Odometer/ speedo error - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 12 (permalink) Old 09-21-2013, 09:28 PM Thread Starter
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Odometer/ speedo error

So my SP1 has the 520 conversion with what I believe is 15/41 gearing. Anyone know what speedo, and odo error I am seeing?

The bike shows 20,800 miles.....but I'm wondering how wrong that is
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post #2 of 12 (permalink) Old 09-21-2013, 10:06 PM
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Hey BDG,
It's hard to say with the information you've given. All factory speedos are off by about 5% at least with to the stock 16/40.
When was the 15/41 mod done?
James

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post #3 of 12 (permalink) Old 09-21-2013, 11:35 PM
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I also changed to 15/41. I used the calculator on Speedo Healer's website which said -13.3%. Entered that into my SH, and now my speedo matches my GPS within +/-1 mph.

I still have the OEM rear tire size 190/50.
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post #4 of 12 (permalink) Old 09-22-2013, 11:50 PM
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Hey extrapoltor where did ya get your RC 51 shirt ?
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post #5 of 12 (permalink) Old 09-23-2013, 09:35 AM
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Hey extrapoltor where did ya get your RC 51 shirt ?
It's only a mock-up ... so far. The guys on this board are discussing getting a batch of shirts made, but can't seem to settle on a design. The discussion is in this thread, with the first shirt mockups started being posted in post #123: https://www.rc51forums.com/forums/sho...t=25945&page=4
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post #6 of 12 (permalink) Old 09-25-2013, 07:24 PM Thread Starter
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Originally Posted by extrapolator View Post
I also changed to 15/41. I used the calculator on Speedo Healer's website which said -13.3%. Entered that into my SH, and now my speedo matches my GPS within +/-1 mph.

I still have the OEM rear tire size 190/50.
DAMN, -13%????

so 130 is really 116, geez I might have to get a speedo healer
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post #7 of 12 (permalink) Old 09-26-2013, 08:22 AM
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Originally Posted by TheBeeDeeGee View Post
DAMN, -13%????

so 130 is really 116, geez I might have to get a speedo healer
You should. When my speedo is GPS checked, I am 7% off and that is with stock gearing and tires.
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post #8 of 12 (permalink) Old 09-26-2013, 09:34 AM
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Originally Posted by TheBeeDeeGee View Post
DAMN, -13%????

so 130 is really 116, geez I might have to get a speedo healer
OK, you started making me second-guess my figure ... I was going from recent memory (which is still questionable for me). But this confirms it ... and as I said -13.3% results in my speedometer reading +/-1 mph of my GPS.

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post #9 of 12 (permalink) Old 09-26-2013, 10:11 AM
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Those values change if you're running a 190/55.
I'm only running a -11% with 15/42 and the taller rear tire.

John, 2000 RC51 #000100

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post #10 of 12 (permalink) Old 09-26-2013, 05:12 PM
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The speedo error is non-linear. With stock gearing it is about 7-8% optimistic at freeway speeds, but riding around at an indicated 35mph on surface streets it is almost dead on accurate. As your speed grows so does the amount of error so by the time you are at an indicated 130mph the % of error can easily be 13-14%

If you have lowered the gearing with a 15/41 kit expect that 7-8% error at freeway speeds to jump to about 12-13% depending on your rear tire size.

What is really interesting though is even with the optimistic error built into the speedo for stock gearing the odometer is still accurate so they did it on purpose when they engineered the bike.
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