Stock spring specs.

[MaximG]

So ok,

Im asking the hive minds on the forum what the U.K. specification for the sprigs would have been for my 1972 S30 240.

Yes I have looked on the forum and couldn’t find the answer.

I sent my stock springs to Springcoil last year and this is what I ended up with.



However this is what it looked like before the new springs.



Now you can see my problem. Trouble is they swear blind they made the new springs to what they found when they tested the old ones (yes I sent them the old ones for comparison). Front springs aren’t a problem.

Im not going to go into the runaround I got last year because I gave them every opportunity with Covid issues in mind. I seriously bent over backwards for them.

However I need to move things forward so if I can figure out what the stock spring specs should be it might give me some idea where things might have gone wrong.

Kind Regards,

Michael

 

[jonbills]

Are the new springs meant to be a copy of the old then?
Anyway, my springs are from springcoil too. I initially specced them wrong and they were too high like yours. I sent them back and asked them to re-set them lower, which they did.
I don't think I was very scientific - just worked out how much lower I wanted and asked them to make the free height that much shorter.

 

[MaximG]

Are the new springs meant to be a copy of the old then?
Anyway, my springs are from springcoil too. I initially specced them wrong and they were too high like yours. I sent them back and asked them to re-set them lower, which they did.
I don't think I was very scientific - just worked out how much lower I wanted and asked them to make the free height that much shorter.

Yes the new ones are meant to a copy of the old ones i.e. stock.

 

[Mr.G]

Did they give you the old ones back? Get both springs tested independently.

 

[Albrecht]

Im asking the hive minds on the forum what the U.K. specification for the sprigs would have been for my 1972 S30 240.

I think spring data is one of the trickiest, most frustrating, self-contradictory and ultimately bewildering areas of technicality surrounding these cars. On the face of it, it *should* all be pretty simple, but it doesn't pan out like that in reality.

There's plenty of data to hand, but how the springs work and how they leave the car sitting after installation depends on many other factors including spring seat height (there are differences depending on the suspension leg part number) and damper type.

A key factor in getting old springs copied is their (uninstalled) 'free length'. Old/used springs will usually have sagged somewhat and if the spring manufacturer uses their sagged length as the 'free length' then their (installed) length will often be wrong. If they take this into account and add a little extra to the new free length it can be a little hit or miss, and overcompensation may leave the car sitting higher than expected.

Factory data (active turns of coil, free length, installed length, spring constant) was usually given to suit factory strut data, using the stock oil-filled 'wet leg' dampers. Switch to damper 'inserts' of either oil-filled type, all gas-filled or gas-charged oil dampers and it moves the goalposts somewhat, even affecting static ride height as the dampers give the car a 'set'. Complicated!

Added to this, there was a certain amount of development for the UK and 'Euro' market cars in the early days of sales which ended up with Nissan producing 'Standard' and 'Hard' suspensions, as well as a 'European' setting. It can be hard to know what was fitted to any individual car at the factory, or what has been changed after 50+ of use. More complication.

I think you might find that more hard data just confuses the situation. Trial and error almost seems a better bet for individual cases. Jon's solution of asking the manufacturer to have another go (to drop the static ride height by a given amount) might be the easiest solution in this particular case.

 

[Rob Gaskin]

I had to experiment when I wanted 'standard' springs on my standard car (the PO had changed them). I got it more or less right in the end but changing springs is a maul.

https://zclub.net/community/index.php?threads/240z-standard-road-springs.20070/

Just bear in mind that road springs (and wheels/tyres) fitted to 'sports cars' of the early 70s were not as 'sporty' as you might remember. My car drove 'nicely' (sorry Sean) but I certainly knew I was in an old classic. My wife thought it quite comfortable as a passenger.

If it was an MGB, Spitfire, TR6 etc it might be ok but 'our' cars look far more modern than those and perhaps need slightly upgraded suspension unless you are going for the 'original' feel (which I was).

I know you've been around Zs for a long time but just be careful what you are wishing for. You could go to a lot of trouble and not like the result?

As a matter of interest if you push down on the rear quarter is it compliant (can you bounce it), with standard springs this will be quite easy. The other 3 cars I've owned wouldn't enable me to do that.

I managed to obtain some NOS from a member for the front and from memory I used 260Z 2/2 front springs on the rear.

