Why the Speedo Overstatement?

[adventurelounger]

This is not unique to my SuperT—it was roughly the same thing on my former BMW F800GS:

The speedometer overstates my speed by a consistent 5 mph. Easiest to see when I set the GPS screen to display trip info with a large e-speedo.

My question is...why?

• A built-in passive safety device?
• The New Math?
• GPS calculating your air speed vs ground speed?

Anyone know why?

 

[TXTenere]

This is not unique to my SuperT—it was roughly the same thing on my former BMW F800GS:

The speedometer overstates my speed by a consistent 5 mph. Easiest to see when I set the GPS screen to display trip info with a large e-speedo.

My question is...why?

• A built-in passive safety device?
• The New Math?
• GPS calculating your air speed vs ground speed?

Anyone know why?

I guess sort of a safety device. GPS knows nothing of "airspeed," and will always display ground speed.

 

[Mellow]

On the 2014, it's only about 2mph off... glad Yamaha addressed that because every other bike I've had has been about 5mph off... 2 is acceptable enough to make the display useful.

 

[Mike91]

It is rare for any vehicle to read perfectly accurate. My Tenere reads about 12% high, which is in the range as most of the other bikes I've owned. My truck reads about 8% high. My wife's car reads almost completely accurate, maybe 1% high. It is the result of a number of things, but ultimately I think they take a conservative approach to tolerance stack-up and just calibrate them high so they won' t end up with some percentage of bikes that end up reading too low.

 

[Bug Dr.]

My bike is 9% - 10% off under 50 mph and then it is 5 mph off at all speeds above 50 mph......kinda strange. Both my RT and my NC 700 were within one half of a mph between the speedo and the GPS so I know it can be done......even on a budget bike like the NC. Oh well, I just have to calculate speed in my head unless I have my GPS mounted.
Mike

 

[fredz43]

As Mellow pointed out, they have corrected that on the 14. Mine is only 1 mph fast at 70, per my GPS. My 12 was 6 mph fast at 70.

 

[Gen2S10]

As Mellow pointed out, they have corrected that on the 14. Mine is only 1 mph fast at 70, per my GPS. My 12 was 6 mph fast at 70.

::026::

My 2014 also ready very close to what my GPS indicates. When I was at 75MPH indicated (CC engaged) the GPS read 73. This was on I-10 from Las Cruces, NM to Demming, NM which is a loooong straight flat road.

HTH.

-Lee-

 

[Bushyar15]

I've seen on sportbikes something called speedo-healer or something like that. I dislike that mine is off as well.

 

[Andylaser]

They all read hight deliberately. Stops the manufacturer getting sued if you get a speeding ticket.

 

[OldRider]

I guess sort of a safety device. GPS knows nothing of "airspeed," and will always display ground speed.

I bet he was just kidding about the airspeed thing!!!

I put on a Speedohealer and now at 70mph on the speedo, the GPS is reading 69.8

My 13 Honda CRV is dead on with the GPS.

 

[Checkswrecks]

From one of the previous 15 (really) threads on the same topic:


The error is intentional to make sure the manufacturer can use different sources of tires and still meet the United Nations agreement on accuracy. Vehicle manufacturers who spec only one or two tire models as standard equipment (Harley for example) are typically more accurate because they only have to make sure the calibration never goes low. (They will still be slightly high because new vehicles can absolutely never be low.)

The following is the source of the rules:

Vehicles conform to United Nations Requirement #39, which is called: UNIFORM PROVISIONS CONCERNING THE APPROVAL OF VEHICLES WITH REGARD TO THE SPEEDOMETER EQUIPMENT INCLUDING ITS INSTALLATION (See: http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf) The speedo accuracy may be found on Page 8, Paragraph 5.3, which states:


The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).
0 ≤ (V1 - V2) ≤ 0.1V2 + 4 km/h






This formula is where your speedo INaccuracy is designed in. Your dealer can't do a thing about it. Neither can Yamaha USA (or Canada/UK/AUS/etc) as an importer, which really is just a subsidiary that buys vehicles from a foreign manufacturer and then resells/distributes them. The manufacturers for the US also have to account for NHTSA coming in with a measurement error, keeping with the requirement to NEVER display less than actual speed.

 

[OldRider]

One more thing about the speedohealer. If you put one on, it is a lot easier to tap into the blue/white wire where it comes out of the ABS unit instead of where it goes into the ECU. There's a lot more room to work on the wiring. The sheathing around the wire harness coming out of the ABS unit doesn't even have to be cut open, you can just pull it apart.

