Sheared off studs on Danica's wheel

[garyshell]

How the hell do the studs get sheared off with the main nut still in place? That was the strangest bit of damage I have ever seen.

Gary

[tbyars]

How the hell do the studs get sheared off with the main nut still in place? That was the strangest bit of damage I have ever seen.

Gary, the easiest way for that to happen is for the center lug not to get tightned completely.

A couple of years ago, the IRL added a positive lock mechinisim in the nut to keep the wheel from totally coming off if it doesn't get tightened totally during a pit stop.

I think you saw that work today, but the result was that the extra movement in the wheel in not having it secured totally allowed the wheel to wear down the lugs.

Note that Danica said she had something going on with that rear wheel on that last stint. Now we know what it was.

[BobGarage]

A couple of years ago, the IRL added a positive lock mechinisim in the nut to keep the wheel from totally coming off if it doesn't get tightened totally during a pit stop.

thats interesting. If you watch Moraes practice crash on indycar.com you can see the right rear wheel nut fly off as he starts to spin. as the car hits the wall on the left side the right rear wheel pops off completely.

Is the mechanism you mention above not manditory or did it just fail completly on Moraes car in practice?

[tbyars]

Bob, I do believe the locking mechanism is indeed mandatory.

Hard to tell what happened there. Maybe the spindle not was cross threaded on the spindle. Maybe the spindle stripped for some reason. Hard to tell.

"Nothing is ever foolproof because fools are so ingenious."

[dataman1]

I believe the safety devices are tapered & spring loaded within the main shaft, so as the wheel nut is tightened the safety pins (for lack of a better technical term) compress into the main shaft and once the nut is past they pop out of the main shaft which keeps the main wheel nut from backing off. Obviously if the wheel nut is not tightened past the pins and/or the springs are broken the pins will not work.

[bblocker68]

It looked like a lot of extra stress was being put on the studs if you looked at it closely. To me, it looked like the holes in the rim were being expanded by the studs and finally just were clipped off.

I would think that has to be a locking mechanism failure.

Maybe it was EJ Viso's fault :)

[tbyars]

I believe the safety devices are tapered & spring loaded within the main shaft, so as the wheel nut is tightened the safety pins (for lack of a better technical term) compress into the main shaft and once the nut is past they pop out of the main shaft which keeps the main wheel nut from backing off. Obviously if the wheel nut is not tightened past the pins and/or the springs are broken the pins will not work.

I think you are exactly right. The key here is that the pins pop back out BEFORE the nut is actually completely tight. If that nut isn't tightened sufficiently to tighten the wheel, the wheel will still have a little bit of play, and eventually wear the lugs away, even though the locking mechanism keeps the center nut from coming off completely. I think that is what happened with Danica.

If you don't get the center lug tightened past a particular point, the lug nut can STILL spin off. Probably what happened to Moraes. Probably even caused the accident.

[Vegasguy]

If you don't get the center lug tightened past a particular point, the lug nut can STILL spin off. Probably what happened to Moraes. Probably even caused the accident.

And this boils down to a Air Wrench Failure. The tire changer pulls the trigger, then lets go once the gun bottoms out the nut. If the gun has a failure it doesn't get the nut tight enough.

[tbyars]

And this boils down to a Air Wrench Failure. The tire changer pulls the trigger, then lets go once the gun bottoms out the nut. If the gun has a failure it doesn't get the nut tight enough.

Not necessarily. I can think of two other causes.

The first is just human error; pulling the gun off before the nut has actually bottomed out.

The second may be more likely. If the car came off the jack before the center lug was tight, the lug may not have tightened completely because the wheel was sitting somewhat askew on the wheel lugs. The tire changer may have felt like the lug was tight because of the resistance the tire sitting on the ground caused, but it actually wasn't. I know this has happened before.

[Vegasguy]

Not necessarily. I can think of two other causes.

The first is just human error; pulling the gun off before the nut has actually bottomed out.

The second may be more likely. If the car came off the jack before the center lug was tight, the lug may not have tightened completely because the wheel was sitting somewhat askew on the wheel lugs. The tire changer may have felt like the lug was tight because of the resistance the tire sitting on the ground caused, but it actually wasn't. I know this has happened before.

One is possible but unlikely, but possible.
In the event of #2 the guy on the gun is supposed to recognize that the car came down early and not release that corner so yea, that would be human error.

I would love to see tape of the prior pit stop. Usually they are done changing tires long before the car is done being fueled and would still be up on the air jacks.

[IWUTitan90]

In my totally uneducated guess, I assumed that the wheel was put on without being "seated" on the studs, and the nut tightened, pinning the hub against the studs. When Danica went out and loaded the wheel in the corners the hub then "seated" itself, leaving the wheel loose, because the nut was locked. It then "seated" and "unseated" itself until it sheared the studs off completely.

Hold water? :confused: