Bicycle Computers - what do they do?

Michael J. Klein said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment?

There are many models with different capabilities. The simplest are
basically speed/odometers which give you trip and cumulative distance
and current/average/maximum speeds. Most GPS units can provide those
same functions, but of course are subject to reception problems under
some conditions. Some bicycle computers offer additional functions such
as cadence (number of rpms of the pedals), heart rate, altitude, road
grade, timing functions, etc.

On Fri, 25 Jun 2004 19:08:10 -0700, Peter <[email hidden]>

Quoted message said:

Michael J. Klein said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment?

There are many models with different capabilities. The simplest are
basically speed/odometers which give you trip and cumulative distance
and current/average/maximum speeds. Most GPS units can provide those
same functions, but of course are subject to reception problems under
some conditions. Some bicycle computers offer additional functions such
as cadence (number of rpms of the pedals), heart rate, altitude, road
grade, timing functions, etc.

Oh, now that I did not know. I had no idea that any model featured
heartrate, and road grade. Those 2 functions are useful! Thanks for
that info. Time for more searches I think.

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

In article <[email hidden]>,

Michael J. Klein said:

On Fri, 25 Jun 2004 19:08:10 -0700, Peter <[email hidden]>

Quoted message said:

Michael J. Klein said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment?

There are many models with different capabilities. The simplest are
basically speed/odometers which give you trip and cumulative distance
and current/average/maximum speeds. Most GPS units can provide those
same functions, but of course are subject to reception problems under
some conditions. Some bicycle computers offer additional functions such
as cadence (number of rpms of the pedals), heart rate, altitude, road
grade, timing functions, etc.

Oh, now that I did not know. I had no idea that any model featured
heartrate, and road grade. Those 2 functions are useful! Thanks for
that info. Time for more searches I think.

Cateye makes the CC-HB100 heart rate cyclecomputer. I have one, and
would be really happy with it if it had 2-bike wheel memory and recorded
Max heartrates.

It's quite common to have a bike computer and then a separate heart rate
monitor, but I believe some Polaris bike-specific models integrate some
fairly funky features (the CC-HB100 integrates a fairly bogus "calorie
counter" based on heart rate and speed, but it doesn't even have an
entry for rider mass, so I would suggest it is only useful as a relative
effort measurement).

--
Ryan Cousineau, [email hidden] http://www.sfu.ca/~rcousine/wiredcola/
President, Fabrizio Mazzoleni Fan Club

On Fri, 25 Jun 2004 23:08:21 -0700, Ryan Cousineau <[email hidden]>

Quoted message said:

In article <[email hidden]>,

<snip>

Quoted message said:

Cateye makes the CC-HB100 heart rate cyclecomputer. I have one, and
would be really happy with it if it had 2-bike wheel memory and recorded
Max heartrates.

It's quite common to have a bike computer and then a separate heart rate
monitor, but I believe some Polaris bike-specific models integrate some
fairly funky features (the CC-HB100 integrates a fairly bogus "calorie
counter" based on heart rate and speed, but it doesn't even have an
entry for rider mass, so I would suggest it is only useful as a relative
effort measurement).

Hmmm... gives me some new product ideas. I'll be talking with some
suppliers on Monday.

Thanks for the info Ryan.
Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

Peter <[email hidden]> aszonygya:
:Michael J. Klein wrote:
:
:> I use a GPS on my bike. I've read some info about bike computers, and
:> it seems like they don't do anything that my GPS does. Is that a
:> correct assessment?

I use both a Panoram and a Garmin ForeRunner. Both are excellent. The
amount of info I can view simultaneously is amazingly entertaining. Gives no
meaning to the notion of information overload. I love it.

BTW, the Panoram is more accurate on curvy roads whereas the GPS is more
accurate on straight roads. I'll leave it to your intelligence to figure out
why.

BTW, the bike computer, in principle, needs to be recalibrated according to
the current tire pressure. Otherwise there can be a misreading with error up
to 1% or even 2%. In my experience a tire underinflated by 10 psi may result
in about a 20 meter per mile error [I am bilingual in terms of the
metric/English system].

Best regards, Paul

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

Quoted message said:

Peter <[email hidden]> aszonygya:
:Michael J. Klein wrote:
:
:> I use a GPS on my bike. I've read some info about bike computers, and
:> it seems like they don't do anything that my GPS does. Is that a
:> correct assessment?

I use both a Panoram and a Garmin ForeRunner. Both are excellent. The
amount of info I can view simultaneously is amazingly entertaining. Gives

no

Quoted message said:

meaning to the notion of information overload. I love it.

BTW, the Panoram is more accurate on curvy roads whereas the GPS is more
accurate on straight roads. I'll leave it to your intelligence to figure

out

Quoted message said:

why.

