Dumb Newbie Qs on Gears and Speed

Ok, so the first one is really dumb: does the gear setting affect how
fast you go when you are coasting? My instinct tells me no, since
coasting involves not using the pedals, and I presume the only thing
affecting speed as you coast down a hill is the gravitational
accelleration that Galileo proved. But perhaps the chain setting can
affect how fast the wheels are allowed to turn?

Second one: can a bike with 30 gears actually go faster in top gear than
a bike with only 5 gears? Or is it just a mattter of the 5 speed having
less nuance between slowest and fastest speed? If faster, is it
proportional

Third one: is the coasting speed of a bike without use of brakes its
maximum speed? Say I coast freely down a hill and the online counter
shows me at 29 kmph. That is faster than I can pedal in my highest,
fifth gear (or would want to). But if I were a speed freak on a
different bike, could I "refill" the pedalling by upping the gear to
thirtieth and outrun gravity by pedalling at my normal rpm?

Fourth: I know I'm not allowed to change gear when the bike is not
moving. But can I change gear during a coast, or does it have to be when
I am actually pedalling? Not long ago I tried changing gear while
coasting and there was a problem, the gear did not change well. Since
then I have not tried it again, but I don't know whether I did something
wrong or it was just a common and garden gear malfunction, due to poor
indexing or insufficient greasing.

Thanks for your patience. I only coasted for the first time about 3
weeks ago.

Elisa Roselli
Ile de France

Elisa Francesca Roselli wrote:
Ok, so the first one is really dumb: does the gear setting affect how
fast you go when you are coasting? My instinct tells me no, since
coasting involves not using the pedals, and I presume the only thing
affecting speed as you coast down a hill is the gravitational
accelleration that Galileo proved. But perhaps the chain setting can
affect how fast the wheels are allowed to turn?

No


Second one: can a bike with 30 gears actually go faster in top gear than
a bike with only 5 gears? Or is it just a mattter of the 5 speed having
less nuance between slowest and fastest speed? If faster, is it
proportional

To speak of the number of "speeds" for a bicycle is an error.
The more correct term would be gear "ratios" -- the relation
between the pedalling cadence (RPM) and the rear wheel
revolutions per minute. A ratio of 1:1 would mean that one
revolution of the pedals would produce one revolution of the rear
wheel. That would be a "high" gear used for going fast on level
or downhill roads. A ratio of 3 or 4 pedal revolutions to produce
one wheel revolution would be a "low" gear suitable for uphill
travel.

Speed depends on gear ratio and pedalling speed (RPM), not the
number of ratios available. The "5-speed" usually has greater
gaps between its 5 gear ratios than one with more ratios but not
always. It depends on the manufacturer and the purpose, not the
number.

Third one: is the coasting speed of a bike without use of brakes its
maximum speed? Say I coast freely down a hill and the online counter
shows me at 29 kmph. That is faster than I can pedal in my highest,
fifth gear (or would want to). But if I were a speed freak on a
different bike, could I "refill" the pedalling by upping the gear to
thirtieth and outrun gravity by pedalling at my normal rpm?

You can always make the bike go faster by pedalling faster (if
you are able).

Fourth: I know I'm not allowed to change gear when the bike is not
moving. But can I change gear during a coast, or does it have to be when
I am actually pedalling? Not long ago I tried changing gear while
coasting and there was a problem, the gear did not change well. Since
then I have not tried it again, but I don't know whether I did something
wrong or it was just a common and garden gear malfunction, due to poor
indexing or insufficient greasing.

Changing gears is accomplished by "derailing" the chain from one
ring to another, hence the name of the mechanism "deraileur".
Just as a train could not be derailed when standing still, the
chain cannot be derailed unless it is moving (you are pedalling).
It is often possible to make a single change in the setting
when not pedalling which will not actually happen (cause the
derailment) until you begin pedalling again.


Thanks for your patience. I only coasted for the first time about 3
weeks ago.

Elisa Roselli
Ile de France

In article ,
says...
Ok, so the first one is really dumb: does the gear setting affect how
fast you go when you are coasting? My instinct tells me no, since
coasting involves not using the pedals, and I presume the only thing
affecting speed as you coast down a hill is the gravitational
accelleration that Galileo proved. But perhaps the chain setting can
affect how fast the wheels are allowed to turn?

Nope. Air resistance and gravity are the only factors, so your instinct
is correct.


Second one: can a bike with 30 gears actually go faster in top gear than
a bike with only 5 gears?

