S! Springs

[Claret]

Have read the various comments with regard to springs, however for a non purest (for now anyway) would someone help translate my needs into simple English.

I have already bought AVO Dampers (718's) for my S1(yes a budget choice and yes I should have read the stuff in the gassing station first) however I need to replace all four springs.

I have no idea about the spec of the existing springs (may well be original however the dampers have clearly been changed in the past)

In order to buy replacements I need to know length and poundage for front and rear in laymans language for a reasonably hard ride/cornering on open roads.

I think they were originally supplied 240/280 front/ rear no idea on length or whether length is an important factor (in this instance !)

Oh - forgot to add that the S1 has got S2 trailing arms

Thanks in advance


>>> Edited by Claret on Friday 17th May 16:38

>>> Edited by Claret on Friday 17th May 17:24

[GreenV8S]

quote:Have read the various comments with regard to springs, however for a non purest (for now anyway) would someone help translate my needs into simple English.

I have already bought AVO Dampers (718's) for my S1(yes a budget choice and yes I should have read the stuff in the gassing station first) however I need to replace all four springs.

To answer the question you need to know what length springs the new dampers take, and what effect you want to achieve with the new springs. Are you just trying to replace like with like, are you trying to change the handling balance or improve the body control or anything?

Assuming that you just want to get new springs because the existing ones won't fit on the AVOs, and you don't want to disturb the handling, then you want the original spring rates or maybe 20% stiffer (because the new springs won't be rising rate like the originals). Somewhere round 300 lb/in (f) and 350 lb/in(r) would be about right. You could go a lot harder of course, but that wouldn't suit normal road use. And I don't think those cheap AVOs will be much fun when you start stiffening them up. Spring diameter and length will have to be chosen to suit the dampers, of course. The overall damper length will need to be roughly 360mm at full droop, normal ride height 320mm and bump stop coming in around 300mm. On the front the amount of travel on the top ball joint is marginal if you increase the camber and I'd suggest reducing the fully open damper length to 350mm to be on the safe side, if you have the option. Given these damper lengths, you then need to measure the distance between the spring seats on your new dampers (they are probably adjustable so pick a position in the middle of the adjustment range) and from that you can work out the length of spring you need. I.e. open the damper to 320mm length, measure the distance between the spring platforms, add 35mm or so for spring deflection and that's roughly the free length you want. Doesn't need to be exact as long as the dampers have adjustable spring seats.

Hope this helps,
Peter Humphries (and a green V8S)

PS when I tried AVOs I hated them - hope you get on with them better. Don't be tempted to set them too hard, and do remember to check periodically for stress cracks in the outer tube of the trailing arms where it joins the main diagonal channel. AVOs are quite harsh, and if you set them too hard they will beat the living daylights out of your trailing arms.

[Claret]

I guess replacing like with like is difficult without knowing the rate of the exisiting springs.

The overall damper length is 360mm at full droop with bump stop at 270 mm measured from the centre of the shock eyes. I don‘t think I can adjust the damper length although the spring seats are adjustable.

If a ride height of 320mm is normal, the maximum spring length with the spring seats fully open is 8 ½ in - adding a further 35mm (1 ¾ in.) that would give a spring length of 10 ¼ in. They are 2 ¼ diameter – so that’s the dimensions sorted ?

With poundage, and with weight distribution around 55 Front/45 Rear would you still recommend putting stiffer springs at the rear?

And finally, would you recommend that I cut out the bushes supplied in the damper eyes in order to replace them with poly?

(Since established the dampers have poly bushes already, so not a good idea to cut them out eh !)


Many Thanks


>> Edited by Claret on Saturday 18th May 22:20

[GreenV8S]

quote:
I guess replacing like with like is difficult without knowing the rate of the exisiting springs.

I don't have first hand knowledge of the V6 S spring rates, the only figures I have came from Jason "Paceracing" who gave me the figures of 240/280 - presumably the same figures you got. I can't confirm these other than to say they look reasonable given the smaller engine. You could always measure your springs once you've taken them off, to double check. If you're going to do this, one way is to measure the length of the spring at normal ride height, very carefully. Then take the dampers off and take the spring off the damper and measure it's free length. Given the weight on the spring (which we know) you can calculate the spring rate from this. Most tuning places also have a spring gauge and will measure it for you exactly.

quote:
The overall damper length is 360mm at full droop with bump stop at 270 mm measured from the centre of the shock eyes. I don‘t think I can adjust the damper length although the spring seats are adjustable.

On mine the fronts had a longer tapered progressive bump stop on the front which starts to come in at around 300mm, the rears had a more conventional bump stop at about 270mm. Sounds like yours are similar, but make sure the front bump stop is long enough to stop the wheel bottoming on the wheel arch. The damper length is normally fixed when the damper is assembled, but often the manufacturers can reduce the length for you if you ask. Not a problem, at 360mm you're about right as long as you stay below about 400 lb/in springs and keep the camber and ride height standard.

quote:
If a ride height of 320mm is normal, the maximum spring length with the spring seats fully open is 8 ½ in - adding a further 35mm (1 ¾ in.) that would give a spring length of 10 ¼ in. They are 2 ¼ diameter – so that’s the dimensions sorted ?

By "fully open" do you mean the spring seat is wound right down, giving the longest possible spring length? If so, I'd suggest you put it somewhere around the middle of its adjustment range. This would probably shorten the spring by about an inch, and rounding to the nearest inch would suggest 9" give or take. That's a couple of inches shorter than the standard springs on the V8S so I'd just double check that you're measuring the right dimensions if I were you, but different dampers have different spring seat locations so it is credible. Just to recap, you are measuring the distance between spring seats with the overall damper length at 320mm and the spring seat in the middle of its adjustment range to get the loaded length, and adding 35mm to get the free length.

quote:
With poundage, and with weight distribution around 55 Front/45 Rear would you still recommend putting stiffer springs at the rear?

