
one that ever mastered the stop light balancing act (thank god for
clipless pedals). So I'm sure I'm more dependant on gyroscopic action
than some other riders. <grin>

Get to work on it!:-)

Seriously though. Here is food for thought. When was the last time you
taught a child to ride a bike? I've taught 4 of them in the past few
years. There is no gyroscopic action to speak of. You've got tiny
little 12" wheels made of aluminum that are barely rolling. The child
has to learn how to ride from a stop. OK the first few tries you give
them a push. But I've put a lot of effort into teaching people to
ride--I also taught 4 other kids 8 years ago, and some high school
girls when I was in HS, how to ride.

Do you know what gets them success? It isn't the gyroscope. It is
learning to steer the wheels under the center of gravity. "If you feel
yourself falling to the left, then turn left". The reason it is more
difficult to balance at 4 inches per second than at 4 feet per second
is a function of the acceleration of gravity relative to the angular
acceleration you can generate through turning. You could ride slower on
the moon.