 

[MaximG]

As a matter of interest if you push down on the rear quarter is it compliant (can you bounce it), with standard springs this will be quite easy. The other 3 cars I've owned wouldn't enable me to do that.

Bare in mind I don’t have anything to compare to apart from a leaf sprung Landy, I would say the springs are quite hard. Definitely not a lot of give.

 

[MaximG]

I think spring data is one of the trickiest, most frustrating, self-contradictory and ultimately bewildering areas of technicality surrounding these cars. On the face of it, it *should* all be pretty simple, but it doesn't pan out like that in reality.

There's plenty of data to hand, but how the springs work and how they leave the car sitting after installation depends on many other factors including spring seat height (there are differences depending on the suspension leg part number) and damper type.

A key factor in getting old springs copied is their (uninstalled) 'free length'. Old/used springs will usually have sagged somewhat and if the spring manufacturer uses their sagged length as the 'free length' then their (installed) length will often be wrong. If they take this into account and add a little extra to the new free length it can be a little hit or miss, and overcompensation may leave the car sitting higher than expected.

Factory data (active turns of coil, free length, installed length, spring constant) was usually given to suit factory strut data, using the stock oil-filled 'wet leg' dampers. Switch to damper 'inserts' of either oil-filled type, all gas-filled or gas-charged oil dampers and it moves the goalposts somewhat, even affecting static ride height as the dampers give the car a 'set'. Complicated!

Added to this, there was a certain amount of development for the UK and 'Euro' market cars in the early days of sales which ended up with Nissan producing 'Standard' and 'Hard' suspensions, as well as a 'European' setting. It can be hard to know what was fitted to any individual car at the factory, or what has been changed after 50+ of use. More complication.

I think you might find that more hard data just confuses the situation. Trial and error almost seems a better bet for individual cases. Jon's solution of asking the manufacturer to have another go (to drop the static ride height by a given amount) might be the easiest solution in this particular case.

Allan I very much appreciate the time and effort you put into replying to my post. I had a feeling things wouldn’t be straight forward.

I’m kind of coming round to the idea of just putting the old springs back on again. Had them cleaned up just in case and they don’t look to bad.

 

[MaximG]

Although I have found a spring company near me and may ask them to test both sets to see what the difference is

 

[Rob Gaskin]

Bare in mind I don’t have anything to compare to apart from a leaf sprung Landy, I would say the springs are quite hard. Definitely not a lot of give.

The other 3 Datsuns I meant so there's a comparison.

 

[MaximG]

The other 3 Datsuns I meant so there's a comparison.

Yes don’t worry Rob got your meaning

 

[MaximG]

Make of this what you will but I have little update.

This festive holiday has given me the time and inclination to take the rear struts off. One down one to go but thought I would just show the difference between new and old springs. Keep in mind that this is a professional company who I supplied the old springs too, to copy. Doesn’t matter what the rates are I wanted a copy.



So to start the old spring is 9.66 turns where as the new one is 9.75.
The old springs weigh 5.14.5 lb & 5.15 lb where as the new spring weighs 6.7 lb

I have absolutely no idea what difference any of that would make but to me that isn’t a very close copy. I would have expected it to be within an ounce or two?
I’m inclined to put the old ones back on and be done with it. But the whole thing seriously niggles me.

 

[Rob Gaskin]

I think you were perhaps expecting too much. They look fine to me and so I'd fit them and see what the difference is.

 

[MaximG]

Rob see pictures above and you can see the difference. The ones at the top of the page

 

[toopy]

If the new ones have slightly more coil length and therefore a tad more metal and they weigh more, so more metal i guess in the diameter of the coiled metal (not overall spring diameter) and assuming the free height of the new spring is within a couple of mm of the old, does that not imply they will compress less? Looking at the photos though of the car when installed, there is a considerable difference!

I am absolutely not qualified to offer advice on the subject, just thinking out loud

 

[Mark N]

As Toopy mentions, the extra 0.09 turns accounts for slightly less than 1% of the weight increase.
The remaining weight difference (around 7.5%) could be down to different sizes of spring stock, maybe even one being a metric or imperial equivalent of the other.

 

[MaximG]

Thanks for the reply’s. Think I’m just going to stick with the original springs and be done with it. I’m certainly not going to put the new ones on after taking the trouble to take them off. Even if my expectations are some how too high, like the suspension.

 

[moggy240]

Even if my expectations are some how too high, like the suspension.

Lol!!!!