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Discussion Starter · #1 ·
I figured this out pretty quickly.. but don't really know what it's so.. but it's annoying to me. I would rather the speedo just show the 'real' speed...

basically when going 60km/h (needles pointing at 60 exactly) and have car on cruise on flat road.. with speed not fluctuating.. then when I use computer to calculate avg speed it says 56km. Likewise if I was sitting on 100km/h (60mph) the computer says 96km/h.

So I wonder off to my BMW dealer and the service guys says yes.. not many people pick that up but basically 'this feature' of over showing speed on the clock speedo is a well known BMW trait??? He said it's usually between 2-4 km/h.

:dunno:

Is it just me or does that make no sense what so ever?

:eeps:
 

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www.piratecove.org
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do you guys have stock wheels on there, or a different size? That will throw off the speedo a little as well (if the circumferance of the tires is different then stock).
 

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This is relative to your speed. At 30 mph it deviates very little (propbably less than 1 mph). As you get going faster it progressively shows that you're going faster than you actually are. Most cars do this.
 

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Discussion Starter · #6 ·
I have stock 330i wheels on my 325i however this isn't what the problem is as the on board computer knows the exact speed of the car.. it's only the instrument cluster speed clock that is showing a faster speed than you're actually going so it must be calibrated to do this.

And it's not relative on mine.

at 60km it's 4 km faster than I'm really going..

at 150km it's still 4 km faster than I'm really going...

I have tested this.
 

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Discussion Starter · #8 ·
on the dash? I can see the speed from sitting on cruise and then recalculating from my on board computer (I have sat/nav screen). Is this what you're talking about?
 

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Law Enforcer
…’22 992 Carrera C2S arriving soon!!!
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At high speeds it is slightly off, but this could vary between cars. I had my previous 330ci clocked at 139 MPH while my speedo read about 144 or 145 MPH ( I don't exactly remember). I remember the exact clock speed though (I've argued this as well in terms of claims that the speed limiter kicks in at 125 MPH). I had 19" Hamann's on my car when I was clocked at 139 MPH, so maybe if I had my stock 17" rims, it wouldn't have varied so much. My car could have been just a lucky case that the speedo was pretty accurate. I have yet to test my M3, but I will soon....but w/ all of my CHP friends on 12 hour shifts and my city police friends on overtime as well, time isn't available. Soon though...very soon..! :D
 

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i'm not sure how accurate the "average MPH" function is...
because if you are on cruise control... unless if you are on a perfectly flat road ... your engine has to raise and lower your speed to maintain your cruising speed

i think the most accurate way to test your speedometer is to get one of those Gtech things.. and/or using a radar gun

but EVERY car has speedo error ... especially at higher speeds
 
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