Quote:
Originally Posted by mav1178
All OEM studs are weak. They're cast iron...
Here's a list of studs I've broken by hand, via breaker bar:
OE Nissan
OE Toyota
OE Subaru
Nismo
ARP
The question of how it breaks/shears is a question of what caused you to put so much torque on it that it breaks. Keep in mind that you're supposed to tighten the lugs to around 80-90 ft-lb of torque, so if it stops moving and you're still applying torque, it will break. 80-90 isn't a lot of force if you're doing it right, especially if you are using a longer breaker bar or torque wrench.
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They are not cast iron they are heat treated hardened steel.
The majority of broken studs I have seen had little to do with over torque. People side load them when putting them on and off and snap them. They have very poor side stress resistance due to the hardening.
Easy enough to tell since ones that are over torqued will twist off flush with the hub since that is where the stress is. Ones that snap off at or outside of the rim were side loaded.
It is very easy to do without even realizing even by hand. I would be willing to bet that is what happens to most of the guys that have it happen frequently even if they want to blame everything and everybody else.
Over torqued ones are more likely to strip or stretch threads than to just snap off.