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Reply to "PROPOSED USE OF TIRE PRESSURE TO IMPROVE CALIBRATION"

Pete:
Thank you for the kind compliments.
I have read your report covering the calibration factors derived from a tire over five years, but find that your conclusion is opposed to one derived from my study. I assume that you pumped your tire to 125 psi, took the temperature, and measured the calibration factor from the calibration course. Although your results show a lot of scatter, you were surprised that there was a trend to a lower calibration factor with increasing temperature. You had expected since you always pumped up the tire to the same pressure, that it would have the same size regardless of temperature. Actually my results meet your expectation, and I am proposing we use this very finding to improve the accuracy and ease of certification.
The method of constant tire pressure obviously works very well with the moderately high performance wheel I use, but I am hopeful that further investigation will show that it is of general applicability.
Change in tire size can be monitored by tire pressure, but I do not see why you believe it is necessary to attach a gauge to the wheel for continuous readout.
It is true that postcalibration can detect a leak, but pressure monitoring can detect it much earlier and avoid much wasted measurement effort.
You recommend setting up a calibration course next to the race site. However to make the most accurate calibration course you must be able find a long straight section of traffic-free road, and lay it out at close to 68 F on a overcast day with a helper. This is usually not possible at the race site. Even if I was able to find a suitable location, it would take me twice as long to set up a calibration course as to do the actual measurement of the race course. The point is though why do this when a constant pressure method gives better results?
Last edited by neville
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