Speedometer Accuracy - Wowee Zowie!

[webbmeister25d]

So, I've been riding Nimrod a lot - much time in parking lot drills and more and more time in neighborhood streets and, lately, the highway! The main road out to the highway is 30 MPH, then 40 MPH, and then 50 and 55 depending on where one travels. It has always felt like the speedometer wasn't keeping up with the actual acceleration of the bike, so I got a speedometer app that keeps a record of the top speed reached. On a nice clear traffic-free stretch, I got the bike up to what the speedometer registered as somewhere between 45 - 50. The GPS-powered speedometer application registered 59! That, of course, means that the bike's speedometer is "off" by as much as 14mph at 59 mph (over 20%!) I am so glad I checked this out before zipping past a patrol car!

Has anyone else experienced this degree of inaccuracy? Have you noticed that the difference is parallel from some point in the range of speeds, or, if the faster you go the greater the inaccuracy becomes? Does this have something to do with the 16T sprocket?

:??:

Jim

[blaine]

It wouldn't have anything to do with the 16t sprocket as the speedo is run off the front wheel.If the front tire is a different size than the original,that would effect the speedo.
:cool:

[Water Warrior 2]

The sprocket will not make a difference, the speedo is driven off the front wheel. The speedo is very unusual on your bike. Normally they read 7 or 8% higher than the actual speed. Your reads totally different than would be expected. Did you, have you tried for an actual distance confirmation to check out the odometer function? They are usually quite acurate.

[webbmeister25d]

The front wheel and tire are original. I will do a distance check tomorrow afternoon. Thanks for getting back!

Jim

[Water Warrior 2]

You might want to determine if you have the correct speedo on your bike. If the bike is new you have a warranty issue. If the bike was used then some one may put a different speedo on the bike.

[webbmeister25d]

It's the right speedo - and it is raining tonight. Will try odometer check tomorrow.

[webbmeister25d]

Not a thing wrong with the speedo. I now understand that it is the line BEFORE the number that represents the 10 MPH increment. I also mistook the "40" mark for "50" last time out. Tonight, At 50 MPH on the speedo the GPS registered 52 MPH. That seems reasonably within the margin of error.

Gee, I wonder if there might be something more I can do to broadcast my novice status!

This brings up the question of windshields. I'll start a new thread and leave this embarrassing episode to the archives.

[Water Warrior 2]

It is not broken and you do not have to fix it. What could be better??

[IndyGoat]

I always wondered why cars were going so slow, until I took my GPS out and did a speedo check. I have a handlebar mount for my GPS, for when I Geocache. My speedo was consistently 5mph below actual.

[Water Warrior 2]

Originally Posted by IndyGoat

I always wondered why cars were going so slow, until I took my GPS out and did a speedo check. I have a handlebar mount for my GPS, for when I Geocache. My speedo was consistently 5mph below actual.

That is unuasual. Normally a speedo will show a higher speed than actual speed.