Lotus Elan

S4 Front Springs - Part 2

PostPost by: MyLotus » Mon Sep 09, 2013 12:39 pm

Victory at last! I removed both front springs to find out they were the longer type and one was taller than the other... A friend of mine had a set on standard length front springs which I installed and ...bingo, the front end does move now! It is slightly lower and when I press on the front fenders, there is up and down movement. On the road, the ride is totally different. So problem solved but I'm still perplexed that a 1.5 cm shorter spring would make such a difference. Or is it that something else was 'jammed' in the supension? Of course, I made sure to tighten all suspension nuts once the car was resting on the floor. One last thing, there is ubnormal stiffness on the rear driver side suspension. It won't droop as far as the passenger side when lifted and when pressure is applied on the fender, it won't depress as readily... I suspect that the bushings are twisted are not correctly tightened. This week's project...
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PostPost by: rgh0 » Mon Sep 09, 2013 1:30 pm

I suspect you may have non matching shockers and perhaps springs as well given the problems you had with the front. I would take a close look at both.

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PostPost by: collins_dan » Mon Sep 09, 2013 1:32 pm

Interference from the bushings can definitely stiffen things up. I installed poly bushings this winter and it took quite a few attempts to get everything to move smoothly. Dan
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PostPost by: MyLotus » Tue Sep 10, 2013 12:07 pm

As suggested by Dan, I loosened all bushing nuts and let the suspension droop to max. A strange 'clunk' was heard while the rear end was raised... then I noticed that the droop was extended on the driver side suspension! I then lowered the car and retightened the nuts and drove the car. It seemed that the driver side was softer and equal to the passenger side. Now this is just an impression and I guess the only way to find out if all is now correct is to ask an Elan owner to try the car or vice-versa. Since the car sat for years after initial restoration, could it be that 'something' in the damper was sticking? Anyway, my Elan is 'driveable' now and I am moving on to another activity: enjoying the drive. Thanks to all for your kind assistance.

Alain :)
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PostPost by: Galwaylotus » Tue Sep 10, 2013 6:47 pm

UAB807F wrote:Hi,

I wouldn't have expected a longer spring to have a different rating in terms of lbs/inch, the extra length will just give it a bit extra height when installed on the same damper as a shorter spring of the same rating.

Actually, all other features being equal (metallurgy, heat treatment, wire diameter and coil diameter) a longer spring will have a lower (softer) spring rate and vice versa.
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PostPost by: collins_dan » Tue Sep 10, 2013 8:39 pm

Alain, Try jacking up the rear of the car and disconnecting the strut assembly on each side. then manually move each wishbone up and down and see if they feel the same. What can be happening is that there is interference on the rear inner bushings causing it to not rotate completely. After you have driven a bit, of course. Enjoy! Dan
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PostPost by: MyLotus » Tue Sep 10, 2013 9:18 pm

Thx Dan, I'll try that.

Alain
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PostPost by: MyLotus » Tue Sep 10, 2013 9:21 pm

Galwaylotus, assuming two similar springs of different lengths installed in on a damper, are you saying that the preload will be lower (softer) on the longer spring?

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PostPost by: Galwaylotus » Wed Sep 11, 2013 6:46 am

No. Preload and spring rate are two different things, The preload (force) is a function of the spring rate (force/change in length) and the compression distance (change in length). Although the rate will be lower on a longer spring, the compression distance will be greater on the same length damper. Once the applied load exceeds the preload, the softer spring will compress more for increasing load.
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