Suspension Problems

[fixitman]

The ride height dimensions noted in the beginning of this post were supplied by two Classic Z Car members with stock suspensions on early 260Z's, not 240's. The suspension was installed properly. But as a check, all suspension pivots were loosened and re-torqued with the car on grade yesterday. To obtain the proper rear ride height, it took two men standing on the rear bumper shocks. One seat, carpet, a few plastic panels and the spare tire have to be added yet. But these items will not add 350-400 lbs. to the car.

Bilsteins are gas pressured shocks. According to one of Carl Beck's post, they work well on one of his 240's.

Due to the ride height, the car cannot be driven because the sway bar pivots up and hits the drive shaft yoke. The shop is going to install the original springs and see if that makes a difference. What else can account for a rear ride height 2.5" over spec?

Fixitman

[doradox]

The ride height dimensions noted in the beginning of this post were supplied by two Classic Z Car members with stock suspensions on early 260Z's, not 240's. The suspension was installed properly. But as a check, all suspension pivots were loosened and re-torqued with the car on grade yesterday. To obtain the proper rear ride height, it took two men standing on the rear bumper shocks. One seat, carpet, a few plastic panels and the spare tire have to be added yet. But these items will not add 350-400 lbs. to the car.

Bilsteins are gas pressured shocks. According to one of Carl Beck's post, they work well on one of his 240's.

Due to the ride height, the car cannot be driven because the sway bar pivots up and hits the drive shaft yoke. The shop is going to install the original springs and see if that makes a difference. What else can account for a rear ride height 2.5" over spec?

Fixitman

260-240 whatever. What I said still holds. Factory not modified.

I'm sure the Bilsteins work just fine. I was just pointing to another variable in your search for the ride height you want.

The few missing parts obviously won't add up to 350-400 lbs but they will make a difference.

Why don't you remove the sway bar so you can drive the car then remeasure the ride height.

If you don't there's a chance that when you finally do and everything settles you'll end up lower than you wanted if you get it set where you want in the shop.

I'm trying to provide some help. I've seen what I have described happen many times. You may very well have bad springs. But if you don't account for all variables you might not be happy with your end result.

Steve

[fixitman]

I appreciate everyones responses, wise consul and willingness to share their experiences. After all the bits are added, I'll ask the shop to readjust the suspension again. For now, the shop is going to powder coat the orignal springs and reinstall them. I'll let you know what happens to the ride height in a week or two.

They tell me the rear springs are much stiffer than the originals. I'm wondering if Nissan actually shipped Stage 2 springs for the rear. It wouldn't be the first time Nissan shipped the wrong part with the correct part number.

Thanks again,

Fixitman

[fixitman]

In the last two weeks, the Euro Stage 1 springs were removed and the original springs were powder coated and installed. The top of front bumper height is now 20.3" front vs. factory spec of 18.9", +1.4". The top of rear bumper height is now 20.0 vs. factory spec of 20.3, -0.3". These measurements were taken with a full tank of gas and the spare tire installed. This is a big improvement over the ride height with the Euro Stage 1 springs. Once the interior is added, perhaps the front will come down a little.

The interference problem between the rear sway bar and the drive shaft yoke was resolved by reducing the ride height and lengthing the link spacer by 3/4".

Here's how she stands as of today. On to the interior...

Fixitman

[doradox]

Looks nice!

Steve

[Carl Beck]

The top of front bumper height is now 20.3" front vs. factory spec of 18.9", +1.4". The top of rear bumper height is now 20.0 vs. factory spec of 20.3, -0.3". These measurements were taken with a full tank of gas and the spare tire installed..

Fixitman

Hi Fixitman:

Where did you get "factory spec's" for the height of the top of the front and rear bumpers for a 260Z?

So far - almost all of us have been using measurements taken at:

1. The center of the headlight - that is the headlight adjusting screw on the outside of the headlight nacelle.

2 The height of the front wheel arch - from the ground, measured though the center of the wheel.

3. The height of the rocker panel in front - measured from the bottom of the rocker (not the lip that sticks down), to the ground - at the cutouts that show where to place the jack.

4. The height of the rocker panel in the rear - measured from the bottom of the rocker (not the lip that sticks down), to the ground - at the cutouts that show where to place the jack.

5. The height of the rear wheel arch - from the ground, measured though the center of the wheel.

The only measurement that I have found - given by the factory - is the distance from the bottom of the front frame rail to the ground - taken below the front frame rail where it meets the firewall. That is given as 6" in the FSM.

So with the "bumper height" spec's you list - we have really no idea how that compares to all the previous measurements gathered. If you get a chance, can you take the 5 measurements above and report them?

