Speedometer off.

[mistermojorizin]

Originally Posted by jeremyc74

You're missing the entire point.

The point is, we think they made a wrong decision by making the speedometer read this much ABOVE actual speed. There's no law anywhere that requires that, and modern manufacturing doesn't require the tolerence to be that high to keep the car within international laws either. No one here is even suggesting hacking into the computer to fix it.

fixed

[jeremyc74]

Originally Posted by mistermojorizin

fixed

Thanks.

[Mad Dragon]

Since no one read it the first time around.

Originally Posted by Horse Necromancer

GROUP 62
Instruments B 62 02 96 Woodcliff Lake, NJ
Product Engineering May 1996


SUBJECT:
Maximum Permissible Speedometer Error

MODELS:
All

General Information:
A certain amount of "speedometer advance" is necessary to compensate for negative tolerances in tire diameter, electronic controls, and other factors. This advance reduces the risk of the speedometer displaying a speed that is less than the vehicle's actual speed.

The amount of speedometer advance can be calculated by inputting a frequency (using the DIS Tester, "Kombi Test Schedule") that corresponds to a given speed and noting the speed that is indicated by the speedometer. The maximum permitted speedometer advance is 10% of the actual (input) speed plus 2.4 mph.

Example:

Actual Speed = 50 mph

50 mph x 10% = 5 mph; 5 mph + 2.4 mph = 7.4 mph

Therefore, the permissible displayed speed is 50 to 57.4 mph.

(Note: The displayed speed must never be less than the actual speed).

No repairs should be attempted if the speedometer advance is within 10% + 2.4 mph.

NOTE: The amount of speedometer advance has no effect on recording of accumulated mileage in the odometer display. The odometer records total mileage digitally and does not incorporate any "advance" tolerances.

That bulletin was published 12 years ago. If BMW ever had any intention to appease the minority who absolutely have to know exact speed, they would have done it already.

[jeremyc74]

Originally Posted by Mad Dragon

Since no one read it the first time around.

That bulletin was published 12 years ago. If BMW ever had any intention to appease the minority who absolutely have to know exact speed, they would have done it already.

We all read it and still think their stance is just as poor now as it was then. A 10% inaccuracy is absurd in a modern vehicle.

[Wolfpack]

Amazing to me how much some people care about speedometer error. I have never owned a car in the last 30 years that was dead on from the factory.

If you really have an issue, change the tires and find ones with rotational specifications that will put the speed dead on. For all those who are putting on bigger wheels and tires or changing out the runflats, you are making changes that will affect the speed readout anyway. Almost every tire brand has rotation differences for the same size tires based on compound, sidewall, etc.

[ARES45]

Once again, when I change the tires I would be just as inclined as I am now to have a correct speedo. Meaning after new tires, I would take it somewhere for adjustments. So that argument doesn't hold water with me. They probably have a note in the Owner's Manual that states any tires other that OEM may affect the speedo, BMW knows the exact spec of the tires out of the factory so the 5% it is off is a little much on 'an engineering masterpiece.'

[ucbsupafly]

Originally Posted by ARES45

Once again, when I change the tires I would be just as inclined as I am now to have a correct speedo. Meaning after new tires, I would take it somewhere for adjustments. So that argument doesn't hold water with me. They probably have a note in the Owner's Manual that states any tires other that OEM may affect the speedo, BMW knows the exact spec of the tires out of the factory so the 5% it is off is a little much on 'an engineering masterpiece.'

Keep in mind that even OEM tires can have an effect on the speed reading. Tire wear changes the circumference of the tire and yes, it could translate to as much as 5% "speedo error". No one is going to have the speedo recalibrated every 1000 mile or so to compensate for all the changes in tire, weather, and road condition. Therefore, auto manufacturers add in varing degrees of safety measure in the speed readout to cover their asses. Some just offset it more than others. Unless you can manufacture your own car, it's a fact you'll have to live with.

As for asking BMW to include a way of manually changing the speeo offset to the owners liking, imagine the extra cost and liability issues. It's just not feasible.

Personally, I look more at the Tachometer than I do at the Speedometer. I choose my cruising speed based on the flow of traffic and road condition, not at the speedo.

[Kiety]

easy fix, see those lasers used in mice these days? mount 3 of them under your vehicle to monitor the speed. Would work with any tire, and wouldn't exactly cost much money. It would NOT correct the +3 on speedo though.

One other thing to note, GPS speeds are only accurate if you are on a 100% level surface. Portable navis(consumer ones) don't consider your current grade of ascent or decent.

[jeremyc74]

Originally Posted by Kiety

One other thing to note, GPS speeds are only accurate if you are on a 100% level surface. Portable navis(consumer ones) don't consider your current grade of ascent or decent.

That's not the case. The speed is based on triangulation, and it doesn't matter if you're on flat ground or not.

[Omega Man]

When you say it's the law what you mean is it's within legislated tolerable limits. If I'm the manufacturer ,I'm going low to avoid liability. It's not that they are trying to protect you. They are trying to protect BMW. And they had the law written to allow it so they win.

