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280z Rear Suspension Uneven


NC280z

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Good evening all,

 

The rear suspension in my '75 280z is uneven, the driver's side is 2 1/4" from tire to fender lip, and the passenger side is 1 3/4" from tire to fender lip. I've adjusted the transverse link bushings (inner and outer) according to the manual by having people sit in the car as the bushing bolts are torqued to spec. I've got Tokico 5022 lowering springs in the rear, and KYB Gas struts. 

 

When I purchased this setup it was not known that KYB Gas struts aren't supposed to be used with lowering springs, and now I'm guessing that this is my issue. Would this be the most-likely culprit? Thanks in advance to anyone who can point me in the right direction. Also, what struts and vendors should I use? MSA seems to be sold out of Tokico HPs.

 

 

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Put a 1/2" rubber spacer under the passenger side spring to shim it up. I use a hunk of conveyor belt for things like this.

 

Swap the springs side to side. If the low side/high side swaps, maybe the springs are not matched.

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Both rear springs are marked "Tokico 5022R", are you saying that they may have worn at different rates? I've had the set on for ~4 years. What else is odd, is that before I took the car out today the passenger side was around 2 1/8" from tire to fender, it's dropped over the course of a short night's worth of driving. 

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OK.... has it always been higher on one side or, only since putting the KYB struts on.  If always higher on one side, maybe one of the springs has a lesser spring rate. You could swap sides and see if it moves also. If this happened when the KYBs were installed then I would say the KYBs are causing this imbalance. 

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I'm thinking that maybe it's the KYBs. I just went outside and brought the rear of the car up far enough to lift the tires off of the ground. I let the car back down, and the passenger side went back to a 2 1/4" distance tire to fender. It would seem that maybe the strut isn't holding up? It would make sense, given that these struts apparently aren't good to use for lowering. Also, thank you for your help tonight, datzenmike! I appreciate it greatly. 

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Gas shocks are under pressure. You have to compress them to get them into the car, then they push up on it and may affect the ride height slightly. I have fought with them to compress by putting my full weight on them, and would guess 50-80 or more pounds of upward pressure  I don't think it matters if you have stock or lowering springs.... ride height is ride height. Conventional shocks are neutral and have no effect on ride height.

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for starters on this the strut cartridge does not hold the cars weight up it is the springs that do this job , they can maybe ever so slightly being gas charged effect this though but not much at all 

if the springs are 4 years old they have worn some the motor puts stress on the chassis under throttle and torques the frame in one direction causing a twisting motion on the chassis 

if the lower side is on the torque pressure side the springs have worn un evenly due to this 

I would try swapping springs side to side and see if the opposite side is lower . if so swap springs with new ones or put a spacer shim as mike suggested 

also check the rubber isolator mounts at the top of the strut i have seen these break before 

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So looking at the strut tower insulators, it looks like the driver's side insulator is torn and the centerpiece of the insulator has dropped out. I'm guessing that this is what is causing the driver's side to sit higher? Now here's the difficult question, I can't find 280z size rear insulators anywhere. I know you can use the 240/260 mounts, but this would lower the car and I've already got lowering springs on the vehicle. What are my options?

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I've found spacers on Zcardepot that will let me use 240/260z insulators, so I've order new insulators for the front and rear. 

 

Here's an odd question for you all, would the fact that the fuel tank is primarily situated on the passenger side contribute to the height difference? I've got around half a tank of fuel, and the passenger side is a little less than 1/2" lower than the driver side (rear only). The front wheel gaps are even. 

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