How Accurate is your Computer?
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How Accurate is your Computer?
How accurate is your cycle computer? I just put on a Sigma BC1200. I road a mile and marked exactly on the road where it came up a mile. I then jumped in my truck and drove the same route. It probably came out to be about 1/15 of a mile off.
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
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This is from one of my posts last year.
An easy way to do a roll out measurement it this:
1) Pump tyres up to pressure
2) Find a line to follow, gutter, concrete groove in driveway etc.
3) Place valve at bottom of tyre
4) Sit on bike and roll out 5 complete rotations. Measure the distance.
5) Repeat 2 more times.
6) Add the 3 measurements together and divide by 15. This should give a very accurate measurement.
Even with an accurate measurement it can still only get to within +/- 1% as when we ride we rarely ride in a perfect straight line and we take different lines through corners than other cyclist's.
CHEERS.
Mark
An easy way to do a roll out measurement it this:
1) Pump tyres up to pressure
2) Find a line to follow, gutter, concrete groove in driveway etc.
3) Place valve at bottom of tyre
4) Sit on bike and roll out 5 complete rotations. Measure the distance.
5) Repeat 2 more times.
6) Add the 3 measurements together and divide by 15. This should give a very accurate measurement.
Even with an accurate measurement it can still only get to within +/- 1% as when we ride we rarely ride in a perfect straight line and we take different lines through corners than other cyclist's.
CHEERS.
Mark
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Originally Posted by Person
How accurate is your cycle computer? I just put on a Sigma BC1200. I road a mile and marked exactly on the road where it came up a mile. I then jumped in my truck and drove the same route. It probably came out to be about 1/15 of a mile off.
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
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I was wondering that too. Theoretically, the faster moving part of the wheel is higher up, but then again, no matter where on the wheel you put the sensor, it still is going to pass the sensor the same amount of times...Anyway, my CatEye enduro seems to be pretty right on. It once registered that I was traveling at 37 mph in a 20 mph zone on m mountain bike(steep downhill in a park), and my favorite local trail, which is 2.5 miles one way, came up as 2.3 miles on the computer, but I carried over a muddy area.
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Originally Posted by Koffee Brown
I believe mine to be pretty accurate, since it's based on a satellite signal I get in real time that tracks me as I'm moving.
Koffee
Koffee
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Originally Posted by Koffee Brown
I believe mine to be pretty accurate, since it's based on a satellite signal I get in real time that tracks me as I'm moving.
Koffee
Koffee
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Originally Posted by Koffee Brown
I believe mine to be pretty accurate, since it's based on a satellite signal I get in real time that tracks me as I'm moving.
__________________
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
#10
Still kicking.
Very Accurate.
Don't use one.
Don't use one.
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Appreciate the old bikes more than the new.
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Originally Posted by Koffee Brown
I believe mine to be pretty accurate, since it's based on a satellite signal I get in real time that tracks me as I'm moving.
Koffee
Koffee
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Assuming the organisers of the ride did accurate measurements themselves, I'd say my bike computer isn't entirely all that accurate... well... at least not on the second day.
First day was supposed to cover 100 miles....
Second day, 106 miles..
Also keep in mind that stray EM can sometimes screw with the readings too. Here's a maximum recorded speed on one descent that ended with me standing on top of a traffic sensor. The EM pulses that the sensor (essentially a metal detector) uses to induce an EM response field in order to detect the metal of cars can play havoc with your wheel pickup and create anomalies.
First day was supposed to cover 100 miles....
Second day, 106 miles..
Also keep in mind that stray EM can sometimes screw with the readings too. Here's a maximum recorded speed on one descent that ended with me standing on top of a traffic sensor. The EM pulses that the sensor (essentially a metal detector) uses to induce an EM response field in order to detect the metal of cars can play havoc with your wheel pickup and create anomalies.
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"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
Last edited by khuon; 05-03-04 at 11:14 PM.
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146.1 miles/hour...hmmm...New York to Chicago in.....
As for the first pic, COMEON! for a 206mile ride your bound to be a bit off! For that distance I would give or take 10 miles
As for the first pic, COMEON! for a 206mile ride your bound to be a bit off! For that distance I would give or take 10 miles
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Originally Posted by mindbogger
146.1 miles/hour...hmmm...New York to Chicago in.....
As for the first pic, COMEON! for a 206mile ride your bound to be a bit off! For that distance I would give or take 10 miles
As for the first pic, COMEON! for a 206mile ride your bound to be a bit off! For that distance I would give or take 10 miles
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"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
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"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
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I calibrated both of mine (roadie and MTB) by measuring the rollout while on the bike and found that there's about a 2-3% difference from what is given in the wheel sizing charts. Not a big difference, but enough to notice on longer rides like khuon mentioned.
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Originally Posted by Grendel
I calibrated both of mine (roadie and MTB) by measuring the rollout while on the bike and found that there's about a 2-3% difference from what is given in the wheel sizing charts. Not a big difference, but enough to notice on longer rides like khuon mentioned.
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"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
1999 K2 OzM 2001 Aegis Aro Svelte
"Be liberal in what you accept, and conservative in what you send." -- Jon Postel, RFC1122
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Any recommendations as to where to mount the Cateye Micro Wireless sensor (distance from hub) to attain a fairly accurate measurement. The manual says at the top of the fork, but this seemed a little unclear...any tips?
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Suggestion ...
Originally Posted by deuce_nuts
Any recommendations as to where to mount the Cateye Micro Wireless sensor (distance from hub) to attain a fairly accurate measurement. The manual says at the top of the fork, but this seemed a little unclear...any tips?
My hunch for making a unit more accurate is to get an extra sensor and put the second one on the exact opposite spoke. Than you input a circumference half as much as you roll out. This will keep the speedometer from jumping around and making large jumps.
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... oh yeah, thanks! Sometimes my fingers type before I think...
Happy trails!
Happy trails!
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Originally Posted by deuce_nuts
Any recommendations as to where to mount the Cateye Micro Wireless sensor (distance from hub) to attain a fairly accurate measurement. The manual says at the top of the fork, but this seemed a little unclear...any tips?
I have mine mounted about 8-10" above the axle to and it's well within the 70mm specified. Remember, the sensor mount doesn't have to sit square on the fork - the sensor swivels in the mount so you can get it close to the magnet and still have the face of the sensor square to the magnet. If you like, I'll take some pics later on tonight to illustrate what I mean.
Edit: BTW - the manual says to have the magnet within 5mm of the sensor as it goes by...
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Originally Posted by Person
How accurate is your cycle computer? I just put on a Sigma BC1200. I road a mile and marked exactly on the road where it came up a mile. I then jumped in my truck and drove the same route. It probably came out to be about 1/15 of a mile off.
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
My truck could be off or the computer could be off; I am not sure. Is it impossible to get them to read perfectly accurate?
Thanks,
Person
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there's also a lot of discussion in this thread from the mechanics forum:
https://www.bikeforums.net/bicycle-mechanics/187869-circumference-question.html
https://www.bikeforums.net/bicycle-mechanics/187869-circumference-question.html
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my 1200 was dead accurate after doing the wheel measure thing. I started at the valve stem down and marked a spot then rolled the wheel until it was down again and made another mark then measured. different tires use different settings, even ones with the same width.
I have done the same thing with my 1600 and its just as acurrate
I have done the same thing with my 1600 and its just as acurrate
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I just got the same computer today as the poster did. After calibrating with the instructions, I found that mine was about 6/100 of a mile off (under). That's good enough for me. I might recalibrate based on what I've been reading here, but i don't think i'll get or need much better.