XK120 lower ball joints

Just a quick question. I’m about to embark on fitting new lower ball pins and cups. I have the brass cups with the steel locating ring (spigot). My car has the grease nipples.

Once wheels are off and the car’s weight is supported under the lower suspension arms, what is the procedure for fitting new ball pins and cups in situ? Is it necessary to disturb the upper ball joints, or does taking them off make access much easier? Can the job be done without removing brake hoses, which would require brake bleeding later?


Well, it can be done with just removing the bolts out of the lower ball cap and top ball joint, so you can tilt the stub axle carrier outwards, and wire it up to something so it doesn’t fall, so you can get the bottom ball joint nut off, so you can whack out the lower ball pin with a pickle fork. Then you fit the new lower ball pin, new gaitor and ring, and new cup, and then by trial and error determine the amount of shims you need on the lower ball cap.

But this job is a whole lot easier with the stub axle carrier upside down in your bench vise. This is how I’ve always done it.

I was going to say I can’t imagine doing it on the car, but I’ve just imagined it above. :grinning_face_with_smiling_eyes:

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Chris L.
TOTALLY “Second” on doing the job on the bench, INSTEAD of “on the car”…
And, “shimming” the lower ball-joints is a fairly easy task. I used a “depth-type”
dial indicator… and it did NOT take long to hit 0.010"!! (the key is to buy several
thicknesses of various shims… Worked for me!)
Do note, a new lower ball joint kit will probably NOT have the Brass Cups and
steel rings… “modern” kits have the ferrobestos cups and new ball joints…
The “lower cap” can retain the Grease Fitting… I kept mine… just DON’T over
fill the new ball joint set-up with grease!!
Charles Ch # 677556

Thanks guys. I’ve done it in the past, but a long time ago. Actually, an Iso Grifo is very very similar, as it uses Jag Mk 1 bottom ball joints and uprights.
I have my sets of brass cups and steel rings all ready, together with shims, gaiters and retainers, etc. I notice the new balls and cups have grooves cut into them to aid with lubrication.

Hi Chris…I will be doing this job soon on my 150…what and whos parts are you useing…you mention brass cups…were these part of a “kit”…thanks…Steve

Steve, I got mine from Coventry Auto Components. You can buy the cups/rings separately, or a kit that also includes shims, gaiter, gaiter retainer, etc. £78 per side. The only other bits you might want are the locking tabs for the cup retainer bolts - £6 for all 4.

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New bronze ball joints installed today - all seems good!

Hi Chris…Bronze or brass?..cheers…Steve

Well, I’m not sure! They look like brass, but the originals were “Morganite”, which I think was some kind of bronze? Was it an oilite bronze? Maybe others can enlighten me… An engineer told me that brass is not a good bearing material, but I’m not sure I would describe a ball-joint as a bearing…?

Hi Chris…i looked on the coventry auto site when i asked you what ball joints you have…they sell Brass seats seperatly. …but they mention “morganite” and then say the “alternative” nylon cup is included in their ball joint kit…im probably over thinking it…the nylon will probably be ok…maybee not last as long but far cheaper…Steve

I think both brass and nylon would be fine, as long as there’s plenty of grease in there, and any water is kept out, Steve.

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Morganite is an oilite bronze.

That’s fascinating to know, Rob. I wondered if Morganite was some type of Oilite bronze… I read a bit about oilite and there were several different compounds, varying in strength/hardness. The Jag cups were probably one of the stronger ones, as they bear quite a bit of weight, I guess. Shame nobody still makes them in oilite bronze.

The Ferobestos that Jaguar briefly replaced them with was some kind of a resin mixed with asbestos strands, and apparently needed no routine greasing, instead relying on whatever (if any) lubricant was initially provided in the joint. I have fitted them in the past, and just used grease as normal… I have seen them worn right through the cup, even wearing away the cup housing itself.

I suppose the modern nylon equivalents were introduced to get around the asbestos issue, but I have no idea how effective or long-lasting they are.

Yes, the Ferrobestos cups and eliminating the grease fittings is one of those “seemed like a good idea at the time” moments in bad engineering. Thus worn lower ball joints became a chronic problem with XK120 and Mark VII until they went back to Morganite bronze with XK140.