Car & Driver '04 test results
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From: Rochester
As stan mentioned, wheel weight has an effect on the ride and handling from the "unsprung mass". And it adds rotational inertia on top of the usual weight (="linear inertia").
But I do not agree with the rule of thumb. It's actually a pretty simple calculation. If the wheel weight is evenly distributed, a fair assumption, then each lb of wheel weight adds an additional half pound of inertia over the normal one lb. Unless I'm missing something??
But I do not agree with the rule of thumb. It's actually a pretty simple calculation. If the wheel weight is evenly distributed, a fair assumption, then each lb of wheel weight adds an additional half pound of inertia over the normal one lb. Unless I'm missing something??
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From: Lisbon
Originally posted by Swede_S2k
... and perhaps not with the EDM MY04 either)
:
...
... and perhaps not with the EDM MY04 either)
:...
Gearing remains the same, so does the engine, the only change is a better Cd, so...
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From: Rochester
Warning: here comes a physics digression...
For a disk, I=0.5*m*r^2. So, half what you wrote. And while a bit more of the weight is toward the edge, I don't think even distribution is that wild an assumption.
Okay, so we have the following eqns:
I = 0.5*m*r^2
I = torque/alpha (alpha=angular acceleration)
alpha = a/r (a=accel)
torque = F*r
substituting:
F=0.5*m*a
So, the rotational inertia contributes and additional half of the normal F=ma.
Thus, adding a lb to the wheel has the effect of a pound and a half on acceleration. Probably a bit more for the non-even distribution, but not as much as the worst case of all at the edge which would result in 1 lb wheel = 2 lb effect.
For a disk, I=0.5*m*r^2. So, half what you wrote. And while a bit more of the weight is toward the edge, I don't think even distribution is that wild an assumption.
Okay, so we have the following eqns:
I = 0.5*m*r^2
I = torque/alpha (alpha=angular acceleration)
alpha = a/r (a=accel)
torque = F*r
substituting:
F=0.5*m*a
So, the rotational inertia contributes and additional half of the normal F=ma.
Thus, adding a lb to the wheel has the effect of a pound and a half on acceleration. Probably a bit more for the non-even distribution, but not as much as the worst case of all at the edge which would result in 1 lb wheel = 2 lb effect.
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From: Indian Land SC
Originally posted by Road Rage . . .Unless i am mistaken, the top speed in both calcs is theoretical. The current car will not pull to redline in top gear (few cars do these days), nor will the MY04.
Originally posted by Road Rage . . .the MY04 has better aerodynamics - at high speeds, you are fighting ther wind. But then again, the wider tires play significant roles in drag, so the aero advantage may be offset. But with the higher gearing in 6th, and the fact that the car makes peak HP 50 rpm lower, I would tend to favor the MY04 is faster clan. As to whether the car is quicker, that will depend on conditions and expectations - it certainly will certainly be more tractable in the cut & pary of urban and suburban commuting.
Originally posted by FCGuy . . .To me, top speed doesn't matter much anyway.
My idea of perfect? - My '00 car (with current SC) and the new '04 tranny. Better accelleration down low and essentially the same highway gearing.