rlaifatt

The wheel flew about 30 feet into the air then bounced in the infield. Good thing I was far enough back at turn 2, thanks to Dave's blinding speed. The 1:51 was the lap just completed as he crossed the line in the video, and in that lap he had to pass me which which definitely cost him some time! Maybe you could have broken 1:50 Dave.

Were you in first gear coming out of turn 11?

dhayner

That is a fatigue crack (actually five cracks), not a tensile failure. It grew through many load cycles (in the thousands), not one or a few offs.

The root cause could be too sharp a fillet radius or some other manufacturing defect in the hub, or somehow you're putting a much higher load than normal on the hub in everyday driving (wheel offset, alignment, ?).

rlaifatt

Dave's rear hubs probably were stressed more than most would with the many track days, many sets of large Hoosiers, many miles of trailering, supercharger, and now slicks that generate even greater lateral G's.

ultimate lurker

I agree, looks like a fatigue crack, but I can't see the crack that well. BTW, what happened to the brake rotor? Kind of wish I could have been there (not for the morbid fascination that goes with seeing an off, but to get a closer look :-)

Like Elistan said, this is probably going to be something you just have to check as best you can, and perhaps pre-emptively replace each season or two. Certainly off course excursions aren't going to help anything, but if you're running full race slicks you're putting a hellacious load on the hubs. Usually hubs are not a failure point on race cars, but that's often because the uprights go first :-)

Whatever the case, glad you're o.k. You're really pioneering a lot of parts, fitments and stresses on the S2000, so I suppose if anyone is going to find weaknesses, it'll be you. Do you have a roll cage yet? Lightening the car a bit will help reduce stresses too.

UL

ultimate lurker

BTW Dave, that's really freakin fast and it sounds like you could have been even faster that day. Find a few more seconds and you might make the back of the grid at the next ALMS race :-)

UL

krazik

The brake rotor sheered off. The sheered bolts just outside the hub on the wheel are where the brakeman wave rotors were attached.

The rotors were found sizzling on the grass a way's away from the wheel. They now aren't "flat" but you can see how they were bent off as the wheel came loose.

krazik

UL any guesses how to look for this? Seems to me that there is no way to see around into the hub where the failure occured.

davepk

[QUOTE]Originally posted by dhayner
[B] That is a fatigue crack (actually five cracks), not a tensile failure.

davepk

rlaifatt,

Thats second gear coming out of tun 11 (the hair pin).

In the video you hear a couple of clicks as i'm entering turn 3 thats when i knew something was going wrong and you can hear that after the clicks i'm nolonger on the throttle where normaly i'd be WOT. I actually had time to think about many of the possible things that could have gone wrong with the first being that i forgot to tighten the lugnuts but i couldnt imagine all the nuts going at once. The second thought was that the wheel broke off the hub like gernby mentioned. I've seen that happen before to a 300ZX and thought for sure thats what it was because of how sudden it happened. However, as the car spun i was able to see that the wheel still had its center so at that point i was at a loss and a stand still till the saftey crew got there.

davepk

For those that are interested >HERE< is a link to my 1:51.x lap at Sears Point...