Independant Rear Suspension

[VisaGTi16v 1]

Dont really have one but if you look at these two photos you can kinda see how much narrower the back is as the front wheels come out to the arches which themselves stick out more than the rears, but the rear wheels dont come out as far as the arches

 

Photo 1 Photo 2

[Shepp354 0]

The core reason I see for a FWD car like the 205 lifting the inside rear wheel is a matter of weight distribution and the packaging of the design. Even a well sorted and corner weigted clubman FWD race car is going to have something like 60% of the weight towards the front due to the engine, gearbox and driver being positioned up there. So on no throttle turn in to a corner most of the weight will shift onto the outside front leaving the offside rear with little to no weight on and no work to do hence lifting the rear wheel if suspension travel is short and the shell is stiff. Even if the suspension design has enough droop to keep the inside rear wheel on the ground then the wheel will be doing little towards adding grip anyway Unless the car weight distribution is different (like a 4WD, mid engine or Porsche sillyness).

 

The 205 trailing arm setup as said is flawed in the ratio it offers between suspension and damper movement. Turreting the rear to allow a 1:1 ration would help greatly in improving damper control. In forrest rallies I don't think a car with an engine above 1.9 group A would be an advantage as the standard setup doesn't allow the rear damping to be controlled well enough to make the car stable at constant higher speeds. On a smooth circuit things are probably different though as the thing isn't bouncing along as much.

 

So on a 205 it might be a bit irrelevant to redesign the torsion bar arrangement without a dramatic redesign to change this weight distribution. Maybe you could be a touring car driver and sit in the back!

 

In fact what about looking at alternatives to the current design to change camber, track and toe such as 309 beam or ZX traling arms or going down the lines of the Varey hot hatch setup to improve damper control within the standard suspension pickups and have an adjustable anti roll bar. In fact, does the roll bar do anything if the wheel is raised on the other side anyway?

 

Just some food for thought on an interesting topic

 

Cheers

 

Matt

[AdamP 0]

In fact, does the roll bar do anything if the wheel is raised on the other side anyway?

 

If you mean the anti-roll bar then yes it does, it increases the spring rate on the side with the load as not only is it having to twist the torsion bar but either the ARB or the opposite torsion bar as well.

[Cameron 16]

And in doing so lifts the inside wheel.

[AdamP 0]

And in doing so lifts the inside wheel.

 

Exactly But its effects don't stop at the point of the inside wheel leaving the ground.

[Goliath 94]

Where has the photo gone that was posted up on this thread of the 205 rear beam with a short coilover setup?

[Batfink 201]

to be honest that short coilover setup is a bit rubbish and pointless.

Speak to Colin Satchell about a setup that does not use rear turrets. Though not perfect its better than the current setup.

 

Kev

[DrSarty 90 1 Cars]

Where has the photo gone that was posted up on this thread of the 205 rear beam with a short coilover setup?

 

That picture didn't look at all like a 205 to me; unless it was a complete custom rear. I thought it was just an example.

 

EDIT:

Looking at the front suspension set-up on a Lotus/Caterham type car earlier today, I wondered and am hereby asking whether angled dampers/springs would be an option worth considering for the rear of a 205. To clarify, I mean instead of vertical turrets, how about building a structure in the rear that tied the dampers and/or springs nearer the centre line.

 

If my question is still not clear, then just look at a photo of the front of a Caterham type car.

Edited May 16, 2009 by DrSarty

[richsmells 2]

Didn't Autograsser post a picture of the rear of his car, although spaceframed, I think it used an angled coilover setup.

[Cameron 16]

Exactly But its effects don't stop at the point of the inside wheel leaving the ground.

 

Spent ages writing a reply but some sodding authorization mismatch error won't let me post it.

[welshpug 1,657]

As mentioned, some of the best handling FWD cars still cock a rear wheel, I've seen some RWD cars cocking a front wheel.

 

Maxi/kitcar spec cars are a case in point and illustrate it quite well.

 

[Powers 13]

They were however governed by regulations so they had to stick with a beam/trailing arm/torsion bar arrangement. So IMO the "best" could have been even better!

I am sticking with a standard setup for my project not because of funds but because I still want it to be a 205 at the end of the day.

[Rippthrough 98]

As mentioned, some of the best handling FWD cars still cock a rear wheel, I've seen some RWD cars cocking a front wheel.

 

I see it quite often

[aCe 0]

I think after looking into all the differnt aspects that its un-questionable that a fully independant rear set up would be best. However the gains against financial costs are minimal and therefore i have opted for a trailing arm set up with upright dampers in turrets. As well as this im going to test out a few different arms and go for stiffer TB's, also run it without a ARB.

 

Thoughts?

[Rippthrough 98]

Thoughts?

 

 

A trailing arm IS fully independent, for the second time

[DrSarty 90 1 Cars]

therefore i have opted for a trailing arm set up with upright dampers in turrets.

 

Welcome to the club.

 

I now believe the orginal design is good, but whilst entertaining was a compromise to provide boot space and low manufacturing costs.

 

This is why in several concurrent threads at the moment which seem to be covering this issue a lot (my Evo II project & the 'Fastest 205 GTI' one to name a couple), I disagree when people are labouring the point of originality. I don't disagree originality is good...on an original car.

 

The EuroTrip showed that standard cars can do this type and possibly more demanding trips, and even the 'Ring quite competently. But some of us don't have standard engines or needs and yearn for more.

 

Choosing, manufacturing and paying for an improved rear suspension from a performance (or even comfort) perspective is nothing to be frowned upon. We're doing this because we loved what we had in the first place, but have moved the goal posts somewhat, bordering on motorsport.

 

Don't forget it's also the challenge and possible desire to have something unique. Sometimes standard just ain't good enough.

 

Good on ya James. Colin Satchell has proved time and time again that this arrangement works. I'll be most interested to see what you do and how you do it (if you'll share it). Maybe you'll do a project thread (?).

Edited May 18, 2009 by DrSarty

[aCe 0]

A trailing arm IS fully independent, for the second time

 

 

NO ITS NOT, ITS SEMI INDEPANDANT

[aCe 0]

Cheers Rich, yes il look into getting it done next month i wanna make sure its all perfect. I think it can be done relatively cheaply as well due to turrets being forsale for this exact reason on some rally websites, then its just simple measuremnts and welding.

 

I completly agree with the originality bit BTW, mines not original its a slag so needs to be undressed and fettled!

 

When are you looking at getting yours done, if i get all mine done first i can pm you all the pics and hopefully help you out to get it cheaper and vica versa!

[Rippthrough 98]

No, a torsion beam is semi-independent, you have independent trailing arms, take the anti-roll bar out and moving one side has no direct effect on the other.

[Sandy 191]

It is independent!!!! (Apart from the ARB)

[aCe 0]

"torsion bar suspension rear suspension, that debuted in the Peugeot 305 estate, was a key ingredient of the success of the 205. This is fully independent using torsion bars (Torsion spring) and trailing arms"

 

Sorry, i made the link with the ARB and assumed that was a direct connection therefore not independant!