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Dodgy adjustable suspension - advice needed!


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Hi all,

Well, I'm in the midst of refreshing the rear suspension on my Turbo SE and am at a bit of an impasse. I know a bunch of folks here are running custom suspension and can probably chime in with some advice.

Long story short, I removed the old shocks and dampers (factory 1991) and replaced them with the only thing I could get a hold of with my budget, Gaz GP8 adjustable dampers and height adjustable springs along with new stem bushes etc.

After installing them and "roughing out" the height with the same amount of thread showing at each damper the car was leaning heavily to the right (driver's side UK car) - more so than before. Odd I thought.

I then adjusted the right side spring by raising it by a whopping 30 mm!!! The car now leans as it used to with the worn suspension. In other words, we're still not even level!

IMG_6087

Pretty soon I will have run out of thread.

The left side (68 mm thread showing):

IMG_5240

The right side (100 mm thread showing, note that the spring is visibly compressed, almost as if pre-loaded):

IMG_5246

It seems that rather than raising the vehicle on the right, all I'm accomplishing is visual "pre-load" - the spring is compressing only raising the height of the vehicle a fraction.

The springs were supplied by Gaz for use with that damper and I believe they were both rated at 250 lb/inch or 45 N/mm (S4 spec) with a marking at the top of the spring.

With this setup, measuring the "free length" of the drooping springs on either side before letting the car down and settling it, I'm getting a 13% difference from left to right (left side compresses less than the right with the weight of the car on it) - and that's WITH the above illustrated height difference (I assume these springs aren't entirely linear as they get compressed further).

So, guys, am I missing something here, or did Gaz supply me with two different spring rates?

I can't find any evidence of damage at the chassis end so I'm ruling that out to begin with.

Furthermore, while I know the weight isn't 50/50 between the rear wheels, an added compression of 30 mm (and still not level) equates to more than 137 kg of weight on that side which is preposterous.

Lastly, I know all of this is pointless until I've had the corners weighed etc, but I'm deferring that until the front suspension and all bushes are changed too. Until then I just want a car that doesn't lean and has 170 mm ride height according to Lotus spec. 

Have I missed anything here? I know a lot of folks are surprised when installing these that the same height per damper doesn't equate to a level car, but 30 mm (probably 50 mm to get them level, and at the end of the thread in the RHS picture) seems excessive.

Thanks a bazillion to anyone who can enlighten me. 

 

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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  • Gold FFM

Assuming both rear springs are correct, the problem seems to be at the front. Which would explain why it still leans to the right with the new springs. You can swap rear springs/dampers, to rule those out, not too much trouble. And I'd definitely check the front as well! If you had a Cayman, a logical explanation would be the spring perch going through the tub, as in posted in another thread. ;-)

Just to add, I recently fitted Protech dampers to the rear of my SE and also guesstimated the suspension settings by adjusting left and right equally until I got ca 170mm central height. They have settled since, so need a bit more preload, but do seem to be level, just like the old ones. I did reuse the old springs, only changed the dampers as one was completely worn and offered no resistance on rebound.

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

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There's definitely a problem at the front - I'm going to be ordering those parts shortly, although in that case original parts since they are still available!

I tried lifting the front of the car (drivers side) to see how this would affect the rear suspension (simulating level setup at the front with a jack) - but even so there was sag. 

My brother suggested swapping the springs and dampers. We can try that although it's still a pain in the butt and will shave many hours off a day.. Otherwise I supposed I can re-use the old springs, they are the same length, but need sandblasting. Could there be any negative effects of using a spring that's not matched to a particular damper?

/V

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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Swapping springs was going to be my first call, but you already know that one. When winding upwards, are pinch bolts on all of the suspension (on all bushes) slackened off slightly?

Have you adjusted the bound/ rebound such that it's not on the hardest setting while winding the springs up? Even if that means softening it then adjusting it harder once ride height sorted.

Have you ensured the car is laden with the required (50kg) each side? It could be that rather than the RHS being too low, it's just the LHS not having settled yet.

 

Definitely agree that the problem could be the front, as you say 50/50 weight distribution, and with a rigid car it's just as easy for the front or rear to upset car's stance. Even if the front components aren't damaged, if the old rear suspension was making it list, then the front needs a chance to re-settle including loosening the bolts.

 

 

At least it's nice and shiny with those calipers and the nice new adapter.

Regards

Andy

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Hi Andy,

I didn't slacken off any of the suspension other than the stem bolt and lower link bolts which I tightened with the weight of the car on the wheels. I wasn't aware you were supposed to loosen all the links if the bushes aren't to be changed. I know the manual states which links are to be done up at ride height + ballast so I can loosen those, put the car on the ground, then tighten again. Will be interesting doing some of those since space is tight and I don't have a pit. 

The springs were on the softest setting throughout all adjustments. 

