My car reads 7% faster than actual. Which means I record more miles than I drive. Is there a way to correct it? I have 430 wheels on my car with a big brake kit.
Mine is about the same. The way to calibrate it is to mentally deduct the extra speed. So if the speed limit is 60, I do 90. Simple math. As for the extra miles, just jack up the rear end and run it in reverse for a month.
No need. Its not out of the norm and everyone knows it. Going down the rabbit hole to correct a 7% error on an electronic instrument is....well its a rabbit hole.
T'is the silly season... It's always going to be difficult on a car like this as vehicle speed is sensed by one of the wheel speed sensors then the sensor data is processed by the ABS/ASR ECU and the speed signal is then sent to a host of other computers (including the instrument panel) on a CAN Bus. There are folks which service the instrument clusters (panels), who might know how to do this. You could help us by filling out your profile so we know where you are and who to recommend.
@Erikazra1 - I shouldn't have been sarcastic. The extra miles aren't important because every 360 has the same problem, hence, you're not at a disadvantage. As @Qavion pointed out, fixing it is major surgery and likely to be expensive. It's best to just live with it and enjoy the fact that you're actually driving slower than your speedo is telling you. If the speedo really bothers you, I suggest having a custom speedometer overlay made that corrects the error. It would be far cheaper, reversible and leave the car's electronics and software untouched.
Larger wheels/tires would make the odometer and speedometer understate speed/miles, not overstate... Ferraris read overly optimistic on the speedo (and odo), every car does it so you are not at any disadvantage, it is what it is.
Many of the speedometers are optimistic while the odometers are pretty accurate. Go figure. Time yourself between to mile markers to see if that holds true for yours.
I’m sure some unscrupulous owners have tried to attenuate the odo. I recall a YouTuber documenting the removal of a device which adjusted the data to keep miles down. Not sure if it was a bimmer or a Mercedes.
Mine has unique "issue." If I maintain normal speeds and normal accel levels, mine actually reads pretty true with GPS. However, the minute I get frisky...the faster I go, the slower it reads! Normally, triple digits by GPS results in school zone speeds or less. Only way to reset it is to stop then it goes back to normal, that is until I need Mr. Scott to engage the warp drive....
