Suspension And How It Works

[NickR 10]

Damn you !

 

Just updated my article:

 

http://www.lbft.co.uk/articles.asp?id=2

[TT205 42]

Fabulous set of articles Adi

 

Now, how about a recipe book

 

Assuming that someone has ungraded their suspension - dampers/arb's/torsion bars etc and that the front dampers are adjustable.

(i.e. the position I am now in)

What would you say is the best order in which to do your testing to get the best set-up for your individual 205?

 

eg

 

1) Ride height

2) Tyres pressures

3) Tyre/rim widths

4) Front damping

 

etc

 

Cheers

Dave

Edited October 6, 2003 by TT205

[Ahl 4]

These posts really are excellent. Thanks adi.

I'll make sure and reference them next time some twerp recommends slamming a 205 by 60mm for the best handling!

[Adi 0]

1) Ride height

2) Tyres pressures

3) Tyre/rim widths

4) Front damping

 

 

1) Tyre/rim width

2) Ride Height

3) Damping should be adjusted front and rear to tune balance.....and as a general rule.....the rear should be set firmer than the front.

Saying that....you could choose a favourite set of corners and run thru with all dampers set to 0. Then turn the rears upto 2 and try again. If you prefer the balance....then whatever the fronts finally finish on.....just keep the rears firmer than the front.

4) tyre pressures

 

What spring rates have Leda supplied.......and have you changed the rear torsion or arb??

[NickR 10]

Adi, was just wonder how things change for 4wd and rwd cars

[fiji bob 0]

adj do you think a 309 gti rear set up is a good upgrade on a 205? i think it has thicker anti roll bar torsion bars and is slightly wider but someone will know for sure

[TT205 42]

What spring rates have Leda supplied.......and have you changed the rear torsion or arb??

Springs are - 270's ( Ithink)

Rear ARB now 23mm, and uprated torsion bars

 

Dave

[red 0]

Thanks for that great section ADI and putting in the time and effort , that really gives me somthing to ponder over and look at with respect to testing, as one or two of us sprint I was wondering how seting the car up differs from say a circuit race as we are on cold tyres and normaly get one-two circuits at best at most venues, this is in respect to tyre pressures and the type of compound used, with me it would be a rd tyre from list 1A in the MSA blue book, I use the Bridgestone SO 3's and currently I'm the only one who likes them? do you have any preferences on tyres yourself.

Regards Russ

[Adi 0]

was just wonder how things change for 4wd and rwd cars

 

RWD cars are generally set up with the frotn end stiffest.....which is why you will see RWD track cars lifting the inside front wheels at extremes. In F1 GP at USA last week.....Mr Schumacher was lifting an inside front wheel in turn 2.

 

4WD cars are generally set up in a similar way to RWD cars with the front end being the stiffer but not as stiff as say a RWD.

 

adj do you think a 309 gti rear set up is a good upgrade on a 205?

 

Yes in theory it is a good upgrade. The major improvement is the increased rear track of the 309 axle. Apart from lowering...increasing the track is the best way of reducing weight transfer.

Because I have never actually driven a car back to back with and without the 309 axle....I can't really comment how the 2 differ in feel.

 

do you have any preferences on tyres yourself.

 

I've never tried some of the more exotic Pirelli tyres which are supposed to be very good. But IMO the Goodyear Eagle F1 is very good. Especially in the wet, the Eagle F1 inspired confidence. The Toyo Proxes I have now.....are certainly not as good in the wet.

[Doof 11]

Bloody hell, suspension guru!!

 

Pitcrew?

[Adi 0]

Pitcrew?

 

No not at mo.......just studied in the past.

[Doof 11]

Muppet

[Adi 0]

[pug_ham 244 3 Cars]

Bloody hell, suspension guru!!

 

Pitcrew?

To late Adi, you've had an upgrade!

 

This is a fabulous topic to keep up to date with, keeping NickR busy updating the article on his site as well.

 

Graham.

[Guest puggti]

You certainly know your stuff! Sell your info on Ebay!

[Guest puggti]

These posts really are excellent. Thanks adi.

I'll make sure and reference them next time some twerp recommends slamming a 205 by 60mm for the best handling!

I think thats wrong to say to be honest! If it is set up proberly then it will handle well! Well thats what im doing anyway but im gonna use in-situ adjustable track control arms and eccentric top mounts therefore i should have the best of both worlds as this also means that i can apply about 1.5 negative camber at the front and probably 0.8 at the back or 1, depending on how it handles.

 

Ross

[Adi 0]

I think thats wrong to say to be honest! If it is set up proberly then it will handle well!

 

Chassis height isn't really the important issue with lowering cars. It is the knock on effect of how much suspension travel remains. That is why WRCs on gravel are set a lot higher than on asphalt.

