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stevem

Rear Suspension, which springs ?

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Today I took apart the rear suspension of my 88 Esprit Turbo, to replace all the bushes and a pair of shocks and springs. The Shocks and springs were from SJ's and are the Protech adjustables that were supplied with new springs as a package.

Having managed to get the lower link studs and split spacers out ( bugger of a job ) and taken off the upper and lower links, shocks and springs, I've popped the old bushes out, sandblasted all the parts ready for paint and will fit new bushes. So far so good.

The extended length of the Protech is the same as the original old rusty ones, but when fully closed the Protech's are about 1 inch shorter. Also I noticed the new springs are about 1 inch longer than the originals and not quite as thick gauge steel. ( I am guessing that the longer length and lighter gauge equals similar compressed length )

I'll set the bottom spring support on the Protech to be the same height measured from the bottom stud mounting as on the originals to get a starting point for ride height. Question is should I put the new springs on, or clean up the old ones and put them back ? I've read a few reports that the SJ supplied springs that come with the Protechs are not real good. On the other hand the springs that were on havn't been changed in at least 12 years and possibly could be originals from 88.

The car is used for normal road use, no track events, and the roads around here are as pot-holed as you can get. Also we have the largest speed humps I have ever seen, so I don't want to be bottoming out regularly. I'm stuck with the Protechs for now, so which springs ?

I have read the forums and am aware that I need to leave the bolts slack until it's back on the gorund. I can tighten the bolts up when the wheels are back on as I have good access from underneath, or alternatively use Roger's trick of jacking under the hub to simulate being on the ground.

I am looking forward to your suggestions.

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Hi steve,

Im pretty sure that the problems that you have read about the sjs springs off memory is not that the springs are poor quality it is that they dont go as low as some people would expect! so as long as your not looking for a low rider motor you should be ok! And yes the springs will seem thin compared to the old ones,but not weaker in anyway at all they are tested etc to the same loads.

Regards danny

Edited by silverfrost

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Don't supose you measured the compressed length of the spring at normal ride hight before you dismantled ?

So measuring spring rates is a bit difficult because they are different lenghts, and need to be compressed to a common length to see how much it takes on each one. I retained my original springs as they measured up fine. But in your case having bought the springs I go with the new ones.

If you want to measure the rates and compressed ride hights I can tell you how to do it but you need access to more than the batheoom scales.

Go with the new ones you paid for them, what's the worst that can happen?

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Steve there are formulas for calculating springs. I've got them somewhere here... if you want them let me know. Alternatively can you make a jig to load each and measure how much each spring compresses with the same load? That'll not only give you a comparison between what you've got but also good to know if you decide to play with springs later on.

Basically fewer coils and/or thicker wire equals harder springs. So you could have thicker springs but with more coils and end up softer.

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Danny, I would'nt mind seeing those formulas, I used to do it on a press with some industrial scales and a measuring tape.

Steve, it occurs to me that Steve at SJ ought to be able to tell you the spring rate and David at Hethel should be able to give ypu spring rate of the original equipment.

Though I have a feeling you might live to regret asking this question.:P

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I've recently taken Protech and SJ springs off my car, really not impressed with them and they were too soft.

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Thanks for the answers gents, I'm stuck with the Protech's for now so they are going on regardless. I'll put on the new springs too and set then to the same ride height as it was before + 10mm to allow for bedding in and go from there.

If the experience ends up being as bad as Bibs and Andy suggest, at least they will be quick to change now i've got all new studs, nuts, bolts etc. I'll only do about 3000 miles a year in it, so if they last 3 years i'll be happy. I bought all the suspension parts almost a year ago, so they are already paid for and have to be better than what came off the car.

To be honest the calculations for spring rate etc is something I'm not going to get into, I will leave that to owners with a fetish for formulas and calculations.

I should get it all back together today, so next week I'll start on the front, that's my Easter gone.

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Steve, when I did the bushes on mine it transformed the car, when I did the ABR it was another leap forward, and the Protech shocks have proven th be excelent. Funnyly enough when they arived I measured them up, tested the bump and re-bound, and guestermated the ride hight at the front would drop by half an inch and I would end up with settings between 5-7.

What I actually got was the ride hight dropped by half an inch and after beding in I settled on a setting of 6. When I first had the car the back end was very loose into high speed corners on a trailling throttle or braking. It is now what I expect of a Lotus, rapid change of direction with no fuss, does everything it should, and does it bloody fast.

It does take time and I would suggest you run them at no more than 3, I ran mine at zero, for 100 ks or so and then start to adjust them up. Make sure your tyre pressures are correct, intially early morning when it's cold they will feel different, this goes away.

And most important, it is a falacy to believe the harder the shock the better the handling, it's a road car and there is no advantage to vibrating your eyeballs out of their sockets, you won't improve the handling.

Roger

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When I first had the car the back end was very loose into high speed corners on a trailling throttle or braking.

A small but important point is that you should have done your speed reduction before the corner, not when entering it. A neutral throttle through the corner will massively reduce slip angles, a trailing throttle or braking will massively increase them.

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The quick way is to be able to brake right into the corner as close to the apex as you can, correctly set up you can use the attitude of the car to assist braking, correctly done (and with the right set up) you can also predetermine your exit attitude and speed, the sooner you can get back on the power the faster you will be all the way up to the next deceleration.

It’s the point of transition from brake to throttle that is crucial, the shocks controlling the rate of the weight transfer from front to rear and left to right. The nice thing about the Esprit is it well capable of doing this on a standard set up.

Mine may be a little stiff in the front for others, but it is set up for my driving style.

(of course I don’t drive like that all the time officer)

Just found this, might explain it better.

Trail Braking

Edited by Roger the Dodger

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Well the rear is done, Protech shocks and new springs along with top and bottom link bushes. I torqued up all the bolts from underneath whilst the car was on it's wheels. The ride height is 15mm higher than it was originally, if it doesn't settle down in a couple of weeks I'll re-adjust the bottom spring platform and bring it down a bit.

Here's a question, if I do bring down the ride height a bit, will I need to slacken off those bolts and retorque them again at the new height ?

I see in the manual it says the clearance from the bottom of the chassis under the rear axle to the ground is 170mm. It used to be 185mm so a bit high. i;ll drop back to 170 in a week or two.

i'll be making a start on the front next week, a little easter Project.

Edited by stevem

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The front and rear suspension has now been completed using Protech shocks and the 'matching' springs from SJ's along with all new link bushes, ball joints and ARB bushes etc. For anybody who is planning to do this, it's a good idea to set the lower spring platform to about the right height before you install the springs, to make major adjustments to them afterwards is a pain in the butt.

To get the correct ride height ( 170mm from the chassis to the ground front and rear ) the distance from the bottom of the spring platfrom to the centre of the lower shock mounting bush/stud on my car was 90mm at the front, and 100mm at the rear. The photo shows the front shocks and springs installed.

After driving the car for a week or so, and making adjustments to the Protech damper settings, I have ended up with 9 clicks at the back and 7 clicks at the front. The ride is firm, but not back breaking, and the handling is way better than it was with the 20 year old suspension that was on there. I'll report back in a year or two and confirm whether the shocks are still working OK or not.

post-5938-127163581534.jpg

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Steve have you been higher than your respective settings of & & 9, I ask because you have to go over to settle on the optimum, ie crank them up untill they get too hard then bring them back to where is best. Though 7 & 9 sounds as hard as you would want tpo go. Just asking.

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