Rear dampers

[PeterGinger]

I have a week of work soon, so I was thinking of getting the front dampers refurbished. However, having seen a new suspension setup on another car (more in a minute), I want to do some suspension mods at the same time. Ok, in my opinion, The car is far too soft, more so at the rear. This is primarily due to the low spring rates. So I want stiffer springs, Eibachs of course. I also want adjustable rears. but 25% stiffer just isn't going to be enough for me.

Now my brother has a Lotus Elise S1. Totally different car I know, but I feel what works on one car should be possible on another. He has just had a new suspension setup fitted and I'm just blown away and very jealous too. It was done by a guy called Chris Randall. He is currently in the lead in the Elise Trophy race series, he's won before too. He works for Hoffmans of Henley. The damper of choice for the elise is the Nitron adjustable damper. He is running 750 lb springs at the rear, 550 lb at the front. This is combined with helper springs to give it compliance over small bumps. He also had new wishbones, ball joints, arb and full rose joints. Now his car is as soft and comfortable as a regular saloon, but as soon as you corner - absolutely no body roll. There is not a hint of noise or harshness and is just bloody perfect. So I want to try to do this on my Trophy!

Looking at my rear suspension, i noticed that the springs and dampers are separate, nothing like coilovers. So do I need to change anything at the rear to fit coilovers? The idea is that if the springs are stiff enough, the car wont lean so much, you get more grip. Can i get the sachs front dampers modified at BG Motorsport with longer shafts to run helper springs? I'd need probably 650 lb front as there is more weight at the front on the trophy.

Any help most welcome!

 

[scott]

If you think the ride in the Trophy is soft then i would say your dampers do need referbishing, it sould be solid at the front, when you push on the front of the car there should be very little movement.
As for the rear alot of people seem to go for Koni adjustables, dont thing any mods are needed to fit them, just a bit playing about to get the correct setting.
IMO i would just leave the fronts as they are, possibly with the addition of STM's, just get them referbished.

 

[BenG]

Looking at my rear suspension, i noticed that the springs and dampers are separate, nothing like coilovers. So do I need to change anything at the rear to fit coilovers?

When you buy coilovers the rear dampers and springs will still be seperate. The rear springs are not 'coiled over' the dampers like the fronts are. So no, you dont need to modify anything.

Some coilovers have 'helper' springs fitted on them anyways.

 

[PeterGinger]

but what if i did want to. I believe you cant fit helper springs without going "coil over"?

 

[PeterGinger]

I believe on the Super2000 clio rally cars they do change the rear strut so they can fit the ohlins three ways. Yozza mentioned this too. But I dont know which part this is or where to get it from?

 

[BenG]

Anything is possible if you have money.

Im not too sure whether you can fit helper springs to the Sachs dampers without it becoming expensive and possibly a waste of time, + if your going to be running very stiff springs on them wouldnt you need a shorter shaft.

Why dont you phone up BG motorspots and ask. or PM GeorgeK on here.

 

[PeterGinger]

no cause the helper springs and normal springs go together. The idea is that the helper is fully compressed and only extends down potholes and in corners etc (droop). The damper needs to seemlessly change from one to the other.
BTW the work my bro had done came to £5000 lol

 

[BenG]

You would have to have the shaft totally re designed as well as the damper. The nitrogen adjustable dampers your bro has are infact coilovers, right ?

 

[Jonc]

What works on an Elise won't necessarily work for the Clio. The Elise is mid engine with independent double wishbone all round and has near 50/50 weight distribution. The Clio has torsion beam rear suspension and Macpherson front suspension with about 65% of the weight over the front axle where most of the roll occurs hence why the rear is stiff enough to lift the inside rear on a hard corner. Stiffening up the suspension will make it more snappy and less forgiving to human error. It is the job of the anti roll bar to prevent body roll so by putting stiffer ARB to the front to counter the roll will increase understeer, stiffening the rear will increase oversteer. I could be wrong but this is my basic understanding of how the suspension works. IMO Renault have got the right balance considering what they have to work with.

 

[PeterGinger]

Yes they are coilovers. Also, he has both stiffer springs and a very stiff ARB thats about an inch thick. So I assume that both together keep the car neutral. I also thought that stiffer front springs compared to mid engined car will help to counter the extra weight and conering loads.

 

[Luke335]

I would think about giving Mark Fish a call. He has the experience to set your car up for the track, not just for fast road. Perhaps you should invest in a new car though. I don't think the Trophy will never drive like that. As Jonc said the weight is all in the wrong place. You could stop it rolling but it will be very stiff.

 

[PeterGinger]

Thats the idea of the helper springs. My bros car doesn't feel stiff at all, but it is. You have to experience it to believe it. It seems impossible. Id go out and by an elise tomorrow. I probably know more about them than I do my T, through my brother. However, my mum could never get in an elise, and she would need to. So atm its out of the question. Unfortunately, there really isnt another car like it. There is always a down side, eg petrol hungry, more costly to own etc. Which is why I'd rather keep the Trophy and spend the money getting it exactly how I want it. I love the car and probably wont ever sell it. I think calling Mark is a good idea. He has mentioned three way adjustables before in passing, but never qualified it with info. I'm sure he could sort something out for me. If he can make solid engine mounts and stuff, he should be able to tell me what is and isn't possible.