 

If you lower a road car a silly amount......you will not get the best out of the suspension....or handling. That is because the tyres & springs need to absorb the bumps. If the spring/tyre doesn't do that......any energy the spring doesn't absorb is passed onto the chassis. The chassis is sent in the upward direction and this leaves the tyre not in full grip with the road surface. If this happens at the wrong time.....whilst cornering for example.....the car can be sent into the hedges or a wall.

 

Now if you happen to live in a unique place for the UK.....where the roads are smooth and bump free......then the suspension can easily cope with a lot less travel. But it will only be suited to those roads.

 

People are frequently asking me, why are my dampers leaking after only a few months on the car??? The first question is....is the car lowered a lot. 99% of the time.....the answer is YES. This happens cos the dampers are constantly slamming shut and bottoming out. The hydraulic seals don't last long in this situation.

[Swilki 0]

How much wider is the track on the 309 rear axle? Is it a simple change over from the 205?

[pug_ham 244 3 Cars]

IIRC it is about 2' wider & it is a straight swap over, all you have to change is the rear mounts need turning 180' to match the 205 body, a two minute job.

 

Try a search, it is quite a common topic.

 

Graham.

[pug_ham 244 3 Cars]

I was reading through an old Practical Classics today which featured Steve.c's car among with a few others but at the end of the article the author says that he is surprised that a reputable firm offers a coil over set up for the 205, he states 'that a strut must have an offset spring to counter a sideways bending force on the piston rod, otherwise the excess friction will render the ride appalling'

 

Any thoughts?

 

Graham.

[Adi 0]

offset spring to counter a sideways bending force on the piston rod

 

One of the disadvantages to the McPherson strut set up is the sideways bending force. There is a high sideways load on the piston and rod guide. This produces friction which not only increases the wear rate.....but can have detrimental effects on ride/handling.

One of the ways engineers have found to reduce this effect is to offset the spring axis on the strut. If you have a look at the standard front strut on most cars, the lower spring pan will be offset to the outside.....so the spring will be closer to the back of the strut.....than the front (transversely).

 

Now whilst coilovers with 2.25"dia spring, will have a central mounted spring, certain damper manafacturers have changed the design of the damper to counteract this sideways movement.

Rally bred "inverted" struts were used on Subarus and really helped reduce this sideways "bending" force. The inverted strut looks like a conventional strut, but the internals are actually upside down. The piston rod operates in the lower section of the strut with a secondary tube above. This secondary larger diameter piston will then fix to the inner wing as would the piston rod on a convential strut. It is this larger diameter rod that takes the brunt of the bending force instead of the piston rod on a normal strut.

"Inverted" struts can even be found on the front of production road cars such as the Peugeot 307.

 

I have said many times that coilovers are becoming more like a fashion accessory on cars.....more for the use of excessive lowering........rather than the proper use of fine tuning chassis set up in motorsport. As such, the design of certain aftermarket coilovers are not as critical to detail, and such, can actually make the performance of the suspension worse.

[Guest Batfink]

Adi hes another one to pick your brains:

 

Im fitting a 309 rear beam to my car. To match the front up I see two options

1. Fit 309 wishbones - this will give me negative camber though and will require more cash and will wear tyres quicker..

or

2. Fit spacers - this will change the offset though. Could mean more torque steer?

 

Am I best off with 309 wishbones or with spacers

[Adi 0]

Am I best off with 309 wishbones or with spacers

 

Forget spacers......a bad idea.....and will only work for the visual aspect of widening the front track.....otherwise......will create bad steering effects.

 

Do I remember you getting coilovers for the front of urs??? If you did, you could always try an eccentric top mount. That way you could gain -ve camber without extending the front track. You could gain caster as well.

 

If not.....the only other way is to use the 309 wishbones.

 

Ideally you will widen the rear track.....but leave the front track the same. That way the balance will be improved further.

 

As far as gaining camber and excessive tyre wear..........well that depends on how excessively the outside of the front tyres are wearing at present.

I have just gained some -ve camber on the front of my 206. B4 the front tyres were always wearing heavily on the outer shoulders. Now there is less pronounced wear on the shoulders.......and I haven't noticed any increased wear on the inside.

That is really the idea of camber......to make sure the tyre is used more evenly and you use of the full grip available.

[Guest Batfink]

Ideally you will widen the rear track.....but leave the front track the same. That way the balance will be improved further.

so this will be changing the handling for the better??? Not sure I understand quite what this will do. So are you also saying that there is no point to fitting the 309 wishbones unless you are looking for negative camber on a budget??

[Adi 0]

Ideally you will widen the rear track.....but leave the front track the same. That way the balance will be improved further.

 

so this will be changing the handling for the better??? Not sure I understand quite what this will do.

 

 

On fwd production road cars, the front track will be wider than the rear. This is one of the ways (combined with others) that manafacturers make cars understeer.

So, by widening the rear, this helps to reduce the weight transfer....and therefore role. If you then go and widen the front......then this reduces the effect of widening the rear.........as far as balance front to rear is concerned. If this is the only way to gain camber (thru widening front).......then it has to be done. But if there is an alternative.....like thru the top mounts.....then try that first.