I recently had to replace my instrument cluster in my 97 Camaro SS.The replacement cluster reads high(by about 10% eg at 60 mph it reads 66 mph).My guess is that it came off of a car with 16" wheels,mine has 17'. Has anybody run into a similar situation or know if this can be calibrated to match my tire size?

 

If you have larger tires, the speedometer should indicate a lower speed than the the speed the car is really traveling at. Ex. if the car is traveling at 70 MPH the speedometer should be showing a lower speed, someting like 65 MPH. Yours is going in the oppsite direction. This aside, the spedometer is driven electrically by the PCM, based on what the PCM sees from the VSS (Vehicle speed sensor} and the easiest way to calibrate the speed is to adjust the PCM. It could also be that your cluster has problems such as voltage to meters.

 

Thanks for the info,How do you adjust the PCM or go about getting info on how to adjust it.....JohnJr

 

You can buy a programmer for this off ebay or several other places for around $250-$300. This will allow you to make certain changes to the car. It plugs straight into the port under the dash.

 

Hello,I dont know if this will help , buy hey I figured this out by trial and error. I bought a simulated carbon fiber graphic overlay for the gauge unit and I had to remove the needles off the gauge for the speedometer and the tach. Put the overlay on and it was nice put the needles on and back in the car and a few days later, I noticed the needles were not moving for either. The other gauges were working just fine, so I knew it was not electrical. I tried pulling the battery loose just to see if that would help. It did not, so I looked inside and noticed that the needle base rotates in an electrical mass like an alternator. So I removed the needles and replaced them at a different location and noticed that the tach was working but the speedpmeter was off about 35 miles and hour. So I kept moving the needle so the speedometer was set at the proper speed for idle and set the speedometer to 0 and when I drove it , it was back to normal. When doing all of this , I had noticed when I bought my car that it was off a few miles on the speedometer setting in park, now it does not, so hopefully I fixed it. ONE WARNING: If you end up doing this, work the needles off the stem very carefully, very little rocking motion, cause they WILL break easily. I did not break them, but I could tell they were very fragile. Hope this helps someone.

 

Here's a good tire size calculator to calculate speedometer difference with different sized tires.