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Discussion Starter #1
For illustration, if you speedometer were off about 10% (very common) you would be traveling at an indicated speed of 100 mph and actually be doing an actual 90 mph. The error caused by the altered gearing would be another 7% so that now you would be doing 84 mph at an indicated 100 mph.
 

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That makes sense in theory, but if it is a 17% error "now" I would be doing an actual 24.9 when the spedo read 30... As I stated earlier, the difference between the spedo and the info on the "actual speed calculator" was a very close comparison.. (and with a needle on the speedo, I couldn't realize a difference....
 

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O.k.. I've tried to read all that I can, but I am still confused... I bought my '00 ZX6R used, with the guy already doing a sproket change to 15/43. The Speedo cable feeds into the front case cover. I thought that I would be getting the wrong speeds on my spedo, but when I wrote down all of the "actual speeds" from the calculator, all of them (atleast in 1st/2nd/3rd/4th, from 4000-6000 RPMs) were basiclly reading the same on the spedo...

Is this correct? or should I just give and die???
 

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I'm running 14/40. My speedo/odo are just about 10% off, based on mileage comparisons with other bikes and roadside radar readings.
 

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Discussion Starter #6
Lots of thing affect speedometer reading including tire diameter. Tires from differenct manufacturers have different diameters even though they are marked the same size. If you are concerned about accurate speedometer reading get a "Yellow Box" or a Sigma bike computer. You can get a Sigma for about $25.
 

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thanks... the sigma???? A bike computer on a motorcycle??? I have a computer on my Cannondale... Hmmm.... Have people done this?? How do they end up setting the correct wheel diameters??
 

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O.K.. thanks... just did a google search on the sigma, and am seeing that a lot of people Are doing it... I am going to give it a try!
 

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sw.. a wheel setting of 1120? I measured my tire yesterday and got 71.5 in. which calculated to a 1127.7 for the MPH.. Which one would be a "better" reading to go with? 1127 or 1128? Does it matter?
 

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Discussion Starter #11
It depends on how you got the measurement. Calculating the circumferance is not very accurate. If you got it by rolling the wheel it should be very close. I usually get mine by rolling the bike with my weight on it after the tires are warm, about ten revolutions and then average. The difference between 1127 and 1128 would amount to about 1/10 mph at 100 mph.
 

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wait... 1/10 @ 100 mph? Correct me if I'm totally wrong, but that is like saying 10 miles @ 100mph.. isn't this close to the speedo inaccuracy? Sw... How would you round the .7? Up or down?
 

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oh.. k.. I was wrong.. I was thinking 10% when it should have been 1%.. Thanks SW.. you the man!!

Hey SW.. you wouldn't by chance have a pic of where/how you mounted the magnet would u?
 

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Discussion Starter #15
Mount the pick-up first with just a cable tie on the fork leg. When you have found a good spot take the magnet out of the holder. All you need is just the little bar magnet. Find a spot on the brake disk where it will set parallel to the pick-up and epoxy it in place using 5 minute epoxy that comes in the little two chamber syringe. After it has set up take some silicone and apply it to the back of the pickup and stick it in place on the fork tube using the cable ties to hold it. Turn it until it will hit the magnet and the place a piece of paper folded in two between the magnet and the pick-up. Turn the wheel so that the pick-up is pushed out of the way. This will give you the clearance you need between the pick-up and the magnet.
 

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K...I think I got it.. I have that exact epoxy that you are talking about.. When I get home today, it is going on!! I was going to tie strap the magnet (in its holder) but I will think more about glueing it..
 
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