Wide Track 309 Gti Rear Beam - A Few Questions

[niklas 1]

just quick question after reading all this, if i had a 309 beam on my 205, would it handle better with 205 or 309 front suspension sets ups? eg: which front suspension would you use if you ran a 309 rear beam to get rid of most of the LOO ( i know its impossible to completly rid it but which would be better)

 

To get rid of most of the LOO, you should use solid rear beam mounts!

309 track control arms and 205 antiroll bar would be my suggested front setup.

[Sandy 189]

Personally I think that the front should be widened, not the rear. wider track at the rear with standard front track will increase the weight transfer at the front, relatively, which will certainly improve stability, but at the expense of grip and traction. I think it's the 20mm bars from the 309 that bring the improvement, not the extra width.

 

My 205 Rallye with standard width 20mm rear bars, Eibach 106 50mm front springs (35mm on the 205) and 309 width front was quite simply the best handling 205 i've driven, by a country mile. Oversteer to neutral is the balance and incredibly benign and controllable between 4-wheel drift and oversteer, bringing a whole different level of exploitability to the 205's character. I drove it again the other day and it really did slap me with it's edgy but friendly nature. I didn't realise how poor the front end grip on the normal 205 is until I used this set up.

 

Still prefer my 309 though

[camgti 56]

Wouldnt it be a great start to learn to drive properly to be able to control the lift off oversteer. Sure it would be a good thing if you can calm it down but it is such a great tool to be able to use when its needed. Getting rid of the LOO (or whatever it is you say) is like taking a hammer from a carpenter. Learn to use the tool properly and you can create something amazing.....

 

Do you not agree...

[smckeown 1]

Do you not agree...

 

Yes I've had it mentioned to me a few times by racing drivers / instructors how they would unsettle the rear to provide a great turn in, especially on tight corners. We all know the benefits of taking corners with the car in more of a straight line

[Sandy 189]

When you've got used to a 205 that corners with <balance blending into varying degrees of oversteer>, the normal <understeer or forced into oversteer> set up is binary and frustrating! My driving style has changed since having that set up and it's made me focus more on smoothness, correct entry speed and using power all the way through the corner.

Edited August 27, 2006 by sandy309

[Rally Slag 0]

Still prefer my 309 though

 

yeah, still gota agree there, i own a 205 and 309, both 1.9 gti, both standard, gota say the 309 handles simply amazing, i know alot of people will disagree and alot will agree but i wrote my old 205 of by driving like a nutter and spinning it, where as the 309 feels so more glued to the road. when my 205 is done i guess i'll try sticking that on a 309 rear beam and front wishbones and take it round the track before i boot it on the b roads, but at the moment i just love the way my 309 feels

[niklas 1]

Wouldnt it be a great start to learn to drive properly to be able to control the lift off oversteer. Sure it would be a good thing if you can calm it down but it is such a great tool to be able to use when its needed. Getting rid of the LOO (or whatever it is you say) is like taking a hammer from a carpenter. Learn to use the tool properly and you can create something amazing.....

 

Do you not agree...

 

Nope

 

Inconsistent passive rear steer is a hack, but a good compromise for making it a funny road car. However, consistency is one of the cornerstones to learning to drive properly. Especially on the track!

What you really want is an as balanced car as possibly without any weight transfer reaction that bites back.. Obviously a FWD like the 205 can only be so balanced but an uprated rear beam (23/25 + solid) is a great way to go!

[camgti 56]

Nope

 

Inconsistent passive rear steer is a hack, but a good compromise for making it a funny road car. However, consistency is one of the cornerstones to learning to drive properly. Especially on the track!

What you really want is an as balanced car as possibly without any weight transfer reaction that bites back.. Obviously a FWD like the 205 can only be so balanced but an uprated rear beam (23/25 + solid) is a great way to go!

 

Agred. As i said calming down the effects of the overteeer would be a positive. But also using it to your advantage is very useful. The 205 has one of the most balanced and exploitable chassis around, if your driving stlye is so inconsistant that you dont know when its going to happen. Then maby a few more laps might do you some good.....

 

Cam

[niklas 1]

Agred. As i said calming down the effects of the overteeer would be a positive. But also using it to your advantage is very useful. The 205 has one of the most balanced and exploitable chassis around, if your driving stlye is so inconsistant that you dont know when its going to happen. Then maby a few more laps might do you some good.....

 

Cam

 

You are wrong on both the things you said.

The 205 does not have one of the most balanced and exploitable chassis around, it does have an excellent chassis for being a cheap FWD production car. But it's not in any way close to ie the Elise or any other serious RWD car.

