Re: Driving 4000+ miles from California to Florida for Flight Judging!
Okay, guys, here's the algorithm you need to program into the supercomputer; 225/60R-15s average about 815 revs/mile.
Speed = RPM(60)/(axle ratio)(tire revs/mi)/trans ratio
My ancient TI calculator yields 69.6 MPH at 3500 for Luke's car, assuming a 3.70 axle, so his speedometer is reading 21 percent high. My Excel gear chart that I posted here a few weeks ago yields the same result.
The short tires only account for about 9-10 percent, so I suspect (assuming the tach is reasonably accurate) the speedometer gearing is mismatched to the installed axle ratio.
If the objective is to accumulate as many miles as possible... the same error applies to the odometer.
Duke
Okay, guys, here's the algorithm you need to program into the supercomputer; 225/60R-15s average about 815 revs/mile.
Speed = RPM(60)/(axle ratio)(tire revs/mi)/trans ratio
My ancient TI calculator yields 69.6 MPH at 3500 for Luke's car, assuming a 3.70 axle, so his speedometer is reading 21 percent high. My Excel gear chart that I posted here a few weeks ago yields the same result.
The short tires only account for about 9-10 percent, so I suspect (assuming the tach is reasonably accurate) the speedometer gearing is mismatched to the installed axle ratio.
If the objective is to accumulate as many miles as possible... the same error applies to the odometer.
Duke
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