BTW, the bike computer, in principle, needs to be recalibrated according

to

Quoted message said:

the current tire pressure. Otherwise there can be a misreading with error

up

Quoted message said:

to 1% or even 2%. In my experience a tire underinflated by 10 psi may

result

Quoted message said:

in about a 20 meter per mile error [I am bilingual in terms of the
metric/English system].

Best regards, Paul

Just curious...

Short of a measured mile (that you really believe to be accurate), how do
you calibrate a cycle computer to significantly less than 1% error anyways?

Iffn' you ask me... bicycle computers are like crack. It's amazing how
easy it is to become addicted to average speed (wow, 17.6 mph with all those
climbs), or elapsed time (hey, did my last century in 5 hrs 50 mins with
stops). One or two rides and you find yourself selling your soul for faster
elapsed times, never satisfied, always looking to score.

I find that my most enjoyable rides are the ones where I've forgotten to put
the dam thing on the bike and just ridden my own pace.

My advice... just say no.

Mike Lackey
Madison, AL

"Michael J. Klein" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment? Also, I would like to know more about bike
computers and I will read any suggested information.

Thanks in advance!

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

On Sat, 26 Jun 2004 14:22:46 GMT, "rosco"

reverse-the-following'ocsor_g'@hotmail.com said:

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

Quoted message said:

Peter <[email hidden]> aszonygya:
:Michael J. Klein wrote:
:
:> I use a GPS on my bike. I've read some info about bike computers, and
:> it seems like they don't do anything that my GPS does. Is that a
:> correct assessment?

I use both a Panoram and a Garmin ForeRunner. Both are excellent. The
amount of info I can view simultaneously is amazingly entertaining. Gives

no

Quoted message said:

meaning to the notion of information overload. I love it.

BTW, the Panoram is more accurate on curvy roads whereas the GPS is more
accurate on straight roads. I'll leave it to your intelligence to figure

out

Quoted message said:

why.

BTW, the bike computer, in principle, needs to be recalibrated according

to

Quoted message said:

the current tire pressure. Otherwise there can be a misreading with error

up

Quoted message said:

to 1% or even 2%. In my experience a tire underinflated by 10 psi may

result

Quoted message said:

in about a 20 meter per mile error [I am bilingual in terms of the
metric/English system].

Best regards, Paul

Just curious...

Short of a measured mile (that you really believe to be accurate), how do
you calibrate a cycle computer to significantly less than 1% error anyways?

Dear Rosco,

Actually, it's easy to calibrate modern computerized bicycle
odometers to less than 1% error.

They work by a sensor noticing when the magnet whips past on
the spoke and tacking another revolution on to the counter.

The accuracy of the distance travelled is limited by the
accuracy of your measurement of the effective rolling
circumference of the tire.

The industry usually lists a typical 700c tire at 2124 mm.

To discover the truth, you need to roll the tire along a
tape measure on a smooth concrete floor, watching a spoke,
the edge of a label, or a chalk mark on the tire.

After three times or more, you'll find that the same
distance is going to keep coming up to within an eighth of
an inch.

Different brands of tires and indvidual brands of tires seem
to vary only about 1% when measured, a tribute to modern
manufacturing.In the last ten years or so, I've had 700c
tires whose measured circumferences range from as small as
2109 to as large as 2132 mm.

With half a dozen different inexpensive bicycle computers
from Nashbar and Performance, they've all shown the same
distance from the second crack in my driveway to the start
of the ticket hut island in the state park--6.00 to 6.02
miles, hundreds of times every year.

This 0.33% variation is more likely due to how I wobble
down the path--at higher speeds, bicycle tires cover less
ground because there are fewer wiggles in the same distance.

Six miles is 9,656,064 mm, so a single tire spin of 2,124mm
is only 0.022% of the distance.

Another way to look at the ridiculous accuracy of these
things is that a hundredth of a mile is about 53 feet, more
than seven spins of the tire. Just taking a few corners
wider than usual will account for that--but the odometer is
still relentlessly tracking how far the tire went.

If you're all sitting comfortably, I'll begin discussing the
remarkable accuracy shown at the end of my daily ride of
approximately 15.25 miles, plus or minus up to 0.03 miles.

Wait--where are you all going? I haven't even begun to delve
into the exciting question of whether the tire circumference
changes significantly under load! Come back! I'm handing out
pocket protectors to anyone who stays for the whole . . .

Oh, never mind.

Carl Fogel

"Mike Lackey" <[email hidden]> wrote .

Quoted message said:

I find that my most enjoyable rides are the ones where I've forgotten to put
the dam thing on the bike and just ridden my own pace.

My advice... just say no.

Yeah, me too. I have 5 bikes, only 1 has a computer, and that's for doing "cue
sheet" rides. I used to have computers on all my bikes...

