All of our Ubolts are Grade 8 with rolled threads. Cut threads are much weaker than Rolled. Cut threads actually remove material while rolled retain all the original material. They also come with True Tall Nuts and 3/16" Thick Hardened Washers which retain their shape while under the torque loads required. Although our U-bolts are rated to be torqued up to 170ftlbs we recommend torquing to the specified ft lbs recommended by your vehicle/axle manufacturer. Vehicles with 1/8" stamped axle tubes require less torque than 1/2" thick axle tubes
Suspension U-Bolts are manufactured with a smooth rolled thread, while the mating Hi-Nuts are manufactured with sharp cut threads.
When a U-Bolt is tightened to its recommended torque level, the U-Bolt threads stretch as they mate with the Hi-Nuts. Although not always visible to the naked eye, this damages the threads. Removing the Hi-Nuts from the U-Bolt will cause a cross - threading that will not allow the U-bolt to be adequately retorqued.
Common practice in most maintenance facilities is to use an impact wrench to tighten U-Bolts. Consistent, accurate torque is next to impossible to obtain with an impact wrench, and in most cases, an over-torqued fastener is the result.
Our U-bolt manufacture recommends using a torque wrench when installing U-Bolts.