[V8] Tire/rim size and Speedometer calibration

[Gunter]

Here's a question for owners of 'Canadian' spec V8 Q's.

I only acquired mine 4-5 months ago.  The speedometer is metric, of course.  The previous owner claims that the car came factory equipped with 205/60-15 tire/wheel combos.  I am skeptical of his claim and thought that the tire/wheel combo was 215/60-15 regardless of final destination.  In any case, the car is presently wearing 205/65-15 winter tires and I am curious as to whether or not I should be factoring in a small (or perhaps not so small) adjustment, based on differences in overall wheel diameter, into the speedometer reading to bring it in line with the actual road speed.  I have already earned myself one speeding ticket with this car, and feel that I should arm myself with whatever information is available in order to keep within the legal limit...............at those times when I choose not to exceed the limit.

Thanks,
Gunter, Cleveland
1990 V8 Q Canadian Tornado red with 240 000kms