Speedo error
Outstanding HDF Member
Joined: Apr 2008
Posts: 3,140
Likes: 17
From: Wisconsin
HEY! Maybe your GPS is wrong! 
Pretty much all speedos are off on the "high side", saying you are going faster than you are. In order to be perfectly accurate would incur more cost, so they allow them to "err". The key is, thay have to "err" on the "high side", there is actually some government regulation about that. They are not allowed to say you are going slower than you really are. I know of no tolerance range mandated and have seen some pretty far off. Radar guns have a tolerance error also which is why most times you are allowed 10 over the speed limit, that allows for calibration errors with the gun and the speedo. That's my story and I'm sticking to it.
Pretty much all speedos are off on the "high side", saying you are going faster than you are. In order to be perfectly accurate would incur more cost, so they allow them to "err". The key is, thay have to "err" on the "high side", there is actually some government regulation about that. They are not allowed to say you are going slower than you really are. I know of no tolerance range mandated and have seen some pretty far off. Radar guns have a tolerance error also which is why most times you are allowed 10 over the speed limit, that allows for calibration errors with the gun and the speedo. That's my story and I'm sticking to it.
Road Captain
Joined: May 2011
Posts: 710
Likes: 7
From: Colorado
Mine has been off since new as well. I'm not sure the error is linear though. It seems to be off by 2-3 mph whether I'm riding slow or fast.
My cars are dead on accurate. I don't see why motorcycles seem to be off.
My cars are dead on accurate. I don't see why motorcycles seem to be off.
Advanced
Joined: May 2012
Posts: 65
Likes: 0
From: Colorado Springs, CO
The crappy thing about it is that you end up showing more miles on the speedo than you actually have driven. You're riding at 75 MPH's but your speedo says you're doing 80 MPH's. Granted that only off 5 miles after an hour of ridding, but that 5 miles really adds up after a couple of years............
Seasoned HDF Member
Joined: Oct 2006
Posts: 5,977
Likes: 85
From: Nevada
The 3 HDs I've owned have all been about 3% off. Assuming that the accuracy of your GPS is correct I'd suggest your bikes gearing has been changed or you have a much smaller than stock rear tire.
I thought that might be the case too with them being that far out, BUT I used the GPS out of the truck, and then ran them again with the GPS out of the car. Same results.
Rice sucks! I think they set them that way so you think you are getting GREAT gas mileage!
Rice sucks! I think they set them that way so you think you are getting GREAT gas mileage!
Seasoned HDF Member
Joined: Sep 2009
Posts: 17,145
Likes: 6,168
From: SE Michigan
Outstanding HDF Member
Joined: Jul 2007
Posts: 2,241
Likes: 7
From: Daytona, Fla.
[QUOTE=frog13;10266095]HEY! Maybe your GPS is wrong!
/QUOTE]
Think about that.......... If a GPS is wrong, it doesn't work! If it doesn't know how fast you're traveling it doesn't know where you are. If it doesn't know where you are you miss your turn. It doesn't work.............
/QUOTE]
Think about that.......... If a GPS is wrong, it doesn't work! If it doesn't know how fast you're traveling it doesn't know where you are. If it doesn't know where you are you miss your turn. It doesn't work.............
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Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
We covered this in here recently. Most manufacturers work on speedo accuracy of 0 + 5% and in some countries it is legally mandated. Your choice of tyre brand will have a small affect on speedo accuracy, as will worn tyres compared with new ones. So your speedo is never going to be as accurate as an external device like gps.
Outstanding HDF Member
Joined: Apr 2008
Posts: 3,140
Likes: 17
From: Wisconsin
[quote=Jinks;10268148]
You guys remind me of Sheldon on the show "Big Bang Theory", I guess we need to put <sarcasm> or <humor> after our comments .......ummmm, I know how GPS works.
You guys remind me of Sheldon on the show "Big Bang Theory", I guess we need to put <sarcasm> or <humor> after our comments .......ummmm, I know how GPS works.
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