Rear spring specs

[Lotus54]

I am working on the rear suspension, 66 Elan S3.
It has previously had some adjustable spring perches installed, but not done well. The original perches were just hacked halfway off and the threaded tubes slide down. I would like to do it properly.
So far on one side I removed the old perch completely, and working out where to weld it on. It would be nice to have a quite long one, making suspension removeal easier plus I know I can adjust to proper place.

Current adjuster ‘tube’ is ~3” long (if I can find a longer one I would get it).
Now to question, I do not know what springs are in there. Of course, without measuring it likely very hard to know for certain. But…
Spring:
13.75” (35cm) long
3 3/4” (95cm) OD
2 3/4” (75 cm) ID

I cannot seem to find original spring specs, but I am pretty sure quite a bit small in diameter than those.

These do not seem to correlate with ones I see for sale on the ‘usual sites.

Any input please?


Also note that the original owner fit adjustable perch front dampers, _+2 wheels with 175 tyres. I understood he autocrossed it, so who knows?

I am open to just buying new springs too, I will not be autocrossing it or driving all that hard. I already have gotten original steel wheels and fitting 165 Pirelli CN36. I know wider than stock, but closest I could get and the front lips have already been trimmed. I am sure they will fit fine, since quite a bit narrower than those 175 fitted (which fit, but did rub in spots sometimes).

I know likely all the Ouija boards to figure this out are busy but thought I would get some input.

Mark

Edit:

There is green paint, looks like could be done when springs were new? Just in case someone recognizes these.

[RichardHawkins]

Mark,

The information you need is in the workshop manual.

My car is an S4 but should be close.

Number of coils. 8.7
Wire diameter. 0,4”
Free Length. 14.71”
Fitted Length. 8.0”
Spring Rate. 67.5 lb/inch

The manual does not specify the inner or outer diameter of the coiled spring. I have a spring out at the moment, and it measures approximately 4.25” O.D. The spring platform or perch that the spring fits into has and inside diameter of approximately 4.375”

If you can get hold of a workshop manual, it is very useful.

Hope this helps,

Richard Hawkins

[MACCA.GLM]

Hi Mark

If you already have adjustable spring platforms on the rear ,the threaded tube should be welded approx 25mm from the top of the damper tube. Weld it at the bottom not the top, and smear some silicon sealer around the top to stop water and dirt entering.

I have 2 1/4 dia springs from tt fitted and these do not need to be compressed to fit them back into the car. the castleated adjuster nuts allow you to then adjust the height required.

Regards
G

[Lotus54]

Thank you for the replies.

I did not find the spring specs in the shop manual, but I must have missed it. ( I do have a manual)

I think I will just get new springs so I know what I have. Otherwise I’m just guessing. They are certainly not stock.

Thanks very much.

Mark

[StressCraxx]

Thank you for the replies.

I did not find the spring specs in the shop manual, but I must have missed it. ( I do have a manual)

I think I will just get new springs so I know what I have. Otherwise I’m just guessing. They are certainly not stock.

Thanks very much.

Mark

67lbs/inch is correct for the original springs. A very gentle spring rate, with lots of preload, combined with a firm damper. The combination is what gives a Lotus of the period its supple handling and ride like no other sportscar of the period.

[ceejay]

Something to read here re rear suspension mods
Adjustable Rear spring platforms
https://elantrikbits.com/lotus-elan-blog/adjustable-spring-platforms-elan-rear-suspension/

Fast road
https://elantrikbits.com/lotus-elan-blog/fast-road-s2-rear-suspension/
Enjoy.

[MACCA.GLM]

I did this mod 12 months ago with parts from TT and have to say it’s great as you can set the height properly on the rears which was always too low on my sprint

A good mod to any Elan

Cheers

G

[ceejay]

Glad that worked out well for you.
CJ

[Lotus54]

In the end I just ordered new springs, proper adjustable perches (ones on it were very short), new dampers F/R.

Since I had no idea what was on it, I wanted to get it right. It likely would have been just fine like it was, but the original owner autocrossed it (I understand) and probably was setup stiffer than I would like for a road car. But I really do not know since I didn’t know what was on it.
There are a few mods I did not really like,so taking the oportunity to make my own mistakes.

Thanks for all the help,
Mark

[ceejay]

The spring specs I chose for the S2 fast road set up was
Front: 120Lbs.
Rear: 80Lbs.
These rates still supply a nice ride, as noted by several other people who have been passenger in the car.
The improvement in cornering has been great also. It's been quite a journey to get the car where it is today, I really enjoy the drive.