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Discussion Starter · #1 ·
Before anyone jumps down my throat I really did search. I even spent some time on google, but I only found the answer if I had only +2. Right now I'm reading 21k and I want to know what I am actually at. Is there a formula somewhere or anything to help me? All I found was this website which gives only top speed and gear ratio, but not mileage help. http://www.gearingcommander.com/

Any help would be appreciated, thanks.
 

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just a suggestion. two other ways u can do this. find a known gap where u know it is for example, one mile. drive it see what your trip meter shows. or you can have a friend drive in a car or something with their trip meter and mark off an exact mile. then you drive the same distance and see what your trip meter would read. take your mileage and divide it by what your trip meter read after you drove that one mile. :) not as easy as finding an equation online, but it is accurate.
 

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Discussion Starter · #3 ·
I like your 1 mile idea. I could just hop on the hwy and count out 10 posts since they are supposed to be one mile.
 

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I'm guessing you'll have to do more then a mile to get an accurate number. I would suggest 10 or more.
 

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Actually I think ten miles would give you a 100 percent accurate number.
 

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GPS.

Stick it to your tank or in your tank bag or something.

Go 60mph on the GPS, see what your speedo says. Do the math to figure out the % that it's off.

Then use that % to figure your miles.

Then buy a speedo healer.
 

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GPS.

Stick it to your tank or in your tank bag or something.

Go 60mph on the GPS, see what your speedo says. Do the math to figure out the % that it's off.

Then use that % to figure your miles.

Then buy a speedo healer.
sunavabitch
we have a winner.:mfclap
Even some of todays smart phones can give your actual mph.
If you don't have either, pace yourself with someone's car. Cars can still be off but a lot more accurate than bikes. Then figure out your difference.
 

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also unless you know exact mileage when the modifcation of the sprockets was, your only gonna be guessing at the "true" odo reading. as far as speed, im + 5 on my rear sprocket on my 636 and doin 80 in 5th gear is actually 65. i would have to drive past a lot of those speed showing radars to actually learn how to compensate for my speed.
 

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Depending on what you ride but most motorcycles have the speedometer sender driven from the front wheel so changing your sprockets will not alter the reading. Motorcycle speedometers are not know for their accuracy. It's even thought that some manufacturers have their units read fast to help keep riders a little slower than they think they are going. The only way to to alter the speedometer with out changing the sender or head itself is to change the front tire size.

What will change though is the wear on the engine and chain componets. Changing the sprockets alters the rpm band the engine runs in. Lower gearing means the engine turns faster and in turn wears more. If it is enough to matter is anyones guess unless you really ride hard or alot of miles. If you are just wanting to know for service intervals then it is a simple math problem. Take your service interval (or odometer reading) and multiply it by the change in the gear ratio and you will have your new service windows. If you are really wanting to know how accurate your current speedometer is then the best way is the GPS.
 

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Depending on what you ride but most motorcycles have the speedometer sender driven from the front wheel so changing your sprockets will not alter the reading. Motorcycle speedometers are not know for their accuracy. It's even thought that some manufacturers have their units read fast to help keep riders a little slower than they think they are going. The only way to to alter the speedometer with out changing the sender or head itself is to change the front tire size.

What will change though is the wear on the engine and chain componets. Changing the sprockets alters the rpm band the engine runs in. Lower gearing means the engine turns faster and in turn wears more. If it is enough to matter is anyones guess unless you really ride hard or alot of miles. If you are just wanting to know for service intervals then it is a simple math problem. Take your service interval (or odometer reading) and multiply it by the change in the gear ratio and you will have your new service windows. If you are really wanting to know how accurate your current speedometer is then the best way is the GPS.
Mines not. If I remember correctly from when I did my sprockets, mine is connected to the dront sprocket.
 

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Keep in mind, the error is a PERCENTAGE. Not X mph.

I am so tired of people saying "but my speedo is only 5 mph off" and then getting confused as fuck when I ask them "at what speed".
 

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Well, assuming we are talking about an '03 ZX6R, your stock sprockets would be 15 and 40 teeth, with a final drive ratio of 2.67. Now, assuming that the -1 is your front sprocket and +2 on the rear, you have a final drive ratio of 3.00. This should provide 11.1% more torque and less speed. Multiply your displayed speed by .889 to get actual speed. So, if your speedo says 100 mph, you are at 88.9 mph. You can find a final drive calculator at sprocketcalculator.com. If it's your rear sprocket with the -1, then you would be off by + 16.1%, and you would multiply displayed speed by 1.162. 100 mph displayed would actually be 116.2 mph.
 

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Just count one front sprocket distance traveled in chain each rotation with both rear sprockets and measure it in meters of chain past over the front, that your percent difference in speed. Delta meters over delta shit.
 

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Discussion Starter · #16 ·
Keep in mind, the error is a PERCENTAGE. Not X mph.

I am so tired of people saying "but my speedo is only 5 mph off" and then getting confused as fuck when I ask them "at what speed".
It definitely reads in the back. So I passed a speed sensor they put on the road before construction sites and I was going my speedo said 84, but the sensor said 66mph. I'm not sure how to do the math though, because when I go faster it does not change at the same pace. If I go five mph faster for example then my speedo isn't just five faster. I would have to find out the ratio before I did anything I think?
 

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It definitely reads in the back. So I passed a speed sensor they put on the road before construction sites and I was going my speedo said 84, but the sensor said 66mph. I'm not sure how to do the math though, because when I go faster it does not change at the same pace. If I go five mph faster for example then my speedo isn't just five faster. I would have to find out the ratio before I did anything I think?
What?
 

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It definitely reads in the back. So I passed a speed sensor they put on the road before construction sites and I was going my speedo said 84, but the sensor said 66mph. I'm not sure how to do the math though, because when I go faster it does not change at the same pace. If I go five mph faster for example then my speedo isn't just five faster. I would have to find out the ratio before I did anything I think?
You need to look at a percentage, not the 5 mph or any mph. That's what squidge was saying.
You must have a big gear change. Your speedo is about 22% off.
If you're going 50mph according to your speedo, you're actually going 39mph, 22% off.
You can't say your speedo is off by 11 mph because at 84 mph, it's off 18mph or 22%.
if I'm wrong just kick me in the nuts. I tried.:tard
 

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Discussion Starter · #20 ·
^exactly, that's what I meant when I said I needed to figure out the ratio (percent) first. I just wanted to test out a couple more speeds and make sure the percent difference was the same at every speed, but I sure you are right and it is.
 
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