Speed sensor

esqu1re · 11-02-2010, 04:26 PM

Does anyone know which wheel(s) / axle the speed sensor is on? I can't stand that my speedometer is off and am considering increasing the tire size to compensate. Naturally, there may or may be handling effects due to the slight increase in sidewall height, but I'm curious as to which wheel / axle the sensor is on. Thanks in advance.

jragan · 11-02-2010, 05:30 PM

Your spedometer is not off. It is purposely telling you a different value to keep you from overspeeding. The car knows how fast you're going (you can see this in the test functions of the cluster), it just doesn't want you to know that.

ZZZZ · 11-02-2010, 06:02 PM

If the Z4 is like every other bimmer, then the speed sensor for the speedo is not on a wheel/axle... it's on the differential. The 'speed sensors' for the wheels are used to detect if a wheel is slipping for DSC/DTC, or if the wheels are locked during braking (ABS). How much is your speedometer off by... how did you measure, with a GPS positioning unit?

jragan · 11-03-2010, 08:06 AM

Don't know about the non-M Zed, but for the Ms, the car indicates a faster speed by ~5% across the board. However if you put the instrument cluster into test mode and set it to display the speed component, you'll see a speed much more in-line with the actual (although not exact).

If it bothers you that much, it would be easier (and serve a dual purpose) If you just get a nice little Escort 9500ix that will display your GPS speed while you're driving.

ZZZZ · 11-03-2010, 09:43 AM

Do these instrument clusters go into test mode like the e36/e46/e39s?... hold down the reset button while ignition to POS2? Is there a list of available functions on the Z4 instrument clusters anywhere?

esqu1re · 11-03-2010, 09:57 AM

Quote:

Originally Posted by ZZZZ

If the Z4 is like every other bimmer, then the speed sensor for the speedo is not on a wheel/axle... it's on the differential. The 'speed sensors' for the wheels are used to detect if a wheel is slipping for DSC/DTC, or if the wheels are locked during braking (ABS). How much is your speedometer off by... how did you measure, with a GPS positioning unit?

I checked actual speed with a GPS; indicates about a 5% difference. So, I take it that the speed sensors can be affected by messing w/ the diameter of the rear tires.

Quote:

Originally Posted by jragan

Don't know about the non-M Zed, but for the Ms, the car indicates a faster speed by ~5% across the board. However if you put the instrument cluster into test mode and set it to display the speed component, you'll see a speed much more in-line with the actual (although not exact).

If it bothers you that much, it would be easier (and serve a dual purpose) If you just get a nice little Escort 9500ix that will display your GPS speed while you're driving.

I actually have a 9500ix which helps, but I'd like the speedometer to tell me the actual speed. I understand why BMW does it-----but the fact of the matter is that the speedometer isn't displaying the correct speed on purpose, which unfortunately bothers me more than it should. Heh.

Nhopkins1394 · 11-03-2010, 11:17 AM

-----but the fact of the matter is that the speedometer isn't displaying the correct speed on purpose, which unfortunately bothers me more than it should. Heh.[/QUOTE]

REALLY???
I thought you were kidding.
BMW REALLY manufactures a speedometer that intentionally gives the wrong speed?????

REALLY?? WTF!

rps · 11-03-2010, 11:26 AM

When I changed to M fitment 18" wheels my speedometer was dead on. Previously, it had been reading 3-4 mph faster than actual. Now it is within 1 mph of the actual speed on the GPS.

esqu1re · 11-03-2010, 01:06 PM

Quote:

Originally Posted by Nhopkins1394

REALLY???
I thought you were kidding.
BMW REALLY manufactures a speedometer that intentionally gives the wrong speed?????

REALLY?? WTF!

Yes. They do this so you think you're going faster than you are; probably for insurance purposes.

Like me setting my alarm 10 minutes ahead and tricking myself into getting to work on time.

gcochard · 11-03-2010, 02:05 PM

Is the needle just wrong or is the mileage count wrong too?

If the mileage count is wrong, then you should fix that ASAP since it will run down your warrantee and scheduled maintenance faster...

esqu1re · 11-03-2010, 04:25 PM

Mileage displays actual. Legally, BMW cannot mess with odo mileage.

Dammmittt · 11-03-2010, 04:47 PM

Here are the results of my speedo test.

http://www.bimmerfest.com/forums/sho...=356166&page=3

gcochard · 11-03-2010, 05:03 PM

Alright good.

Thank you Dammmittt for an informative thread.