Only if the gear ratio is higher on the 30-speed, which it typically is.
A common size for the smallest cog on a 5-speed is 14 teeth, while a 27-
or 30-speed might have a 11 or 12 tooth smallest cog. The front
(chainwheel) on a 5-speed is often smaller than the largest cog on a 30
as well. My 10 speed (2 on the front, 5 on the back) has 52 and 39 teeth
chainwheels on the front, and 14 to 28 tooth cogs on the back. A 5-speed
would likely have something like 46 teeth on the front chainwheel.

Whether or not you can use the hightest gears depends on your leg
strength and how well your knees will handle the pressure. I have pretty
strong legs, but I rarely get into my top gear on the flats unless I'm
going with the wind.


Or is it just a mattter of the 5 speed having
less nuance between slowest and fastest speed?

That is the main reason for many speeds; it makes it easier to get the
exact gearing you want for any given conditions. I often find myself
wishing I had a gear between my 7th and 8th gear speeds.

If faster, is it
proportional

Third one: is the coasting speed of a bike without use of brakes its
maximum speed? Say I coast freely down a hill and the online counter
shows me at 29 kmph. That is faster than I can pedal in my highest,
fifth gear (or would want to). But if I were a speed freak on a
different bike, could I "refill" the pedalling by upping the gear to
thirtieth and outrun gravity by pedalling at my normal rpm?

If your gear ratios are high enough, you can can easily pedal yourself to
speeds higher than you could achieve just by coasting. You will probably
find that as you ride more, you can comfortably pedal faster than you
could at first, so you can drive yourself faster down the same hills.


Fourth: I know I'm not allowed to change gear when the bike is not
moving. But can I change gear during a coast, or does it have to be when
I am actually pedalling? Not long ago I tried changing gear while
coasting and there was a problem, the gear did not change well. Since
then I have not tried it again, but I don't know whether I did something
wrong or it was just a common and garden gear malfunction, due to poor
indexing or insufficient greasing.

You just need to have the pedals turning to shift gears. It doesn't much
matter how fast they are moving (as long as it's more than just barely
turning), and if you are coasting, you can just turn the pedals against
no resistance if you want to shift. Turn them at whatever speed feels
comfortable to you and it should shift ok.


Thanks for your patience. I only coasted for the first time about 3
weeks ago.

Keep at it; coasting is your reward for cranking your way up the hill!!


--
David Kerber
An optimist says "Good morning, Lord." While a pessimist says "Good
Lord, it's morning".

Remove the ns_ from the address before e-mailing.

On Fri, 18 Jul 2003 14:14:32 +0200, Elisa Francesca Roselli
wrote:

snip
Fourth: I know I'm not allowed to change gear when the bike is not
moving.
This is true only for external gearing.

Internally geared hubs (the Classic Sturmley-Archer, SRAM, et al.) require
shifting while _not_ pedalling. If you can't see gears, then you shift
while not pedalling; if you can see gears, you shift while pedalling.

snip

--
Nobody but a fool goes into a federal counterrorism operation without duct tape - Richard Preston, THE COBRA EVENT.

Elisa Francesca Roselli wrote:
Ok, so the first one is really dumb: does the gear setting affect how
fast you go when you are coasting?

No. A coaster gear/freewheel is not like an automotive transmission
and so it won't slow you on a downhill (at least not enough that you'll
notice).

My instinct tells me no, since
coasting involves not using the pedals, and I presume the only thing
affecting speed as you coast down a hill is the gravitational
accelleration that Galileo proved.

Essentially correct. Your speed is also affected by your initial velocity
when you begin coasting and, of course, wind direction and velocity.

But perhaps the chain setting can
affect how fast the wheels are allowed to turn?

No.

Second one: can a bike with 30 gears actually go faster in top gear than
a bike with only 5 gears? Or is it just a mattter of the 5 speed having
less nuance between slowest and fastest speed? If faster, is it
proportional

Not exactly. The number of gears here is less important than the gear
ratios of the two bikes. You could have a single gear bike that has a
higher gear than a 30 gear bike's highest gear. In fact, when one has
many gears, the gears will be a lot closer together than on a 5 speed
bike. The highest gear will probably be higher but not by a huge amount.
The lowest gear will also probably (but not neccessarily) be lower. It
all depends upon how the people who put the bikes together set up the gears.

Third one: is the coasting speed of a bike without use of brakes its
maximum speed?

It depends upon the gearing and how fast you can pedal.

Say I coast freely down a hill and the online counter
shows me at 29 kmph. That is faster than I can pedal in my highest,
fifth gear (or would want to). But if I were a speed freak on a
different bike, could I "refill" the pedalling by upping the gear to
thirtieth and outrun gravity by pedalling at my normal rpm?

Yes. If you have a high enough gear you can go faster down almost
any hill by pedaling though somewhere around 75kph it starts to get
a little on the crazy side. A gear big enough to pedal at that
speed is almost useless anywhere but on a long steep downhill.

