Harley Speedos
Seasoned HDF Member
Joined: Sep 2009
Posts: 17,148
Likes: 6,171
From: SE Michigan
It can be done with a power vision. There is some simple math involved (a ratio I believe). If you bought it from Fuel Moto you can call them. There was a post a few years ago with instructions, will update this post if I find it...
Update - here you go: https://www.hdforums.com/forum/ignit...ons-tuner.html
Update - here you go: https://www.hdforums.com/forum/ignit...ons-tuner.html
Last edited by Keithhu; Jan 15, 2020 at 07:52 AM.
Thread Starter
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Seasoned HDF Member
Joined: Dec 2019
Posts: 5,276
Likes: 4,055
From: central Fl
It can be done with a power vision. There is some simple math involved (a ratio I believe). If you bought it from Fuel Moto you can call them. There was a post a few years ago with instructions, will update this post if I find it...
Update - here you go: https://www.hdforums.com/forum/ignit...ons-tuner.html
Update - here you go: https://www.hdforums.com/forum/ignit...ons-tuner.html
Seasoned HDF Member
Joined: Sep 2009
Posts: 17,148
Likes: 6,171
From: SE Michigan
Grand HDF Member
Joined: Nov 2017
Posts: 4,252
Likes: 3,135
From: Texas
My Harley reads 5% fast.
My adventure bike read 10% fast.
My Benelli read 13% fast.
I haven't checked my SUV, but I wouldn't be surprised to find it reads faster than real too.
Road Master
Joined: Nov 2009
Posts: 1,229
Likes: 417
From: Outer Banks, NC
With brand new tires (OEM) you're going to be slightly slower than the speedo reads. As the tire wears the error will increase. If you have a baldy the error may be 4 or 5 MPH. (worn tires turn more times per mile) Non-stock tires, who knows.
On older bikes the speedo cable came off the front tire, like my old Suzuki. With my Ultra it comes off some speed sensor which may get it's info from the rear tire. Anybody here know on later bikes?
Last edited by glasspilot; Jan 15, 2020 at 01:26 PM.
Good answer. GPS units are about as close to dead on as you could want. (The guy that brought up steep climbs and descents, that makes sense.)
With brand new tires (OEM) you're going to be slightly slower than the speedo reads. As the tire wears the error will increase. If you have a baldy the error may be 4 or 5 MPH. (worn tires turn more times per mile) Non-stock tires, who knows.
On older bikes the speedo cable came off the front tire, like my old Suzuki. With my Ultra it comes off some speed sensor which may get it's info from the rear tire. Anybody here know on later bikes?
With brand new tires (OEM) you're going to be slightly slower than the speedo reads. As the tire wears the error will increase. If you have a baldy the error may be 4 or 5 MPH. (worn tires turn more times per mile) Non-stock tires, who knows.
On older bikes the speedo cable came off the front tire, like my old Suzuki. With my Ultra it comes off some speed sensor which may get it's info from the rear tire. Anybody here know on later bikes?
You have that backwards- New tire goes further per revolution making it faster. Wore out tire goes less distance and would be slower.
Thread Starter
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Seasoned HDF Member
Joined: Dec 2019
Posts: 5,276
Likes: 4,055
From: central Fl
ohh ok hahaha i know iam not full of **** i just took a great dump. picasso himself would have been proud of
Last edited by IBE; Jan 15, 2020 at 06:02 PM.
Road Master
Joined: Sep 2010
Posts: 1,138
Likes: 457
From: Littleton CO
My speedo was reading a bit fast until I zeroed it in with my Power Vision. It is dead nuts exact now!
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Joe Kucinski
Seasoned HDF Member
Joined: Jan 2015
Posts: 8,196
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From: San Francisco
I have been impressed by how accurate bike and car speedos are. On every bike and car I've been on or in the last fifteen years, the speed on the odo and the speed on the GPS were always within a mile per hour of each other. The only exception was a BMW K1200LT which the factory admitted after protests that they purposely set the speedo to read higher in an attempt to keep riders going slower and in their opinion safer. They got heavily criticized for that. I simply relied on the gps. The difference was about 10%.
Road Master
Joined: Nov 2009
Posts: 1,229
Likes: 417
From: Outer Banks, NC
The long and short of it is, the manufacturers usually build a machine to "keep us safe" from ourselves. On a new bike if your actual speed is say, 60, the speedometer will read slightly higher than that. As the tire wears it will turn more revolutions per mile and the speedo will read slightly higher MPH (in addition to the error when new) to keep you "safe".