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Old 12-21-2011, 11:52 AM   #18 (permalink)
gone-ot
...beats walking...
 
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...a tires' revolutions-per-mile (rpm) number are measured at 45 mph test speed and its rated load capacity, but that number varies with changes in speed and/or load.

...for example, below are the speedometer-vs.-actual results for my '70 AAR 'Cuda (S=speedometer; A = actual):

S = 100.0 mph, A = 102.0 mph, or 2.00% high.
S = _90.0 mph, A = _91.5 mph, or 1.67% high.
S = _80.0 mph, A = _81.2 mph, or 1.50% high.
S = _70.0 mph, A = _71.0 mph, or 1.43% high.
S = _60.0 mph, A = _60.5 mph, or 0.83% high.
S = _50.0 mph, A = _50.0 mph, or 0.00% no error.
S = _40.0 mph, A = _40.0 mph, or 0.00% no error.
S = _30.0 mph, A = _29.0 mph, or -3.33% low.

...thus, tire "error" is not static, it gets bigger above & below 45 mph!

Last edited by gone-ot; 12-21-2011 at 12:02 PM..
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