Fixed Pan Suspension - Custom Spring Rates?

[Henry 1.9GTi 36]

Does anyone know if a company exisits that will sell a fixed pan spring for a Bilstein challenge spec damper with custom free lengths and spring rates?

 

Or what do the challenge spec cars run?

 

I am looking for an 8" free length 250lb/in fixed pan spring to try on some fixed pan dampers for stiction and friction!!

[welshpug 1,646]

Faulkner race springs is the one one that "springs" to mind

 

I'd imagine 250 lb would be too much for those dampers unless they were re-valved, a figure of 180 lb stands out IIRC for the challenge cars.

[Rippthrough 98]

Or try the cleverly named Coil Springs in Sheffield.

[Henry 1.9GTi 36]

quote from the coil springs sheffield website:

 

" If your Corsa rolls like a jelly when your doing donuts in Tesco’s car park - steal a mobile and phone us first" - lol

 

I did send faulkers an e-mail but didn't get a response.

 

tbh the challenge spec dampers cope well with the rear suspension with 23mm bars which give a similar wheel rate to a 250lb spring. I imagine some more damping would be benificial but I will hopefully have less unsprung mass than standard anyway.

 

Also getting rig or circa 100kg stiction in the front suspension has got to be worth a little under damping

 

I shall try this sheffield place.

[pug_ham 243 3 Cars]

Give Faulkners a call & ask to speak to Peter.

 

They need to know a few measurements of your present spring length (on & off car) & ride height to calculate the free length, wire thickness & compressed length to give the poundage you want for a custom spring but they have a few they've made before which might suit you exactly.

 

When I spoke to them they had some 225lb springs with a 45mm drop on catalogue & they were to be about £120 a pair iirc.

 

Graham.

[Alan_M 66 1 Cars]

Peter Lloyd Rallying sold the springs for the Challenge spec dampers, 180ib depending on forest or tarmac. I didn't get on with them though and promptly sold them to Anthony. Much happier with the now fitted Eibach jobs.

[pug_ham 243 3 Cars]

Alan,

 

What didn't you like about the PLR front springs?

 

Graham.

[matt.f 16]

Quite a few people who road rally 205's use PLR springs and rate them.180lb iirc

[Henry 1.9GTi 36]

Need them a little harder for circuit use. At the moment the car has 250lb/in 2.25" ID springs with 21mm ARB, 23mm torsion bars 25mm rear ARB and it is still tending to understeer.

 

This is due to alot of stiction in the front suspension (guesstimate, can't be helping thats for sure) which is basically causing the car to bounce on the tyre when negotiating and kind of bump input. 4.6Hz natural frequency for a 43N/mm spring on a 205, i dont think so! So yeh, bouncing on the tyre. It will still roll after transfering enough weight to overcome the stiction though. I am hoping that by fixing this it wont turn into an oversteer monster with the same spring rate and require another set of custom springs though :/

 

anyway no joy from sheffield yet either.

 

Will phone around next when I have some time and see whats what.

[Rippthrough 98]

Well, there's also SpringCoil in Sheffield, but they tend to be more expensive as they're not all that interested in small orders any more.

Edited April 4, 2011 by Rippthrough

[Tom Fenton 1,536]

Need them a little harder for circuit use. At the moment the car has 250lb/in 2.25" ID springs with 21mm ARB, 23mm torsion bars 25mm rear ARB and it is still tending to understeer.

 

I am hoping that by fixing this it wont turn into an oversteer monster with the same spring rate and require another set of custom springs though :/

 

My red car has a pretty similar set up, 275lb springs with 19mm front ARB, 23mm torsion bars 24mm rear ARB, 309 stuff all round, Xsara VTS rear arms.

 

It certainly isn't an oversteering monster, if anything it will still tend towards understeer when you push it, although the big lumps of torque coupled with the plate diff dragging it around doesn't always help matters.

[Henry 1.9GTi 36]

I believe you are running Gaz coilovers as well?

 

I don't want to put a downer on GAZ as its probably the effect of changing the spring axis and making it even worse with longer wishbones, but i'd bet you have a similar problem to me. I certainly did not know and it took a rig test to even see what was going on. I have heard back from sheffield now and they can make me some springs; hopefully keeping the top of spring a 2.25" ID to fit the coilover top spring pan and keep the eccentric top mounts.

 

I will hopefully be getting the car back on the rig assuming my lecturer holds to his work so will update with the results. Hopefully getting the GAZ on the dyno as well to double check its not a damper issue.

