Quote:
Originally Posted by Buddman
The car's going in for it's second service in about a week and I was going to get the dealer to check it out.
Adam
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Hi Adam,
There will be nothing wrong with your speedometer.
All new cars on the Australian market now have speedometers calibrated so that
the speed indicated is higher than the actual speed you are traveling.
The two documents cited by Doug, including the Australian Design Rules, provide
the mathematical relationship.
Your indicated speed of 100km/h and your actual speed of 93km/h is
not uncommon on late model cars and is intentional.
It is intentional for two reasons -
1) It falls within the Australian Design Rules standard
2) It help protects a car maker from litigation in the event of a driver receiving
a speeding fine or being involved in an accident where excessive speed was
a factor.
Since the advent of GPS systems that can estimate and display the actual
speed of the vehicle, the fact that speedometers on newer cars will tend
to indicate the speed to be faster than what it actually is has become
evident to motorists who were previously unaware of this convention.
At lower speeds (i.e. 0 to 60 km/h) you will note that there is typically
less of a discrepancy than in the range of speeds higher than this.
The good news is that most new cars are calibrated in much the same way
so that if you are in a 100km/h zone on a freeway, adjust your speed so
that the indicated speed is 100k/h and then engage cruise control, other
motorists who have done the same in late model cars will tend to be going at
nearly the same actual speed as you.
Your dealer will most probably provide you with effectively the same advice
as above and recommend that you leave the speedometer at its factory
calibrated setting. Your GPS unit will then provide you with a different estimate.
Happy motoring!