[hbiscuit]

this is normal. my e36 328i did the same exact thing.

[Kayne]

Wow, you guys think 3-5% is huge.

My VW is 10% off. When I'm at 100, my gps tells me 90 mph, and it feels like it too. I went in for the TSB. When I came out, my car was about 8% off. What a great company VW is! *insert sarcasm*

There are those who were scared that the odometer would be reading much higher mileage than the car is actually traveling.(IE: Driving 1000 miles vs 900 miles in my case.) I did some tests with my Toyota and have concluded that only the speedometer is off, but the car accurately records how far it's traveling.

[spankrorie]

i think we should do 130 past the officer around the corner and see what he says about the optimistic odometer! or get a radar gun cuz gps uses averages in position/time; and hops thru several different signals to calc those positions. Have you ever stood still with a GPS and seen how unstable a signal gets? GPS is not a reliable source for real-time ground speed vs. an odometer!

[ky_soldier]

we in the military have been using gps for years and even availed it to the commercial sector but to less stringent tolerances (unless you have the proper COMSEC you won't get the avail accuracy by design). we set radio frequency encryption timing to it, and it is used for numerous other applications. assuming you have clear line of sight to 3+ birds, it will be dead on accurate. no s**t your garmin isn't going to work in a garage, it can't see the birds.

as for it bothering some, seriously buy a $125 cheapo garmin/magellan, etc and they will give you dead on speedo, regardless of your tires. it's not perfect but its the best this problem is going to get.

using ares45's analogy, in this case, if you know 84 is really 80 then it should be consistent (in your case consistently annoying) but consistent either way. yeah it's a pain but if it's the worst complaint we have, that's a charmed thing. at least you can still enjoy it ;-)

PS - as for tire sizing, here is GREAT site I used to size my jeep wheels/tires that can help with your problem should you choose to play with it on your next set of wheels/tires http://www.miata.net/garage/tirecalc.html

[ARES45]

Thanks ky, It is nice to have such minor problems and I hope this is the worst thing that I have to deal with. Obviously I don't plan on getting a different car because of it, but I am hoping that my dealer will do me a favor and adjust it if it is easy enough for them to do. If they don't, the toughest thing will be to retrain the wife so she knows how it works.

[jeremyc74]

Originally Posted by spankrorie

i think we should do 130 past the officer around the corner and see what he says about the optimistic odometer! or get a radar gun cuz gps uses averages in position/time; and hops thru several different signals to calc those positions. Have you ever stood still with a GPS and seen how unstable a signal gets? GPS is not a reliable source for real-time ground speed vs. an odometer!

GPS is DEAD accurate when it's properly tracking (which is about 99% of the time in a car).

I've got two GPS systems in my car, and both agree completely. I have also had the speed of the car LASER verified, and the speedometer is off by 4 at 91MPH.

At this point, there's no question that it's off. BMW built it that way. The question now is "can we adjust it somehow?"

[ky_soldier]

Im not sure if its simply a mapping issue in the electronics, and even if it was, you might incur come risk to bring the tolerance down. At least your tickets won't be for as much as you think they will be :-o

[ChrisK]

Originally Posted by Wolfpack

Amazing to me how much some people care about speedometer error. I have never owned a car in the last 30 years that was dead on from the factory.

What he said. I have never owned a car in my life that had a accurate speedo.

[Tom K.]

Originally Posted by ChrisK

What he said. I have never owned a car in my life that had a accurate speedo.

Hard to understand why some folks feel an accurate speedometer is part of their birthright. Back in the '60s, R&T routinely published speedo error at 30 and 60 mph as part of their road test data panels - and some of the worst offenders were Porsche and Ferrari with speedos up to 20% fast. We just learned to do the easy math and read our true speed from the tach (non torque convertor models).
Tom

[jeremyc74]

Originally Posted by Tom K.

Hard to understand why some folks feel an accurate speedometer is part of their birthright. Back in the '60s, R&T routinely published speedo error at 30 and 60 mph as part of their road test data panels - and some of the worst offenders were Porsche and Ferrari with speedos up to 20% fast. We just learned to do the easy math and read our true speed from the tach (non torque convertor models).
Tom

Yeah and you also had to do a tune up every 10k miles. We expect a little progress in 50 years of manufacturing.

[Tom K.]

Originally Posted by jeremyc74

We expect a little progress in 50 years of manufacturing.

Like the part you now can't get because it's part of another part?

Regarding the speedo error, has any manufacturer specified accuracy better than BMW's 10% +2.4 mph? As most BMW speedos are within 5% (on the high side), what error do you consider to be acceptable?
Tom

[jeremyc74]

Originally Posted by Tom K.

Like the part you now can't get because it's part of another part?

Regarding the speedo error, has any manufacturer specified accuracy better than BMW's 10% +2.4 mph? As most BMW speedos are within 5% (on the high side), what error do you consider to be acceptable?
Tom

The Ford truck line I just did speced +0-3% at 70MPH. In reality the units going out the door were within .5%. This is why I don't understand why their tolerance is so high. It's totally unneccesary with todays manufacturing capabilities.