In article <[email hidden]>, Michael J. Klein

Quoted message said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment? Also, I would like to know more about bike
computers and I will read any suggested information.

Except for some things like gear inch and cadence probably nothing. Most bike
computers are much smaller than a GPS.

Tom Gibb <[email hidden]>

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> aszonygya:
:Just curious...
:
:Short of a measured mile (that you really believe to be accurate), how do
:you calibrate a cycle computer to significantly less than 1% error anyways?

I am a mathematician. The measured mile is the best. However, even a few
measured feet/meters can be amazingly accurate as long as you are very
careful. I live next to several bike paths and all have measured miles. I
can safely assume that they are accurate since according to my bike computer
they are within 1 meter of each other. Also, with a GPS and a straight road,
you can easily find very accurately a measured mile for you.

BTW, I created a measured mile on the street next to me prior to having a GPS
and when measured with GPS it turned out to be 1,607 meters [1 mile is
1,609.344 meters].

Best regards, Paul

[email hidden] aszonygya:
:The accuracy of the distance travelled is limited by the
:accuracy of your measurement of the effective rolling
:circumference of the tire.

True but the circumference depends on many factors, including the tire
pressure, outside temperature, and your weight [+ weight of shoes etc.].
Probably it even depends on your speed and the wind speed.

Best regards, Paul

On 26 Jun 2004 21:45:04 GMT, [email hidden] (Paul

Nevai) said:

[email hidden] aszonygya:
:The accuracy of the distance travelled is limited by the
:accuracy of your measurement of the effective rolling
:circumference of the tire.

True but the circumference depends on many factors, including the tire
pressure, outside temperature, and your weight [+ weight of shoes etc.].
Probably it even depends on your speed and the wind speed.

Best regards, Paul

Dear Paul,

Actually, the circumference keeps rolling out the same
figure, day after day--6.00 to 6.02 miles from the second
crack in my driveway to the start of the ticket hut's
concrete curb.

The circumference of the tire simply doesn't vary
significantly according to normal weight, temperature, or
psi. much less ordinary speed or windspeed.

Take a $15 speedometer from Nashbar or Performance, put it
on your bike, punch in the default 2124 mm for a 700c tire
(doesn't matter what it actually is or if it's a 26-inch
mountain bike tire), zero it, and ride the same route for a
week or two. Unless you wobble rather more than usual or
face heavy traffic, 10.00 will keep coming up in about the
same place.

Mine just came up with 15.25, as usual. It does the same
thing when I get a new front tire, measure it, and punch in
the new measured size before taking it out for its first
ride.

The damned things are just ridiculously accurate at
reporting how many times the front wheel spins on a ride,
and that distance just doesn't seem to vary even 1% with the
same front tire under normal riding conditions.

Cheers,

Carl Fogel

[email hidden] (Paul Nevai) wrote in message news:<[email hidden]>...

Quoted message said:

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> aszonygya:
:Just curious...
:
:Short of a measured mile (that you really believe to be accurate), how do
:you calibrate a cycle computer to significantly less than 1% error anyways?

I am a mathematician. The measured mile is the best.

Cyclometers themseves are quit accurate so the issue is simply the
calibration. Many accept wheel circumference in mm, which provides a
resolution of about five hundreths of a percent for a typical 700C
road wheel (which will have a circumference somewhere in the range of
2090 mm)

So you can use the measured mile and simply (re)set the calibration to
make it accurate.

And if you don't have a measured mile, but do have a flat surface and
a long tape measure you can achieve pretty remarkable accuracy by
doing a rollout that measures numerous revolutions of a wheel (at
appropriate tire pressure and weighted to simulate riding) and then,
of course, dividing the total distance by the number of revoltions.
It's pretty easy to do the rollout consistently to within a half inch
or so, and even an inch over, say, 8 revolutions of typical 700C road
wheel (~55 feet i.e. 660 inches )is well under the 1% mentioned.
For even greater accuracy do a few rollouts and average the results.

KF

On 26 Jun 2004 12:59:22 GMT, [email hidden] (Paul Nevai)

Quoted message said:

Peter <[email hidden]> aszonygya:
:Michael J. Klein wrote:
:
:> I use a GPS on my bike. I've read some info about bike computers, and
:> it seems like they don't do anything that my GPS does. Is that a
:> correct assessment?

I use both a Panoram and a Garmin ForeRunner. Both are excellent. The
amount of info I can view simultaneously is amazingly entertaining. Gives no
meaning to the notion of information overload. I love it.

BTW, the Panoram is more accurate on curvy roads whereas the GPS is more
accurate on straight roads. I'll leave it to your intelligence to figure out
why.

