FlightDeck Calibration problems

[Gary Smiley]

I've used a FlightDeck on my road bike for 7 years (Ultegra triple, 700 x 23
tires), and it worked fine until about a month ago. Now, it registers
mileage about 10-12 % too high. I went on a 40 mile ride and it registered
44 miles. So I recalibrated it. Even measured the wheel by rolling the bike
one revolution with me seated on it. But for some reason, it measures way
too high - but - when I am riding alongside a fellow rider and compare
speeds, they are the same. Has this happened to anyone else in this group?
Is there anything I can do about it?
- Gary

 

[Mike Jacoubowsky]

> I've used a FlightDeck on my road bike for 7 years (Ultegra triple, 700 x
> 23 tires), and it worked fine until about a month ago. Now, it registers
> mileage about 10-12 % too high. I went on a 40 mile ride and it registered
> 44 miles. So I recalibrated it. Even measured the wheel by rolling the
> bike one revolution with me seated on it. But for some reason, it measures
> way too high - but - when I am riding alongside a fellow rider and compare
> speeds, they are the same. Has this happened to anyone else in this group?
> Is there anything I can do about it?
> - Gary

You're using a calibration number in the range of 2080 or thereabouts?

Bike computers basically cannot determine distance incorrectly without also
messing up with the speed. It's a hardwired computation that cannot be
altered or become wrong with time. They can often have problems with maximum
speed without an effect on mileage, because the spikes are momentary and it
doesn't make much difference in the end if, for a couple seconds, it thought
you were traveling at 60mph instead of 20. It might add a hundred feet to
your ride, which is way under the .1 mile display update.

So looks like I only have more questions, not answers for you.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

 

[Chris Y.F.N.W.]

Bike computers work by counting wheel turns. The number of turns over
time determines speed, number of turns by itself measures distance, all
are based upon the wheel size you entered into it. Some computers use
one measurement along with a little arithmetic to calculate other
measurements. However all are based upon exactly how big the computer
_thinks_ your wheel is.

Some units will lose this information when power is lost, such as when
the battery dies or when changing it. you might want to go into your
settings and see if the number you originally set is still there.

BTW, simply measuring a wheel turn and punching in a number is SETTING
the computer, not "calibrating' it. It's not 100% accurate, or even 99%.
as it doesn't take into account factors that are only encountered while
actually riding the bike.

To calibrate (test against a measurement of known accuracy) your
computer, you must ride the bike for an accuratly measured distance (at
least a few miles) then compare your comp's reading against the known
distance and make any necessary corrections.

http://www.geocities.com/czcorner/tech17.html

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[Gary Smiley]

This is why I posted this thread - it is a mystery. The speed reads the
same as that of my fellow riders. Every now and then I'll ask my
friend: "What's your speed now?". And it's always the same as my speed
- but my distance/mileage is way too high. And no, it's not set to
kilometers. It's as if the mathematical algorithm for calculating
distance has failed. Hmm... could it be that the battery is starting to
go?

Chris Y.F.N.W. wrote:
> Bike computers work by counting wheel turns. The number of turns over
> time determines speed, number of turns by itself measures distance, all
> are based upon the wheel size you entered into it. Some computers use
> one measurement along with a little arithmetic to calculate other
> measurements. However all are based upon exactly how big the computer
> _thinks_ your wheel is.
>
> Some units will lose this information when power is lost, such as when
> the battery dies or when changing it. you might want to go into your
> settings and see if the number you originally set is still there.
>
> BTW, simply measuring a wheel turn and punching in a number is SETTING
> the computer, not "calibrating' it. It's not 100% accurate, or even 99%.
> as it doesn't take into account factors that are only encountered while
> actually riding the bike.
>
> To calibrate (test against a measurement of known accuracy) your
> computer, you must ride the bike for an accuratly measured distance (at
> least a few miles) then compare your comp's reading against the known
> distance and make any necessary corrections.
>
> http://www.geocities.com/czcorner/tech17.html
>
> - -
> Comments and opinions compliments of,
> "Your Friendly Neighborhood Wheelman"
>
> Messages sent to the above "E" addy will be lost forever!
>
> to E-mail me:
> ChrisZCorner "at" webtv "dot" net
>
> My website:
> http://geocities.com/czcorner

 

[Buck]

Gary Smiley wrote:
> This is why I posted this thread - it is a mystery. The speed reads the
> same as that of my fellow riders. Every now and then I'll ask my
> friend: "What's your speed now?". And it's always the same as my speed
> - but my distance/mileage is way too high. And no, it's not set to
> kilometers. It's as if the mathematical algorithm for calculating
> distance has failed. Hmm... could it be that the battery is starting to
> go?

That might be the problem. I have found that Cateye computers produce
strange readings when the batteries get low or the computer / mount
connections need to be cleaned.

-Buck

 

[Paul Hobson]

Chris Y.F.N.W. wrote:
> BTW, simply measuring a wheel turn and punching in a number is SETTING
> the computer, not "calibrating' it. It's not 100% accurate, or even 99%.
> as it doesn't take into account factors that are only encountered while
> actually riding the bike.
>
> To calibrate (test against a measurement of known accuracy) your
> computer, you must ride the bike for an accuratly measured distance (at
> least a few miles) then compare your comp's reading against the known
> distance and make any necessary corrections.

