Garmin GPS vs KZ Speedometer

I think that you may find that most bikes read just under 10% fast speed wise and correct distance wise.
My two sons and I were out for a ride a couple of weeks ago and found that all the bikes were right around the 10% error number. The bikes were a 2004 Suzuki Burgman 650, 2004 Trimuph Speed 4 and a 2008 Kawasaki Versys. The GPS was a Garmin 2610.

I have a handheld Garmin Vista that I've mounted to my Yamaha FZ1. The Garmin is EXTREAMLY accurate as far as speed and distance are concerned. My FZ1's Speedo is somewhat high.

At 120 indicated, the Garmin showed a top speed of 116... bummer. I don't think my KZ would hit that speed

OH - And it was on a CLOSED ROAD with a professional driver. :woohoo:

I'd bet on the accuracy of a simple gear mechanism (speedometer) before I would believe the GPS.

There are a number of issues that can affect speedo accuracy - tire pressure, tire size, tire wear all have an effect. The speedo itself is a somewhat arbitrary instrument - a magnet spinning in side an aluminum cup! So, I am not surprised at the error (my 650 also reads 70 at 65). On the other hand, GPS units are very accurate when measuring speed and distance. Any error they have is in position, so it does not affect the speed/distance calculations.

It is worth bearing in mind that the tach on most of our bikes works the same way (a spinning cable) - and "may" be just as inaccurate:S

Sorry, BeeSting, but in this case the tech wins.

Back when these bikes were new Cycle World included speedometer error as part of the test and reading 10% high was generally the norm for all Japanese models as I recall. Over the years wear and tear won't improve the accuracy nor will the modern close-but-not-quite-right-size tires.

Incidentally, I drive a 2002 Dodge Ram for a company truck and noted recently that while the GPS and the speedometer matched a few years ago that it has now drifted off, if only slightly, by now reading about 1 MPH high on the speedo.

This is also why the Japanese attacked Pearl Harbor BEFORE they declared war. They'll never get it right!:woohoo: :ohmy:

I'm going to print this thread out and carry it around with me in case I ever get pulled over.

How much are the GPS units and do you have to pay extra cause it uses satellites?

I gave $400 for my Garmin c330, they usually run about (car models) $250 and up. Once you own it the big eye in the sky is free. There is NO charge what so ever! These things are friggin cool..

I paid $250 for my Garmin Nuvi 250W which I love - I have rigged it so that I can use it on the bike with the GPS in the clear map-pocket of my tank bag. The vibration resistant devices are expensive (close to $1,000) but you can get a cheap eTrex for about $100 - it won't give you maps but they work great as a backup speedometer!