Question about Speedometer Accuracy

karbosshack · 03-06-2006, 02:22 AM

Is there any way to get it fixed? Is there any device I can get to test the accuracy? I know I can have somebody pace me, but how would you know who's speedometer is more accurate

I was drivin on the freeway today, and usually in my other cars when I go 10 over I pass most people, this time I was goin 10 over in the e90 and was getting passed by everybody....felt like I was goin slower than it actually read.

alpinewhite3 · 03-06-2006, 02:36 AM

The best way to check your speed is if you have one of those speed digital read out signs in your town that tell you your speed electronically.
I set my cruise to 60mph and went past it. The sign read 56mph. So it's off by about 4-5mph. It's actually been pretty annoying ever since i found that out b/c now i constantly find myself checking my speed and then subtracting 5 from that number. I know it sounds simple enough but on the highway i check it a lot and it gets kind of annoying and tedious knowing that i have to subtract every time.

Macfreak7 · 03-06-2006, 02:38 AM

I thought I knew this at one point... but what's the exact reason for the lack of accuracy? How is the speed calculated?

sdorn · 03-06-2006, 02:42 AM

Here is the thread discussing this. I used a handheld GPS device to figure out how far off my speedometer was. There is no way to get it fixed. I asked the dealership and a local speedometer calibration company. They both said it couldn't be fixed. BMW does it on purpose.

Mine is off by about 4 - 5mph at freeway speeds. So, if the speedometer says I am going 74, I am really going about 70. If it says I am going 85, I am really going 80. The inaccuracy gets bigger the faster you are going. Those roadside speed signs are only useful if you are going pretty fast. At lower speeds, the speedometer is only off by 1 - 2mph so it isn't that big of a deal.

http://www.e90post.com/forums/showth...ht=speedometer

meruyailir · 03-06-2006, 04:54 AM

Quote:

Originally Posted by sdorn

Here is the thread discussing this. I used a handheld GPS device to figure out how far off my speedometer was. There is no way to get it fixed. I asked the dealership and a local speedometer calibration company. They both said it couldn't be fixed. BMW does it on purpose.

Mine is off by about 4 - 5mph at freeway speeds. So, if the speedometer says I am going 74, I am really going about 70. If it says I am going 85, I am really going 80. The inaccuracy gets bigger the faster you are going. Those roadside speed signs are only useful if you are going pretty fast. At lower speeds, the speedometer is only off by 1 - 2mph so it isn't that big of a deal.

http://www.e90post.com/forums/showth...ht=speedometer

I also noticed this and hate it why BMW does it on purpose. Did BWM really tell you that they did it on purpose?

I asked the dealer and no one knew about this.

stressdoc · 03-06-2006, 08:07 AM

All car manufacturers are required by law in many countries to make sure that their speedometers are not pessimistic. We can't have citizens exceeding the speed limit and using the excuse that they were just going by what their speedometer read. The amount that the speedometer is optimistic needs to cover slight variants in tire size, so most are set to be about 2-3% high, that is, they will read 100 mph when the car is actually going about 97 mph. Probably saves the world a little gas, a few lives, and some warranty coverage (because odometers are often set with the same gearing). Many old threads on this topic. The drive-by speed readouts are not reliable. Use GPS or the old stand-by of time/distance travelled on a stretch of highway with precise distance markers.

sdorn · 03-06-2006, 03:42 PM

Quote:

Originally Posted by meruyailir

I also noticed this and hate it why BMW does it on purpose. Did BWM really tell you that they did it on purpose?

I asked the dealer and no one knew about this.

Yes, the dealership told me that BMW does it on purpose. If you read that thread I linked to, there is an article from Car and Driver that I cut and pasted into the thread explaining the problem and comparing all the car manufacturers. It also explains some of the reasons car manufacturers have for doing this.

e90rocks · 03-06-2006, 03:55 PM

Quote:

Originally Posted by karbosshack

Is there any way to get it fixed? Is there any device I can get to test the accuracy? I know I can have somebody pace me, but how would you know who's speedometer is more accurate

I was drivin on the freeway today, and usually in my other cars when I go 10 over I pass most people, this time I was goin 10 over in the e90 and was getting passed by everybody....felt like I was goin slower than it actually read.

Yeah, when I first got my 325xi I was pleasantly surprised at how quick it was 0-60. That was before I found out I was estimating the 0-54 interval.

krndanic307 · 03-06-2006, 04:09 PM

So all this is real? I got a speeding ticket and the police said he paced me at 78. Which I wasn't really going 78 when he started pacing me. I was going 75 and the judge knew because I think the cop didn't have his speedometer calibrated right so thats mean I was actually going 70!! Is there anyway that I could get another trial date after I paid the ticket already?

sdorn · 03-06-2006, 04:50 PM

Quote:

Originally Posted by krndanic307

So all this is real? I got a speeding ticket and the police said he paced me at 78. Which I wasn't really going 78 when he started pacing me. I was going 75 and the judge knew because I think the cop didn't have his speedometer calibrated right so thats mean I was actually going 70!! Is there anyway that I could get another trial date after I paid the ticket already?

