Speedometer error

[RiverRunner]

Have any of you checked the accuracy of your speedometer? Mine is off by about 6%. At 70mph on GPS, speedo reads 74. At 90 mph, reads 95 mph. Odometer likely will be off by same amount, so will read higher miles than actual. My wife's 740i off by about 3% also reads higher than actual. I've tested the GPS in other vehicles and with radar, it is correct.

[Spencer25]

What devise did u use to check the speed?

[noushy]

Yeah I noticed this too. The speedo above 60 reads about 4mph faster than actual speed

[RiverRunner]

Has anyone tested the odometer for the same 5-7% error? Interesting that the errors I see reported online are all erring on the side of BMW. For leases that are held to certain miles, 7% of 36,000 miles = 2,520 miles.. what's the penalty or cost to go 2,520 miles over on your lease?

[RichardP]

All speedos, except those that have been specifically calibrated for police use for example, will over read. It's illegal to have an under reading speedometer, they must be within the range 100% to 110% so most are in the region of 105% which is not far from where yours is. As the tyres wear the reading will decrease as the rolling radius of the tyre reduces, so they have to be set to over read on new tyres.

[bjayfan]

This is normal for all BMW's, they'll only recalibrate if the speedometer is more than 10% off. It's only illegal in certain jurisdictions/countries, but that's the reason they do things this way.

Note that the car does know the proper speed, and the mileage on the odometer is correct, several ways you can test that.

[RiverRunner]

Originally Posted by RichardP

All speedos, except those that have been specifically calibrated for police use for example, will over read. It's illegal to have an under reading speedometer, they must be within the range 100% to 110% so most are in the region of 105% which is not far from where yours is. As the tyres wear the reading will decrease as the rolling radius of the tyre reduces, so they have to be set to over read on new tyres.

My other vehicles are near exact, my GM vehicles can be easily calibrated based on tire sizes changes. I'd prefer it to be no more than 2-3% over on new tires. That would still be over slightly on wore tires. There's no need to be off by more than that.