Setting up Princess Balljoints
Many aftermarket tubular front suspensions use princess balljoints to locate the stub axle. They are great units and well suited to the purpose but require installing correctly if they are to be safe in use. If the units are installed too loose, i.e. all the shims just shoved in then it is possible for the complete joint to unscrew as there is insufficient pressure from the internal spring to hold it tight in its thread. Too tight a pressure can lead to the nut on the tapered pin undoing. Either of these situations can lead to catastrophic suspension failure.
The design of aftermarket units vary with some having no method of locking the balljoint in place. Some have a flat section so the original lock washer can be used, others use grub screws. Firstly make sure there is some method of locking the balljoint once its correctly installed and secondly, as a belt and braces approach, use a Loctite “stud and bearing fix” on the threads. Regardless of how the unit is located the lock washer must be used in the shim stack as its thickness is factored into the build. Also ensure that your arms are fitted with grease nipples, if not fit them as they are necessary for longevity of the joint.
So on to setting the joints up and a micrometer would be of great help to determine the thickness of the various shims before starting. Mark them up in felt tip pen first as this will speed the job. There should be enough shims supplied in the pack if the machining of the cup has been accurate. Assemble the unit into its cup with all shims and lock washers, grease well and them tighten to “as finished” torque. If correct the balljoint should require a firm pressure to move it around. If its floppy remove the smallest shim and try again. Repeat this procedure until it requires firm pressure to move it. Now you need to check whether this is too firm or loose and this can be established by starting to fit the nyloc. The correct tension is when you fit the nut and as it just starts to bite into the nylon the taper stub starts to rotate within the balljoint. If you can wind the nut on its too tight and if it turns as you just come into contact its too loose.
An alternative method of setting up is to fit the lock washer only, tighten right down and back off until the nyloc behaves as above. Measure the gap between the washer and ball joint with a feeler gauge and install a shim pack to match. This will give you a quicker starting point from which to fine tune.
You can then finish installing remembering to use your loctite and other locking method. Pass the taper through the stub axle and then install a washer between the taper and lock nut. The washer should allow a minimum of two threads to protrude through the nut and this should also be loctited. Sometimes it may be necessary to apply a slight load i.e. a jack or similar to ensure the taper locates correctly to prevent it turning when tightening the final nut.
Should your balljoints fail the MOT in years to come, its simply a case of following above procedure again as removing shims tighten the joint. Don’t forget to grease at least once a year. Once the car is on the road, keep an eye on the joints and tightness of fittings for an initial 500 mile. Get it right your life, and that of others, depends on it.
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