It may seem strange to put the stiffer springs on the rear but remember the leverage is different - the front wheels see half the spring rate while the back ones only see around a third. So in terms of *wheel* rate you're probably running 120 lb/in at the front and 80 lb/in at the back.

The V8S is slightly stiffer all round and uses similar spring rates front and rear, so the rear wheel rate is a lot softer than the front. This gives more traction and less weight transfer at the rear, to compensate for all that extra torque

quote:
And finally, would you recommend that I cut out the bushes supplied in the damper eyes in order to replace them with poly?

Not really. The damper bushes play an important role in absorbing road harshness, and unlike suspension bushes they don't compromise wheel location. Given the relatively harsh characteristics of those AVOs, I think you're going to need all the help you can get. If you have a really good damper, it will work better with less flex in the bushes because it starts working sooner. My Nitrons have no bushes at all and they're quite comfortable and give superb body control. Of course they do cost £250 or so per corner, whereas you could probably get a complete set of AVOs for that.

Hope this helps,
Peter Humphries (and a green V8S)

[Claret]

Loaded length(between spring seats)with damper at 320mm is 6 ¾ in with adjustment set in the *middle*, adding 35mm gives 8 ¼ in – mmmmm

Loaded length(between spring seats)with damper at 320mm is 8 ¾ in *max* adjustment adding 35mm gives 10 ¼ in – mmmmm

(measuring damper length from the middle of each eye)

So I could use 9in springs, and then, by adjustment, set the loaded length to 7 ½ inches.

Poundage 300 front – 350 rear

[Paceracing]

When you fit new springs, with the car jacked up, you can only adjust the platforms up as far as the free length of the spring really. If you start to compress the spring by using the adjustable platform before the weight of the car has been applied to that spring, you will be 'preloading' the spring which can cause handling problems and is generally regarded as dangerous. The best solution is to use the correct spring length in the first place, especially as companies like Rally Design sell Ten Star Springs for about £15 each, in a wide variety of widths, lengths and poundages.

Jas.

[Claret]

That is appreciated Jas, however it is the correct length of spring for the AVO damper that I am attempting to determine(now poundage has been decided)

Claret

>> Edited by Claret on Sunday 19th May 09:19

[GreenV8S]

quote:
When you fit new springs, with the car jacked up, you can only adjust the platforms up as far as the free length of the spring really. If you start to compress the spring by using the adjustable platform before the weight of the car has been applied to that spring, you will be 'preloading' the spring which can cause handling problems and is generally regarded as dangerous. The best solution is to use the correct spring length in the first place, especially as companies like Rally Design sell Ten Star Springs for about £15 each, in a wide variety of widths, lengths and poundages.

Jas.

Have to disagree with you there Jason. The static deflection is determined by the spring rate, and the load on it. This determines how far the suspension would have to droop before the springs are completely unloaded. With normal road spring rates, this is more than the maximum length of the damper and you have to use a spring compressor to fit the spring. With very stiff springs (like you and I have) the static deflection will be far less and damper may extend far enough to unload the spring, especially if you lower the car at the same time. Having the springs actually come loose is dangerous as they can come off the seats or get misaligned, the seats can fall out, basically lots of ways for that to end in tears.

With a moderately soft spring like 300/350 lb/in, you will definitely need to preload the spring to get the right ride height. If you are doing this yourself, you can do it the safe way using proper coilover spring compressors (not strut compressors) or you can cheat and wind up the spring seat under load. This is hard work and will not do the threads any favours but OK if it's greased and you don't make a habit of it.

[Paceracing]

Peter,
That is a very good point! I hadn't thought about preload on normal road springs and of course you are correct.
When I was setting up my corner weights at Leda, I was happilly winding on more and more preload to get each corner exactly balanced and when they saw what I was doing, they pointed out that I shouldn't preload when the suspension is in full droop.
In practice, most of my spring seats are just nipped up to touch the base of the spring under full droop, but I am running a small amount of preload on one of the front springs just to get the corner weights spot on.

Jas.

[Claret]

So gentlemen - do you think that a 9in spring preloaded to 7 1/2in will be OK?

[Claret]

Thanks for loads of advice and in conclusion, this is what I will be doing:

Relacing all dampers with AVO adjustable 718's
Replacing all springs with 9" preloaded to 7 1/2 " (aiming for a ride height of 320mm)
300 lb/in Front 350 lb/in Rear

Replacing upper and lower ball joints sourced from Saab and Lada UK in Cumbria who where dead cheap at £9.00 each !)

Replacing all front and rear trailing arm bushes supplied by TVR at £115 the set(talked out of Poly by Wedge and budget won't run to Nylon)

Unless anyone can think of any major objections, I will let you know how I get on after fitting next week.

Claret

[johno]

quote:
Thanks for loads of advice and in conclusion, this is what I will be doing:

Relacing all dampers with AVO adjustable 718's
Replacing all springs with 9" preloaded to 7 1/2 " (aiming for a ride height of 320mm)
300 lb/in Front 350 lb/in Rear

Replacing upper and lower ball joints sourced from Saab and Lada UK in Cumbria who where dead cheap at £9.00 each !)

Replacing all front and rear trailing arm bushes supplied by TVR at £115 the set(talked out of Poly by Wedge and budget won't run to Nylon)

Unless anyone can think of any major objections, I will let you know how I get on after fitting next week.

Claret

I'd put the 350lb on the front and the 300lbs on the rear.

You have the ability to swap them around and I would to see the difference. I have 400lbs at the front and 300lbs at rear. Although I am considering going slightly harder I wouldn't have the rear stiffer than the front.

All IMHO......

Cheers

Mark