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Hey Guys,
I'm getting a speedo healer soon but I'm trying to figure out what my actual speed is. Today I got -1 +2 sprockets.
From the factory my bike was off 9%. According to gearing commander switching from stock to -1 +2 is a 10% inaccuracy. Is it as simple as adding the two %s together and thats my total inaccuracy?
Meaning if my speedo reads 60 in reality it'd be 19% high meaning i'm actually going 48.6? Thanks.
 

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not sure what version speedohealer your getting but im running the v4. the best way to get your precise speed would be gps if ya have one. im also running the -1,+2 gearing on my K7 750. Healtech has a online calculator on their site and according to their estimated online calculator with the gearing im running i should run -9.9% without compensation for factory speedometer error and -14.6% with error. i run the -9.9%. i was told by a mechanic that the factory speedometers are not really off by much unless your close to topping out, and the factory speedometers are usually pretty dead on till you hit a lil past 100 mph. dont hold me to it but that is what i was told. i at first ran the -14.6 but looking at the speedometer while it was reading 65 mph, i know i was going a lot faster than 65. when i switched it to -9.9 it seemed like it was where it should be. like i said running with a gps is the best way to get the most precise reading.
 

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You didn't say what year and model your bike is, but let's say your stock gearing is 17F 43R (04/05 750). The math would go something like this for a -1/+2 combination:

You multiply the ratios: new speed = original speed x new front teeth/old front teeth X old rear teeth/new rear teeth.

For an original speed of 60 mph, 60 x 16/17 x 43/45 = 60 x .94 x .96 = 60 x .90 = 54 mph. Meaning, if your speedometer reads 60 mph, you are going 54 mph with the gearing change.

If you were ALREADY reading, say, 5% high before the gearing change, you can factor that in as well by multiplication: .95 x .90 = .86 or 16% total error. If it were reading 5% low, instead of 5% high, it would be offsetting = 1.05 x .90 = .95 or 5% total error.
 
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