Here is a quick tech tip explaining the differences between a King Pin and Ball Joint front end on your classic car, old school hot rod, truck, and even air-cooled VW Beetle or Dune Buggy.
There are a few easy ways to tell the difference between the early King Pin and late Ball Joint style front ends.
Spindles:
King pin spindles mount with a large vertical king pin on which the spindle rotates. This pin is held onto the torsion arms with two horizontal link pins on the top and bottom of the king pin.
Ball joint spindles mount directly on two ball joints and have threaded bolts visible underneath the ball joints. On a stock VW beetle spindle, they face each other, on a VW Thing spindle they will both be facing down.
Shock Mounts:
King pin shocks have an eyelet mount at the top and bottom. Ball joint shocks have an eyelet bottom mount and a stud top mount.
Beam Height:
King pin beams usually measure 7″ in height. Ball joint beams usually measure 8″ in height.
What is different between a kingpin knuckle and a ball joint knuckle?
Kingpin or ball joint refers to the pivoting parts between the inner and outer knuckles–kingpin knuckles rotate on machined bushings and bearings, while ball joint knuckles rotate on a ball-and-socket joint.
Why would I want kingpin knuckles?
Kingpin knuckles are generally stronger, easier to maintain, and more durable than ball joint knuckles. Also, if you break an axle, the broken chunks can pop out the ball joints in a ball joint knuckle–kingpins cannot be popped out like that.
Kingpin knuckles also use a conventional spindle, wheel bearing, and hub assembly. Most ball joint knuckles are designed to use an expensive dealer-only “Unit Bearing” wheel hub assembly that is not maintainable separately–you just wait till it wears out, throw it away, and buy a new one.
Pros and Cons:
Even with heavy off-road use, king pin front ends are extraordinarily strong and rarely break – typically you can still drive a buggy with a bent king pin back to your campsite or trailer. They are a little more difficult to work on, requiring a special reamer & press tool to replace.
Ball joint beams typically have better road manners, allowing smoother suspension articulation. The downside – break a ball joint and you will find yourself trying to strap and support the torsion arm back in place. Torn boots, water and dirt intrusion will also wear the ball joint out more quickly – keep the boots in good shape and free of dirt.
Conclusion:
Generally, we would recommend sticking with whichever beam you already have in the car or buggy. You can swap a beam by welding new head mounts on, but it is usually best to use the suspension already on your car and use quality components to replace anything worn or broken. Keeping your suspension clean and lubricated is the key to smooth operation with either front end style.
