is your speedometer accurate?

[X6 Eddy]

I am still learning my X6 35 with 20" wheels.. A friend wanted to take some pics while moving so he said stabilize at 60mph and I did. He said I was going 57. Pulled out my trusty smart phone, pulled up my GPS and sure enough.. bouncing between 57-58. I tried 70mph.. GPS showed 68. for the ULTIMATE driving machine from the factory, should it not be SPOT on?

Thanks

[motex]

Originally Posted by X6 Eddy

I am still learning my X6 35 with 20" wheels.. A friend wanted to take some pics while moving so he said stabilize at 60mph and I did. He said I was going 57. Pulled out my trusty smart phone, pulled up my GPS and sure enough.. bouncing between 57-58. I tried 70mph.. GPS showed 68. for the ULTIMATE driving machine from the factory, should it not be SPOT on?

Thanks

If you did change the size of your wheels+tires, this link will help you find out, what is your speedometer error, also is a great link for those who want to change a tire width or diameter, easy to use and great easy to understand results, hope it will help you
http://www.dakota-truck.net/TIRECALC/

[theaudir8fan]

this is normal, coming out of the factory, many different companies increases the speed by around 3-4 km/h, not sure why, could be just a built in margin for speeding accuracy

[X6 Eddy]

I did not change my wheels they are factory.. I am not one of those people that has to set my watch 5 minutes fast so that I am not late. If my watch reads 1 O'clock, I want it to BE 1 O'clock. If my speedometer reads I am going 60 MPH I want to be going 60 MPH! Is that too much to ask?

[DrewBert]

My speedo/HUD is 7 km/h off. Have passport 9500 and when it's says I'm going 131 the speedo says 137 this was confirmed today with my 131 km/h speeding ticket lol

Not sure why it's so far off.

[Draper]

The 3mph overestimation can be corrected through coding.

[theaudir8fan]

Originally Posted by X6 Eddy

I did not change my wheels they are factory.. I am not one of those people that has to set my watch 5 minutes fast so that I am not late. If my watch reads 1 O'clock, I want it to BE 1 O'clock. If my speedometer reads I am going 60 MPH I want to be going 60 MPH! Is that too much to ask?

it's not, i think it's more that the manufacturer did it for a safety margin, altho i'm not sure, but it's not just your car, many cars are like this

Originally Posted by DrewBert

My speedo/HUD is 7 km/h off. Have passport 9500 and when it's says I'm going 131 the speedo says 137 this was confirmed today with my 131 km/h speeding ticket lol

Not sure why it's so far off.

It's actually somewhat proportional, when my escort max shows 70 km/h, the car shows 74, and the corrected speedo which is enabled through the coding shows 71-72. when you go faster, the error is larger

[X6 Eddy]

Speedometer test with Chevy Cruze speedometer, GPS speedometer APP and Garmin Car GPS.. and then in the X6. -

[DrewBert]

Yeah my gmc Sierra was bang on. Not sure why the x6M is so bad

[X6 Eddy]

This Service Information bulletin replaces SI B62 02 96.

SUBJECT
Maximum Permissible Speedometer Deviations

MODEL
All

situation
The vehicle speed displayed in the instrument cluster displays a speed that is higher than the actual speed.

information
Most speedometers have tolerances of approximately +10%. A “speedometer advance" is necessary to compensate for negative tolerances in tire diameter, electronic controls, tire temperature, tire pressure, vehicle load and other factors.



Vehicle manufacturers usually calibrate speedometers to read high by an amount equal to the average error, to ensure that their speedometers never indicate a lower speed than the actual speed of the vehicle.





Excessive speedometer deviations can come from several causes, but most commonly are due to nonstandard tire diameter and wheel size.





This SI defines the maximum and permissible speedometer reading tolerance.





The instrument cluster is a sealed unit and cannot be calibrated. Any tampering to the cluster will void the related component or vehicle warranty coverage that is applicable.





