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Suspension And How It Works

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Adi
With the secondary shocks/springs won't you get an odd oscillatory system

 

Yes you will. I think to a certain degree.....it depends on how closely the spring rates are rated. As long as the 2 springs aren't rated too closely.....then the torsion bar part should work like an overdamped system. If you have too soft a torsion bar......and stick a stiff damper on......then the torsion bar is only really supporting the weight of the car. The damper will be doing the main of the work.

A coilover should work in a similar fashion. But again only trial and error will prove whether it works well enough.

 

Supposing one got round to making up trailing arm braces would this help tighten the rear end? Also what kind of joint is required to connect the brackets to the bracing bars?

 

Tightening the rear end???? That could mean 2 different things depending on your interpretation. But basically what the brace will do.....is stop the rear arms flexing under load. As the car corners under load......the rear arm bearings tend to flex and allow the outside rear wheel toe out more......so creating more oversteer. By bracing the rear axle/arms.....there will be less flexing and the rear outside wheel will remain more inline.

I am not sure how Peugeot have designed the rear brace on the 206SW. I would advise you to take a look at the rear of either the SW or the 206GTI180.

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DrSeuss

When reading about NASCAR they described the suspension settings as being tight and loose. The tight set up gives poorer feel but more stable handling. The loose set ups were those which gave greater turn in and ability to change lines mid corner but also provoked less controllable over steer and twitchy handling.

 

I presume from what you've just said rear bracing would help reduce loo. I'm currently considering a 309 rear beam and some home made bracing, but don't want to lose the spry handling of the 205.

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Adi

Bloody yanks......they never could speak proper :lol: Why can't they call it understeer and oversteer :wacko:

 

It is possible to retain a good balance whilst removing the axle twist (bushes) and bracing the arms. But you will have to experiment with spring/damper rates and roll bar sizes. The wider rear axle will certainly help with weight transfer but the bars available for the 309 axle may be limited. I may have a pair of 309 torsion bars (21.5mm) for sale in a few weeks. But not 100% sure wha I'm doing with them yet.

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smckeown

I have a few questions for you then Adi for my track day 205

 

I am planning the following for the rear

23mm Torsion bars

23 or 25mm ARB

 

Would these items from peugeot sport be a good combination for the front:

 

205 309 -7221 Grp-N - Spring - tarmac - 9" free length "

205 309 -7235 Grp-N - Bilstein insert - long top spindle - tarmac

 

And for the rear:

205 309 -7237 Grp-N - Bilstein damper - 205 tarmac

 

As i'm running with Yokohama 038r tyres, i really need some negative camber to get the best out of them. I can buy adjustable rose joined bottom arms, and was thinking of getting skip brown's rear negative camber kit also

 

Can you adjust the castor on the 205's ?

 

I'm hoping the above will give me a good track day setup, what do you think ?

 

cheers

sean

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Adi

The idea of using PS tarmac Bilstein bothe front and rear is a good one. But, I've seen a few people not happy with the height of the front end when using the adjustable struts. Even with the height adjusted to the lowest point. So that really depends on what you want. Obviously the Peugoet Sport cars are set up for handling and not looks. So the height is governed by the lower arm angle etc and not the tyre to arch gap.

I also don't know the rate of the tarmac spring from PS.....so maybe something for you to find out.

As an alternative.....I know a few others have chosen the Leda front struts which are coilover type and adjustable in rebound only.

 

The 23mm torsions and 25mm roll bar could be a good idea.....but again it depends on the rate of the front springs as to how the balance is effected. If the front rate is too low.......the car could be quite twitchy.

 

Depending on which front struts you choose....as long as you use a coilover type, eccentric top mounts can be used which will allow more -ve camber and more +ve caster. For even more -ve camber......you could try the 309 lower arms. But the best way to get -ve camber would be thru the hub as PS and SBC used to do it. But whether the parts are still available I'm not sure.

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Batfink

when running a 309 rear beam, what would be a better setup (if the same camber is used). A 309 wishbone setup on the front, or 205 wishbones and adjustable mounts. Iss there any point in the wider track?

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Adi

To try and keep the front track as similar as possible would be of benefit. So by either using adjustable top mounts or using the hub to get the necessary camber would be of use.

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Guest bigbadbanjo
When reading about NASCAR they described the suspension settings as being tight and loose. The loose set ups were those which gave greater turn in and ability to change lines mid corner but also provoked less controllable over steer and twitchy handling.

"...Loose is fast but on the edge you're out of control..." Legendary Crew Chief Harry Hogg - Days of Thunder :)

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TVH
The roll centre is an invisible imaginary point within the geometry of every suspension set up. So every car has 2 roll centres. One front and one rear.

Hello all!

 

I've been lurkin on this great forum for a while, lots of knowledge here! ;)

 

Back on topic, how is this imaginary point deteremined? Does it need complex calculations?

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Adi
how is this imaginary point deteremined? Does it need complex calculations?

 

They can be found on the front suspension by making a drawing to scale and measurements etc and plotting certain lines till they intersect with lines from the opposite suspension. The point the lines intersect is the roll centre.

As a rough guide.........it will be on the longitudinal centre line of the car, and half way between the inner wishbone mounting point and the ground.

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Rafe Dent

Truly excellent stuff.

 

If you've got the time Adi, I'd be extremely interested to know what happens when you go round a perfect (flat) corner in a perfect 205 GTi:

 

from straight line to the limit of adhesion in the corner (at front and rear)

 

then:

1. brake, or

2. accelarate

 

I used to be a mech eng, but didn't quite get to your giddy heights and can't quite seem to see the whole picture.