Fourth: I know I'm not allowed to change gear when the bike is not
moving. But can I change gear during a coast, or does it have to be when
I am actually pedalling? Not long ago I tried changing gear while
coasting and there was a problem, the gear did not change well. Since
then I have not tried it again, but I don't know whether I did something
wrong or it was just a common and garden gear malfunction, due to poor
indexing or insufficient greasing.

You can move the lever but the gear won't usually change until you
pedal. You can pedal to change gears even when you're going too fast
to pedal to make the bike go faster.

I do this every time I ride. Typically, when I'm approaching a red light,
I will coast and shift to a lower gear, pedaling only enough to change the
gear but not enough to make the bike go faster or even maintain speed.
That way, I can start from the green light in a lower gear; which tends
to be easier and get me back up to speed faster.

Thanks for your patience. I only coasted for the first time about 3
weeks ago.

Keep at it!

--Bill Davidson
--
Please remove ".nospam" from my address for email replies.

I'm a 17 year veteran of usenet -- you'd think I'd be over it by now

Elisa Francesca Roselli wrote in message ...

Not to discourage you from asking questions here, but
there are many other useful resources.

I think you'll find a lot of information at
the fount of all knowledge, aka

http://www.sheldonbrown.com

There's a glossary of terms, articles for beginners,
as well as articles on repair, links to other bicycle
sites, etc. Even if you don't plan to fix your own bike,
it's good to know why they're charging you $30 for a new
lefthanded framwhizzer bolt.

www.chainreactionbicycles.com is another site I've found
handy.

Probably tons more - I often find what I need with a GOOGLE
search of the web, or GOOGLE GROUPS search for old articles
posted here. The latter can be confusing, since a lot of
mythology and opinion and general pigheadedness is mixed
in with useful information.

There's a frequently asked questions (link posted here
periodically). A GOOGLE search turned up:

http://www.faqs.org/faqs/bicycles-faq/part1/

number of speeds and how it affects top speed, there
is a gearing calculator at www.sheldonbrown.com which shows
speed in a given combination (front chainring and rear cog)
at a given crank rpm.

Third one: is the coasting speed of a bike without use of brakes its
maximum speed?

Coasting speed depends on the length and slope of the
hill and factors such as wind (tailwind helps, headwind hinders)
and rolling resistance (related to tire width, tread, and
inflation pressure.)

I can coast faster down some hills than I can pedal on a flat
road, but I'm a puny weakling. I can usually increase my downhill
speed by pedalling. I choose to limit my top speed, so usually coast,
and have been known to brake. Oh, the shame :-(



Fourth: I know I'm not allowed to change gear when the bike is not

I infer that you have a derailleur-equipped bike, rather
than an internally geared one.

Now to illustrate why you're better off reading sheldon brown's explanations :-)


If you're at a bike shop (or at home with a co-operative friend)
ask to see how the chain is moved from one rear cog to the next.

This means holding the rear wheel off the floor and shifting
the dearilleur(s) back and forth while turning the pedals. A
shop may put the bike in a work stand.


You'll watch the chain run over the rear pulleys which shift
it sideways so that it "walks" from one cog to the next. If you
move the pulley without rotating the cranks the sideways force
just bends the chain, it doesn't "walk" from one cog to the next.
If you shift several steps without pedalling, the chain is bent
at a sharper angle and will complain loudly when you next try to
pedal. "Ho-ow can you treat a poor chai-ain so ...."

The front derailleur nudges the chain from one chainring
to the next - nowhere near as elegantly IMO as the rear, and if you
move the front cage (metal part through which the chain passes)
without pedalling, it can just jam against the chain.

It's also possible for the chain to drop inside the smallest
chainring or outside the largest chainring (misadjusted derailleur
and/or faulty technique). I've had the chain drop between the
chainrings on my older bike (new chains are narrower than old).


And the chain can drop bewteen the largest rear cog and the
spokes (ouch) or outside the smallest rear cog (ouch). This is
usually due to misadjusted or bent rear derailleur. I consider
the embarassment of having a plastic spoke protector (prevents
the chain from jamming into the spokes) a small price to pay.

I'm sure there are illustrations of front and rear derailleur
operation somewhere. Picture is worth 1000 words, etc.

hth

Elisa Francesca Roselli wrote:

: Third one: is the coasting speed of a bike without use of brakes its
: maximum speed?

The maximum speed is when you drop your bike from an airplane...

But really, I think you meant to ask if it's somehow related to
gears. Well not really.

Bicycles are not automobiles, but when it comes to speed they are
quite similar. I see two factors limiting the maximum speed: power
and resistance. If your engine is a high-performance one, it can
push very hard to overcome resistance and achieve high speed. The
other part of the equation is having low resistance on your
vehicle. For cars and bicycles this means mainly that they need
(for speed) good aerodynamics.