11-02-2010, 04:26 PM	#1
esqu1re Lieutenant Colonel 41 Rep 1,855 Posts Drives: M Coupe Join Date: Jul 2010 Location: East Coast iTrader: (0)	Speed sensor Does anyone know which wheel(s) / axle the speed sensor is on? I can't stand that my speedometer is off and am considering increasing the tire size to compensate. Naturally, there may or may be handling effects due to the slight increase in sidewall height, but I'm curious as to which wheel / axle the sensor is on. Thanks in advance. __________________ ///M Coupe: RPI Scoop, OE Strut, CDV, Volk RE30, SS Brake Lines, Stromung Exhaust
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11-02-2010, 05:30 PM	#2
jragan Imola Lover 26 Rep 749 Posts Drives: 2007 Imola Red M Coupe Join Date: Jul 2008 Location: Fort Worth, Texas iTrader: (0)	Your spedometer is not off. It is purposely telling you a different value to keep you from overspeeding. The car knows how fast you're going (you can see this in the test functions of the cluster), it just doesn't want you to know that. __________________ His: RIP-"Ruby" *E86 ///M Coupe: Pics Track Pics Short Vids Long Vids Hers: 997-1 C4S*: Pics
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11-02-2010, 06:02 PM	#3
ZZZZ Captain 50 Rep 753 Posts Drives: Z4 3.0i winterbeater Join Date: Nov 2010 Location: Toronto, Ontario iTrader: (1)	If the Z4 is like every other bimmer, then the speed sensor for the speedo is not on a wheel/axle... it's on the differential. The 'speed sensors' for the wheels are used to detect if a wheel is slipping for DSC/DTC, or if the wheels are locked during braking (ABS). How much is your speedometer off by... how did you measure, with a GPS positioning unit?
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11-03-2010, 08:06 AM	#4
jragan Imola Lover 26 Rep 749 Posts Drives: 2007 Imola Red M Coupe Join Date: Jul 2008 Location: Fort Worth, Texas iTrader: (0)	Don't know about the non-M Zed, but for the Ms, the car indicates a faster speed by ~5% across the board. However if you put the instrument cluster into test mode and set it to display the speed component, you'll see a speed much more in-line with the actual (although not exact). If it bothers you that much, it would be easier (and serve a dual purpose) If you just get a nice little Escort 9500ix that will display your GPS speed while you're driving. __________________ His: RIP-"Ruby" *E86 ///M Coupe: Pics Track Pics Short Vids Long Vids Hers: 997-1 C4S*: Pics
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11-03-2010, 09:43 AM	#5
ZZZZ Captain 50 Rep 753 Posts Drives: Z4 3.0i winterbeater Join Date: Nov 2010 Location: Toronto, Ontario iTrader: (1)	Do these instrument clusters go into test mode like the e36/e46/e39s?... hold down the reset button while ignition to POS2? Is there a list of available functions on the Z4 instrument clusters anywhere?
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11-03-2010, 11:17 AM	#7
Nhopkins1394 Accountant, 1st Class 8 Rep 237 Posts Drives: 2006 Z4 3.0si Roadster, Black Join Date: Jul 2010 Location: Irving, TX where the Cowboys used to play! iTrader: (0)	Speedometer readingg off intentionally? -----but the fact of the matter is that the speedometer isn't displaying the correct speed on purpose, which unfortunately bothers me more than it should. Heh.[/QUOTE] REALLY??? I thought you were kidding. BMW REALLY manufactures a speedometer that intentionally gives the wrong speed????? REALLY?? WTF!
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11-03-2010, 11:26 AM	#8
rps Captain 35 Rep 609 Posts Drives: 2013 X1 Join Date: May 2009 Location: Pace, Fl iTrader: (11)	When I changed to M fitment 18" wheels my speedometer was dead on. Previously, it had been reading 3-4 mph faster than actual. Now it is within 1 mph of the actual speed on the GPS. __________________ NB8S Past Garage: Z4, 135i. Present Garage: 2013 X Drive X1 2.8i.
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11-03-2010, 02:05 PM	#10
gcochard Captain 24 Rep 784 Posts Drives: 2011.5 E90 M3 Join Date: Oct 2010 Location: South OC iTrader: (2) Garage List 2011 BMW M3 [0.00]	Is the needle just wrong or is the mileage count wrong too? If the mileage count is wrong, then you should fix that ASAP since it will run down your warrantee and scheduled maintenance faster...
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11-03-2010, 04:25 PM	#11
esqu1re Lieutenant Colonel 41 Rep 1,855 Posts Drives: M Coupe Join Date: Jul 2010 Location: East Coast iTrader: (0)	Mileage displays actual. Legally, BMW cannot mess with odo mileage. __________________ ///M Coupe: RPI Scoop, OE Strut, CDV, Volk RE30, SS Brake Lines, Stromung Exhaust
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11-03-2010, 04:47 PM	#12
Dammmittt My favorite sign. 167 Rep 4,333 Posts Drives: 2007 M Coupe Join Date: Dec 2006 Location: Der Autobahnen iTrader: (0)	Here are the results of my speedo test. http://www.bimmerfest.com/forums/sho...=356166&page=3 __________________ 07 ///M Coupe (Premium Package) Black Saphire Ext. Imola Red Int. Best Website EVER!
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11-03-2010, 05:03 PM	#13
gcochard Captain 24 Rep 784 Posts Drives: 2011.5 E90 M3 Join Date: Oct 2010 Location: South OC iTrader: (2) Garage List 2011 BMW M3 [0.00]	Alright good. Thank you Dammmittt for an informative thread.
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