Rotating vs static vs sprung and unsprung wt - Third Generation F-Body Message Boards

va454ss · 11-07-2009, 08:29 PM

Some say every lb of rotating wt is equivalent to 6 lbs of static wt.

Does lowering sprung vs unsprung wt have the same effect on acceleration?

I've replaced the stock front rotors with an aluminum hub and 2 piece rotor, resulting in a wt loss of 14 lbs per side. Also going to wheels that are 2 lbs lighter per wheel.

So is this gonna help with lowering ET or is it wishfull thinking? I know wt loss is supposed to lower ET; just trying to quantify what I did.

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Stephen 87 IROC · 11-07-2009, 09:18 PM

Unsprung weight is dead weight. It can't be controlled by the shocks and springs. Since it can't be controlled, you want it as light as possible.

Lightweight tires and rims. Aluminum brake parts such as calipers and front hubs. Tubular a-arms. Aluminum components in a diff such as a spool and with a 9", the case and bearing support. A lightened ring gear can shave off a little more weight. With large diameter axles, gundrilled cuts down on weight.

radical82 · 11-08-2009, 09:43 AM

Sprung v unsprung weight is more of a handling issue then an acceleration issue.... The old equation is that a 1 lb. reduction of unsprung weight is equal to a 6 or 7 pound reduction in sprung weight...

The weight v acceleration concerns the overall weight of the car, a 100 lb. reduction equals a 1/10 sec. reduction in ET... Reducing weight in the rear end, as Stphen 87 stated, allows the components in the drivetrain to accelerate faster, therefore lowering your ET... Any reduction of the rotating mass in the engine and drivetrain will make for quicker acceleration.

Just keep in mind the basics of physics, an object at rest tends to stay at rest and the greater the mass (weight) the slower the rate of acceleration.... However, remember the other side of physics laws--an object in motion tends to stay in motion....so things like a 40lb. flywheel on a five speed car v a 20 pound aluminum flywheel, the heavy flywheel will help to keep the revs up when you shift.....