Ball joint loosened

[sandsandsand]

I discovered that I had to replace the front right ball joint, and did so.
When tightening the lower aluminum nut I used the torque specs - 50 Nm + 40 degrees.

One month later I started to experience oversteering. I discovered that the lower nut had loosened completely.
I decided to torque it to 100 Nm instead.

Just wanted to hear if this is the right solution. I don't want this to happen again...
Thanks...

[oragex]

Sorry to sound negative but I don't feel comfortable about double the torque. The metal has its limits, and a snapped ball joint rod after hitting a pothole would not be good news

Normally it should not loosen up with the correct torque, so maybe a few questions: which brand was the part? Was there any grease on the threads or on the washer? Was the large washer clean of corrosion? Could it be it was torqued with the wheel on the ground?

[sandsandsand]

I appreciate the feedback. The brand is Febi Bilstein. No grease or corrosion on threads or washer. The car was on the jack when I torqued.

Yes, I also think it is strange that this happened. Could it be that my torque wrench is inaccurate? I remember that when I mounted the ball joint I had that feeling that I was surprised about the low torque.

I don't think I have double torqued the nut. Remember it is 50 Nm + 40 degrees. I don't know how many Nm these 40 degrees would create.

I found this post: viewtopic.php?t=82018
It says "Ball joint in control arm aluminum: 50 Nm + degrees" and "Ball joint in control arm steel: 100 Nm".
Looks to me that the ball joint rod should manage 100 Nm.

But I think this whole situation is strange, so good to talk about it and hear some opinions...

Thanks.

[oragex]

Agree about the end rotation, hard to say how much it adds

This line makes me think.. "when I mounted the ball joint I had that feeling that I was surprised about the low torque"

This is typical to either grease on the threads or - worse - stretching metal (the metal would stretch just before breaking, it's called plastic deformation). When I say grease on the threads, it really can be a very small amount, for example some grease smear on the gloves/fingers then we grab the bj by the threaded rod and the grease transfers to the threads. Almost all torque on a bolt is caused by the friction at the threads surface - the smallest amount of grease will spread and reduce dramatically the friction (torque) and cause the metal to stretch with very little force - think maybe 1/3 or 1/4 of the normal torque on that bolt.

I also think the ball joint has a different number for the later steel arms - not sure if the construction is different though

Torque wrenches often times go bad when left tensioned for a period of time... maybe that is another possibility. It can be tested an easy way (worth doing once in a while) Only thing is I'd try to hang the weight in the middle of the handle - because that's where the hand puts the resultant force, not at the very end