Help with 240sx rear suspension

[dan240]

Hi,

I have a 1989 240sx that I've installed an Energy Suspension master bushing kit on. Immediately afterward I noticed how bound up the rear suspension is. I've tried playing with the bolt torque numbers in the rear arms but I don't think I've improved things much. Can you offer any suggestions to get the suspension moving again?

I plan to start replacing the rear suspension with spherical units but my budget does not allow me to do this all at once. I've heard great things about splparts but they are also on the high end of the price spectrum. Have any of you had any luck with anyone other brands of arms? I have thought about buying some cheap ebay arms and replacing the tie rod ends with quality units. Bad idea?

If I have to do this in steps is there an order of most importance to get the rear moving properly again? I have read the RUCA but intuitively it seems like the toe arm. At my current ride height (its pretty high, relatively) I do not have problems getting the camber and toe to where I want them even with the factory arms.

Comments and suggestions are appreciated.

Thanks

[erlrich]

Hi,

I have a 1989 240sx that I've installed an Energy Suspension master bushing kit on. Immediately afterward I noticed how bound up the rear suspension is. I've tried playing with the bolt torque numbers in the rear arms but I don't think I've improved things much. Can you offer any suggestions to get the suspension moving again?

I plan to start replacing the rear suspension with spherical units but my budget does not allow me to do this all at once. I've heard great things about splparts but they are also on the high end of the price spectrum. Have any of you had any luck with anyone other brands of arms? I have thought about buying some cheap ebay arms and replacing the tie rod ends with quality units. Bad idea?

If I have to do this in steps is there an order of most importance to get the rear moving properly again? I have read the RUCA but intuitively it seems like the toe arm. At my current ride height (its pretty high, relatively) I do not have problems getting the camber and toe to where I want them even with the factory arms.

Comments and suggestions are appreciated.

Thanks

If you're just trying to move the suspension arms by hand, they're going to be tight; the poly bushings aren't going to help any there. Unless something is bent or broken, or the bushings were not properly installed, the suspension should move just fine when the weight of the car is on them.

SPL also sells replacement spherical bushings for the stock control arms - that would save some over buying the new aftermarket arms. I'm hoping to replace the poly bushings with sphericals over the winter, and may go with the the SPL units just for sake of ease.

As far as the SPL arms, pretty much anyone who will post here is racing their 240SX in IT, and so BETTER NOT have any experience with their trick control arms :D

If I had to rank the importance of replacing the bushings, I would probably do the upper arms first - the LCA has a pair of bushings that keep it from moving in more than one plane, so I would think the poly bushings would be less likely to bind there. That's just my opinon though.

Btw, what is the RUCA?

[dan240]

Hi Earl,

A little more background....

I have a car that has some handling issues that I attribute to the rear end. It has a lot of lift throttle oversteer and the rear end just never seems settled to me in any corner. I'm a relatively new driver (not brand new) coming from an AWD car with limited experience in either car. I've checked the alignment. It should be a good starting point for me, doesn't have any toe...I still have a spring and strut set up with spring rates that are not much higher than stock (due to my limited budget). I've read several times (through unreliable sources) that the rear suspension can have binding problems with poly bushings throughout, which I have.

I believe I installed all the bushings correctly, lubricated them and torqued them to spec. The rear suspension will droop some if I jack the rear of the car up but if I simply bounce on the back of the car the rear will hardly move at all. The front, with nearly the same spring rate, moves normally and compresses a few inches. I realize this is an extremely crude test but it seemed relevant to me.

Since I'm reading* that I might have a problem and the car seems to be having these problems I'm looking at the bushings. What I heard from you is that you are not having issues with them. Can I ask what spring rates you are running (ballpark)? I wonder if I am just noticing it more with my undersprung car.

RUCA = Rear Upper Control Arm

...your suggestion to replace the RUCA first with sphericals goes along with other stuff I have read.

Thanks,

[Tristan Smith]

Dan ,

The rear suspension is very sensitive to bind. Here is what I would do. Remove the shock and as much weight as you can from the rear suspension. That would be the tire, rotor, hang the caliper and remove the axle and bearing if you can. I would loosen all the bolts so that you can lift the suspension with your hand through it's full arc, but not so much that any bind would would be masked by a loose bolt. If it does bind up, you will be able to tell.

My sense is that it will. The reason sphericals are the only real choice is because you get movement on two planes at various connecting points on the control arms as it goes through it's range.

The stock rubber bushings are soft enough to allow that dual plane movement.

What happens when the suspension binds, is obvious. Your spring rate goes from whatever you have to instantaneous infinite rate.

For what it's worth you can use delrin on the LCA bushings as that moves only on one plane. But if you are getting bind, you may want to get a new set of stock rubber bushings until you can do the full spherical set up.

I did all my own spherical development. It's a bit cheaper, but very time consuming.

[CRallo]

I would take out the rear strut/coilover with the car on stands/a lift and move the suspension through its range of motion with a jack. If something is binding you should be able to see it/hear it.

We have all spehericals in the back of our car, so I can't comment much more than that...

[CRallo]

update?