Seems like this would be a useless exercise due to the infinitesimal
probability that you're going to ride perfectly along the same line* as
the road (or trail) was surveyed. Why not just just measure the
circumference of the wheel (in any number of ways) several times and
take the average? (that's what you do with proctor molds in a soils lab)
\\paul

*most streets are surveyed along the center, IIRC

 

[Mike Jacoubowsky]

> BTW, simply measuring a wheel turn and punching in a number is SETTING
> the computer, not "calibrating' it. It's not 100% accurate, or even 99%.
> as it doesn't take into account factors that are only encountered while
> actually riding the bike.

I think you'd have a difficult time showing that a bike computer is less
than 99% accurate when properly calibrated. The "factors that are only
encountered while actually riding the bike" account for a very tiny
variation in total mileage. To be less than 99% accurate is to suggest that
an error of 1 mile in a century should be considered normal, while I would
argue that an error of .25 miles (representing over 1000 ft of distance
either traveled or not traveled) would be at the upper end of normal.

You can try and come up with all manner of extreme examples (somebody
endlessly weaving back and forth across a wide, long, steep grade?) but in
the real world, cycling computer accuracy is very, very good. And why
shouldn't it be? What could be simpler than measuring the number of turns a
wheel takes, when you know what the diameter of that wheel "actually" is (by
doing a rollout and confirming it based upon known mile markers if you
really want to get picky about it).

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA

"Chris Y.F.N.W." <[email protected]> wrote in message
news:[email protected]...
> Bike computers work by counting wheel turns. The number of turns over
> time determines speed, number of turns by itself measures distance, all
> are based upon the wheel size you entered into it. Some computers use
> one measurement along with a little arithmetic to calculate other
> measurements. However all are based upon exactly how big the computer
> _thinks_ your wheel is.
>
> Some units will lose this information when power is lost, such as when
> the battery dies or when changing it. you might want to go into your
> settings and see if the number you originally set is still there.
>
> BTW, simply measuring a wheel turn and punching in a number is SETTING
> the computer, not "calibrating' it. It's not 100% accurate, or even 99%.
> as it doesn't take into account factors that are only encountered while
> actually riding the bike.
>
> To calibrate (test against a measurement of known accuracy) your
> computer, you must ride the bike for an accuratly measured distance (at
> least a few miles) then compare your comp's reading against the known
> distance and make any necessary corrections.
>
> http://www.geocities.com/czcorner/tech17.html
>
> - -
> Comments and opinions compliments of,
> "Your Friendly Neighborhood Wheelman"
>
> Messages sent to the above "E" addy will be lost forever!
>
> to E-mail me:
> ChrisZCorner "at" webtv "dot" net
>
> My website:
> http://geocities.com/czcorner
>

 

[Chris Y.F.N.W.]

Group: rec.bicycles.misc
Date: Tue, Sep 26, 2006, 12:44pm (EDT-3)
From: [email protected] (Gary Smiley)

>This is why I posted this thread - it is a
>mystery. The speed reads the same as
>that of my fellow riders. Every now and
>then I'll ask my friend: "What's your
>speed now?". And it's always the same
>as my speed

>- but my distance/mileage is way too
>high. And no, it's not set to kilometers.
>It's as if the mathematical algorithm for
>calculating distance has failed. Hmm...
>could it be that the battery is starting to
>go?

Hmm. One of the "factors" affecting comp. readings is how straight a
line you rode whithin the measured distance. Since not everybody follows
the exact same path, there will always be some discrepancy in overall
difference between rider's units, even if current speed reads the same.
How off is "Way off"? if it's a lot (for example 3/4 of a mile after
riding only 25 miles), then try changing the battery. if that doesn't
fix it, then there's probably something more amiss. and I would contact
Shimano. Bike computers are not "user serviceable".

- -
Comments and opinions compliments of,
"Your Friendly Neighborhood Wheelman"

Messages sent to the above "E" addy will be lost forever!

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[Chris Y.F.N.W.]

Group: rec.bicycles.misc
Date: Tue, Sep 26, 2006, 8:42pm
From: [email protected] (Paul Hobson)

>Seems like this would be a useless
>exercise due to the infinitesimal
>probability that you're going to ride
>perfectly along the same line* as the
>road (or trail) was surveyed. Why not
>just just measure the circumference of
>the wheel (in any number of ways)
>several times and take the average?

My point exactly. Since there's no way you are going to ride "perfectly
straight" that is no wavering in your course, then your wheel is going
to travel a longer path than the road does. Simple geometry.

However, by riding a measured distance of, say 10 miles, then your
"weaving" will be taken into account (along with other factors). And
after riding the "surveyed" ten miles, the distance your computer reads
will also be ten miles. IOW, this will be that actual distance as if you
HAD ridden a perfect, unwavering line. The link I gave in my first post
will take you to a page that explains this better.

Simply measuring the wheel distance, even over a distance of four turns,
with my weight on the bike, only gave me an accuracy of 97%, or about as
accurate as a car odometer. OK, so I'm a perfectionist. This is probably
accurate enough for most people, but I like the 99.99% I get now a lot
better :-3)

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Comments and opinions compliments of,
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Messages sent to the above "E" addy will be lost forever!

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