Are iPhone speedometer apps accurate

Mark e90 · 03-05-2013, 08:14 AM

How accurate are the smart phone speedometer apps ? I tried one out today and either my cars speedo is not accurate or is it more likely to be the phone. For example the car tells me I'm doing 60 mph the phone tells me 56 and when the car tells me I'm doing 70 the phone says 65. It's seems to be round about 50 mph u get mixed figures when I'm doing 30 or 40 the car and phone give the same reading ? My car is 2005 model could my speedo just have lost its accuracy over the years ?

georgelb · 03-05-2013, 08:36 AM

They're designed to read high to account for changes in tire size so that it shouldn't be possible for the speedometer to display a speed slower than your actual speed. BMW usually sits around 5% or so, but the standard says it has to be within 10%.

e92oholic · 03-05-2013, 08:36 AM

All BMW speedos are off. They all read faster than you are actually going from the factory. If I remember correctly it has something to do with a law in Germany. Your GPS/iPhone speed will be accurate.

jacobsed · 03-06-2013, 08:12 AM

Yes it's a German thing. They have very harsh speeding laws. I coded mine to read actual speed on the digital display. Always matches exactly to my Garmin.

03-05-2013, 08:14 AM	#1
Mark e90 Captain 111 Rep 716 Posts Drives: BMW e90 Join Date: Aug 2011 Location: Scotland iTrader: (0)	Are iPhone speedometer apps accurate How accurate are the smart phone speedometer apps ? I tried one out today and either my cars speedo is not accurate or is it more likely to be the phone. For example the car tells me I'm doing 60 mph the phone tells me 56 and when the car tells me I'm doing 70 the phone says 65. It's seems to be round about 50 mph u get mixed figures when I'm doing 30 or 40 the car and phone give the same reading ? My car is 2005 model could my speedo just have lost its accuracy over the years ? __________________ BMW 325i M sport - Custom stainless exhaust ( 335i set up ) - Piano black interior trim - Gloss black kidney grills - Ferric grey 18" MV3 alloys -
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03-05-2013, 08:36 AM	#2
georgelb nsomneeak 39 Rep 501 Posts Drives: E92 RB 335i Join Date: Apr 2010 Location: DFW, TX iTrader: (3) Garage List 2007 335i [8.00]	They're designed to read high to account for changes in tire size so that it shouldn't be possible for the speedometer to display a speed slower than your actual speed. BMW usually sits around 5% or so, but the standard says it has to be within 10%. __________________ RB Turbos w/ N20 TMAP Sensor \| 93 Octane Protune by Cobb Plano \| xHP Stage 3 \| BMS DCI \| STETT CP \| Forge DVs \| RB PCV \| Helix FMIC \| CP-E Catted DPs \| Walbro 450 \| Bilstein B12 \| M3 Control Arms \| Defiv Lockdown Kit \| BBS CH \| Michelin A/S 3+ Hixson BMW of Monroe, LA - Shady Dealer \|
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03-05-2013, 08:36 AM	#3
e92oholic Banned 66 Rep 850 Posts Drives: 2013 MINI JCW GP Join Date: Feb 2012 Location: Buffalo NY iTrader: (6)	All BMW speedos are off. They all read faster than you are actually going from the factory. If I remember correctly it has something to do with a law in Germany. Your GPS/iPhone speed will be accurate.
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03-06-2013, 08:12 AM	#4
jacobsed Lieutenant 23 Rep 463 Posts Drives: 2006 330xi Join Date: Feb 2012 Location: United States iTrader: (2)	Yes it's a German thing. They have very harsh speeding laws. I coded mine to read actual speed on the digital display. Always matches exactly to my Garmin.
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