Which is better/more accurate speedo?
#1
01-12-2007, 10:13 AM
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Which is better/more accurate speedo?
Well today i had a interesting debate about which is better and more accurate speedo. what do you guy say?
My point of view about it was that a digital speedo has less of and error % vs. a cable driven speedo.
His was that a cable driven was more accurate b/c it is reading the speed of the front tire..
My point of view about it was that a digital speedo has less of and error % vs. a cable driven speedo.
His was that a cable driven was more accurate b/c it is reading the speed of the front tire..
#3
01-12-2007, 10:54 AM
RE: Which is better/more accurate speedo?
A cable driven speedometer has no delay for read. There isn't a division by zero time problem. It simply displays the speed as it sees it. That said, it's far harder to get EXACTLY the right gears than to get EXACTLY the right decimal places.
A digital speedometer has to count revolutions, therefore it has to display the AVERAGE speed over a short period of time. It can not display instanteous speed - it simply doesn't make sense. On the other hand, it's easier to calibrate a digital speedometer because all you are tweaking is a constant.
A digital speedometer is also easier to correct after you purchase the bike - install a speedohealer and tweak away until you get what agrees with your choose measure of accuracy.
BOTH types of speedometers, no matter what you do, will be wrong. Tire size changes with tire wear and tire preasure. As you go faster small 'rounding' errors become more noticable...
Measuring with the GPS will only tell you which bike was closest to the GPS. The GPS although by most measures is highly accurate it isn't perfect... also if you do this test it will only measure how close your bike is currently to the GPS readout... in a week after a few burnouts the error might be worse. After a new tire it mightbe more accurate.
Personally - I like front tire driven cable speedometers... but in the end it doesn't really matter so long as it's close.
Woot
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01-12-2007, 10:55 PM
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RE: Which is better/more accurate speedo?
ORIGINAL: woot
A cable driven speedometer has no delay for read. There isn't a division by zero time problem. It simply displays the speed as it sees it. That said, it's far harder to get EXACTLY the right gears than to get EXACTLY the right decimal places.
A digital speedometer has to count revolutions, therefore it has to display the AVERAGE speed over a short period of time. It can not display instanteous speed - it simply doesn't make sense. On the other hand, it's easier to calibrate a digital speedometer because all you are tweaking is a constant.
A digital speedometer is also easier to correct after you purchase the bike - install a speedohealer and tweak away until you get what agrees with your choose measure of accuracy.
BOTH types of speedometers, no matter what you do, will be wrong. Tire size changes with tire wear and tire preasure. As you go faster small 'rounding' errors become more noticable...
Measuring with the GPS will only tell you which bike was closest to the GPS. The GPS although by most measures is highly accurate it isn't perfect... also if you do this test it will only measure how close your bike is currently to the GPS readout... in a week after a few burnouts the error might be worse. After a new tire it mightbe more accurate.
Personally - I like front tire driven cable speedometers... but in the end it doesn't really matter so long as it's close.
Woot
A cable driven speedometer has no delay for read. There isn't a division by zero time problem. It simply displays the speed as it sees it. That said, it's far harder to get EXACTLY the right gears than to get EXACTLY the right decimal places.
A digital speedometer has to count revolutions, therefore it has to display the AVERAGE speed over a short period of time. It can not display instanteous speed - it simply doesn't make sense. On the other hand, it's easier to calibrate a digital speedometer because all you are tweaking is a constant.
A digital speedometer is also easier to correct after you purchase the bike - install a speedohealer and tweak away until you get what agrees with your choose measure of accuracy.
BOTH types of speedometers, no matter what you do, will be wrong. Tire size changes with tire wear and tire preasure. As you go faster small 'rounding' errors become more noticable...
Measuring with the GPS will only tell you which bike was closest to the GPS. The GPS although by most measures is highly accurate it isn't perfect... also if you do this test it will only measure how close your bike is currently to the GPS readout... in a week after a few burnouts the error might be worse. After a new tire it mightbe more accurate.
Personally - I like front tire driven cable speedometers... but in the end it doesn't really matter so long as it's close.
Woot
#6
01-13-2007, 03:09 PM
#8
01-14-2007, 10:24 AM
RE: Which is better/more accurate speedo?
It's not just the wires that give it the lag - because that would be next to nothing... and the lag really isn't that much.
It depends on where the sensor is exactly... if it does the 'instantaneous speed' of one revolution of the front sprocket then it is less than the circumference of the rear tire off... and infact would have less lag on a bike with a huge rear sprocket.The only time it would be noticable would be under EXTREME acceleration or braking in this case - and most people don't look at the speedometer then.
So Tahoo SC is right, the more I think about it the less the lag means... we're talking about the time it takes to move 12"-48".. the faster you go the less it matters. At slow speeds that's actually a fairly long lag...
It depends on where the sensor is exactly... if it does the 'instantaneous speed' of one revolution of the front sprocket then it is less than the circumference of the rear tire off... and infact would have less lag on a bike with a huge rear sprocket.The only time it would be noticable would be under EXTREME acceleration or braking in this case - and most people don't look at the speedometer then.
So Tahoo SC is right, the more I think about it the less the lag means... we're talking about the time it takes to move 12"-48".. the faster you go the less it matters. At slow speeds that's actually a fairly long lag...
#9
08-23-2007, 01:49 AM
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RE: Which is better/more accurate speedo?
Doesn't it depend on how much time you spend on one wheel? The cable driven speedo reads the front wheel, but of that wheel is off the ground most of the time, then my vote is that it isn't that accurate at all. The digital reads sprocket revolutions (unless I am totally wrong), and then it doesn't matter how much time you spend on your rear wheel!
In case it isn't painfully obvious, this is a totally BS answer.
In case it isn't painfully obvious, this is a totally BS answer.
#10
08-23-2007, 05:12 AM
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RE: Which is better/more accurate speedo?
There is a difference between accuracy and precision. Accuracy is how close to the actual truth you are and precision is kinda like how it is described. If is very easy to have a well calibrated accurate cable speedo (police cars for example) or very precise digital speedos without any accuracy (bike speedos usually read high). So which type of speedo is more accurate, the one that was calibrated better, the one that was designed better, the one that is maintained better.
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