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Discussion Starter · #1 ·
OK, I was driving around 80MPH the other day and noticed an odd situation. Look at the picture (sorry its not that clear) and tell me how fast I was really going.. is it 80 as the digital speedo says or is it 81ish as the speedo says?
 

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Its not true speed its what the speedo sees based on tyre/wheel size etc, you can code the car to show GPS speed (if you have something else which shows GPS speed you can confirm) but I always find that 53 is GPS 50, 74 is GPS 70 etc
 

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Even gps isnt absolute. Gps satellites only know your position within a 15 meter radius so theres an innacuracy there as well
 

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And they're wrong if you are on a hill too.
 

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I never said it was, just that its different :)

Agree that it should only be used as an indication, but pointing out that mini/bmw also can show digital GPS speed vs speedo speed in the dash.
 

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This is why I don't use the speed display, except under very specific circumstances (late or early in the day, when I'm wearing sunglasses, and the analog display is too dim to see against all the ambient light).

Watching the display spazz between 44 no 45 no 49 no 47 no 44 no 47 no 49! drives me crazy. I feel compelled to hold precisely 45 and my inability to do so makes me feel inadequate.

I like the analog display because it smooths out the speed. I find the car (in sport mode, at least) is a bit of a challenge to keep at a constant speed, and in addition the car likes to go fast and I find myself creeping up (it was the car's fault, officer!). The analog provides a coarse visual clue of my speed that feel is much easier to track.

But anyhow. My digital display seems to match the analog pretty closely. I'll stare at it today on the commute. If there is a big discrepancy, I don't know what can be done about it. My advice would be to use one or the other and retain your sanity.
 

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Mine does the same. I don't have GPS though so I'm not sure that's a factor

I had the car on track and the difference seemed amplified the faster you go. Not by much, but when I looked down I was going 110 mph on the digital readout and about 105 mph on the dial. It doesn't bother me as speed indicators aren't absolute. But my slight case of OCD has had me take notice.

For my car specifically, it really only affects me at around 80 mph, which here in my city will get you a ticket regardless of a few mph difference ;)
 

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Yes weird they differ but I suppose digital v analogue .... alignment of the needle etc.had a watch whose hands never lined up .slightly annoying.
 

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There is a tolerance band with the actual speed. I too notice a slight discrepancy between the analogue and digital.

I also don't think it is a good idea to take a picture whilst travelling at 80moh!
 

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I watched the display this morning, and I think my analog and digital are pretty close.

One thing that was interesting, though. I set Cruise Control for the test so I would stay at a constant speed, and noticed the the CC display said 46 while the analog speedo said 45. WTF?

It's almost like there are 3 different systems interpreting speed data from the sensors, as opposed to a single system promulgating speed data to be consumed by the various subsystems.
 

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My MCS is exactly the same; the dial showing +1mph over the digital readout. The digital readout on mine is the most accurate I've ever encountered in a car - when tested against a separate GPS device on the flat using cruise control. At 60mph there is a 1mph difference.
 

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I don't know about the F-series MINIs, but the second gen MINIs' digital speedo was always ~3 mph over what your actual speed was. It was actually something you could specifically code out and when you did, the analog speedo would still overestimate, but the digital would be more accurate, closer to GPS or radar speed traps.
 

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Discussion Starter · #14 ·
My Service Advisor (NorCal) said that due to federal law, the speedometer has to register 2-3 MPH over actual speed. I didn't try to verify that, but interesting.
 

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Discussion Starter · #16 ·
I will try it.

I missed out on President Carter's push to learn the metric system! So, no promises that I can figure it out. :)
 

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My Service Advisor (NorCal) said that due to federal law, the speedometer has to register 2-3 MPH over actual speed. I didn't try to verify that, but interesting.
Having worked in the automobile industry, all manufacturer's speedometer calibration (primary device) is generally as follows.

Actual 30mph - nominal 31.5mph - tolerance 30-33
Actual 60mph - nominal 63mph - tolerance 60-66
Actual 80mph - nominal 84mph - tolerance 80-88

I guess originally it was part of SAE / Federal regulations that were later also adopted worldwide (with Kph equivalents). Any other secondary speed indication is probably 'for indication only'.

A speedometer should never underestimate the true speed for safety reasons.
 

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My speedo is almost right on based on a GPS reading. I know about the nanny-state overstating on the R56, and was surprised that my speedo reflects actual speed.
 

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How much over the limit?

OK, I was driving around 80MPH the other day and noticed an odd situation. Look at the picture (sorry its not that clear) and tell me how fast I was really going.. is it 80 as the digital speedo says or is it 81ish as the speedo says?
Were you speeding?>:D>:D
 
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