BTW, the bike computer, in principle, needs to be recalibrated according to
the current tire pressure. Otherwise there can be a misreading with error up
to 1% or even 2%. In my experience a tire underinflated by 10 psi may result
in about a 20 meter per mile error [I am bilingual in terms of the
metric/English system].

Best regards, Paul

Wow, that's a considerable error Paul. That's only because the outer
diameter changes that slightly? Doesn't tire wear cause a creeping
error then?

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

Quoted message said:

On 26 Jun 2004 21:45:04 GMT, [email hidden] (Paul

Nevai) said:

[email hidden] aszonygya:
:The accuracy of the distance travelled is limited by the
:accuracy of your measurement of the effective rolling
:circumference of the tire.

True but the circumference depends on many factors, including the tire
pressure, outside temperature, and your weight [+ weight of shoes etc.].
Probably it even depends on your speed and the wind speed.

Best regards, Paul

Dear Paul,

Actually, the circumference keeps rolling out the same
figure, day after day--6.00 to 6.02 miles from the second
crack in my driveway to the start of the ticket hut's
concrete curb.

The circumference of the tire simply doesn't vary
significantly according to normal weight, temperature, or
psi. much less ordinary speed or windspeed.

Take a $15 speedometer from Nashbar or Performance, put it
on your bike, punch in the default 2124 mm for a 700c tire
(doesn't matter what it actually is or if it's a 26-inch
mountain bike tire), zero it, and ride the same route for a
week or two. Unless you wobble rather more than usual or
face heavy traffic, 10.00 will keep coming up in about the
same place.

Mine just came up with 15.25, as usual. It does the same
thing when I get a new front tire, measure it, and punch in
the new measured size before taking it out for its first
ride.

The damned things are just ridiculously accurate at
reporting how many times the front wheel spins on a ride,
and that distance just doesn't seem to vary even 1% with the
same front tire under normal riding conditions.

Cheers,

Carl Fogel

Of course, my GPS is not measuring distance rolled, its measuring my
movement in space. For me, that's accurate enough because basically I
just want to see how far apart different waypoints are from each
other.

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

On 26 Jun 2004 21:42:27 GMT, [email hidden] (Paul Nevai)

Quoted message said:

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> aszonygya:
:Just curious...
:
:Short of a measured mile (that you really believe to be accurate), how do
:you calibrate a cycle computer to significantly less than 1% error anyways?

I am a mathematician. The measured mile is the best. However, even a few
measured feet/meters can be amazingly accurate as long as you are very
careful. I live next to several bike paths and all have measured miles. I
can safely assume that they are accurate since according to my bike computer
they are within 1 meter of each other. Also, with a GPS and a straight road,
you can easily find very accurately a measured mile for you.

BTW, I created a measured mile on the street next to me prior to having a GPS
and when measured with GPS it turned out to be 1,607 meters [1 mile is
1,609.344 meters].

Best regards, Paul

I read that the Greeks measured the distance between 2 cities using 2
measuring sticks, placed end to end, over and over until they reached
the far city. Its been said that the measurement was accurate to with
..250" but I have no idea whether that is really true.
Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

Mike Lackey said:

Iffn' you ask me... bicycle computers are like crack. It's amazing how
easy it is to become addicted to average speed (wow, 17.6 mph with all those
climbs), or elapsed time (hey, did my last century in 5 hrs 50 mins with
stops). One or two rides and you find yourself selling your soul for faster
elapsed times, never satisfied, always looking to score.

I find that my most enjoyable rides are the ones where I've forgotten to put
the dam thing on the bike and just ridden my own pace.

My advice... just say no.

I can see that happening. Once, when I was fishing, a passerby walked
over to me and asked "Hey, whatcha fishing for?" My reply: "For fun,
of course." He just smiled and walked away.

I'm definiately not into "miles" per se. Sure its nice to know some
stats and its important when planning trips and goals, but certainly
each ride I take is not a measured trial. I'm doing it because its
fun and I'd rather not treat it like a career. Once I do that it will
be over.

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------

(TBGibb) said:

In article <[email hidden]>, Michael J. Klein

Quoted message said:

I use a GPS on my bike. I've read some info about bike computers, and
it seems like they don't do anything that my GPS does. Is that a
correct assessment? Also, I would like to know more about bike
computers and I will read any suggested information.

Except for some things like gear inch and cadence probably nothing. Most bike
computers are much smaller than a GPS.

Tom Gibb <[email hidden]>

Tom, if the display gets much smaller, it'll be mounted on a display
console which protrudes from my chest so I can see the darn thing up
close!

I have mine mounted on the stem (pics posted on my website). I have
to look down a bit to see it, so its very easy to ignore if I wish.

Michael J. Klein [email hidden]
Dasi Jen, Taoyuan Hsien, Taiwan, ROC
Please replace mousepotato with asiancastings
---------------------------------------------