<img src=http://ZHome.com/FixitZMeasure.jpg>

FWIW,

Carl B.

[Zs-ondabrain]

I did'nt read the whole thread but if I had to throw something into the mix, I say that your end-links need to be shortened by 3/4". That should clear the axles and allow the rear to sit correct without lowering too much.

By the way, Why so big on the sway bars?

Dave.

[fixitman]

The bumper height specs came from page BF-9 in the 260Z FSM. See attached page. I'll record the current measurements the next time I visit the shop. But the measurements might be more meaningful once the interior is completed. I suspect that the front is higher than spec due to the Bilsteins.

Dave, these sway bar sizes (1 1/8" front and 7/8" rear) were the only sizes offered by Quickor for an early '74 to '78 Z in the early 80's. Back then, Quickor had a good reputation. So, I followed their advise.

Fixitman

Datsun 260Z-Ride Height.pdf

[FilipeA]

Hi fixtman

I know you have the same problem that i have once before.

I have the Hp tokicos blues in my car, both front & rear with the European Stock springs that were standard in all European cars.

After a couple of times of road and after 1600 km done in my car this is how it looks.

I think it looks very nice and original as well. The shop didn`t do anything to suspension and the tank gas was not full :classic:

Any away i still have here the Eibach springs if some day i will put them...

I do belive it might have been some mistake with those springs that you had before, but anyaway the car sits a light high to me.

Besides that your car looks GOOD

Filipe

[fixitman]

Thanks, FilipeA. Your Z looks pretty good. It certainly has a lower ride height than mine did with Euro springs. I'm going to wait until the interior is completed before revisiting the suspension.

I have read speculation on Classic Zcar Club threads that the spring perch is at a different location on the Euro cars. If there is a location difference, it would account the the ride height problems on USA Z's. Could you measure the distance from the spring perch to the base of the strut tube? Perhaps provide a sketch of exactly where you took the measurements. We would appreciate your efforts.

Regards,

Fixitman

[FilipeA]

Hi

I will do that, but you can send a PM with details for measurements, because my tecnhical english sometimes is not so good.

If you could send me a picture where you want me to measure i will do that with no problems .

Thanks

FilipeA

[Carl Beck]

Fixitman:

Coil springs provide a fairly constant rate of compression, once they are compressed to about 80% of their Free Length.

If you look at the Spring Spec's for a stock US Spec. 260Z produced between 8/73 and 8/74.. you will see that the Free Length is 15.4 inches, the Installed length 8.7 inches. The load on the installed spring is 706 lbs. The stock spring constant (rate) is 106 lbs/in.

So if you divide the load 706 by the spring constant 106 you get 6.66 inches of initial spring compression when the car is sitting on it's struts.

If you subtract the listed Installed Length of 8.7 inch, from the listed Free Length of 15.4 you get 6.7 inches. (rounding errors etc) - so close enough.

Now change the rear springs - to one's with a spring constant of 140 lbs/in. (the spring rate you provided) Looking strictly at the picture of the springs you Posted above - I'd guess that the Euro Spec. Spring is the clean one on the far left - and it looks like it might be 1 inch shorter than the others.. So call it 14.4 in. Free Length.

Divide the load of 706 by the spring constant of 140 lbs/in and you get 5 inches of initial compression.

14.4 Free length minus 5 inches of initial compression = should be close to 9.4 inches installed length.

9.4 minus the stock 8.7 inch is only 0.7 inch increase in ride height.

I'd have to have the exact length of that "Euro Stage II" spring.... to be sure, I would also have to know for sure what the spring constant is (to be sure you have the springs that you think you do)

However it strikes me that it was NOT only the Euro Springs that could account for the huge difference in ride height, as pictured on the rear of your 260Z in your first Post.

Where did you get your Shocks? Now old are they? Billstein hasn't sold OEM replacement shocks for the 240/260Z's since the mid 80's. Back then they were low pressure gas shocks. With the Euro Spec. springs removed, and stock springs back in the car - it still looks like it is sitting a couple inches higher - but that just may be the angle of the pictures... We'll know more when you measure the usually places...

THE STOCK SPRINGS - according to the Field Service Manual:

-The two rear and the Left Front are the same - the Right Front is the shorter one.

-The two rear and Left Front have a free length of 15.4 inches

-The Right Front has a Free Length of 14.9

FWIW,

Carl B.

BTW - thanks to Will (HLS30.com) for the info on the 260Z springs from the 260Z FSM.

Edited September 22, 2008 by Carl Beck