You're confused about what unsprung weight is. It doesn't matter whether it spins or not, the fact that it's a mass that is not supported by the spring but which will have an effect on the suspension movement due to inertia is what matters. You want to keep unsprung weight as low as possible. 5 lbs added to a caliper will have the same effect on UNSPRUNG weight as 5 lbs added to a rotor, as long as the car is moving at a constant speed. You're thinking of ROTATING MASS which is also a killer and 5 lbs added to a rotor is 5 lbs of rotating mass which will hurt acceleration more than 5 lbs added to the caliper.
Unsprung weight affects suspension operation. Rotating mass affects acceleration.
Pacific Green '96 Contour LX V6
â??98 GTP, light mods, 14.66/94
Calypso Green '92 Mustang LX coupe, 13.56/101
Crown Autocross Club 1999 Street Tire Champion, 2000/2001/2002 Street Modified Champion
KCR SCCA 2002 Solo II Street Modified Champion
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