Hot Rod Fastening Hardware - Thunder Bolts

Grade	Nominal Size Range	Min. Yield Strength	Min. Tensile Strength
2	1/4" to 3/4"	57,000 psi	74,000 psi
2	3/4" to 1 1/2"	36,000 psi	60,000 psi
18-8	1/4" to 5/8"	80,000-90,000 psi	100,000-125,000 psi
	3/4" to 1"	45,000-70,000 psi	100,000 psi
	Above 1"	45,000-70,000 psi	80,000-90,000 psi
5	1/4" to 1"	92,000 psi	120,000 psi
5	1" to 1 1/2"	81,000 psi	105,000 psi
8	1/4" to 1 1/2"	130,000 psi	150,000 psi

Lockers, Lubes & Torque
One frequently arising issue involves the effect of thread locker or antiseize lubricant on torque specs. One disadvantage of stainless is that it is more likely to gall than other materials, especially when using stainless fasteners with stainless or aluminum. Therefore, thread locker or antiseize is recommended to reduce friction and prevent this. Some care is necessary when using lockers, however, since the compounds set very quickly. Bob Florine recommends adding the compound and installing each bolt one at a time, so it doesn't have a chance to set before you want it to. When using antiseize, which is slicker than oil, Doc Hammett recommends reducing the torque setting by approximately 30 percent.

Adequate torque is required to stretch the bolt, allowing it to fasten like a clamp. The following chart, taken with permission from the Totally Stainless catalog, lists recommended tightening torques.

Single or Double Shear
Why do you need beefier suspension fasteners on your mild street rod than on your musclecar? The chassis bolts on factory cars going back for decades are double shear, meaning that the bolt runs through a double bracket, with a piece against the head and a piece against the nut. Some current aftermarket chassis use a single-shear bracket. This design puts more bending load on the bolt, making it easier to bend it or break it. The solution is to use stronger fasteners.