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Speedometer accuracy...

Discussion in 'E46 M3 (2001-2006)' started by mdheller, Oct 20, 2008.

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    mooseheadm5

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    Basically GPS or 5th wheel are the only two super accurate choices. Some people have had luck with bicycle speedometers since you calibrate them to the rolling radius of the tires you have mounted.


    Because they list that exact set of responses on the FHWA website as being given in April of 2006. Initially I thought you were asserting that these people had contacted you directly, but I realized that you grabbed those responses off the interwebs. Others can read the exchange here:

    http://knowledge.fhwa.dot.gov/cops/...552797&Group=Travel Monitoring&tab=DISCUSSION

    Since the FHWA is not the correct department to ask, and neither the is the Washington state DOT, that is why they thought NHTSA could help. It sounds like the C&D article pretty much clears things up. The USDOT is the department that has all the little sub departments like the FHWA, NHTSA, FLHA, etc. but the ones at the top are the US DOT.

    BMWtoyz guest

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    I inquired my self but before I found those responses on the web and no they still have not got back to me. I am ready to give up on an "official" answer they seem to be too busy to reply!

    MPower11 guest

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    Mine is about +5.

    timcarswell guest

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    my tom tom shows + 5 on the M3; but spot on in the wife's mazda. i like the fudge factor anyway.

    JackinMidtown guest

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    My '90 M3 is off by 3 mph @ 70 according to my GPS.
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    CRKrieger

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    Yeah. Get over it. They all do that. What are you, Monk?

    [IMG]

    mdheller guest

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    thx, but ur a bit late. no need to be a dick about it either.

    JimAvery guest

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    If the speedo reads faster does not the odometer also read faster? This would have the effect of making the warranty period shorter. What a conspiracy theory.:eek:

    mdheller guest

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    hmmmm.... seems crazy enough to be true
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    CRKrieger

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    The only dick around here is anybody who thinks Tony Shalhoub isn't absolutely brilliant/hilarious in that role. Check your humor sensors; I think they might be clogged.

    mdheller guest

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    I'll get them checked, thx for the heads up : )
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    mooseheadm5

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    Not necessarily. I have checked some BMWs and the odo seems spot on while the speedo seems to read high on all of them (with the correct tires.) They probably program the odo to read real mileage whle programming the speedo to read high.
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    granthr

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    Actually, the odometers are pretty accurate, this is just a speedometer issue that BMW does on purpose.

    pclayton2 guest

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    speedometer issues

    My new 2009 128i speedometer shows 70 when both my GPS show 65. I called the dealer and customer relations and they both told me that they are setup to a -0 +10% error so we dont get a ticket. I told them that this was a bunch of *(&^%&^&^&^ and that they should calibrate it on the money. My Ford F150 is only off 1mph, not 5. Only if it is more than 10% will they recalibrate it. Since it's all electronics/software, I'm sure someone, somewhere nows how to calibrate this so it's right on the money.

    pclayton2 guest

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    speedometer accuracy

    My new 2009 128i speedometer shows 70 when both my GPS show 65. I called the dealer and customer relations and they both told me that they are setup to a -0 +10% error so we dont get a ticket. I told them that this was a bunch of *(&^%&^&^&^ and that they should calibrate it on the money. My Ford F150 is only off 1mph, not 5. Only if it is more than 10% will they recalibrate it. Since it's all electronics/software, I'm sure someone, somewhere nows how to calibrate this so it's right on the money.

    billloyd guest

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    I agree with some of the other posts that the speedometer is simply going to overstate the speed by varying degrees ... mine is off about 2 mph at 40, 3 mph at 60, 4 mph at 80, etc ... so, if I want to cruise at 75, I set the cruise control on 79 ... I think you get the picture ... so, I wouldn't worry about trying to fix it (which I doubt you can) nor would I spend money on a gadget to get a correct reading ... just check you actual speed once or twice and keep the difference in mind as your driving.
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    CRKrieger

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    Maybe someone does, but we don't know him. This is one of those "They all do that" things. It doesn't matter what other manufacturers do. This is what BMW does. In 25 years as a very involved enthusiast, I have never seen a fix for this issue.
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    scotthuck

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    Speedo Accuracy

    Judging by this thread and my own experience, it is well know BMW speedometers are intentionally inaccurate (both of mine have consistently read higher than actual). The question is, does anyone know of a fix to make it accurate (besides fitting larger tires)? Obviously the dealer/factory won't deal with it if it's within their acceptable tolerance. I personally find it very annoying since my M3 seems to be at the high end of what they deem "accurate".
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    CRKrieger

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    Do a Google search for "speedometer calibration services" ... and have your credit card handy.
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    bcweir

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    Here's the problem with calibrating a speedo "on the money"

    If you could say with absolute certainty that you would never change your wheel and tire size, and were never going to sell your car (with the subsequent owners promising the same thing), then I could see the value in calibrating a speedo "on the money."

    The problem is that the aftermarket wheel and tire industry is a multi-BILLION dollar racket. Car owners are constantly altering their wheel and tire specifications to tailor their vehicle to their tastes. The first time a car owner mounts a tire that is so much as a millimeter off from the original spec, it's going to immediately throw off the speedo by a proportionate measure. What then was the point in having the manufacturer calibrate it "on the money" if the first time you change to a different wheel and/or tire spec it's going to be off calibration again?

    The manufacturer is required to make certain that the speedometer comes within a certain tolerance of the correct speed. 5 to 10 percent is not going to be the end of the world, and it leaves the owner free to deviate from the original wheel and tire spec and still be within that 5 to 10 percent fudge factor. As long as the wheels and tires are upgraded properly (not going to an obviously different overall wheel and tire size diameter for example), I doubt that a 5 or 10 percent speedometer error is going to be the end all and be all reason you got a ticket.

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