Speedo running fast, how do i ajust it?

[FASTCAT]

i just recently put 215/40/16 tires on my coug. when going down the hwy i noticed my speedo is running about 10% faster than i really am going. other than being annoying, cause i always have to deduct 10% from what my speedo says, my odometer will end up reading more miles in the long run than is actually being put on it. can anyone help. buying 17" rims and tires isn't an option right now. thanx billy

[mcon99]

take your dash apart to get access to the needles, put your computer display in diagnostic mode to display your real speed on the digital display, drive around the block, then reseat the needle on the pivot point until you can match the speeds.

I had to do this when I did my indiglos cause you have to pull the needles right off to install them.

[Fett]

Yea, that is true. It won't make a lot of difference now, but those extra miles will add up. If you are really off that much, I would take your car and have it calibrated.

[Mowgli]

How do you put your computer display in diagnostic mode ?

[AuburnCougar]

Well to get to diagnostic mode with an ATX start the car while holding the reset and units button on your trip computer, and then release the reset button first after the car has started. If it's an MTX you can just turn the key while the car is running while holding the two buttons and it will do the same.
To everyone who say it will affect his miles, I think that the analog display has no real affect on the milage because it's all taken by the computer so it reads what the digital display shows. The needle is just there so you can see roughly what the speed is. Cause mine is like that too, and I just haven't gotten around to taking car of it.

[Black99Cougar]

will that work?

10% of 20 mph is 2 mph off....but at 60...it is 6 mph off.

or is it a set number of mph off no matter what speed? (in that case, it would woe\rk)


anyone else understand what I mean?

[AuburnCougar]

Mine is a constant 4.5 mph off.