And speaking from the track perspective, which I could've been clearer on, anything based on energy transition effects of rubber is not even close to desirable. You want absolutely no change of wheel angles that are not within the suspension setup! Driving on the limit, there's no room for wheels changing angles depending on the effect of rubber mountings/bushes.

 

FWIW, incosistency doesn't mean I don't know how it behaves, it means that the car is not always behaving in the same way in comparable situations.

[bales 1]

As I've said before, for a road-going 205 I think a 309 GTi rear beam is one of the best suspension modifications that you can do - you get better turn in, more planted through the bends, but plenty of controllable LOO on demand.

 

Why do you get better turn in?

 

When we built our formula student racing car we always had a narrower rear track than front to aid manouverability and the ability to change direction quicker.

 

I understand all the stuff about load transfer because of the wider track and also the stability issues but in terms of turn in (which in itself is quite subjective) I dont see how in a purely dynamic sense it would make any difference. In fact I would expect it to make the car less agile in quick direction changes due to the track differences in the front and rear axles.

[niklas 1]

Why do you get better turn in?

 

When we built our formula student racing car we always had a narrower rear track than front to aid manouverability and the ability to change direction quicker.

 

I understand all the stuff about load transfer because of the wider track and also the stability issues but in terms of turn in (which in itself is quite subjective) I dont see how in a purely dynamic sense it would make any difference. In fact I would expect it to make the car less agile in quick direction changes due to the track differences in the front and rear axles.

 

The antirollbar is 1 mm thicker on the 309 beam, so thus being a little longer it's still overall stiffer than the 205 antiroll bar!

[bales 1]

The antirollbar is 1 mm thicker on the 309 beam, so thus being a little longer it's still overall stiffer than the 205 antiroll bar!

 

I see what you are saying, that you are stiffeneing the back so you get more load transfer at that end and less at the other (the front) so you reduce grip at the end that you stiffened. Which would reduce understeer and increase oversteer.

 

I think that we mean slightly different things though as you are decreasing understeer so that the car doesn't understeer when you enter a corner (which depends on how you drive it) so I suppose you could say that turn in is better. But I mean in a more of an agility sense and the speed the car can change direction, with a wider rear track I still think that this actually makes this worse. However in a race car the added stability I suppose makes up for this and unless you are doing autocross or slow speed stuff then the lost agility may not make a difference. Which I think makes you right and me wrong

 

I also think that the generalised idea about stiffening one end of the car and increasing grip at the other is over-simplified and not always true. I think in the case of the 205 which has front independent suspension and a rear beam axle it can have the opposite effect in some cases, i.e stiffen the front and add grip at the front too.

 

This is because mac-phearson strut suspension has very poor camber recovery in roll, i.e the wheel changes angle as the car rolls. The rear axle as it is a beam gives 100% camber recovery in roll so this stays un-affected. As the front of the car becomes loaded the reduction in roll due to stiffer springs improves their camber so much that it more than makes up for the unequal loading between front and rear and hence actually grips better.

Edited August 29, 2006 by bales

[Sandy 189]

Until it goes over a bump mid corner, or you try to accelerate.

[bales 1]

Until it goes over a bump mid corner, or you try to accelerate.

 

I assume that is reffering to my previous post, and thats kind of the point I was trying to say. That handling is completely 3 dimensional and its not just as simple as having "set" rules that can be applied to any car. There are so many factors that affect the handling that its pretty impossible to change one thing without it having an adverse effect elsewhere.

[niklas 1]

I assume that is reffering to my previous post, and thats kind of the point I was trying to say. That handling is completely 3 dimensional and its not just as simple as having "set" rules that can be applied to any car. There are so many factors that affect the handling that its pretty impossible to change one thing without it having an adverse effect elsewhere.

 

What makes it easier in the 205 case is the limited abilities

There are only so many rear beam configurations to choose from.

 

But I agree totally with your point in your previous post.

In the 205 case you get the stiffest rear beam setup you are able to/can afford, you get the desired wheel lift and you stiffen up the front as much as you can without loosing the wheel lift. In the end you get what you descibred, a 205 that is pretty stiff in roll and pitch but still as balanced as it gets.

 

I haven't completely worked out the effects of track width, but I'm onto an idea that it affects the speed of the weight transfer whereas the stiffness affects the amount of weight transfer...

But it's a stated fact what you say, narrow rear track width is desirable on a 205 race car. I just can't fully explain the theory behind it