My 85 300D speedometer reads about 5-10 MPH slow. Is that a common issue and does anyone know an easy fix?


Bob
300D 157K

Check the odometer to see if it is accurate. If not, check tire size to make sure the external diameter is correct -- if is is not, get the correct size next time you get tires.

If the odometer is correct, the speedo is off. Not all that uncommon, but you will need to remember that it is off! Can be fixed, but probably not worth it unless the odo breaks, too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I think there is a guy that rebuilds them for about $125.... sure would hate to get a ticket due to it being off... police usually allow about a 10% error on speedometers... but you can't bank on that...

My '79 300SD speedometer does the same thing (4% slow). The odometer is correct. If I put on 225x70R14 tires, the speedometer is correct but the odometer is off about 4%.

P E H

My dad once told me that if you were pulled over by an LEO for speeding and you're within 5mph of the speed limit, you can take it to court and win unless they tracked your speed with a laser gun. This is due to the possibility of the LEO's car's speedo being off by that much...unless he happened to have recently had his speedo calibrated.

That said, I typically don't take that risk...

Cops love to tell you that laser is dead nuts on, no room for error. Laser is nothing like radar. Radar gives correct speed based on the dopler effect. All parts of the car are moving at the same speed. Laser on the other hand is nothing more than a fancy tape measuring device. Say he aims at the normal range of 500-600 feet (think he could hit a 7" moving target at 500' with his service revolver?)at your 7 inch headlight, a moving target, and the first part of the beam hits your windshield, the last part bounces off your headlight or even a car next to you. The resulting distance will throw the speed off by a very large margin.

Warden,

You used the term LEO. Don't you mean RG? I'm assuming LEO stands for law enforcement officer. RG stands for REVENUE GENERATOR.

Peter

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Auto Zentral Ltd.

Mine used to read about 7mph fast. These mechanical 123 speedo's weren't the most accurate devices around.