that's a good point, Nik !
I can't tell for sure what has broken in the ball joint, as I was a bit shocked and the car was lying on its disk when we removed the wheel, in order to tow the car on the trailer...
the short story is : when I swapped the 16" wheels for the 15" ones, I noticed that there was a very small play in the upright... I put the wheel on, and went to the local MOT shop, who's a good friend of mine, ask him to check. he shaked the wheel side to side and up and down, and didn't noticed any play; then, wheel on the ground, he used a bar to try to move the upright and didn't found any play... so I left, confident, but my guess now is the ball joint was already weak, but when loaded, it couldn't be noticed [
] ! I SHOULD have replaced it anyway !
Jim, the PO, told me that he has changed the right side one, few years earlier, and I kept the ref. part (TRW JB252, saab 900 '69-->ç") , in my Iphone... it was very helpful as the local workshop was able to change it and then the car was able to be moved on its wheels, reducing possible further injuries !
during this trip, we had very good and fast blasts, and roads there are sometimes quite harsh, with polholes... I assume it has accelerated the wearing !
to summarize : I assume it a very good thing to check your cars for ball joints wearing, especially on fast and powerful cars as ours. furthermore, I think it can be a wise thing to replace them BEFORE it wears, as even if cars may only have few thousand miles on the odometer, ball joints can be 30 years old ! provided the replacement part is a good quality one, of course ...
Jim, can you tell us why the RS ball joint was replaced, during your ownership ?
PS : Caron replaced two upper A Arm rose joints as well, as he found a very smal play in them ...