Speedo Accuracy - '94 E36

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On Thu, 01 Sep 2005 18:47:51 GMT, "SteveG


Sorry, but that's ridiculous. The thing's job is to report your speed. I no more want a high-reading speedometer than I want a fast-reading watch that may "save me" from being late to an appointment.
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I don't want to start anything new and don't feel like bringing myself into this but I often set my watch a minute or two fast just for that reason, although I do prefer a more precise watch. I guess you are right, it is better to have the precision and then decide what you want to do with it.
Maybe bimmers read the speed high just in case there is a change to the car that would make the speedo read a little low and get you closer to a ticket?
To be honest with you guys, I really don't care that much about what my speedo reeds, I don't think 2 mph in any direction will do any harm or good.
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snipped-for-privacy@gmail.com wrote:

SG: It's not just BMW - ALL European manufactured cars do the same thing. In fact any car sold within the EU irrespective of where it is manufactured should also not read low - it's a legal requirement on the manufacturer (not the owner/driver I hasten to add).

SG: Hooray, some sense at last :-)
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Steve G
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wrote:

It's not even an EU Thing.
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But there's no requirement for the speedo *not* to be accurate. Merely that it must not under-read.
And assuming it's spot on with brand new tyres, wear on those will cause it to over-read.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

My guess, and my expereince by the way, is that the speedo is pretty close to dead nuts accurate with the largest factory tire available. As the tire size moves down the available fitment table, the speedomer becomes increasingly fast. I see no requirement for the manufacturer to precisely calibrate the speedometer for each and every tire that might be fitted on the car beczuse this would require the owner to recalibrate the speedo -- or the dealership -- when a factory optional tire package is installed. If they make the speedo work well for the largest tire they recommend/install, then all is well with the universe.
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dizzy wrote:

And I'm sorry that you didn't recognise my tongue in cheek comment.
Whether you want a high reading speedometer, or not, is irrelevant. Current EU construction regulations make it compulsory for designers and manufacturers to ensure that the instrument doesn't read low under normal working conditions (i.e. taking into account tyre wear, differences in tyre circumferences, mechanical tolerances in the instrument itself and transmission, etc.) so they err on the safe side and make them read high.
The fact that your BMW costs umpteen tens of thousands of Pounds/Euros/Dollars/whatever is also irrelevant. BMW don't actually make the speedo; they buy them in from whichever manufacturer offers them the best price and, therefore, potential profit margin.
The fact that you don't like it bothers neither them nor I one little bit.
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Steve G
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That's quite a different statement than the one I responded to, which said something about thanking them for their high-reading speedometer. That's the statement that I objected to, understand?

Please point-out where I claimed that my car's cost was relevant.
Oh, you can't, because I didn't.

Please point-out where I claimed that they did make the speedo.

Please point-out where I asked whether twits like you are bothered by my opinion.
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The problem withthat analogy is that if YOU set youir own watch, then you know that it's fast, and you compensate accordingly. If _I_ set your watch fast, you will not know until you have had a chance to check it against another watch or clock. Assuming you do not get the chance, you will end up being early to wherever you are going until you figure out that the watch you are using is set ahead.
Your car is much the same, if the speed limit sign says 45, or whatever, then you tend to plant the speedometer needle on what the sign says is the limit. The sign says 45, you go 45. You don't want the cops nailing you for doing 48, and they are not going to bother nailing you for going 42, so you prefer the speedometer to error on reading your speed faster than actual, not slower.
The discussion was that some people claim that their speedo reads from 5 ~ 7 mph too high, I suggest that the error is really more like 2 mph too high, or maybe even a bit less. Mine is under 2 mph fast at 80, and I assume the error is pretty much linear, so it should be 2 mph fast at other speeds as well. I haven't measured this though, and I have no idea that the error is linear or proportional to the actual speed, and don't much care.
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I'd be most surprised if it were. It's likely to be a percentage error.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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J Strickland wrote:

You started a good one here, mate :-))
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Steve G
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