Nissan 370Z Forum - View Single Post

shabarivas · 08-21-2009, 04:15 PM

ok if we assume the wheel is a uniform disc... of weight M then the moment of inertia of that wheel is 1/2 * M * R^2 ... so... with a 19'' wheel - lets say it weighs 25lbs the moment of inertia is about - 1/2 * 25lbs * 19 * 19 = 4512 lb*inch^2

now lets say the new wheel weighs about - 24 lbs so a 1lb saving... moment of inertia = 1/2 * 19 * 19 * 24 = 4332 lb*inch^2

ratio of difference = 4% less moment of I w/ 1lb diff in wheel

so ... what that tells us is... roughly - shaving 1 lb off per wheel - makes it 4% easier to spin that wheel ... hope that makes sense

EDIT: for more info: http://hyperphysics.phy-astr.gsu.edu/Hbase/tdisc.html

08-21-2009, 04:15 PM	#232 (permalink)
shabarivas A True Z Fanatic Join Date: Apr 2009 Location: Sacramento, CA Posts: 2,188 Drives: 370z MB 6mt Rep Power: 914	ok if we assume the wheel is a uniform disc... of weight M then the moment of inertia of that wheel is 1/2 * M * R^2 ... so... with a 19'' wheel - lets say it weighs 25lbs the moment of inertia is about - 1/2 * 25lbs * 19 * 19 = 4512 lbinch^2 now lets say the new wheel weighs about - 24 lbs so a 1lb saving... moment of inertia = 1/2 19 * 19 * 24 = 4332 lb*inch^2 ratio of difference = 4% less moment of I w/ 1lb diff in wheel so ... what that tells us is... roughly - shaving 1 lb off per wheel - makes it 4% easier to spin that wheel ... hope that makes sense EDIT: for more info: http://hyperphysics.phy-astr.gsu.edu/Hbase/tdisc.html