Removal torque will always be higher than final application torque. I’ve measure both many times in industrial applications when evaluating designs. If the application torque is too high, the removal torque may be high enough to break the stud.
One othre variable is that excess torque can stretch and weaken that material in the final threads, especially at the concentrated stress area in the acute angle that is the inside of the thread, the “stress riser”. That can create weakness in the structure that can manifest itself as a failure when removal torque is applied. That would actually be the most common cause of removal failure.
The reason impact wrenches are so great for breaking loose stuck nuts and bolts is simply that vibration reduces friction. Just as vibration can cause a pallet of concrete blocks to slide around in a pickup bed, it can also assist in removing a lug.
But I did like your argument. It’s a well thought out argument and likely is the one they’d’ use.
I would go with CapriRacer’s theory. With the lug overtightened, it’s hard to keep the wrench “normal” (at 90 degrees) to the mounting plane of the wheel. No offense to nft987, though. With an over-torqued nut, it’s tough to keep everything “hunky dory”!
“Is my broken bolt Sears’ fault?” Is It McDonalds’ Fault If One Gets Fat Eating There All The Time ? People Are Advised Here All The Time Not To Go To Quick Oil Joints & Chain Repair Shops.
Fool me once, shame on you. Fool me twice, shame on me.
Also, I agree with the others that you have a hand in breaking the lug. One key to doing your own work is knowing your own limitations.
You should have stopped attempting to remove the nut when it wasn’t going anywhere when you were turning it incredibly hard because in your words it was “incredibly tight”. You didn’t think it might break ?
Look at it this way, if overtightening a bolt doesn’t break it, why would loosening it?..
Easy, if it were overtightened to the point that the threads were galled then when trying to remove the bolts/nuts they would then break. It’s happened before and it will happen again.
Yes he thought it would break, but he also thought someone else whould pick up the bill,a sign of the times as in, “yes the oil light was on but I paid for that oil change so I am 100% protected”, “I pulled over first place it was safe, bad neighborhood and all”
It’s also possible that since we’re just now getting through a pretty nasty winter that repeated applications of road salt (should be outlawed in my opinion) may have had something to do with this. Just a theory anyway.
First day of spring in sunny temperate OK and we’ve got 8 inches of sleet and snow with numerous stories on the news about salting the beejeezus out of the roadways; to the tune of half a million dollars over budget road salt in OKC.