According to my stopwatch and a TOMTOM, our analog speedometer is off by 5mph when cruising at highway speeds. If it says we are going 70, we are really only going 65. Is this a normal tolerance, or should it be better than that. Will the dealer be able to correct that? It is an '05 with 33K miles on it. Thanks, Rob.

 

My OBC speedo is 4 mph high according to those roadside speed readouts. I was just reading a Porsche owners' magazine about a time-speed-distance rally they were planning, and the author warned that Porsche speedometers are 3 to 4 mph fast. Maybe it's a conspiracy.

I'm not sure if the dealer can fix it or not. Here in San Diego there is (was?) a shop that specialized in calibrating speedometers so it might be a difficult thing to do.

Forgot to mention: when I changed out my speedometer's face, I messed up and the speedometer needle is now 5 mph slower than my OBC. You could do the same thing, and voila, now it's correct!

 

Tire sizes can effect speedometer readouts. Also it might just be a little out of calibration.

 

All auto's speedometers accuracy are rated +-2%.

But in your case, are you running a different tire/rim set up than what came with your MINI from factory ? If your present set up has a different circumferance, that will make your speedometer read faster/slower than actual speed.

 

It's not uncommon for the MINI's speedometer to read high... lots of folks have posted their observations (blah blah search the forums blah blah). The tolerance for reading high is generous--but they are not allowed to read low. Best I can tell, MINI dealers will not fix it if you're not exceeding 10% higher than actual.

 

I have a TomTom, a ScanGauge, the regular speedo and the OBC speedo all running at the same time and none of them read the same number! One day soon I'll put my Garmin in the car and see if I can get 5 different readings.
From lowest speed to highest...
TomTom
ScanGauge
OBC
Analog

Difference from low to high is about 4MPH.