 

Thanks for the recomendations above anyway guys, gtidrivers win again and hopefully a faster car because of it

[Anthony 1,002]

Going away from the springs and dampers for a minute - have you tried removing that 309 front ARB and fitting the standard 205 GTi 17mm one?

 

Best thing that I ever did on my 205 frankly - whilst the balance coupled with rear 24mm ARB initially felt good and worked at 5/10th's, once you started pushing on I'm pretty sure what was happening was that the ARB was stiff enough that it was taking all the weight off the inside wheel, resulting in poor traction (I was only running an ATB diff at the time) and ultimately front end grip. With the original ARB back on, the car was far keener to hold its line and you could actually put the power down in wet conditions.

 

I know that I'm not the only person to remove a 309 front ARB for similar reasons either, although equally others run them apparently quite happily.

 

I can't comment on the damper and stiction issues other than to say that from what I've driven of them, Gaz Golds subjectively feel a hell of alot better than whatever the lower spec Gaz coilovers are (GHA?). However, I was involved with building a car that's loosely the same spec as yours - alloy block engine, Tran-X diff, 300lb springs on Gaz Golds, 205 17mm front ARB, 205 rear beam with 25mm rear TB's and I think a 22mm rear ARB - and the balance and grip levels on that was very good, and it dealt with bumps and broken tarmac well.

 

Not saying that your not onto something with what you've discovered on the damper dyno, but I do wonder if the understeer/balance issues you're having are actually being caused by something far simpler and easier to address.

[Henry 1.9GTi 36]

Dont get me wrong, its not understeering wildly and infact feels quite good on a track. It is something I should perhaps try on a dry day

 

We did disconnect the roll bar on the rig and it made no difference what so ever to the stiction issue. And thinking about how the car drives, very poor turn in; have to be super agreesive with the wheel to get the nose to point in, it does lend its hand to stiction causing this. Remember this isnt just a little its 1000N ~100kg before the suspension even moves. Thats a 1/3 of the weight of a front corner :|

 

Once the stiction has been solved and the car is responding as it should I will definately try different configs of ARBs, i still have the 17mm item is it? or 19mm and will take it to a test day with me.

 

On a side note can anyone point me in a direction on the forum regarding using eccentric top mounts with standard dampers? Can't seem to find anything, unsure if the shaft needs modding etc..

 

edit: I did get some positive comments about the rear of the car though; thanks for the beam rebuild!

Edited April 5, 2011 by Henry 1.9GTi

[feb 47]

Someone I know did use springcoil and has been very happy with the results.

 

Have you tried e-mailing Gaz to get hold of the damper spec graph (velocity vs force) then you can work out what rates of springs you need to match them.

 

When I asked Bilstein they were really helpful and gave me the graph for some dampers they do for the Forester.

It turned out that with their uprated dampers I needed even stiffer springs than the Sti aftermarket ones I was planning to get so I stayed with the KYB OE shocks and got the Sti springs (designed for them), glad I did as the car damps really well now.

 

FYI, when a coilover manufacturer was developing dampers for the FSTI, it turned out that inverted monotube ones did not work due to too much stiction, the car would bounce everywhere.

I had exactly the same problem with non-inverted ones after rebuilding them with appropriate valving and new design pistons but the car was intolerable to live with (bouncing everywhere even at crawling speeds of less than 5mph indicating too much stiction I believe) hence I found a second hand OE suspension set that I put back and with the Sti springs I have never looked back.

 

I am interested to learn how you get on with yours though and what the issue is as I never really managed to find out with the coilovers and did not have any more time or money to spend experimenting!

Edited April 5, 2011 by feb

[Henry 1.9GTi 36]

Still making guesstimates but;

 

coilovers change the spring axis. Standard fixed pan suspension should have the spring offset slightly from the damper around the bottom mounting. This puts the spring axis inline with the kingpin axis and when the suspension sweeps through its movement there will be minimal bending load. With coilovers the axis is inline with the damper and so is not inline with the kingpin axis (bottom ball joint to top mount joint), this induces quite a bit of bending load in the damper shaft when trying to compress the spring. Adding negative camber at the top mount helps the issue, making the wishbone longer makes it worse. I did reassemble the suspension without the spring to check everything is free and I can move it fully by hand.

 

There are some papers on side load springs and L springs and such like to help matters even more, I believe audi use some different spring configs or atleast the paper I read was testing on an audi.

 

The GAZ dampers are adjustable so I will simply match the dampers to the springs rather than the other way around as the springs are required to be what they are for weight transfer properties and natural frequencies. Will get the dampers on a dyno myself to check this. Also the GAZ are twin tube.

 

Gonna take some time before all the avenues are sorted but will definately update!

 

Cheers,

Henry.