 

[Propsoto]

My 2014 ES reads 1-2 MPH high from 25 to 100MPH compared to GPS. Close enough for me. My Silverado is 0-1MPH high. Like others have said, every other bike I've owned read 7-8% or more high.

 

[adventurelounger]

The Check is in the mail! Thanks Checkswrecks for an excellent re-explanation (and apologies for asking first without searching). The answer is as fascinating as it is logical...it really makes sense! Except why the UN?

And I wonder if S10 riders experience a real world speedo variance depending on tire type. If you have a 5 mph difference on say, OEM Battlewings that shrinks to 2 mph on say, knobby Heidenaus, that'd be physics AND the UN rule in action!

 

[Checkswrecks]

The Check is in the mail! Thanks Checkswrecks for an excellent re-explanation (and apologies for asking first without searching). The answer is as fascinating as it is logical...it really makes sense! Except why the UN?

And I wonder if S10 riders experience a real world speedo variance depending on tire type. If you have a 5 mph difference on say, OEM Battlewings that shrinks to 2 mph on say, knobby Heidenaus, that'd be physics AND the UN rule in action!

No problems.


The UN is involved because of how much money is involved with selling cars in multiple countries and for vehicles to be able to safely operate across borders. For us in North America and the Aussies, we don't cross borders too often. Most of the rest of the world lives MUCH closer to a border. There are some things that are cultural and intrinsic, such as which side of the road is used, and those wont change. Otherwise, it's to the benefit of everybody for most parts and controls to share basic properties.


For example, there are some 3rd world countries making vehicles with essentially no safety standards (maybe an ISO certificate). I REALLY would not want my teen daughter restrained by a seatbelt made to the quality that those countries have or riding on tires recapped there. With the UN standards, they can build them for domestic use, they just can't export them because they can't even achieve a minimum agreed level of safety.

 

[fredz43]

From one of the previous 15 (really) threads on the same topic:


The error is intentional to make sure the manufacturer can use different sources of tires and still meet the United Nations agreement on accuracy. Vehicle manufacturers who spec only one or two tire models as standard equipment (Harley for example) are typically more accurate because they only have to make sure the calibration never goes low. (They will still be slightly high because new vehicles can absolutely never be low.)

The following is the source of the rules:

Vehicles conform to United Nations Requirement #39, which is called: UNIFORM PROVISIONS CONCERNING THE APPROVAL OF VEHICLES WITH REGARD TO THE SPEEDOMETER EQUIPMENT INCLUDING ITS INSTALLATION (See: http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf) The speedo accuracy may be found on Page 8, Paragraph 5.3, which states:


The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).
0 ≤ (V1 - V2) ≤ 0.1V2 + 4 km/h






This formula is where your speedo INaccuracy is designed in. Your dealer can't do a thing about it. Neither can Yamaha USA (or Canada/UK/AUS/etc) as an importer, which really is just a subsidiary that buys vehicles from a foreign manufacturer and then resells/distributes them. The manufacturers for the US also have to account for NHTSA coming in with a measurement error, keeping with the requirement to NEVER display less than actual speed.

All that is well and good, but it still remains that if they wanted it to read closer to actual speed they could and in fact did do that on the 2014 model, just as many other late model cars and motorcycles now read a lot closer than the typical 6-10% that we have seen thru the years on many bikes and cars.

 

[FrontRangeRider]

My 2014 ES reads 1-2 MPH high from 25 to 100MPH compared to GPS. Close enough for me. My Silverado is 0-1MPH high. Like others have said, every other bike I've owned read 7-8% or more high.

+1 My 2014 reads 1 mph high compared to my GPS at all speeds I've ridden to date.

 

[XtreemLee]

at 100 mph I am 3mph high indicated.

 

[shrekonwheels]

My bike is 9% - 10% off under 50 mph and then it is 5 mph off at all speeds above 50 mph......kinda strange. Both my RT and my NC 700 were within one half of a mph between the speedo and the GPS so I know it can be done......even on a budget bike like the NC. Oh well, I just have to calculate speed in my head unless I have my GPS mounted.
Mike

I noticed under 50 mph my bike seems to be high and over 50mph It seemed to be closer, I thought I was crazy ::014::

 

[Marty]

Is the odometer also off?