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.
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.
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.
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)
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
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.
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).
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.
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.
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.
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.
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. 
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?
1 mile = 1,609 metres or 1.609 km
Re: 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” <siafirede@NoEmail.Message.Poster.at.Unicyclist.com> wrote in
message news:siafirede.18892z@NoEmail.Message.Poster.at.Unicyclist.com…
>
> 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.
>
>
> –
> siafirede - unicycleXcore
> ------------------------------------------------------------------------
> siafirede’s Profile: http://www.unicyclist.com/profile/6057
> View this thread: http://www.unicyclist.com/thread/33370
>
Re: Cycle computer help for my 29"
“johnfoss” <johnfoss@NoEmail.Message.Poster.at.Unicyclist.com> writes:
> 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
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.