T/C Rod Failure & PU Bushings

[Bambikiller240]

I don't know how many of you'all are on the 240z.org mail list, but this message came though today and I feel it is important enough to pass on.

Message: 3

Date: Sun, 09 Nov 2003 11:27:04 -0800

From: Alex F

To: 240Z Mailing List <list@240z.org>

Subject: [240z.org] T/C Rod breaking/failure

A local Z buddy (afshin) had a TC rod failure this weekend, and this

brought into the light possibilities of TC rod failure due to use of the

PU bushings. Carrman posted a good read on how to prevent this failure,

which was snipped from the dime quarterly list:

http://www.hybridz.org/phpBB2/viewtopic.php?t=27871

I think I'll either switch to drill out the PU bushings to give more

flex, or get stock bushings and the g-machine tc rod alum/delrin kit.

-alex

[2ManyZs]

I think the key words to his problem are "worn control arm bushings". With an abnormal amount of control arm deflection occuring with worn out bushings, the amount of stress on the T/C rod would increase ten-fold or more.

It's odd, that in the 15+ years of going to the race track, I've yet to see the T/C rod snap. Maybe we were lucky, or perhaps it's because everything in the suspension is in top notch condition.

I know for a fact the 75 280 of mine is still running the same control arms, bushings, T/C rods that I put on it in 89 with no failures yet and no bushings have been replaced either. If any were going to fail, I'd say it would be that car considering it weighs 2700+ lbs, with 300 in-lb springs and is getting ten times the abuse a street car would.

Perhaps this is just another example of considering the whole package when upgrading and not just the individual pieces.

[Zedrally]

I also find it hard to imagine.

The only time I've heard of a similar event was in Dirt Rally competition with 510's.

There control arms have a habit of breaking and the solution was to replace them with gemini ones. Longer thread and no problem.

Which begs the question.

Didn't the zed suspension evolve from the 510? If so then the control arms must be of a different design as I've never heard of complete failure as such. On the other hand if the control arm in question was from a 510 then it doesn't surprise me?

[auxilary]

quite the opposite, actually. the polyurethane bushings cause LESS deflection, so the TC rod doesn't travel as easily as needed and the forces act opposite the tensile strength, so it winds up snapping. I think ideally one wants to run the delrin TC kit MSA sells for 30 bucks with a PU bushing in the back, or rubber bushing front, PU bushing in the back

-alex f