Brand new tension rod bushings split after 10 miles

[fusion]

I have a 280z that I recently finished building.  On the tension rods I installed brand new bushings.  Rubber on the front side and poly on the back, as I believe was recommended by several people here.  Torqued the nut to 40ftlbs.  I was just under the car for something else and noticed that the rear bushings on both sides are split very badly.  This is after only about 10 miles of driving.  Wondering how this could be.   I will switch the rear bushings to rubber but still want to know how this could have happened.

 

Comments welcome

 

 

 

 

Edited August 12 by fusion

[NewZed]

Actually it's rubber in the back, poly in the front.  The front bushing takes the force under braking on the Z's, under compression, and is the one that you don't want compressing too much, making the steering squishy.

 

But the poly should not have split.  It does take a lot of side forces as the rod moves up and down with the suspension.  But usually it causes the rod end to fatigue and break off.  Seems like you got a bad batch of polyurethane.  Bad chemistry, or a knockoff.

[74_5.0L_Z]

I used to run this:

https://www.thezstore.com/product/6551/tension-rod-t-c-kit-70-8-87-240z-260z-280z-280zx-300zx

It worked pretty well.  I have since gone to rod ends and a clevis.

 

[fusion]

On 8/12/2025 at 10:56 PM, NewZed said:

Actually it's rubber in the back, poly in the front.  The front bushing takes the force under braking on the Z's, under compression, and is the one that you don't want compressing too much, making the steering squishy.

 

But the poly should not have split.  It does take a lot of side forces as the rod moves up and down with the suspension.  But usually it causes the rod end to fatigue and break off.  Seems like you got a bad batch of polyurethane.  Bad chemistry, or a knockoff.

Hmm, well having the rubber and poly switched was pretty dumb of me.  How much worse is it to have all rubber vs poly up front/ rubber on the back?  This is a street only car

[NewZed]

Probably just fine.  The polyurethane products were developed as a performance improvement.  More precise steering, less wheel movement.  The aftermarket will hype and sell whatever they can.

[baby_Carlton]

On 8/14/2025 at 12:01 PM, fusion said:

Hmm, well having the rubber and poly switched was pretty dumb of me.  How much worse is it to have all rubber vs poly up front/ rubber on the back?  This is a street only car

Not dumb at all, though I definitely prefer rubber bushings over poly & solid in a street car even if its tracked 1-3 times/year. 

[Zetsaz]

11 hours ago, baby_Carlton said:

Not dumb at all, though I definitely prefer rubber bushings over poly & solid in a street car even if its tracked 1-3 times/year. 

 

After a 2000+mile trip this summer in the Z I'm inclined to agree with this. Part if me is tempted to go back to stock arms on rubber, are at least all poly instead of some of the heim joints on my T3 parts. The performance benefit of some aftermarket arms is marginal at best. That said, the tension rods might be one place where solid almost makes some sense even on a street car because changes will be more noticeable there under braking.