Aerodynamics is one reason why racing bikes are faster: you have a
lower riding position so your upper body provides less resistance.
It is one reason why some recumbents are faster than racing
bikes: the riding position is very low, so your body in general
provides little air resistance. People obsessed with maximum speed
can build a fully closed cover around the recumbent, still
dramatically improving aerodynamics. World-class athletes are
occasionally able to reach speeds of 120 km/h or so on such bikes,
in short sprints on flat ground.

There are some IMO less important nitty gritty details affecting
maximum speed. For example, smooth high pressure tires provide
less rolling resistance. There are also some differences in how
much power you can put out in a certain riding position and type
of bike.

The role of gears is simply that turning the cranks at a
reasonable rpm must make the wheel turn at the required speed.
This is very easy to achieve, so we can assume that gearing is
optimal.

: Say I coast freely down a hill and the online counter
: shows me at 29 kmph. That is faster than I can pedal in my highest,
: fifth gear (or would want to).

If you could pedal at a higher rpm you would go faster. I used to
top at 40 km/h on an old 3-speed upright bike on the flats.

: But if I were a speed freak on a
: different bike, could I "refill" the pedalling by upping the gear to
: thirtieth and outrun gravity by pedalling at my normal rpm?

That's actually a good question that I think hasn't been answered.
I think theoretically, if you want to go faster you need to
provide power through pedals, ie. there needs to be some
resistance felt at the pedals. I think this only happens if your
rpm * gear is higher than the speed you are doing just by
coasting. So you need to pedal fast or use a big gear, maybe
both, depending on the hill and the bike. (Dunno if this is
comprehensive enough, and I'm not entirely sure of it either...)

Practically though, pedalling can increase air resistance so you
might not go faster by pedalling than by simply coasting. I read
about a guy who did some unscientific tests which yielded very
little benefit from pedalling. I guess there is a huge load of
anecdotal evidence against this, but still...

I know it's complicated but you like intellectual challenges I
think :-)

--
Risto Varanka | http://www.helsinki.fi/~rvaranka/hpv/hpv.html
varis at no spam please iki fi

On Fri, 18 Jul 2003 14:14:32 +0200, Elisa Francesca Roselli wrote:

Ok, so the first one is really dumb: does the gear setting affect how fast
you go when you are coasting?

No

involves not using the pedals, and I presume the only thing affecting
speed as you coast down a hill is the gravitational accelleration that
Galileo proved.

I think you mean Newton, but that's OK.

Second one: can a bike with 30 gears actually go faster in top gear than a
bike with only 5 gears? Or is it just a mattter of the 5 speed having less
nuance between slowest and fastest speed?

Typically, a bike with 5 gears will not have as high a top gear, nor as
low a bottom gear, nor as many choices in between, as one with 30. The
number of gears has nothing to do with the speed the bike can go, however.
The fastest bikes, land speed record machines, tend to have only one
gear. It's a matter of rider comfort, and adaptability to all sorts of
riding conditions (like big hills), that give the bike with more gears the
advantage.

Fourth: I know I'm not allowed to change gear when the bike is not moving.
But can I change gear during a coast, or does it have to be when I am
actually pedalling?

Depends on the type of gear. Internally-geared hubs are often changed by
a momentary coast, but derailleur-geared bikes need to be pedaled to
change gears.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |

archer wrote:
...
If your gear ratios are high enough, you can can easily pedal yourself to
speeds higher than you could achieve just by coasting. You will probably
find that as you ride more, you can comfortably pedal faster than you
could at first, so you can drive yourself faster down the same hills....

However, pedaling will also increase the overall drag. This can be
demonstrated by coasting down a hill, then pedaling backward at a normal
cadence. At what point pedaling becomes counter-productive will depend
on rider strength and bicycle configuration, but I suspect in most cases
it will be at a speed of 70 kph or greater.

Tom Sherman - Quad Cities USA (Illinois side)

"John Bartley K7AAY (ex-KGH2126)" wrote:

On Fri, 18 Jul 2003 14:14:32 +0200, Elisa Francesca Roselli
wrote:

snip
Fourth: I know I'm not allowed to change gear when the bike is not
moving.
This is true only for external gearing.

Internally geared hubs (the Classic Sturmley-Archer, SRAM, et al.) require
shifting while _not_ pedalling. If you can't see gears, then you shift
while not pedalling; if you can see gears, you shift while pedalling.

The Rolex, er Rohloff 14-speed internally geared hub will shift under
load.

Tom Sherman - Quad Cities USA (Illinois side)