It seems that my speedometer tells me that i am going about 5 mhp faster than i am. this is at any given speed. i know a few cops and had them test this for me with thier lasers and radar, deos anyone know how to fix this?

thanks
dan

 

Check that the needle rests at zero when you're at a complete stop. If it's resting above zero, the speedo will be off scale. You can take off the needle and reposition it correctly if that’s the case.

 

the needle is at zero when im not moving, but thankyou for the response

 

Well you're welcome.

Are the tires the stock size for the car?

 

I have the exact same problem.
my tires are 205/55/16
stock is 215/60/15

Arent my tires bigger than stock? Wouldnt that make my speedo slow?
I know its fast because of those stupid speed trap sensors.

-Brett

 

Your tires are actually smaller and would make your speedo fast.

Not sure what Dan's situation is though.

 

yes, thanks this helps out alot

 

An easy check for your true speed is to time how long it takes you to drive a mile. Get out on the feeway where you can hold a steady speed, then use a stopwatch to time how long it takes you to travel between the mile markers on the side of the road. Take 3600 and divide by the time in seconds to get your MPH. for example: if you ran the mile in 53 seconds, your speed is 3600/53 or 67.9 mph.

 

The tag on the inside of your gas tank lid should tell ya the stock size of this car's tires. Then you could use one or both of the below calculators to get a good idea of error involved. You could have the speedo re-calibrated via sending it to someone like Hollywood Speedometer (?), butt, I don't really think its worth it in most cases. Find out what it is, (you have it sounds like), and drive knowingly.

http://www.dakota-truck.net/TIRECALC/tirecalc.html

http://autocrossing.com/cgi-bin/tiresize.cgi

 

I think all 944s suffer from speedo error. My car has the same problem and that is with stock wheels tire and my 17s. Both are off by about the same 5 or so mph.