Some ball joints and almost all tie-rod ends use a tapered stud and hole with a nut on top to secure the stud to the knuckle. The 7-10º angled taper, along with a threaded stud and nut, lock the components together by tensioning the nut and stud.
Torque-to-yield (TTY) ball joint and tie-rod studs have two advantages. First, they can weigh less and still apply the same clamping loads. Second, the clamping loads are more consistent and controllable.
Identifying TTY Ball Joints and Tie Rods
The metallurgy and heat treatment of TTY bolts and regular bolts are different, and you can sometimes tell one from the other by their appearance. TTY ball joints and studs have an inset hex head at the end of the stud. This can be used when tightening to the specified torque and setting the torque angle.
Always make sure to check the service information to get the right torque for a suspension component no matter what type of fastener. If you see an initial torque spec along with an angle in degrees, it is a TTY fastener.
TTY ball joints and tie rods are usually installed dry. Do not apply any oil, grease, assembly lube or sealer on the stud or tapered bore. Lubricants increase the torque load on the bolt or stud, which may overload and stretch a TTY bolt too far, causing it to break. If a TTY fastener is over tightened, it can stretch beyond its limits and break. The increased torque can also cause the female part of the taper to crack as to much clamping force is applied.
Many ball joints may have an initial torque spec as low as 15-30 ft./lbs. and torque angles are between 140º and 225º. Never guess or try to use your calibrated elbow. Always look up the spec and use a torque wrench. Make sure the washers on the studs are in good condition and installed in the right direction. If a washer splits or fails, it could cause a catastrophic failure.
Reusing TTY Items
Make sure you check the service information to see if a TTY ball joint or tie-rod end is reusable after it has been removed. Some manufacturers recommend a joint should be replaced, while others do not indicate if it should.