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Old 01-09-2018, 12:35 PM   #29
churchx
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Twinz: Best think of wheels (and brake rotors) as four flywheels. Going at constant speed/cruising engine will need same power with wheels of different weight. But you need to input more energy to spin them up to speed, and more energy to slow spinning due more stored rotational energy as with any flywheel. So car will accelerate slightly faster and will stop slightly sooner. Not by much, but with big weight differences it can be noticeable. More so vs removing same amount of weight elsewhere. Also in addition to that being rotational it's also unsprung weight. Lighter wheel/suspension can react better on road defects, as there is less mass inertia for springs to move wheel&brakes assembly&it's suspension arm alongside those bumps/roadholes, impacting slightly grip (wheel is more of a time and with better contact with road) and comfort. For many 'butt dyno' margin of detection error might be larger then slight weight difference, but if difference is much larger (eg. forged wheels and even more so + lightweight BBK), or in opposite to lightening direction (installing for sake of looks big heavy barrels for wheels of too big size, heavy weight and with heavier due width tires), then it can be felt subjectively by most. More so then with empty or full tank.
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