Navigation » Speed: GPS vs Speedometer

While out today riding, I noticed that my speedometer was a bit more optimistic about my speed than the GPS. The GPS would be at 130kph and the Speedometer would be at ~135kph. Anyone else notice this variation?

I find it funny/amusing/slightly annoying when folk go on about the bikes speedo telling lies. Wessie is correct. It is done for a reason and an under-reading speedo is legislated against.

I've owned nearly 40 bikes at the last count and cars? Why bother counting those? They have all done it, some worse some not so.

Peter

I believe the specification for sppedo accuracy is Over read by 10% Under read by -0%

Well, the replies are informative. The RS is the first bike that I have had a GPS with. Before I was old school with the map on the tank bag, so I never knew that the speedometer was calibrated that way.

Zitat von Grumpy Goat im Beitrag #3

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Zitat von Hydrashok158 im Beitrag #1

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While out today riding, I noticed that my speedometer was a bit more optimistic about my speed than the GPS. The GPS would be at 130kph and the Speedometer would be at ~135kph. Anyone else notice this variation?

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Yes, the speedometer on these bikes lie pretty consistently. So much so that I don't even look at the speedometer any more and look solely at the Nav VI for my speed.

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Zitat von Hydrashok158 im Beitrag #6

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The RS is the first bike that I have had a GPS with. Before I was old school with the map on the tank bag, so I never knew that the speedometer was calibrated that way.

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My 1999 Saturn station wagon, my 2002 Yamaha FZ1 and my 2018 Zero all have speedometers that read within one mph of the correct speed. However, my 2005 Triumph Bonneville, 2011 Royal Enfield, 2009 BMW F650GS and 2016 BMW RS all indicate about 5-8% below the actual speed. My take from this is that the accuracy of your speedometer is directly related to in what part of the world your vehicle is manufactured.

In theory, using your speedo to control speed ( versus limits) keeps you safe due to the optimistic readings, the problem comes as we all know the speedo is over optimistic and we start adding our own tolerances. For that reason I like the GPS for being accurate and knowing it’s an absolute measure of speed.

A GPS uses information from sampled points over time. So the distance taken between those sampled points is assumed to be a straight line. So even GPS speed isn't exact but is an approximation.

Zitat von wessie im Beitrag #12

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Zitat von Richard230 im Beitrag #9

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My 1999 Saturn station wagon, my 2002 Yamaha FZ1 and my 2018 Zero all have speedometers that read within one mph of the correct speed. However, my 2005 Triumph Bonneville, 2011 Royal Enfield, 2009 BMW F650GS and 2016 BMW RS all indicate about 5-8% below the actual speed. My take from this is that the accuracy of your speedometer is directly related to in what part of the world your vehicle is manufactured.

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the European speedos read under the actual speed? Sure?

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All of the bikes I have owned (93' Honda Shadow, '13 Kawasaki Vulcan, '15 F800GT, '17 R nineT, '17 R1200RS, and '19 F850GS Adventure (what is it with me and odd-numbered year bikes ) had/have speedometers that read 5 - 10% faster than actual speed, as measured by radar speed signs and/or GPS. I've noticed that the radar speed signs and GPS are usually identical measurements, with the GPS infrequently off by 1 MPH greater. Except for school zones and certain nearby municipalities (Marana, Oro Valley, and Patagonia, AZ) that rely on traffic fines for revenue to offset operating expenses, most of the areas I ride in southern Arizona are ok if within 10 MPH of the posted limit. I don't make a habit of pushing that when passing a traffic cop with the radar gun surveying the area.