SteveM wrote: ↑
Tue Aug 07, 2018 9:05 pm
The lug nuts on a Toyota Sienna are M12 x 1.5.
The manufacturer spec is 80 ft-lbs, which produces a predetermined (but unknown to me) bolt stretch.
The dealer put them on with 130 ft-lbs.
Is there any way with just that information to calculate if the bolts have been excessively stretched?
Wow, that is an incredible amount of over torquing for a thread !
Inform the dealer immediately ! I have worked a lot with Bolt torques on dies when employed
Stretch , or deformity cannot be determined without knowing the stud material composition and strength.
Even so, consider this: Lubricated threads and bolt/nut face reduce torque requirements by 15 %
The finest bolts/screws you can buy are made by Unbrako ( IMHO after many yrs experience and experimentation)
Use their specs for the highest level of performance for most fasteners
Please go here
Start at page 39
Note that Meteric fasteners are graded DIN 8 or 10 or 12 ie.
The best being DIN 12.9
Note the "required strength - 1220 Mpa , which is 177,000 pounds Tensile Strength here in America
Now read down to Unbrako's standard for bolts 16 mm and under and you see1300 Mpa or 189,000 pounds tensile ( quality !)
Now go to the next page (40) and read the Torque value for a Unbrako screw
The 12 mm is rated at 1200 inch pounds, or 100 Foot Pounds of torque
Note also that the torque will induce a 800 Mpa Load on the fastener ( footnote on page)
Note on same page that the "YIELD" point is at 1170 MPA ( which is 46 % higher than max torque of 800 Mps is given)
This is imperative info because once yield is reached, the threads deform and failure is imminent as the torque value decreases
So if we apply the above to your notes-- we have a torque point of 130 FtPounds versus a possible failure point of 146
You do not know the strength of the stud, but I personally doubt it is equal or better than an Unbrako IMHO
What I am concerned with is your personal safety and decided to post commercially available info and reasonable logic rather then my calculations or opinion for your consideration.