Mini Register

Mini Workshop - Front hub ball joints

Replacing the ball joints on the front hub is probably my least favourite job on the Mini, which should be enough motivation to ensure that they are properly greased, however they do wear and when they do, the job has to be done or the car will fail its MOT test.

To check for wear, jack the front wheel clear of the ground and gripping the top and bottom of the tyre, try pushing and pulling (it is easier if a helper looks at the ball joint from under the front. There is a degree of adjustment possible in the ball joint; shims are used to space the cup away from the pin and you may find that some of the existing shims can be removed to tighten up the joint.

If not, or if the pin is pitted through lack of maintenance in the past, then a new ball joint kit will be required.

Interestingly, the original official Mini workshop manual describes a procedure that involves assembling the joint dry and without the tab washer so that the gap between the hub can be measured with a feeler gauge, 35 thou for the thickness of the tab washer is subtracted along with an extra 3 thou and then shims selected to fill what's left, with this lot assembled, the joint should have just the correct amount of movement.

The Haynes manual on the other hand says "Using a trial and error process, remove the retaining nut, take out a shim and then refit the nut and re-check the movement....."

I can understand the Haynes route as despite trying the official way on a couple of occasions, it usually ends with trial and error.

This sequence of pictures shows the steps required

	First, and most important, is cleanliness, having stripped the balljoint, make sure there is no dirt that may affect the adjustment
	The ball joint is adjusted with these shims, the new ball joint kit will include a number of different thicknesses, make sure you don't throw the old ones away, they may be needed as well.
	Fit the tab washer, then some shims along with the pad that the balljoint pin sits on. For the lower joint, the pad sits on top of a spring, leave the spring out for the moment, also at this stage do not add any grease.
	This is the balljoint pin, the smaller radius hemi-sphere sits on the pad, the larger one, within the cover, it is wear on these two surfaces that cause the play in the joint
	The cap holds the pin in place when screwed down onto the hub, the shims determine how far down it can screw and therefore how tight the joint is.
	This is the start of the tedious bit - tighten the cover to check the amount of movement in the pin ...
	I have found that the best situation is when the pin is too tight to move by hand but can be tapped from side to side with the handle of the hammer. If it is too tight, remove the cap and add a shim, if it is too loose, reduce the thickness of the shims. You may well find that it is still too tight when you have added all the shims that come with the kit - hence the need to keep the old ones as well.
	When the adjustments have been made, the spring may be inserted under the pad for the lower joint...
	then plenty of grease added before re-assembly.
	With the cover tightened down, screw the grease nipple into place and bend the tab washer up to prevent the cover from coming loose. Then break out the grease gun and make sure the joint is fully packed, keep squeezing until the grease oozes out around the base of the pin. Now it is just a matter of fitting the rubber dust covers and the hub can be returned to its rightful place.