Lower Balljoint Taper dimensions


(Graham Knight) #1

Rebuilding the XK150 front suspension, bushings and joints.
I’m trying to fit the new lower balljoint part 14-1008 (XK’s Unlimited) and I’ve noticed the taper is quite different to the original one the upshot being that it seats much deeper (a difference of 14") and that means the new nyloc nut or the old castle nut wont tighten since they are bottoming on the threads before tightening up. I could use a thicker washer but I’m second guessing this action since this is a safety critical item. What does everyone think?


(Roger McWilliams) #2

Caution is advised here. If the lower ball pin taper does not match the carrier taper then the fastening load will not be spread throughout the cone. The lower ball pin part numbers vary in the parts manuals for the range of XKs & MkVII, VIII, and IX that XKs Unlimited part number 14-1008 is said to cover. And maybe you could clarify the 14" mention since that seems likely a typo. Getting multiple opinions from people who have installed these particular parts would be good before you continue.

Sometimes reproduction suspension parts are designed for the condition of the expected worn parts in which they will be installed. Sometimes reproduction parts are to original specification and won’t fit into worn parts correctly. Sometimes reproduction parts are just not correct.

On ball pins both the taper angle and the major diameter matter.


(Rob Reilly) #3

Agreeing with Roger, this is a standard part so a misfit sounds suspicious. Better post a picture.


(Graham Knight) #4

Sorry on the typo, the top of the threaded end of the ball sits about 1/4” deeper into the socket than the one I took out. Although the ball part measures very close the taper part is visually different and slimmer, it seats properly on the taper but goes in too deep, it looks like a manufacturing error, but both the new ones are the same. Think I will call XK Unlimited.


(Graham Knight) #5

Oh, and thank you Roger and Rob for your responses, you helped crystallize my thoughts that I shouldn’t just keep plowing on without further investigation, cheers!


(Graham Knight) #6

Merry Christmas to all.
Picture of the original (left) and new (XK Unlimited) lower balljoints. I’ve asked them to advise on why they are different.


(peter balls) #7

Graham, check the taper dimension at it`s largest point, it should be point 75" / 3/4"approx.
Jaguar ball pin tapers,top/bottom and steering are 1 in 8. Photo shows two 1 in 8 ball pin reamers
I obtained to check for deformity in wishbones and.steering arms.
Peter B


(Graham Knight) #8

Thx Peter; nice reamers!
I’ve measured the largest section of the tapers on the old and new balljoints (see attached pics) the old one is 0.762" and the new one is 0.726" or about 36 thou smaller, this seems to make sense since a 1 in 8 taper would seat about 1/4" deeper which is what I am seeing. I also attached a photo of the 2 balljoints side by side where it can be seen that there is a shoulder and a knurled portion on the old joint that does not exist on the new one.


(Art Ford) #9

I just measured 5 lower ball joints I have here. All measure in the .760s at the widest point. There is one that does not have a shoulder and is worn. That suggests these were offered long ago. All 5 had the knurled portion, even the one w/o shoulder. This one odd ball joint was a bit larger at .768.


(Rob Reilly) #10

I suspect your new one is for a later model car such as a Mark 2 or XJ?


(peter balls) #11

Yes Graham, the 35/6 thou will result in 1/4" approx difference as you state. I have , as Art,
various bottom ball pins, some with some without a shoulder.
All bottom ball pins, no matter what model, have the same taper, the major difference is
the larger ball fitted to the MK11/ E Type etc onwards models…
Anyway prob solved, return to sender with an explanatory methinks.
My preferred method these day is to convert the XK type upright and bottom cap to accept
the later integral ball joint fitted to later XJ/XJS models… After machining the later ball joint
assembly it looks a bit of a mess, but does the job.
l I carried out this mod on Nigel Webb`s 1997 Peking / Paris MK7 some yrs ago,
they are still fitted.

Peter B.


(Graham Knight) #12

Just to close this thread out; I contacted XK’s Unlimited regarding the out of spec lower ballpin taper, Michael is replacing them with correct ones; he stated "we have had virtually no problems with XK lower ball joints over the years. I then remembered we recently received a “fill-in” shipment from a vendor we don’t normally use for ball joints. I took a look at our stock and confirmed that you are correct. So just awaiting them now. Thanks for all the help.