Cycle computer help for my 29"

The best thing to do is to ride a measured distance and adjust the
calibration. I suspect some of the difference you see is due to the
"weaving" a unicycle does, that a bicycle does not do.

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

Quoted message said:

I have a Yuni 29" with a Nanoraptor tire, I had someone from a bike shop
set my cycle computer, and he measured the circumference of the outside
of the tire, in mm, it came out to be 2320 mm. I think that it
overestimates the milage though, by about .15 miles per mile. I think
this might be due to the fact that the tire gives in some when i am
riding, it would be less than 2320 when im sitting on the unicycle.
Does anyone with a 29" nanoraptor tire have a cycle computer....if so
what is the circumference in mm.

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I have one but have not measured it. Best way to get an accurate measure
is to do it yourself, with you on the cycle. Mark a spot on the ground,
and put your tire there, valve down. Ride along a wall or something, to
help you stay as straight as possible, until the valve is down again.
Mark that spot, then measure.

If you are really anal, ride several revolutions and then measure,
dividing by # of revolutions. Still stay along a wall or something to
help you stay straight. Though your uni will make a zig-zag path when
you ride, you should not compensate for that in setting your computer.
You are still riding all that distance.

Please let us know what you come up with, though it is best used if you
include tire pressure and rider weight with your number.

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johnfoss said:

Though your uni will make a zig-zag path when you ride, you should
not compensate for that in setting your computer. You are still
riding all that distance.

I'm not sure I agree with this. I'd argue that the length of path
travelled by the rider's center of mass is a better measure of
distance travelled than the path the wheel follows on the ground. In
which case, little of the side-to-side motion of the wheel contributes
to distance (and derived speed).

Ken

29 inches is 736.6mm

Therefore, a 10 mm error in calculating the rolling diameter of the
wheel is an error of around 1.36% = 23.9 metres on a mile.

The error is so small that I wouldn't worry too much - because the
rolling diameter of your tyre will change from day to day and hour to
hour with changes of air pressure (perhaps fluctuating with temperature)
and changes of loading.

Most computers have a programmable function, and most come with a chart
suggesting the "input" figure for any given tyre size and cross
section.

I only ever compete against myself, so all I need to know is that I'm
using the same computer, so the error is the same. That way, a faster,
longer ride is faster and longer, whether my computer reads miles,
kilometres, cubits or pasangs.

And as for the "anal" comment - this pop psychology term is much
misused. An anal retentive is someone who exerts or expresses his power
or control over others by not giving them what they want (compare the
baby who refuses to do his business on the potty), and an anal expulsive
is the opposite: someone who exerts or expresses his power or control
over others by... well, I've got a boss like that.

--
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If it isnt the measurement of the circumference that would give me the
10 percent or so error that i get, what else could it be?

edit: I am using a 40 dollar wireless cycle computer, so it shouldnt be
the quality of the cycle computer...(or at least I hope it isnt)

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I think some (most) of the difference could be accounted for in the fact
that unicycles wobble a lot when you ride. I would suggest free riding
a set distance or a set number of rotations. Try to keep in a straight
line. Divide out and use the number you get. This would measure the
number of rotations it took to cover the distance rather then the strict
circumference of the tire.

And what ever you come up with, keep us posted.

Daniel

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Mikefule said:

*An anal retentive is someone who exerts or expresses his power or
control over others by not giving them what they want*

I shouldn't have used that word; should have known somebody would
comment.

I did not say "anal retentive." Someone who is anal (now this is pure
slang, not psychological terminology) is someone who's very picky,
presumably because their sphincter is so tight. Or vice-versa. Call it
retentive if you want, but we're just talking about measuring...

Otherwise I agree with Mike on the relative accuracy of your settings.
Unless you're comparing with others, the exact numbers don't matter.

If you're 10% off or more, something is way wrong. Make sure the
measurement came out to the right number of millimeters, and that this
was the number entered into the computer. Also, don't assume your tire
is 29" in diameter, measure it. Circumference is easier to measure than
diameter, and roll-out is easier to measure than that.

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all the way down Mt. Diablo (3300'😉, a 20 mile round trip of road and
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I will try the roll out method tomorrow, and enter in the numbers. If
the bike shop guy entered in the correct measurement then it shouldnt be
giving me the 10 percent error even if the pressure of the tire changed.
Hopefully he did enter in the numbers wrong, which would means that the
cycle computer isnt malfunctional. If the roll out method still doesnt
work I am going to just give up and try to get my money back and buy one
of those cheap 10 dollar cycle computers on unicycle.com (because people
I know who use those have no problems).

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Where is your magnet in relation to your crank and favorite idling
position? It is possible that your magnet is positioned so that it
moves back and forth past the sensor every time you idle or mount.

You want to position the magnet so that it is not near the sensor when
you mount, when you idle, or when you rest by holding a sign post or
wall.

If your magnet is positioned in a bad location you could be triggering
the sensor more times than the wheel rotates which would end up
overestimating your actual mileage.

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Perhaps your cycle computer is correct, but your reference source is
wrong? E.g., car speedometers can be way off, and road signs are also
quite unreliable.

Just another detail to check... .

j.

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I just did the roll out method, and i did two rotations of the tire, and
got the average in mm, the average was 2262 mm, which is about 60 mm
less than the measurement the of the circumference (the bike shop guy
did). This would account for about a 2.6 percent error, which still
isnt that much of an error. I will try out the new measurement on a
track or something to see how close it is.

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I just went on the track tonight, and I went around 4 times (which is 1
mile). My cycle computer read 1.0 miles! It only shows accuracy of a
tenth of a mile, so this also could mean that it could have gone up to
1.1 miles in a couple more pedals (which i didnt check), but either way
this means that the error is AT LEAST less than 10 percent, which is
good enough (there probably isnt much of any error, I just wish i check
to see how much further I had to pedal to get that extra .1 mile). I am
going to ride a trail soon that has markers for mileage and I will let
you know how much off the cycle computer is, because you cant really see
error in just 1 mile. But so far I think the magic number for a 29"
Nanoraptor tire is 2262 mm.

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johnfoss said:

* Someone who is anal (now this is pure slang, not psychological
terminology) is someone who's very picky, presumably because their
sphincter is so tight. Or vice-versa. Call it retentive if you want,
but we're just talking about measuring...
*

I knew that. I was just being anal...😉 I don't think I'm picky
though; I'm pedantic - a small difference, but, I think, an important
one.😎

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Well, it all depends on what you mean by "semantics".
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siafirede said:

*I just went on the track tonight, and I went around 4 times (which is
1 mile). *

I think that should be 1600 meters. I can't remember which is more, but
it's pretty close to one mile. That is assuming you rode in the inside
lane.

Congratulations! So where was the "bad" 10%? Sounds like most of it may
have been in the measurement of your first ride's distance?

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John Foss, the Uni-Cyclone
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www.unicycling.com

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all the way down Mt. Diablo (3300'😉, a 20 mile round trip of road and
trail.
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1 mile = 1,609 metres or 1.609 km

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Well, it all depends on what you mean by "semantics".
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I just came back from a 26 mile ride, and the calibration of the cycle
computer is perfect. By looking at a map I found out that my round trip
should be almost exactly 26 miles, which is what the cycle computer
calculated. Thanks to everyone who responded, my problem is solved.

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