I have an 88 and I have 14 inch rims and tires on it. I have thought about getting a set of 15 inch rims and installing it on the car. The question is what will I have to do to the speedometer to make it read correctly with the different size tires?

I wouldnt worrie about it,it's only going to be about 2 or 3 mph diffrence.

quote Originally posted by rustyboltz: I have an 88 and I have 14 inch rims and tires on it. I have thought about getting a set of 15 inch rims and installing it on the car. The question is what will I have to do to the speedometer to make it read correctly with the different size tires?

With your new tires --- and regardless of what rim size they're on --- your Fiero's new speed at a given RPM can be expressed as a simple mathematical function of the rear tires' outside diameter. Use the formula:

Speed with New Tires = [New Tires' Diameter/Old Tires' Diameter] X Speed with Old Tires
By using that simple formula, you then can be confident in deciding whether or not the resultant expected speed difference with the new tires you're considering is even enough to be concerned about.

I hope that helps you out.