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Discussion Starter · #1 ·
I'd been questioning the accuracy of my speedometer since I bought my bike. My daily commute, which is typically 70-75mph in rush hour traffic, became 80mph+ when I'm on my bike.

So last night I was riding alongside a Honda with a digital dash and could very easily read it's speed. Sure enough, as her dash showed 42mph, mine showed 45mph. I watched this for a good mile or so, around that speed and I can confirm that my reading is 3-4mph faster than a Honda with stock wheels.

I did switch to the 14t front sprocket, but the remainder of the drivetrain is stock. I didn't think that sprocket would have changed the mph reading.... would it?

I'm going to try to check this again soon... but I wanted to see if anyone else had thoughts regarding it.
 

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I was told by the dealer to expect my speedo to read about 8% higher than actual speed. Doing some quick math, if the Honda was accurate at 42, then adding 8% makes your speed roughly 45. For 75 mpg, 8% optimistic would make your rolling speed roughly 81 mph on the speedo.

This is consistent with what I have seen too on my Monster since I got it just over 3 weeks ago. I know there are speedo-healers, but i haven't worried about it yet really :)
 

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I became concerned about the accuracy of my speedometer shortly after the purchase. Using a traffic laser speed measurement device I tested the speedometer at speeds in 10 mph increments from 30 mph to 70 mph. I found the speedometer to read consistently higher by about 8%. I decided to check the owners manual (when all else fails) and discovered "the dashboard receives actual speed value from the control unit and displays the value increased by 8%". So I guess that means my speedometer is accurate according to Ducati.
 

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Discussion Starter · #4 ·
"the dashboard receives actual speed value from the control unit and displays the value increased by 8%
Huh? It actually says that in the manual? I wonder what that really means, and why?

Okay... so I get it that our speedos seem to read 8% high, though it seems odd that I hadn't even heard about this until today. Here's the punch line... since our speedos are too high, does anyone have a suggestion on how to lower them? :eek:
 

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Discussion Starter · #5 ·
Google really is a miraculous thing. I found the answer myself via someone elses older post. Thanks though for everyones input!

European Union Directive 2000/7/EC set the requirements for speedometer accuracy.

There are two main requirements when tested:
1. That indicated speed is never below actual speed.
2. That indicated speed is never above 110%+4 km/h of actual speed.

For actual production motorcycles and motor tricycles, the upper limit increases to 110%+8 km/h (but remains 110%+4 km/h for mopeds).

So for a production motorcycle rolling at an actual 80 MPH, the indicated speed can't be below 80 MPH, and can't be above 92.97 MPH.

As this upper limit is 16.2% higher than actual, a built-in 8% error puts the Ducati motorcycle firmly in the middle of the legal range at highway speeds.
 

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Just FYI... At least for Japanese bikes, this is nothing new (the speedo reading higher than actual speed). My Ninja 650R read about 10% higher than actual speed, yet the odometer was spot on accurate... The solution was to install a "Speedo-healer" inline with the ECU to remove this artificial speed increase.

As far as ways to resolve it... this is the company I am aware of, but I assume there are more :)

http://www.healtech-electronics.com/

{edit - nice info, thanks rancyc!!}
 

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Google really is a miraculous thing. I found the answer myself via someone elses older post. Thanks though for everyones input!

European Union Directive 2000/7/EC set the requirements for speedometer accuracy.

There are two main requirements when tested:
1. That indicated speed is never below actual speed.
2. That indicated speed is never above 110%+4 km/h of actual speed.

For actual production motorcycles and motor tricycles, the upper limit increases to 110%+8 km/h (but remains 110%+4 km/h for mopeds).

So for a production motorcycle rolling at an actual 80 MPH, the indicated speed can't be below 80 MPH, and can't be above 92.97 MPH.

As this upper limit is 16.2% higher than actual, a built-in 8% error puts the Ducati motorcycle firmly in the middle of the legal range at highway speeds.
Good to see my efforts aren't wasted. :)

An easy rule-of-thumb for on-the-fly calculation of approximate actual speed is to subtract 2 MPH for every 25 MPH indicated.
 
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