2000 Ex - Rear tire AND wheel flew off and went into a parked car. All bolts SHEARED!
 

Okay - HUH? I just got off the phone with my dad who is on vacation with the Ex. He said that he was driving about 40mph down a road and then the rear tire flew off into a parked car. Says that all of the studs were sheared off. Anyone else hear about this? This CAN'T be normal.

I worked at a tire store for about 4 years during and just after high school and we never had a case like this. I'm sure we would have paid the extra $20 for Ford to have used higher-grade steel for the studs. I would expect this to happen to a crappy sedan - not a "Super Duty" vehicle.

Thank Christ this didn't happen while on the freeway -- that big a$$ tire would have killed someone...

I'm doing the 8hr drive tomorrow to go investigate this further. He already got it repaired ($600) but I want to see exactly what was going on here. This Ex has never been "off roaded" and has about 130k of highway miles.

Good job Ford!

Stock wheel & tire?

Correct lugnuts? (flat not tapered)

yes; all original equipment. even the tires are the OE style Firestones.

Caliper pins may have seized cocking the pad in the caliper and super heated the rotor destroying the studs, could be.

Report back after you see it, but I imagine the brake is trash too.

When was the last time the tire/wheel was off? Was it properly torqued when put back on? Did you put a few drops of oil between the nut and the captured washer?

I can not picture how this is even possible. There are 8 studs on that wheel. All 8 of them failed? Perhaps 7 nuts were over torqued and sheered and the last one was almost sheared, hanging on a thread and finally failed.

At this point it appears that the lugs were not tightened enough. The wheel must have surgically sliced through the studs with the extreme weight of the Ex. The mag wheel is destroyed. I'll get a photo up here.

I'm glad that the studs don't appear to have failed independently (so is Fords). I can't see a 1/2in impact making all of these overstressed. Now a 3/4 or 1in then I would be scared

Loose lugs can allow for the wheel to 'wallow' around on the studs. This enlarges the bolt holes in the wheels enough for them to come over the lugs - as it comes off it will most likely shear the lugs on the way out. I've seen it on steel wheels as well as a few alloys - but never on an 8 lug truck. Our truck lugs need to be torqued to about 155 ft/lbs to avoid this.

FWIW, and just in case it helps, many years ago I forgot to torque the lug nuts on one of the rear wheels of my GTO, and at somewhere around 25 to 35 miles per hour, as the wheel was starting to come lose, I could feel that something was very very wrong. My point here, is that if this was from lug nuts coming loose, man I would think he would have felt it significantly. Or would the weight of the EX just shear them off as they started to become the slightest bit loose?? Good luck, and glad everyone is OK! Mike

I sounds like they were too tight to me which is what can happen if someone lays on a 1/2" air wrench. The lugs will take a lot of abuse from a loose wheel but everything has a breaking point from being overstressed. It would take a lot of time for an aluminum wheel to hack away at those hard studs to the point of breaking them and you would know it first. I would check the other ones before you drive it. You won't even need a torque wrench to determine if the other ones are that tight.

That makes a lot of sense, therefore so does checking the other wheels.
Very scary! Mike

impact tools bad for assembly
 

I worked for GM as a tooling and fastener engineer much earlier in life and impact tools should never be used to drive and tighten any fastener. GM & Ford did some studies on the different types of air power assembly tools and impacts were basically unpredictable statistically (CP/Cpk) and therefor uncontrollable. They had a repeatable torque range of plus or minus 400%.

I know that you see NASCAR use impact tools every week on TV. Impacts are the fasted cycle time tool available so NASCAR teams uses them. But they throw away all the nuts and studs each week. And inspect and replace rims every couple of races. It is the cost of business for them.

Mechanics use them, because impacts are excellent at braking stuck nuts and bolts free. Then they use them to assemble with because its easy for them(all the world's problems look like nails when you have a hammer in hand) and cheeper than purchasing several air stall or clutch controlled assembly tools. Which have much better control statistically speaking.

Typical wheel stud failure is a cascading failure mode.
First one or two studs are miss tightened, loosing clamp load, then the rim starts to wobble and the the remaining studs start to overload and over time elastically stretch loosing further clamp load, then the rim starts to torque excessively and the mounting holes start to wallow out and causes the remaining studs to shear. If you are lucky and can feel the wheel wobble you can replace the studs and nuts hopefully saving your rim. Or as you father had happen, the tire assembly parts company with your vehicle.

Cascading effect.
 

Yep, that's why you just can't use an air wrench to tighten them down and the irony is that it is so easy and the studs are so strong that it must be ok, NOT! Once the weakest and/or most stressed one gives out you will get the cascading effect because the others are now compromised.

Sierra; sorry to piggyback but I just wanted to elaborate.

When I rotate my tires I ALWAYS run the nuts on with my impact set at the LOWEST setting. I then take my 1/2" torque wrench and tighten in a star pattern all the lugs on all four tires. Then, I go back and re-check all the lugs again with the torque wrench. I have NEVER had any issue with this process.

About 4 years ago I was going on my yearly trip from PHX to San Diego pulling a travel trailer and had a wheel come off. I had my tires balanced and rotated at Discount like I normally do before big trips. I made it about 450 miles before the tire started to loosen up. SD is only 370 mile but I had driven a couple of days before the trip.

I was coming down the hill by La Mesa (i think) and the X started acting like it was on ice. Told the wife to hold on because I was swaying into both lanes on either side of me. I pulled over right away and got out. I8 traffic wizzing by my back I look down at my driver side rear wheel and there are 3 or 4 lugs sitting on the wheel and 4 still attached but loose. I tightened up the 4 remaining and picked up the others. I was looking to get off the freeway and try to figure out what to do. With the trailer I was looking for a big parking lot. Of course I went the wrong way and found a side street and pulled through a little clinic driveway. I was doing about 5mph when the 4 remaining lugs wanted to be free and join the other 4. The X hit the ground and dragged on the ground about 10ft. The wheel and tire (315/70/16) went rollong down the road and up the sidewalk right towards a grandmother walking with her daughter and grandchild. The tire was moving so slow she stuck her foot out and stopped the tire right in front of her. I told her sorry, she laughed and said good luck and went on her way.

Had to have X towed to Drew Ford around the corner. They replaced rotor and put my spare tire on. $200 for tow plus trailer a nile and half. $700 at dealership and $60 for a new rim to mount my 315/70/16 on. I have a 285/70/16 on the spare.

When I got home I called Discount corp and told them my story. They told me to take it back to where they rotated and balanced the tires. They paid for everything and gave me new rims. The $2K they spent on fixing my X was a lot cheaper then the millions in claims for me losing the wheel on Interstate 8 doing 55-60mph. The X would have probably flipped because of the trailer and speed. They were more than happy to make me some what happier.

just wanted to share my story with you.