V85 Speedometer inaccuracy

[Huzo]

How has the speedometer accuracy been on the V85 for you guys ?
Mine is about 6 kph out at 100 k and divergent from there on.
I know the model I have has different profile tyres than the basic one, can the speedo be recalibrated by the owner ?
There is a procedure to recalibrate to appease the TC, so I’m asking if the speedo can be brought back into line.

[Knuckle Dragger]

Waaal... at least you've a higher probability of keeping your licence, looking on the bright side.  Vic's Wallopers are - as you well know - utterly intolerant of speedsters, & NSW's equivalent little better.

[Cam3512]

Like every other Guzzi I've ever had, it indicates 3-4 mph faster than actual speed on GPS.  Stock tires.

[Moto Vita]

How has the speedometer accuracy been on the V85 for you guys ?
Mine is about 6 kph out at 110 k and divergent from there on.
I know the model I have has different profile tyres than the basic one, can the speedo be recalibrated by the owner ?
There is a procedure to recalibrate to appease the TC, so I’m asking if the speedo can be brought back into line.

 What model and tire sizes do you have?

[beetle]

No

[MMRanch]

 Huzo

My V-7II was the same way with the 130/80-17 tire that came on it.   The 130/90-17 that replaced it agrees with my Garmin GPS .   Now 60 mph on the Garmin looks like 60.5 on the speedometer.   

So how TALL of a tire can you put on your new bike ?   

[Huzo]

Thanks all.
Where does the speedo get it’s information ?

[beetle]

Typically, the signal from the front & rear wheel sensors goes to the ABS control unit, when then sends the speed signal to the ECU. The ECU crunches it and sends the data to the instrument cluster.

The V85 has a CAN bus connection direct to instrument panel from the ABS unit, so it's possible the instrument panel does its own crunching.

[Mr Revhead]

ALL modern vehicles read slightly fast. It's the way of the world now, read a couple of Ks slower and you will never be liable for legal action if people clock up fines, or crash doing 3k over the limit when the speedo said bang on the limit because we all know how dangerous those 3kmh are! 

[stubbie]

Speedo is usually set 5k faster than you are actually going. It stops the manufacturer from getting their ass sued

[elvisboy77]

How has the speedometer accuracy been on the V85 for you guys ?
Mine is about 6 kph out at 110 k and divergent from there on.
I know the model I have has different profile tyres than the basic one, can the speedo be recalibrated by the owner ?
There is a procedure to recalibrate to appease the TC, so I’m asking if the speedo can be brought back into line.

I think 5 percent accuracy is pretty good when you consider all of the variables in a speedo like that one.  I gave up worriying on speedo accuracy a long time ago. 

[Ncdan]

I have a GPS odometer that I have checked my motorcycle speedometers with and they all have been around 3-4 mph faster than the actual speed. The exception is my 83 honda cb1000c which has a mechanical odometer and it’s mostly spot on. I agree that the discrepancy is intended from the manufacture.

[Huzo]

ALL modern vehicles read slightly fast. It's the way of the world now, read a couple of Ks slower and you will never be liable for legal action if people clock up fines, or crash doing 3k over the limit when the speedo said bang on the limit

I think you meant that the other way ‘round.

[Huzo]

What I’m pondering is..
The sensor that reads wheel rpm gets its data from the tone wheel providing pulse signals up the wire.
The ABS and TC cleverly do their work by comparing differing front/rear wheel rpm.
If I made two more tone wheels with a 6% different number of slots than the standard ones and fitted them front and rear, the ABS and TC would be happy because the wheel rpm’s would be correct compared to each other, but the speedometer would be getting 6% less pulses at a true 100 kph than is currently the case.
Instead of the tone wheel thinking it was at 106 k’s, it’d think 100 k’s.

[Huzo]

I think 5 percent accuracy is pretty good when you consider all of the variables in a speedo like that one.  I gave up worriying on speedo accuracy a long time ago.

Not in bloody Australia you wouldn’t..
Speed cameras get you for 3 k over @ $200 a pop.

[Moparnut72]

My Audace speedometer is fairly accurate. According to my GPS it reads just over a  mph high. It is the same across the range. My former Harley read the same across the range also, but ia little over 3 mph high.
kk

[Huzo]

What model and tire sizes do you have?

Rosso Vulcano.
Not sure of the profile but will check.
Trouble is, a lower profile will only make things worse..A given wheel rpm will only propel you slower, so the discrepancy will be greater.

[Huzo]

My Audace speedometer is fairly accurate. According to my GPS it reads just over a  mph high. It is the same across the range. My former Harley read the same across the range also, but ia little over 3 mph high.
kk

So is it 3 mph out @ 6 mph ?

[jacksonracingcomau]

What I’m pondering is..
The sensor that reads wheel rpm gets its data from the tone wheel providing pulse signals up the wire.
The ABS and TC cleverly do their work by comparing differing front/rear wheel rpm.
If I made two more tone wheels with a 6% different number of slots than the standard ones and fitted them front and rear, the ABS and TC would be happy because the wheel rpm’s would be correct compared to each other, but the speedometer would be getting 6% less pulses at a true 100 kph than is currently the case.
Instead of the tone wheel thinking it was at 106 k’s, it’d think 100 k’s.

Fascinating new world problem, your caring about the abs and tc’s happiness is commendable, if a little misdirected, far better to learn how to not use them imho, abs and tc are also in your fingertips, as true speed is in your gps

Not in bloody Australia you wouldn’t..
Speed cameras get you for 3 k over @ $200 a pop.

And by having speedo read a little high may help avoid this, cameras accuracy has been questioned before
Notably by a policewoman who promised she would never exceed the limit by the 3 whole km/hr she was photographed at.
As an honest person, she was believed and charges dismissed. So the camera must have been faulty.

[Huzo]

Fascinating new world problem, your caring about the abs and tc’s happiness is commendable, if a little misdirected, far better to learn how to not use them imho, abs and tc are also in your fingertips, as true speed is in your gpsAnd by having speedo read a little high may help avoid this, cameras accuracy has been questioned before
Notably by a policewoman who promised she would never exceed the limit by the 3 whole km/hr she was photographed at.
As an honest person, she was believed and charges dismissed. So the camera must have been faulty.

The only reason I mentioned the happiness of the ABS and TC was to acknowledge the fact that rooting around with tone wheels may bugger up the logic in the electronics, I’d hoped that altering the number of slots by equal amounts would keep the pulses at the same frequency relative to each other, but overall 6% less for a given speed.
It’s not “commendable” that I care about it, that sounds like a word you learned yesterday and have been waiting for a chance to use.
Next..
What makes you think that I have not learned how to ride without them, did you read the thread about ABS and the comments made by me and others as to it’s perceived worthlessness on a bike ? It’s only the last two bikes I’ve owned have ABS and only the most recent with TC.
I’m 61 and started riding at 14 and have never had an injury on a bike that stopped me riding..
Just lucky I guess.
I don’t need a built in error in my speedo to guard me against crashing, if I crash it’s because I decided to ride above my level.
I think you may have been on the piss whilst posting, because although you’ve gone close on occasions, I’ve never seen your logic so blurred or misdirected.
If I want to know what you think on this topic, I’ll tell you.
But thanx for the free advice, at least it wasn’t over priced.

[jacksonracingcomau]

The only reason I mentioned the happiness of the ABS and TC was to acknowledge the fact that rooting around with tone wheels may bugger up the logic in the electronics, I’d hoped that altering the number of slots by equal amounts would keep the pulses at the same frequency relative to each other, but overall 6% less for a given speed.
It’s not “commendable” that I care about it, that sounds like a word you learned yesterday and have been waiting for a chance to use.
Next..
What makes you think that I have not learned how to use them, did you read the thread about ABS and the comments made by me and others as to it’s perceived worthlessness on a bike ?
I’m 61 and started riding at 14 and have never had an injury on a bike that stopped me riding..
Just lucky I guess.
I don’t need a built in error in my speedo to guard me against crashing, if I crash it’s because I decided to ride above my level.
I think you may have been on the piss whilst posting, because although you’ve gone close on occasions, I’ve never seen your logic so blurred or misdirected.
If I want to know what you think on this topic, I’ll tell you.
But thanx for the free advice, at least it wasn’t over priced.

Whoa Taff
English is my first language, read carefully please, difference between learn how not to use and learn to use was my point.
Of course you can use them. You’re 61, as you say
But point about speedo accuracy was not to stop you crash, doubt you believe that
Point was that cameras may not be that accurate, as policewoman story suggested, perhaps optimism has a logic ?
And you don’t tell for advice,  you ask, as you did by posting a question.

