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
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
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).
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.
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.
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,
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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