[V8] Tire/rim size and Speedometer calibration

[dsaad at icehouse.net]

I have recently been playing around with my speedo too...

It looks like my old speedo sender was reading a little slow. That seems 
impossible since this is a "digital" sender, but apparently it was missing 
pulses for a long time before it finally failed. I only say this because my MPG 
instantly went up about 2 MPG as indicated by the trip computer, and by my 
calculations, which I do every tank. I am now getting ~17 MPG calculated, 19 
MPG indicated on the trip computer (mostly city driving). I think that is in 
line with other listers as well.

I verified the speedo was within acceptable limits by using a GPS. I now have 
reasonable correlation between the GPS, speedo reading, and speed calculated by 
gear ratio and RPM.

Dave


Quoting Gunter <lorberg at adelphia.net>:

> 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
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