Thinking of changing spring rates

[Inferno]

Right, courtesy of Powerstation I've got a rather odd combination of spring rates on my AST suspension. It's fine in the dry, but understeers heavily in damp/wet conditions. The current springs are:

Front = 170-60-70
Rear = 200-60-51

Which translates to:

Front = 399.574lbs
Rear = 291.1182lbs

Renault have told me that the factory 182 spring rates are:

182 2.43/5.04 daNM/mm F/R
182 Cup: 3.19/5.65 daNM/mm F/R
182 Trophy: 3.19/5.65 daNM/mm F/R

I'm thinking of changing to spring rates that are maybe 10-20% stiffer than these or maybe even matching those rates exactly. The problem I'm having is with the convestion factors. I've found this site - http://www.hraefn.net/projects/spring_rates.php but I'm not sure that I'm using it correctly or that is can convert daNM/mm.

If I enter the AST rate (70) in N/mm it appears to give me a correct looking lb/in figure, but the Renault provided rates are also supposedly N/mm? Have Renault made a mistake? Are the rates they've provided more than likely kg/mm figures?

I'm very confused!

 

[mini-valver]

Raise the front slightly and stiffen up the damping on the rear. See how that feels before you change the spring rates. Easy to revert back to more front rake for dry track sessions too.

 

[Inferno]

I've tried stiffening the rear damping. For track work I had to have them on their hardest setting for it to feel near to how I liked it, but I would have gone stiffer if I could. On the road that's too stiff though.

The thing is I'm missing the B roads! The current suspension just isn't compliant enough to remain planted on a country road. In the rain on the road the other week the front did just wash out taking a roundabout at a reasonable speed too.

After seeing the standard Renault spring rates I'm also now aware that the rears are 77% stiffer at the back than the front, whereas my current set up is 27% softer at the back than the front! To be honest I'm surprised it drives as well as it does at the moment!

 

[Jay Payne]

Got a set of 400lb rears if you want them.

Ive always had to have equal spring rates front and rear on mine to make the thing turn.

When I told Curtis that everyone runs the rears as stiff as poss and soften the rears he said it was the first he had heard of it and obviously the spring rates are wrong

 

[mini-valver]

Tried raising the front abit so you get more bite as the weight pitches forward?

 

[Andrew Cooke]

daN is 1/10 N, so approximately Kg. Just multiply the Renault figures by 10 to use N

 

[Andrew Cooke]

After seeing the standard Renault spring rates I'm also now aware that the rears are 77% stiffer at the back than the front, whereas my current set up is 27% softer at the back than the front! To be honest I'm surprised it drives as well as it does at the moment!

but your springs aren't in the standard position, so unless you convert the lever ratios this is irrelevant.

 

[480bhp.com]

The cup racers only use 400lb springs on the rear (coilovers) so for a road car i doubt you want to be going that heavy, even though the road car is heavier.

You'll always find it difficult to get a good balance between all conditions, motorways, a roads, b roads, pot holes, track, dry , damp, wet, standing water, almost every situation has it's own requirements

once mine's finished i'll probably be starting at somewhere around 72/28 f/r like the cup racers, although probably not quite as heavy as they do 1000lbs/400lbs

Chris

 

[mark123]

Mine is too stiff for B-roads (I have the AST "stiff" setup). I always find sunken man hole covers and M-way/DC compressions to be the most painful (and that's my pain). But my car is only really a comp/toy so I can live with it.

Have you spoken to Curtis?

Have you talked to him about re-valving the dampers? I have wondered about it. I haven't actually done a track day with them yet. But I'm pretty sure my setup would be prone to over steer. I have spun in an auto solo at about 45 mph.

My markings are:

AST spring markings

front

main AST 180-80-64
small AST 100-20 DI=61

back

0500-200-0400 Eibach 04/01
couldn't see the helper spring

And I was told that is 450 400 lb/ft front rear respectively.

 

[Andrew Cooke]

And I was told that is 450 400 lb/ft front rear respectively.

sounds like it from the part numbers

 

[mark123]

What do the numbers on the spring mean?

The AST are obviously different to the Eibach ones, but I don't understand either except guessing the last number on the Eibach ones is in lb/ft and the last number on the AST ones is the spring diameter.

 

[Jay Payne]

^

front 64 newtons (360lbs)
rear 400lbs

 

[Andrew Cooke]

^

front 64 newtons (360lbs)
rear 400lbs

I think it the 80N/mm for the front rate, and 64 is the internal diameter.

180 is the free length in mm

 

[Jay Payne]

Yea you must be right, dont make sense other wise. mine were the other way around

My markings are:

AST spring markings

front

main AST 180-80-64 180mm-80newtons-64mm


back

0500-200-0400 5inch long-2inchwide-400lbs

80 newtons is about 460lbs

 

[Inferno]

Finally got around to having the front springs changed. Now using 300lb rear and 240lb front. Feels so much better on the basic set up with the dampers set to their middle adjustment.

Unfortunately I think I have a problem with one of the rear dampers, so I'll have to get in touch with Powerstation at some point, but overall still very happy with the change!

 

[Jay Payne]

Ive still got a pair of 400lb rear springs lying around if you feel like another change

 

[ForceIndia]

Do the dampers need revalving if changing spring rates?

 

[Inferno]

Do the dampers need revalving if changing spring rates?

After driving it around for a while now I'd have to say no. The right question to ask however would be how were they valved originally from Powerstation! I must admit I lost confidence in them with the odd spring set up.

With the original spring rates provided by Powerstation I had little choice but to set the rears to full hard and the fronts to full soft. I now have some adjustability in the set up and I'm now experimenting with the right damper settings for me. Adjusting the damping is having quite a noticable effect on the way the car drives - although it's not too easy with a busted adjuster on one of the rear units.

I'm much happier with it now, but I did have to spend most of the morning yesterday raising the car up around 25mm as the softer front springs were causing clearance issues with the arch liners. And now I've raised it, I'll be having to adjust the camber again...

Note to self, stick to standard suspension - there's nothing wrong with it!

 

[Fred@BTM]

obviously the spring rates are wrong

i've been saying that since day 1!

 

[Inferno]

i've been saying that since day 1!

I've heard you say that too. Iirc you believe that a Clio's at it's best with a stiff rear and a soft front? It's where I'm trying to get mine.

 

[Fred@BTM]

that's in my opinion to suit my driving style, will be different for other people though!

 

[Inferno]

Well there's only two things I'm sure of at the moment:

The 300lb rear, 400lb front certainly didn't suit my driving style, and I liked the standard Renaultsport suspension!