Anyone else question whether their speedometer is accurate?
 

Last night, I was pulled over by a police officer and given a warning. I had my cruise control set at 63 mph in a 60 zone. He claimed I was going 69! I wouldn't think so much of it except he had been following me for about 4-5 miles....he didn't clock me with radar. My wife had claimed before that I was speeding when she was following me in her car. Of course I blew it off at the time, thinking she was being a little motherly or whatever. Has anyone else had this problem? Will the dealer check the speedometer accuracy? Thanks!<p>Wesley Walls<br>'98 1.8TMS

I checked mine with my portable GPS.
 

Did you change your wheels and or tire size??? I check mine after I put 18" on and it was very close, within 1mph. If you want the forumla to calculate the wheel/tire size vs. stock. Let me know I'll email it to you. That way you can tell if that might be influencing your MPH.<p>Alan

Re: Anyone else question whether their speedometer is accurate?
 

I've checked mine with the stock wheels and tires and it's dead perfect. You can easily check it yourself by driving on a highway at a constant speed and timing how long it takes to go between mile markers. There's a highway near me with painted white lines on it where the second line is clearly marked ".6 mile". I just used the stopwatch function of my watch and drove through the lines first at a constant 60MPH and then again at 80MPH. The time I got calculated perfect in both cases. For instance, if I timed it at 27 seconds,<p>((.6 miles)/(27 seconds))x(3600 seconds/hour) = 80MPH<p>If you do find your speedometer is in error and you still have the original wheels and tires, you can probably get out of the ticket by getting your speedometer measured by a professional. Check your local yellow pages under "Speedometers". There are places that calibrate speedometers, and a large majority of their work is from people who got speeding tickets.<p>Jim Meyer<br>'98.5 2.8QMS

I did the same thing!!
 

Checked with a Garmin GPS III. It was +or- 1mph. That could have been the GPS though - only had 3 satellites.

You're right...I could check myself by clocking a mile!
 

I wasn't thinking clearly at the time! I was just ticked off at getting pulled over. I do have stock sport wheels and tires. Speaking of accuracy, I did enable the "speed" data on the HVAC display onetime, and it was on the money @ 100kph. However, that data likely comes from the same source supplying the speedo with information.<p>Thanks for your help!<br>Wesley Walls<br>'98 1.8TMS

no, I've calibrated it on safety radar in our neighborhood (several diff. units): it's right on the mark, exactly.
 

So is our '89 Saab 900, and so was my '94 M-B C280. My '73 Porsche 911 is about 10% optimistic, i.e., 62 indicated=55 on radar; 70 indicated=63 on radar, etc.