Torsion bar and bushings damaging the tub ???

[Deschodt]

Ok, I did not want to post this as a sequel to my polybronze bushings + TB install as I did not want to imply that anything was related to the products... That said, if you recall, a friend and I installed the polybronze bushings Front and rear and new thicker TBs 921-27). All went well as far as i could tell, and I took the car to be corner balanced at a good local shop...

The guy calls me and asks if I know about a crack on the spring plate bolt hole, the lower one. Apparently the threaded area that you bolt the spring plate into pulled itself out of the tub - or started to anyway! One of the 4, the lowest one, one side only... Holy $hit Batman !

So how does that happen? I mean, the polybronzes were riding smoothly on their sleeves outside the car, lubricated etc. The inner bushing was a easy fit inside the torsion tube, the outer one was a lot tighter, and he says that may have caused it as it had no give, while rubber does...

Ok, educate me please, did I do something wrong there? Or could this have been an issue from before that was aggravated ? Either way it's not the end of the world, the one bolt hole was welded in place and the car adjusted and corner balanced perfectly, but I'd like to know what, if anything, I missed !

[Chuck Moreland]

This a very common problem, the metal tends to fatique on that mounting boss. You did nothing wrong.

It has nothing to do with Polybronze and happens with rubber too.

The fix is to re-weld it. Not a bad idea to put a reinforcing plate on there too.

[Deschodt]

Oh good, thanks ! I had visions of a cracked tub until I saw the issue, it looks fairly minor (especially once repaired) ! Results tomorrow after alignment !