 

All I know is I go off backwards from time to time in a snap spin, and in all the fun and games can never quite remeber what silly thing I did just prior, apart from going too fast.

 

Thanks in advance,

 

Rafe

 

drink.gif

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Adi
I go off backwards from time to time in a snap spin, and in all the fun and games can never quite remeber what silly thing I did just prior, apart from going too fast

 

On all FWD cars......you get a small amount of lift off oversteer. That is when the front slows down as the throttle is shut..... but the rear doesn't and with the remaining energy, the rear arms twist via the bushes......or in the Pugs case, the whole rear axle twists slightly meaning the rear wheels are pointing away from the corner. On the Peugeots this twisting is a design feature. Now if the throttle isn't opened fully again meaning the front end will pull the car out of the oversteer, then quite often the oversteer will turn into a spin.

If you brake at the limit of adhesion.....then the rear will step out of line even sharper. If you accelerate at the limit of adhesion.....then the car will probably just run wider at the front in a power slide.....depending on how tight the corner is.

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smckeown

i understand some race drivers use this to their advantage round some corners to unsettle the back end and bring the rear out etc

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pacey205

You can feel this effect on roundabouts if you change gear mid-way around. If your in second (not flat out obviously) just taking it easy and you go for third midway round the roundabout (i.e. if your going straight on on a 4 exit roundabout, change just before the 1st exit) you should the feel the car tighten its line slightly.

 

At least yuou can in mine anyway :)

 

Michael

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jeremy
On all FWD cars......you get a small amount of lift off oversteer. That is when the front slows down as the throttle is shut..... but the rear doesn't and with the remaining energy, the rear arms twist via the bushes......or in the Pugs case, the whole rear axle twists slightly meaning the rear wheels are pointing away from the corner. On the Peugeots this twisting is a design feature. Now if the throttle isn't opened fully again meaning the front end will pull the car out of the oversteer, then quite often the oversteer will turn into a spin.

If you brake at the limit of adhesion.....then the rear will step out of line even sharper. If you accelerate at the limit of adhesion.....then the car will probably just run wider at the front in a power slide.....depending on how tight the corner is.

I thought this is how you should attack all roundabouts, as have been doing this alot recently since having my 205 back on the road, and it's great fun, however no so sure I'd want to take it to the max on the county lanes as love my little car too much. By the way that was an excellent discription of what LOOS is.

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Adi
i understand some race drivers use this to their advantage round some corners to unsettle the back end and bring the rear out etc

 

This is where experience of the different set ups comes in handy. Cos if you uprate the car in the right way......the rear will move around easily enough without having to shut the throttle. The car then proves to be more predictable.

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Guest red16

Does anyone know the front track widths of the 1.6 and 1.9? ie; for the most similar track front and rear when using the 309 rear beam?

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pacey205

I dont know the exact dimensions but the 1.6 is meant to have a wider front track than the 1.9.

 

Michael

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Adi
Does anyone know the front track widths of the 1.6 and 1.9? ie; for the most similar track front and rear when using the 309 rear beam?

 

The 1.6GTI front track is approx 55.1". The 1.9 front track is 54.4". The 309GTI rear track is 54.01". So as you can see from the figures, the 1.9 front track with the 309 rear beam is the closest match.

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Loffas

what is the standard rear track for the 1.6 and 1.9 ?

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Adi
what is the standard rear track for the 1.6 and 1.9 ?

 

Rear track of 1.6GTI is 52.3" and the 1.9 is 52.7".

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Loffas

ADI, this is really great reading :);)

 

Im thinking of getting av bigger ARB to a 309axel but not by changing the arb, but by adding an extra. same way that vw gti 99+ does. This picture explaines:

 

14720041115_162737.jpg

 

could this also prevent the arms from moving some? it bolts into the arms and helds up under the tube

(its rather hard and exspensive to find bigger arb for the 309.)

 

edit: adding another pic.

 

14720041115_162727.jpg

Edited by Loffas

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Adi
Im thinking of getting av bigger ARB to a 309axel but not by changing the arb, but by adding an extra.

 

LOL and good luck ;) I say this tongue in cheek......as I was contemplating something very similar to my last 206. Actually the Grp A Peugeot Sport cars whether they be the 106, 206 or 306 all had seperate roll bars front and rear. The roll bars were actually fitted thru the chassis legs with tubes welded into the legs and then a bar with bushes fitted and adjutable arms and links rose jointed on the arms both front and rear. The only problem is the amount of room on a normal road car.

I first started off by looking into a similar system as fitted to the VW's but quickly found it wouldn't work simply cos of the different ways the rear axles work on the 2 cars. The VW has a beam axle that moves in 1 so the arms are fixed. Where as the Peugeot has a fixed tube with trailing arms. So only the arms really move up and down. Also there are brake pipes etc running around the tube. So as you'll see when you get under.......room is really a problem hence why the rally cars use the chassis legs as a straight route thru from one side to the other.

 

Let me know how you go on.

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christophe

With regards camber seting, yeah the temperature is important, in racing necessarily road use,in my experiance anything of over 10 degrees difference between inside to outside, is not recomended it will start buggering up tyre psi's etc , but you tend to have as much neg camber as possible, at most 3 degrees. This works the tyre harder, but wears the tyres out quick!!!, and as a car rolls around a corner one side will gain neg and one will gain pos camber, but pos camber is to be all but avoided it looses contact patch and grip.

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