Whaler:
Lot of opinions here.
Lets review some of the engineering going on:
just because they are turning less RPM than a drive shaft; has little do do with vibration; vibrations are noticeable when the imbalance is near the natural or resonant frequency of the system. There will be several different nat. frequencies; usually at mathmatical multiples of one another. Frequently a car has wheel vibs at around 55 mph; slow speed and tire rpm; just a natural freq. on a 15 in tire.
yes, cobras have small, low mass shafts; but a 3 gram imbalance is a much larger percentage imbalance than a 3 gram imbalance of a 30 lb drive shaft.
See the attached:
http://www.dennysdriveshaft.com/html..._kit_car.html.
Granted shafts should not have much imbalance; IF! the ends are welded on concentric; but have and end welded on .015 in off center and it will vibrate.
Dennydriveshaft is a High quality cobra shaft maker; and he balances everything!
Don't spend $thousands on a custom high end Cobra and then skimp on essentials like balancing. Bad economics on several fronts; a shaking half shaft can manifest itself in transmission shake or some other symptom; after speeding many hrs and dollars eliminating that only to find the vib. is originating some where else. Old race car proverb; leave nothing unaddressed and nothing to chance; chance will screw you everytime; Chance is Murphy's bad cousin.
gn