Duece McCracken· Administrator
2023 Jeep Gladiator Rubicon 6spd, 2019 Mustang Bullitt
It's like I'm re-reading one of my textbooks, lol!! Between the post, and the user name, I am going to assume that you may have properly torqued a bolt or two, rofl.If the bolt is indeed an M12, then I would find a flange head M12 bolt long enough to protrude slightly past the end of the nut. I’d get it from the auto parts store before home depot.
Bolt length is measured from under the head to the end of the bolt (not the overall length). Most automotive fasteners are marked 10.9. This is a metric classification of bolt strength similar in strength to an SAE grade 8.
The website indicates a torque spec of 75 lbf-ft (102 Nm) although typical installation torque for an M12 is 84 lbf-ft (114 Nm). This lower torque is probably due to the lower strength of the aluminum threads which you already found the limit to.
You don’t have to go crazy with torque accuracy. Feel how the bolt tightens. The torque should build evenly with as the angle turned. If torque stops building and you’re still turning the wrench, stop, you have gone too far, replace the bolt and try again.
The 10.9 designation is an indication of the max axial stress of the bolt material (10 means 1000 N/mm2).
That means each square millimeter of cross-section can hold a minimum of 1000 N (225 lbf)
The second number (.9) refers to the yield stress of the material being 90% of the max.
The stress area of a M12 x 1.75 is 87 mm2.
That means the ultimate tensile strength of the bolt is 87,000 N or 19,700 pounds!