[MMRanch]

I've had a lot of bikes and have never seen one that didn't have a speedometer that was not a little bit optimistic .   
So
I got my GPS stuck on my Meteor and off I went for a ride.

The Meteor speedometer needed to get up to 53mph for the GPS to read 50mph.
Well
Knowing that "speedometer error" is a linear equation , its easy to see we are dealing with a 6% error.

How to fix it is next ?

The sure way is to use a 6% larger dia. tire on the wheel that has the speedometer pick-up.   
well
That's where the problem comes from :  Both wheels have Speedometer pick-up ! ? !! 

Some bikes have the speedometer pick-up in the transmission , is the Meteor one of them ?   
If so then a simple change of sprockets fixes it ?
 What do you feller think ? 

[Dexter]

I doubt you would find a bike from any manufacturer, unless it is a police model, that didn't have a slightly optimistic speedometer, but it will be highly unlikely you find one that reads too low either. They make 'em that way. My Honda has about a 7% error. That's not something I figured out for myself, but is the consensus from others that monitor things such as this on a ST forum.

Look upon it as a bit of insurance against exceeding a speed limit when you are indicated as already 5 - 10 mph over the limit. I wouldn't worry about it at all.

[michiel]

A certain advance of the speedometer is intentional.

[andif62]

Knowing that "speedometer error" is a linear equation , its easy to see we are dealing with a 6% error.

Don‘t think that it is as simple.
The speedo of my wife‘s new Classic 350 shows 50 km/h when GPS shows only 42 but the difference is getting smaller at 90 km/h displayed (GPS 85 in/h).
So there is no linearity at least with her bike

[SteveThackery]

Knowing that "speedometer error" is a linear equation , its easy to see we are dealing with a 6% error.

How to fix it is next ?

The sure way is to use a 6% larger dia. tire on the wheel that has the speedometer pick-up.   
well
That's where the problem comes from :  Both wheels have Speedometer pick-up ! ? !! 

Some bikes have the speedometer pick-up in the transmission , is the Meteor one of them ?   
If so then a simple change of sprockets fixes it ?
 What do you feller think ?

Your knowledge is a bit out of date.  Even the old spinning magnet speedos had two error sources - a fixed offset and a scaling error.  The first is constant (needle set wrong on the shaft) and is added to the second (magnet too strong or weak), which is linear. That means a 5% error at one speed does not mean a 5% error at all speeds.

But none of that applies to the Meteor.  The speedo is driven electronically by signals from the ABS wheel speed sensors.  These are fed into a microcontroller which then generates the appropriate drive signals for the stepper motor which drives the needle round.  Thus the software in the microcontroller is responsible for how much error is displayed on the speedo.  Also, there is no reason to assume it's linear; it probably is, but not definitely - they can do what they like in software.

You could fool the system by fitting larger diameter wheels / tyres, but you would have to do the same to both wheels.  Otherwise the ABS system will flag an error due to the two wheels reading different speeds.

Nothing is impossible, but I think correcting the speedo error will be much more difficult than you imagine.

[MMRanch]

Thanks Steve , Your probably right (to much truble) . 
I didn't see your reply before posting the above post and now I can't modify it for some odd reason ? 
So what does the stepper motor pull against , ya think ?

[MMRanch]

I had to look up what a Stepper Motor is .

My electronic education was in 1978 and didn't include such things .  Then I spent 33 years in a totally un-related field.   

I like to learn something new everyday and today it was "Stepper Motors" .   
So THANKS for the tip !!

Yes , the bridge picture is less that 3 years old.   I still look the same

[tooseevee]

The sure way is to use a 6% larger dia. tire on the wheel that has the speedometer pick-up.   
well
That's where the problem comes from :  Both wheels have Speedometer pick-up ! ? !! 

 What do you feller think ?

            I know this dead speedo horse has already been well beaten, but I don't believe your math proves out. I don't believe a 6% increase in tire circumference will yield a 6% correction at the speedometer. It just doesn't sound that simple.

            A question for those on the forums here who may be computer-controlled motorcycle wizards: Why isn't there a way to calibrate these electronic speedometers (in conjunction with GPS) using a laptop?* You should be able to hit a compromise where the speedo is more accurate at each 10MPH increments than it is from the factory? I'm sure the Feds would have a hemorrhage.

            * I have NO idea how this could be done on the road  Maybe a smartphone app? I'm sure it would be immediately illegal.

[MMRanch]

tooseevee

I'm new to the forum and didn't know "That horse had already been called up". 

Gearing has always been and can't be nothing but % and linear.  Its pure physics .   Math don't change.   If you double the RPM of the input shaft then you double the RPM of the output shaft , its really that simple.   Unless there is a "Torque-Converter" in the drive line.

Computer controlled can change the read-out according to the program .   In the old BASIC Computer programming we used a command called  "Let".
So :  Let X=X+(X*V) .  It's a way to run the Variable "X" to be a Hyperbolic Curve. 
I know now we just assure the prompts in someone else's program , and that's OK.

My 1999 Astro van is almost 10% off , so it ain't nothing new.

I'll just learn to live with the Speedometer error.      We're dealing with someone else's program , It's just how it is ! 

[tooseevee]

tooseevee

I'm new to the forum and didn't know "That horse had already been called up". 

Gearing has always been and can't be nothing but % and linear.  Its pure physics .   Math don't change.   If you double the RPM of the input shaft then you double the RPM of the output shaft , its really that simple.   Unless there is a "Torque-Converter" in the drive line.

Computer controlled can change the read-out according to the program .   In the old BASIC Computer programming we used a command called  "Let".
So :  Let X=X+(X*V) .  It's a way to run the Variable "X" to be a Hyperbolic Curve. 
I know now we just assure the prompts in someone else's program , and that's OK.

My 1999 Astro van is almost 10% off , so it ain't nothing new.

I'll just learn to live with the Speedometer error.      We're dealing with someone else's program , It's just how it is ! 

          I was only commenting on this thread & all I meant was we all know we just have to deal with speedometer error. It wasn't personal to you as a new guy.

          And all I asked was "would it be possible to have, say, an app to calibrate, in real time, a speedometer, on the bike". Not mine, you understand, just anybody. I don't HAVE any apps or a smart phone & don't want one & don't Care. I'm just asking.

[MMRanch]

 

Yea , Dexter had it right - I'll just learn to live with it.

Hay , on the subject of tire size ?
I've got a 130/90-17 on my Guzzi V7II , that looks wider than the 140/70-17 on the Enfield ??   Its a Shinko 712 and it only lasted 8K-miles , so I'm replacing it with a Dunlop 404 in 130/90-17.  The Dunlop looks taller than the same size in Shinko ?? 
It will be next spring before I'm looking for a rear tire for the Meteor but has anybody tried a different tire size on the forum here ?

[michiel]

Fail

[MMRanch]

Fail ?

[michiel]

I made a mistake and did not know how to delete the post.

[MMRanch]

Same thing happened to me a few days ago.   My VPN changed my IP address and I lost control of editing/deleting my post.   

Thank you Moderator for helping out !