I have discovered that the speedometer reads 3 to 4 MPH faster than actual. The man at West LA Automotive Center explained that the manual specifies that calibration. He said he could correct with a resistor if I wanted to send back to him. Of course that would take another couple of weeks down time, Tn. to Ca.. If one uses this company, I guess you should specify that you want the speedometer to read TRUE. Who wooda thunk it?

I wouldn't rely on those speed radars that tell you your speed, atleast for precision. With all of the cars that drive by those, they can't be the most precise... I am sure the calibration gets slightly of after some time.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

I find that there is a designed error in most older car's speedos. I can tell you the exact error in my bimmer. It is 1.5 mph plus 2.5% of your speed. My friends e34 535 has the same exact error as well. The C class seems to be dead on with the accuracy.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Bill,
Yes, thank you. I have NEVER been in ANY car where the speed of the car corresponds precisely with that of one of those radars, whether it be a Mercedes, BMW, Chevy, Honda, or whatever it may be. Those things need calibration.
Southern Son,
What is your base for your speedometer being inaccurate.

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Actually, I chronographed the speed with the mile markers on the Interstate. Take the number of seconds that it requires to travel between two mile markers and divide that into 3600.

After realizing the difference, I got my handheld GPS receiver that I used to use in my airplane and stuck it to the windshield. It confirmed what I had noticed by the 'timing marker' method.