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B121
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Post by B121 » Wed Sep 12, 2018 6:28 am

Hi All,

I had 2 GPS readers active in my car, and both seemed to confirm the speedometer is 2-4 MPH too high. Only thing I'm thinking is that I'm not running original wheels (put on by a previous owner). Note, I've only had the car for a month. :)

Anyone have any ideas? Is this something I could/should recallibrate? Thanks!
2012 Z4 sDrive3.5I M (Blue)

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markplant
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Post by markplant » Wed Sep 12, 2018 7:05 am

All Speedo read slightly high, from factory
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Smartbear
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Post by Smartbear » Wed Sep 12, 2018 7:08 am

B121 wrote: Wed Sep 12, 2018 6:28 am Hi All,

I had 2 GPS readers active in my car, and both seemed to confirm the speedometer is 2-4 MPH too high. Only thing I'm thinking is that I'm not running original wheels (put on by a previous owner). Note, I've only had the car for a month. :)

Anyone have any ideas? Is this something I could/should recallibrate? Thanks!
Hi, it’s normal but you can bring it closer by fitting higher profile tyres or using Carly or similar to code the speedo to display the correct speed.
You will lose your safety buffer when it comes to speeding offences though! :o
Rob
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e89 Sdrive 20i, plenty of mumbo & good economy-the thinking bears z4
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ph001
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Post by ph001 » Wed Sep 12, 2018 10:02 am

The official specs for a factory speedo are +10% -0% so they always err on the side of reading high (as much as 77mph at a true 70mph). Most over-read by around 2-3%.
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B121
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Post by B121 » Wed Sep 12, 2018 2:42 pm

Thanks everyone for confirming. 👍I appreciate it 🙂
2012 Z4 sDrive3.5I M (Blue)

Busterboo
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Post by Busterboo » Thu Sep 13, 2018 8:33 am

ph001 wrote: Wed Sep 12, 2018 10:02 am The official specs for a factory speedo are +10% -0% so they always err on the side of reading high (as much as 77mph at a true 70mph). Most over-read by around 2-3%.
Thank Goodness they do.
Vidi, vici, veni

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Post by Busterboo » Thu Sep 13, 2018 9:33 am

Come to think of it, though ...

I use the cruise control in my 18"-wheel E89 on average speed camera roads. Limit 50 - set at 50. My GPS-based speed camera locator screams at the same points + 1 mph.

(The the cruise control indicator can be fixed exactly on the speedometer and is easier to read than a wandering speedometer hand.)

So, my speedometer seems to have no margin for error at all.
Vidi, vici, veni

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