Best of luck with the sensor fooling, I wish you well, truly, hope your acronym friends stay happy too.

[Huzo]

Whoa Taff
English is my first language, read carefully please, difference between learn how not to use and learn to use was my point.
Of course you can use them. You’re 61, as you say
But point about speedo accuracy was not to stop you crash, doubt you believe that
Point was that cameras may not be that accurate, as policewoman story suggested, perhaps optimism has a logic ?
And you don’t tell for advice,  you ask, as you did by posting a question.

Best of luck with the sensor fooling, I wish you well, truly, hope your acronym friends stay happy too.

Well.
MY point is that I HAVE learned how not to use them by virtue of the fact that all my limbs still function..
Secondly, my statement was “if I want to know what you think, I’ll tell you”..
(a tongue in cheek reference to the fact that I wasn’t seeking yours or anyone else’s advice on the efficacy of these “aids”.)
What I really want to know is..
Will altering the pulses per second from the tone wheels, keep the ABS and TC from activating since the frequency has dropped from (for example), 80 pulses per second to 75 pulses per second.
The ABS and TC would sense no differential in rpm more than was the case, but the speedometer would register an overall reduction, so spit out a figure 6% less.
ie, for a true 100, the sensor would “see” 100 but there would have been no alteration in the wheel’s rpm relative to each other, so no activation of ABS or TC....

[Mr Revhead]

I think you meant that the other way ‘round.

Yeah!  I did! 

[Huzo]

Here’s another thing..
While y’all were waiting, I broke out my trusty abacus.
An actual speed of 100 kph = 13.6 revs/sec of the rear wheel.
The tone wheel has 48 slots.
So.
13.6x48=656 pulses/sec

At 100 kph I am getting an indication of 107 kph.

At that actual speed of 100 kph, I will be getting 703 pulses/sec and I have to make that look like 100 kph to the sensor, which equals 656 pulses/sec.
Therefore I need to reduce the slots to 48x656/703=45 slots.
That folks is a 6% difference which SHOULD bring 107 back to 101...
As long as I do it for BOTH wheels, why should the ABS or TC wet their collective pants..? 

[piecemealadventurer]

Huzo

I think that this issue of fidling with the speedo is all a result of the shite weather we are having in Victoria which has has resulted in you spending too much time in the shed calculating pulses rather than out of the bike covering kms!!!! 

[Huzo]

Huzo

I think that this issue of fidling with the speedo is all a result of the shite weather we are having in Victoria which has has resulted in you spending too much time in the shed calculating pulses rather than out of the bike covering kms!!!!

Well Mick of all the things I could be accused of, I didn’t think that would have been one of them.
I would get out more, but I’m scared of losing my keys..!

[Idontwantapickle]

Well Mick of all the things I could be accused of, I didn’t think that would have been one of them.
I would get out more, but I’m scared of losing my keys..!

Here:
https://www.amazon.com/Retractable-Will-Well-Keychain-Reinforced/dp/B07GWQF47D/ref=mp_s_a_1_15?keywords=clip+on+keychain&qid=1575306170&sr=8-15

Now go on then.

[Huzo]

Just an addition for the ones following this thread...(both of you)
My reading so far leads me to believe that the tone wheel/sensor relationship, generates a square on/off wave due to Hall effect.
A sensor in close proximity to a permanent magnet, that generates an on/off signal as the bars in the tone wheel pass by the sensor.
Am I heading for certain disaster if I make two new tone wheels with 6% less bars, so for any given wheel rpm (road speed), I will have 6% less pulses so consequently a 6% reduction in displayed speed ?
Please don’t give some lame arsed response like...”I wouldn’t bother..”

[RinkRat II]

 Is the computer for the abs calibrated to the 48 slots or does it just see pulses and figure the differential between front and rear? 

     Paul B

[Huzo]

Is the computer for the abs calibrated to the 48 slots or does it just see pulses and figure the differential between front and rear? 

     Paul B

To be honest Paul, I don’t know.
My Neanderthal thinking suggests that the 48 slots could be somewhat arbitrary, given that the information to the brains is a constant stream of pulses, no more no less, and the velocity down the road is merely a function of rpm x circumference of the rear wheel.
The tone wheel is just a tachometer if you will.
I could understand (but haven’t yet checked) if the front one has a different number of slots to give the same pulse rate for a different circumference, but would not be surprised if that’s all done in the calibration.