 

[Luke335]

I look forward to hearing how you get on Peter. It sounds like the perfect setup if you can get something similar on the Trophy. Certainly just upping the spring rates 25% and the rear dampers has made mine 'relatively' harsh on the road. Adding an anti-roll bar wouldn't affect the comfort though.

Does anyone make really stiff anti-roll bars for the clio? I have added the whiteline rear but I doubt this goes anywhere near stiff enough for what you require.

Also, George K mentioned something on here recently about spring rates not comparing to the Elise. I think the different suspension setup requires different rates but it's over my head!

 

[PeterGinger]

yes I was there, theoretically too. I think its double wishbones verses single, basically. But all race cars run about 800lb on the rear. So if that were true, why arent theirs different? As for ARB, I will try to find out the make of his arb.
I was looking on the ohlins website at their 3ways £500 per corner. Their is a bit where you state the make and model of your car, in order to bring up the right stuff. For the clio it says these dampers, but with this strut (part number .....) . I assume that strut allows you to fit their coilovers and is one of their parts, e.g not a renault part. have a look. Only reason being, BG motorsport do sachs and ohlins. So I could theoretically use the as a one stop shop.

 

[George K]

Peter Ginger

Going to 650 lb front springs is insane unless you are running a dedicated track car with slicks and a strong LSD and can be sure that the tyres are up to temperature. What you must remember is that the Elise has a double wishbone set up with quite steeply inclined dampers and as a result to get the wheel rate you need to divide the spring rate by somewhere in the region of 2.5 (installation ratio x cos of damper angle all squared), so 550 lb springs give a wheel rate of = 220 lbs/in, whereas since the Trophy has a strut set up at the front the factor is a near 1.0 as dammit. Hoolio and I calculate reckon that the Trophy front springs are about 170 lbs/inch.

I never got round to measuring the rear installation ration for the Trophy, but a colleague suggested that the spring rate should be roughly the same if used in the standard position (so allowing for the rear installation ratio and weight distirbution). If a coil over is used the installation ratio changes and it will be need to be much softer (about half the front rate); elsewhere I have posted the rates that the Challenge racers use which show a massive front to rear difference.

Also helper springs are really used not to give a soft ride, but to stop a short stiff spring coming loose on full droop. Sometimes they are used to give a progressive effect, but if the amount of progression is different front to rear you can end up with a very unpredictable car. The Elise uses Nitron dampers, which are very good and probably double adjustable - this is regarded as the best kit for competiton Elises - even against such opposition the Trophy was quicker in the wet!!

Lots of droop is fine at the front for good traction, but is to be avoided at the rear - you will find that the standard Trophy set up is like that, which is why it works so well.

Coil overs are a possible at the rear (talk to Curtis Woodman at AST), but they will put more load through the damper mountings, which may need reinforcing.

Last but not least if going for radical change, remember to make sure that there is plenty of bump travel before hitting the bump stops - aim for 50 mm.

I have never dealt with him, but would guess that Mark Fish is the tried and tested option

 

[PeterGinger]

Lots of helpful info there, thanks. Thats one thing too. Elises dont use top mounts as the chassis is very different, therefore they have no worries there either. I was thinking of going for mark fish strut top mounts, so that isn't a problem.

 

[shiftspark]

I think using coilovers at the rear also raises the problem of loading the top mount as George says and have also "herd" that the lower mount is prone to snapping unless modified and on a road car you would be carrying alot more weight than a race car.

Bilsteins ala clio cup cars are the way to go at around £800 per side and 3 way adjustable, as already said Mark Fish is the man to talk to.

Let us know how you get on.

 

[PeterGinger]

I will do. Bilsteins - I heard about them on the cup cars, they use penske now. So would they be the PSS9 or something better/worse? And are they still damper and spring separate or coilovers?

 

[480bhp.com]

The bilstein cup racer dampers are non adjustable, as for fitting coilovers in the same position as the rear dampers, remember they're mounted single shear and i would guess that bent and broken bottom bolts would be a common occurance.

I'm waiting to hear back from Mark Fish at the moment, as the Mf road springs are still a little too soft for my use and the cars CoG could still benefit from being lower.

One thing i don't think you've mentioned (unless i've missed it :wink: ) is what you want the car for, track use, competing or just road.

Chris

 

[George K]

As I was driving between companies it occured to me that a quick explanation of why stiff springs are a problem, particularly for road use, might help.

Bascially road tyres have soft sidewalls compared with track tyres or racing tyres. If the springs are too stiff they could end up being stiffer than the tyre, in which case the suspension stops working and most of the flexing is in the tyre sidewall. Not merely does this ruin the balance of the car, but also it means that the motion is undamped (if you have ever followed a farm trailer with baloon tyres and no suspension you will know how horrible that looks) - what a waste of yuor lovely Sachs dampers!

This is why as a rule of thumb road tyres will have say front springs of 170 - 225 lbs/in (30 - 40 Newtons/mm), track tyres + 50% = 225 - 340, and race 450 - 700.

As an aside i have chosen 225 lb/inch for the DC5 front - seems quite stiff enough with suitable dampers - rear suspension is totally different so not a valid comparison.

Chirs - depends on how much you want to spend, but AST are very helpful and have a UK service operation in Tewkesbury. I went to them as the only people offering a custom service - Nitron do not do a kit.

Regards to all