Rear suspension tilt

[Jhepb1]

The rear suspension on my 1973 240Z sits lower on the right side than the left by about 5/8 inch. The springs are fairly new, I think (only had the car a year). They're the same length & diameter and the coils are the same size and number.

I tried swapping them over and the right side was still lower when supporting the weight of the car. I've measured the struts (just to make sure there isn't an incorrect or damaged part in there) and measured the strut towers and arches to find any badly-done renovation or repair work. Nothing.

So, whichever way I fit the springs left-right, the one on the right has a compressed length about 5/8 inch shorter than the left one.

I can only think that the right side of the car is heavier, somehow. Of course, the tank is on the driver's side (it's an RHD car) and right now contains about 50 litres of fuel, which weighs about 36 kilos / 80 lbs. Could this be making the difference?

Any other ideas? Thanks.

 

[morbias]

Are the spacers in the strut top mounts in good condition? The original rubber ones tend to deteriorate, maybe one side is in worse shape than the other.

Also are you measuring on a level surface? You might be surprised how much difference an uneven surface will make to the way the suspension sits!

 

[tel240z]

Well if only the rear right side is different then i'd be looking at a twisted chassis i think you need to measure the front at the same time hopefully the left front will be higher

 

[grolls]

Are the spacers in the strut top mounts in good condition? The original rubber ones tend to deteriorate, maybe one side is in worse shape than the other.

Also are you measuring on a level surface? You might be surprised how much difference an uneven surface will make to the way the suspension sits!

Or using a 260 z 2+2 on the left and standard on the right as the 2+2 is taller i seem to remember

 

[Jhepb1]

Thanks for all the feedback.
I could be that the front nearside suspension is sitting too high, tilting the car over to the rear right. So, what I'll do next is lift up the front, remove the wheels and lower it to normal ride height, supported in the middle on a stand or the trolley jack. I'll use a spirit level to make sure the rear tyres are on a level surface too. This should allow the rear to settle without any influence from the front. If that doesn't help, I'll try some ballast on the right side of the boot.
Interesting idea to use a 2+2 OSR spring. Might try that.
I can't do any more until Saturday at the earliest but I'll keep you posted.
Thanks again, guys.

 

[grolls]

Interesting idea to use a 2+2 OSR spring. Might try that.

Nooooo don't do that, the top mount is taller on a 2+2, someone may have used one of these in error or the springs knackered and sagging. Check the top mounts are correct and the same size and haven't collapsed. If there ok id buy a new set of springs from Mr F.

 

[grolls]

Interesting idea to use a 2+2 OSR spring. Might try that.
I can't do any more until Saturday at the earliest but I'll keep you posted.
Thanks again, guys.

Nooooooo don't do that. Check the top mounts as the 2+2 mount is taller, someone may have fitted on in error and could explain the tilt.

 

[Jhepb1]

Good advice. Thanks.

I think the springs on the car came from MJP, but how long ago I don't know.

 

[Stockdale]

I can only think that the right side of the car is heavier, somehow. Of course, the tank is on the driver's side (it's an RHD car) and right now contains about 50 litres of fuel, which weighs about 36 kilos / 80 lbs. Could this be making the difference?

Any other ideas? Thanks.[/QUOTE]

Think you might find 50 litres of fuel will weigh nearer 110 lbs. Add to that perhaps 200 lbs (+ - 20 lbs) for average driver weight (most cars have a single occupant for the most part) and you can see that the RH side of the car over time (presuming it to be RHD) is under very uneven load and springing will become fatigued. Follow along the road many 'classic' cars (particularly sports cars) and you will notice lower ride on the offside. Perhaps a number of ways of dealing with this though I bow to the expert engineering knowledge of this forum to say quite how

 

[Rob Gaskin]

It would be good to get your car 'corner weight' tested.

Pictures ?

Personally I don't think petrol or driver weight are a significant factor.

 

[jonbills]

I did some calcation and measurement a couple of years ago, and I reckoned I make about 1cm difference to left/right ride height.
I have an extra spacer of about 1cm on right side front and back that makes the car level when I'm in it.

edit: here's a thread from when I'd just done it: http://zclub.net/forum/showthread.php?t=22582&page=11 so 6 or 7 mm difference.

 

[Jhepb1]

Success

I've managed to fix the problem. I talked to Richard at Fourways who suggested a 260Z strut top insulator. This is 20mm taller than the 240Z one and should lift the car on that side.
I tried that and it worked. The car now sits level left-right.
This has cured the symptom rather than the fault but it has had the desired effect. I'll live with it for a while and see how it goes.
Thanks to all who contributed.