Join Date: Sep 2013
Location: Tampa Bay, FL
Vehicle: 2011 SLK300 with smart top
Other Toys: 2012 GLK350, 1970 Jaguar E-Type
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Speedometer and odometer are inaccurate
On my slk 230 the speedometer indicates a higher reading than shown on my gps. The odometer on the other hand indicates less mileage than the gps.
More specifically, the speedometer shows 80 mph when the gps shows 75mph. This same ratio applies throughout the speeds. At 40 it is showing 42 and at 50 it is showing 53 and at 60 it is showing 64. Which works out to about 7% high. However the odometer shows 25.1 miles traveled when the gps shows 26.9 miles. This is just shy of 7% low. The gps is accurate within 1-2 mph and the odo is right on with all my other cars, so I am going to assume that it is accurate. These tests were done on straight roads in Florida so the gps readings should match the indicated odo readings.
I could perhaps understand it better if they were both off the same, either high or low, but one is high and the other is low. And I am using the stock tire size on both front and back.
Anyone else experience this? And, the bigger question is -- What do I do to fix it?