I haven't set ride height with ballasts yet - I've been on a few drives with two of us in the car, taken a few hard turns either direction, and the right side droops constantly after each adjustment, whereas the left side has remained fixed since we initially set it roughly. 

With someone sitting in the drivers seat the car lowers by 5 mm or so, so if 2 ppl weighing 75 kg each sit maybe we're seeing 10 mm deflection? Still, with an unladen car (1/2 tank of fuel, no occupants) - having to set one side 30 mm higher just seems wrong. Even if the front leans a bit. When I jacked the front right side up to level the front of the car, the rear didn't really follow suit. 

I'm going to contact the place I bought them from because right now I'm leaning (har har) towards non-matching springs.

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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  • Gold FFM

Having not long done mine, I would say that if you've not really touched anything else then your height is unlikely to be affected too much by tightening the suspension. I found it made little difference to the ride height on my car, even if it still needs to be correct as per the book. I cut some wood blocks to place under the chassis for the height, removed the wheels, placed axle stands under the suspension units, and lowered the car down on the lift before tightening everything. It's a pain in the arse to do, though.

I just checked my photos, and I have GAZ rears with 15 whole threads showing below the adjustable spring platform, and the car is level. I can't help with the front, because I have newish Lotus dampers which aren't adjustable.

Assuming that you have everything correctly seated with no damage to the spring seats (whatever arrangement the SE has), then if you want to know the spring rates, have a measure up and do a calculation next. It's down to wire diameter, and number of coils. There are calculators online like this one -

http://www.bluecoilspring.com/rate.htm

Margate Exotics.

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Hi Ian,

I'm assuming we have exactly the same type of shock - according to the Gaz catalogue the same model is specified for all Stevens Esprits, GP8 4939. 

The springs were marked 80x12x250 which is presume stands for 8" inner diameter, 12" unsprung length, 250 lbs/inch rate. This is equivalent to S4/S4s rear spring rates.

So if we're running the same kit and I have far more threads showing on both sides, something is off. Especially on the right side :S. 

I also checked for chassis damage to rule that out but can find no evidence of anything like that.

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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If you are adjusting the ride height then you need to slacken off both upper and lower link inboard and outboard fixings due to the way the Esprit uses the bushes.

The early S4 had softer rear spring rates than the later S4 because of the unreinforced gear lever aperture in the backbone chassis. The late S4 and the S4s have the same rear spring rate.

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This was a concern when I ordered the springs - I voiced my opinion that the stiffer springs could damage the chassis but Gaz were adamant they were good for all Stevens...hmm.

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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I believe we may have found the answer. @ian29gte, I might owe you a beer. 

Left spring, 12.4 mm.

IMG_5258

Right spring, 11.3 mm:

IMG_5247

 

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Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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Yeah I did exactly that - you get quite a radical difference just changing the wire thickness. From what I could ascertain it's the same 80 mm inner diameter on both. They had the same free length too, so according to the calcs I get just under 30% difference between them in spring rate. 

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Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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Quick update:

After supplying all the above images, and doing a calculation which the manufacturer is no doubt aware of given the input data, they demand that I prop my car up in the air, remove the springs, ship them back at what will probably cost me 100 quid at Swedish postage rates, so they can check the springs in their test rig. 

Considering the lead times on these springs was over a month this would see my car off the road for anywhere between 6-8 weeks. Great. Really great.

Thankfully I found a place round the corner that will blast and powder coat my original springs (still the same length each side!) for 60 quid. So at least I had a contingency, having expected something like this from the beginning. 

So a word of advice to all; yes it might be bloody expensive, but it's probably smarter to just cough up the money and buy LOTAC suspension, than have to go through the fun of having wrong parts sent to you. 

Really really pissed off right now. I lose WEEKS every single year due to parts cock-ups, and in many cases I end up spending AS MUCH the second time round when I sum up shipping erroneous parts back or the sum of shipping + goodwill discounts on replacement parts when suppliers don't want to refund my money outright. 

Why can't I verify they're mismatched here? I can even offer to have the test performed at The Royal Institute of Technology in Stockholm....that ought to be legit enough?

 

Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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  • Gold FFM

It pains me to say it, but I think you need to send the springs back them if they won't accept and independent test result. If Gaz prove that the spring rates are incorrect, then they should reimburse you the cost of postage, as it's their mistake, and therefore their responsibility.

If not, then everyone here will know about their customer service, and they won't want a bad reputation, will they?

Margate Exotics.

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  • Gold FFM

I'd be asking the very same question to another person at Gaz. It's simply unacceptable - they should be able to sort this out in parallel and get some new springs now - not in series.....

 

Only here once

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1 hour ago, Barrykearley said:

I'd be asking the very same question to another person at Gaz. It's simply unacceptable - they should be able to sort this out in parallel and get some new springs now - not in series.....

 

Hold that thought. They seem to be willing to supply me with new ones at cost. Just awaiting confirmation. 

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Vanya Stanisavljevic '91 Esprit SE | '97 XK8

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