That is one of the bad things about either aluminum or steel driveshafts as hustler stated... They do have the capability to punch through the floorpan and hit/impale the occupants in the case of a shear as seen in the photos above. However, when a carbon fiber one breaks/shears like that one it just becomes harmless fibers that cause no additional damage. In saying that, should you buy a carbon fiber one for this safety reason? HELL NO! Will you be putting enough torque on your driveshaft to shear it in normal racing conditions? HELL NO! So I would not worry about this unless you expect either your transmission or rear end to complete lock up while at high speed. But I would just replace the U-joints since they are servicable on your driveshaft.... Just my $0.02.

 

Ive only seen them do this while launching at the drags.

 

I just weighed my spare and it indeed is 11lbs.

 

My memory is good to the best I can remember.

 

Exactly my point...

 

This is why you weld in driveshaft hoops around the shaft. So that it can not do that.

 

Indeed. However, there are a lot of budget builders who take their cars out to the track and fully overlook this and the results can be devastating... Well at least I've seen three at a local drag strip break their driveshafts and have them punch through the floorpan. Not pretty... All were un-injured though.

 

I thought that too, but that's definitely one of the garages at ACS Roval, and those are R888s on that car.

 

I thought the more common accidents with driveshafts, are when they break and impale the ground. This can make the car flip over. Not pretty. Do they not tech cars for driveline loops in road racing? They sure as hell do in drag racing.

 

From what I gather so far, the Al replacement is around 7-8lbs and OEM steel replacement is about 11-12lbs. I'm still taking in more opinions and time before I settle on a replacement. So far, I'm leaning towards the steel replacement or finding a used OEM shaft. IMO, MOI for the weight difference on such a small radius wouldn't provide much in performance gains.

 

I would estimate that the "gains" would not be measurable on a dyno, or in any datalogs of acceleration.

 

Every pound counts, especially rotating mass.

Has anyone seen aluminum driveshafts impale/flip cars, or just steel units?

 

I had alu drive shaft on my previous car, s13. it is quite noticeably different from stock but I dotn think i would bother with one from now on, seems a bit unnecessary spending

 

Road racing isn't typically as harsh on drive line components, standing starts are not common.

Some classes do have a safety requirement for a driveshaft loop, and those classes are very much tech'd for it.

HPDE, or track days do not have such a requirement.

 

Has anyone seen any driveshaft flip a car?

 

I have never seen it, just heard of it. However, I have noticed a certain amount of horseshit from hot rodders. Maybe a myth?

 

Research edit: MYTH BUSTED!

Mythbuster apparently tried this... Link to results: http://www.mythbustersfanclub.com/mb...nt/view/52/27/

Cliffnotes: The car would jump up off the ground slightly but never flip. All adding speed accomplished was to shove the driveshaft further into the trunk... MYTH BUSTED!