Once you pay the ticket, you basically plead guilty. Chances are they aren't going to let you change your plea, unless maybe the court date when you were supposed to have showed up hasn't arrived yet. You can call the clerk of courts and ask. Every one of our speedometers isn't off by exactly the same amount. You need to get a handheld GPS device to see how far off your particular car is. If my speedometer said I was going 75, I would actually have been going 71mph according to the GPS.

karbosshack · 03-06-2006, 05:07 PM

Wow. That really sucks, no way to fix it? That's ridiculous. Then what's the point of a speedometer anyways then lol. How do you use a handheld GPS, I've never used one before?

voltron1011 · 03-06-2006, 05:11 PM

I can't believe we actually started ANOTHER thread about this...

sdorn · 03-06-2006, 05:11 PM

Quote:

Originally Posted by karbosshack

Wow. That really sucks, no way to fix it? That's ridiculous. Then what's the point of a speedometer anyways then lol. How do you use a handheld GPS, I've never used one before?

You can buy a completely self-contained one at Wal-Mart, Best Buy, etc. It just tells you where you are and where you are going. They also give you directions (navigation) if you get the ones with maps built in. Mine is a GPS connection that plugs into my Dell Axim PDA. The GPS receiver attaches to my windshield with a suction cup, and then it plugs into the cigarette lighter and the PDA.

sdorn · 03-06-2006, 05:14 PM

Quote:

Originally Posted by voltron1011

I can't believe we actually started ANOTHER thread about this...

I pointed him to the other thread, and for the most part the questions he has asked weren't addressed in the other thread. Plus, the other thread was really long and mostly just contained people's opinions rather than useful information.

blackE90 · 03-06-2006, 05:16 PM

wait so when i was ticketed for going 90 i was actually going 85-86...and those bastards said i was driving reckless lol

sdorn · 03-06-2006, 05:18 PM

Quote:

Originally Posted by blackE90

wait so when i was ticketed for going 90 i was actually going 85-86...and those bastards said i was driving reckless lol

The inaccuracy of the BMW speedometer wouldn't affect the radar or laser gun the cop was using. If he clocked you at 90, you were probably going 90.

voltron1011 · 03-06-2006, 05:31 PM

Quote:

Originally Posted by sdorn

The inaccuracy of the BMW speedometer wouldn't affect the radar or laser gun the cop was using. If he clocked you at 90, you were probably going 90.

Which meant your speedo was probably reading 96..

Romulus · 03-06-2006, 06:08 PM

ALL car speedos are off guys. there are better things to spend your time crying about, really.

sdorn · 03-06-2006, 06:30 PM

Quote:

Originally Posted by Romulus

ALL car speedos are off guys. there are better things to spend your time crying about, really.

None are as bad as BMW, and if we want to bitch about it why shouldn't we?

Our feelings are valid, too!!!

krndanic307 · 03-06-2006, 06:39 PM

How much is for the gps?

sdorn · 03-06-2006, 06:49 PM

Quote:

Originally Posted by krndanic307

How much is for the gps?

They start under $100 for a basic hand-held unit. They go up to over $1,000 for a nice navigation system.

BMW F22 · 03-06-2006, 07:03 PM

so when they say 330i 1/4 mile is this @ this speed, they were actually off by a few miles then??

