Anyone good at math and has used a Speedohealer???

[blackkat98]

I took my bike out today with handheld GPS on-board. The speedometer was showing 60mph. I was actually going 55mph according to the GPS unit. At 65mph indicated, I was actually going 60mph, etc. etc. So, my speedometer is 5mph fast from the factory. I calculate this to be approximately +8.33%. This is with my stock gearing...15T sprocket in front and 45T in back. I am changing to 14T in the front and staying 45T in the back. The online calculator at www.speedohealer.com is confusing me. They have a setting to optimize for the closest speedometer and odometer readings. The speedometer will end up being approximately +2.5% fast and the odometer will be approximately -2.5% slow? Does this sound right? I want the speedometer to be as accurate as possible but in doing so, I DO NOT want my odometer to read more miles than actual. I can optimize the settings for the speedometer to be 100% accurate, but the odometer would register slightly less than actual miles.
Or, I can optimize for 100% accurate odometer and the speedometer would show more than actual. I'm lost. Can someone show me the way?

[Kat-A-Tonic]

I have a Speedohealer and for the record it's my understanding that you cannot have both the speedometer and odometer reading accurately. You can get reasonably close for both but they will still not be 100% dead on. The reason is for this is that the speedometer was designed to over report while the odometer was designed to be accurate. Since the odometer readings are based off the speedometer, you'll have a discrepency. So, you'll have to decide what is more important for you. For me, I wanted to have correct speeds showning on my speedometer.

To be clear, your odometer will not read more miles than provided the speedometer is over reporting when you compensate for this using the Speedohealer. In your case, the speedometer is over reporting by +8.3% so when you recalibrate to compensate, you odometer will report less miles than actually travelled. You'll have to factor odometer under reporting this into your maintenance schedule and trip mileage. Personally, I wouldn't fret about your odometer under reporting unless you are prone to performing maintenance only when you odometer tells you its time.