Aluminum driveshaft Whats the deal?

RAD said:

hmmm so carbon fiber shaft isn't better then aluminum? oh and I thought with either one cruising on the highway when you let off the throttle car will slow down faster due to lighter shaft which will lead to burning more fuel cause you have to keep your foot on the gas

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I wouldn't say that the carbon fiber shaft isn't any better than the aluminum....just more suited to a different purpose. The carbon fiber shaft would be better IMO for a road racing style application, where power application remains more constant and every little reduction in weight to the power and drive train counts….not to mention the carbon fiber shafts critical speed is higher than both the Steel and aluminum shafts, which would make it better suited for high RPM application. An Aluminum shaft would be better suited to moderately high powered cars (under 700hp or so) and daily drivers, for its ability to combine both high strength, and high critical speed, while still providing lower rotational mass. The custom steel shafts (and no, the stock steel drive shaft doesn’t fall under this category) should be held at bay for the ultra high horsepower cars that will really be shocking the system with high horsepower and high traction applications. And since their usage is limited to short, quarter mile blasts, and not sustained duration of high RPM, the trade off of it’s lower critical speed characteristics isn’t a problem.

Another point to bring up, is as great as the carbon fiber shafts are, they're still subject to rot over time under continuous exposure of the elements (unlike the aluminum or steel shafts) and carbon fiber has a tendency to shatter with impact (which wouldn't bode well in the accidental case the driver encountered some road debris). Yet one more reason they probably shouldn’t be considerer for daily driving status.

As far as reduced fuel economy is concerned.....I'd say your theory is a stretch at best. The lighter rotational weight of the shaft would have next to no affect on the vehicles fuel economy. Factors such as total vehicle weight, wind resistance, gearing, wheel/tire weight, etc would far overshadow the effects upon deceleration that the usage of a slightly lighter drive shaft. On the other hand, any additional weight you can eliminate upon acceleration (aluminum flywheel, lighter wheels, lighter drive shaft) all have shown a measurable advantage in performance.

...and besides, whatever theory presented that the lighter shaft might reduce fuel economy upon deceleration can also be used in order to improve fuel economy upon acceleration, since the lighter drive train components would require less horsepower from the power train to operate. The requirement of less horsepower, would also mean the consumption of less fuel.....however slight.