03-06-2006, 02:22 AM	#1
karbosshack First Lieutenant 16 Rep 350 Posts Drives: 2008 BMW 328i Join Date: Jan 2006 Location: AZ iTrader: (3)	Question about Speedometer Accuracy Is there any way to get it fixed? Is there any device I can get to test the accuracy? I know I can have somebody pace me, but how would you know who's speedometer is more accurate I was drivin on the freeway today, and usually in my other cars when I go 10 over I pass most people, this time I was goin 10 over in the e90 and was getting passed by everybody....felt like I was goin slower than it actually read.
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03-06-2006, 02:36 AM	#2
alpinewhite3 Major 556 Rep 1,067 Posts Drives: Currently searching Join Date: Nov 2005 Location: North Carolina iTrader: (0)	The best way to check your speed is if you have one of those speed digital read out signs in your town that tell you your speed electronically. I set my cruise to 60mph and went past it. The sign read 56mph. So it's off by about 4-5mph. It's actually been pretty annoying ever since i found that out b/c now i constantly find myself checking my speed and then subtracting 5 from that number. I know it sounds simple enough but on the highway i check it a lot and it gets kind of annoying and tedious knowing that i have to subtract every time.
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03-06-2006, 02:38 AM	#3
Macfreak7 Private First Class 3 Rep 135 Posts Drives: E90 330i MT Join Date: Oct 2005 Location: Carlsbad iTrader: (0)	I thought I knew this at one point... but what's the exact reason for the lack of accuracy? How is the speed calculated? __________________
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03-06-2006, 02:42 AM	#4
sdorn Lieutenant 26 Rep 491 Posts Drives: 2006 Jet Black 325i Join Date: Feb 2006 Location: Atlanta iTrader: (0)	Here is the thread discussing this. I used a handheld GPS device to figure out how far off my speedometer was. There is no way to get it fixed. I asked the dealership and a local speedometer calibration company. They both said it couldn't be fixed. BMW does it on purpose. Mine is off by about 4 - 5mph at freeway speeds. So, if the speedometer says I am going 74, I am really going about 70. If it says I am going 85, I am really going 80. The inaccuracy gets bigger the faster you are going. Those roadside speed signs are only useful if you are going pretty fast. At lower speeds, the speedometer is only off by 1 - 2mph so it isn't that big of a deal. http://www.e90post.com/forums/showth...ht=speedometer __________________ 2008 Sparkling Graphite 535i 2009 Land Rover LR2 2003 Porsche 911 Turbo (SOLD) 2006 Jet Black 325i (SOLD) 2001 Bullitt Mustang (450rwhp - SOLD)
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03-06-2006, 08:07 AM	#6
stressdoc Moderator 618 Rep 10,855 Posts Drives: BMW i8; Toy 4runner TRD pro Join Date: Jun 2005 Location: Waco TX iTrader: (0)	All car manufacturers are required by law in many countries to make sure that their speedometers are not pessimistic. We can't have citizens exceeding the speed limit and using the excuse that they were just going by what their speedometer read. The amount that the speedometer is optimistic needs to cover slight variants in tire size, so most are set to be about 2-3% high, that is, they will read 100 mph when the car is actually going about 97 mph. Probably saves the world a little gas, a few lives, and some warranty coverage (because odometers are often set with the same gearing). Many old threads on this topic. The drive-by speed readouts are not reliable. Use GPS or the old stand-by of time/distance travelled on a stretch of highway with precise distance markers.
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03-06-2006, 04:09 PM	#9
krndanic307 Captain 77 Rep 641 Posts Drives: F20 M140 Join Date: Oct 2005 Location: Cali/Buenos Aires iTrader: (0)	So all this is real? I got a speeding ticket and the police said he paced me at 78. Which I wasn't really going 78 when he started pacing me. I was going 75 and the judge knew because I think the cop didn't have his speedometer calibrated right so thats mean I was actually going 70!! Is there anyway that I could get another trial date after I paid the ticket already?
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03-06-2006, 05:07 PM	#11
karbosshack First Lieutenant 16 Rep 350 Posts Drives: 2008 BMW 328i Join Date: Jan 2006 Location: AZ iTrader: (3)	Wow. That really sucks, no way to fix it? That's ridiculous. Then what's the point of a speedometer anyways then lol. How do you use a handheld GPS, I've never used one before?
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03-06-2006, 05:11 PM	#12
voltron1011 Colonel 119 Rep 2,909 Posts Drives: 2011 135i, FJR-1300 Join Date: Apr 2005 Location: Wiesbaden iTrader: (2)	I can't believe we actually started ANOTHER thread about this...
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03-06-2006, 05:16 PM	#15
blackE90 Private First Class 17 Rep 148 Posts Drives: sp blk 330i Join Date: Jun 2005 Location: east coast iTrader: (0)	wait so when i was ticketed for going 90 i was actually going 85-86...and those bastards said i was driving reckless lol
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03-06-2006, 06:08 PM	#18
Romulus Private First Class 15 Rep 171 Posts Drives: 05 M3 Join Date: Jan 2006 Location: Charleston, SC iTrader: (0)	ALL car speedos are off guys. there are better things to spend your time crying about, really.
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03-06-2006, 06:39 PM	#20
krndanic307 Captain 77 Rep 641 Posts Drives: F20 M140 Join Date: Oct 2005 Location: Cali/Buenos Aires iTrader: (0)	How much is for the gps?
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03-06-2006, 07:03 PM	#22
BMW F22 Major General 3566 Rep 9,788 Posts Drives: ///M235i Join Date: Nov 2005 Location: Bay Area iTrader: (8)	so when they say 330i 1/4 mile is this @ this speed, they were actually off by a few miles then??
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