Quote:
Originally Posted by jdoublehcubed
BMW speedometers read 4% higher than actual by design. If you have lower profile tires than stock (say 40 aspect ration instead of stock 45) thats about another 5%. there's your 10% error.
There's an option to fix the design inaccuracy in NCS expert, I believe its called True Speed or something similar (although probably in German).
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I have stock spec tires. The speedometer is not really my concern, is the RPM. If the RPM is accurate, then it means we are not going 69mph at 2750. If the RPM is inaccurate like the speedometer, then how would I know my true RPM?
Sorry if my concern sounds dumb to you, but it really bothers me…