GPS devices are positional speedometers, based on how far the receiver has moved since the last measurement. Its speed calculations are not subject to the same sources of deviation as the vehicle's speedometer (wheel size, transmission/drive ratios). Instead, the GPS' positional accuracy, and therefore the accuracy of its calculated speed, is dependent on the satellite signal quality at the time.





If you are using a known accurate GPS system as a reference speed, you need to use the formula below to calculate the maximum permitted speedometer advance, which is 10% of the actual (input) speed plus 2.4 mph.





Example:





Actual speed = 50 mph





50 mph x 10% = 5 mph; 5 mph + 2.4 mph = 7.4 mph





Therefore, the permissible displayed speed is 50 to 57.4 mph.





(Note: The displayed speed must never be less than the actual speed.)





No repairs should be attempted if the speedometer advance is within 10% + 2.4 mph.





Use ISTA ((Integrated Service Technical Application) diagnosis or the instrument cluster self-test to make sure the needle for the speedometer is moving smoothly.





NOTE: The amount of speedometer advance has no effect on recording accumulated mileage in the odometer display. The odometer records total mileage digitally, and does not incorporate any "advance" tolerances.



warranty information
Not applicable.

[ Copyright ©2012 BMW of North America, Inc. ]

[dreamalaska]

My 2013 X6 3.5i consistently reads +2mph over actual speed...I asked a tech about it during my Spartanburg factory tour and he gave me the same spiel quoted above...now I wonder how far off the fuel gauge is :/

[Da M3nace]

I just put new wheels and tires on my X535d. I noticed right away that my MPG display was showing a higher number driving around the same route I usually do to and from work. Where I used to get 19 mpg, I am now getting 23 mpg on average. I also compared my phone GPS speed to car speedometer and at 50 mph the car seems to be 2-3 mph faster than phone GPS.

I did the wheel diameter configurations using a website tool and found that my OEM tire diameter was 29". My new wheels/tires ate 28.7".

Is this difference enough to justify the speedometer difference I am getting??

[denaliman]

Originally Posted by Da M3nace

I just put new wheels and tires on my X535d. I noticed right away that my MPG display was showing a higher number driving around the same route I usually do to and from work. Where I used to get 19 mpg, I am now getting 23 mpg on average. I also compared my phone GPS speed to car speedometer and at 50 mph the car seems to be 2-3 mph faster than phone GPS.

I did the wheel diameter configurations using a website tool and found that my OEM tire diameter was 29". My new wheels/tires ate 28.7".

Is this difference enough to justify the speedometer difference I am getting??

No, that is an insignificant difference.

[upstate650]

Originally Posted by Da M3nace

I just put new wheels and tires on my X535d. I noticed right away that my MPG display was showing a higher number driving around the same route I usually do to and from work. Where I used to get 19 mpg, I am now getting 23 mpg on average. I also compared my phone GPS speed to car speedometer and at 50 mph the car seems to be 2-3 mph faster than phone GPS.

I did the wheel diameter configurations using a website tool and found that my OEM tire diameter was 29". My new wheels/tires ate 28.7".

Is this difference enough to justify the speedometer difference I am getting??

With a smaller diameter tire, your car should be reading slower than it was with bigger tires - it measures revolution, and you are going a smaller distance per revolution than you were before. Are these stock sizes? BMW speedometers are well documented to read 3-4 mph more than actual speed. To be reading lower than actual speed is a significant difference from where it should be.

As for your mileage increase, harder tires with less rolling resistance can make a significant difference. Are they the same brand?

[Da M3nace]

OEM was Bridgestone dueler A/S 255/18/55 all around. The new wheels ate staggered. 275/20/40 up front and 315/20/35 on back. New tires are Toyo proxes S/T.

[denaliman]

with the wider tires you should be getting slightly lower MPG or perhaps you were running your old tires underinflated or new tires overinfalated
Seems strange.

[denaliman]

Try resetting your MPG using the button on the lever stock and let it re-calibrate and reset your TPMS and see if that make a difference.

[doug_999]

Come on guys, this is old news.

http://www.caranddriver.com/features...ometer-scandal