309 Front 205 Rear

[Iain-gti 6]

Hi,

 

Would anyone recommend or totally disagree with running 309 front wishbones and driveshafts with 205 rear beam.

 

Advantages or disadvantages?

 

 

Thanks Iain

[j_turnell 134 3 Cars]

No problems atall, the wider front track will help improve turn in and the camber will give you a larger footprint when cornering so improve front end grip.

[Iain-gti 6]

But wont it make the back end lighter causing that to push out?

[ashwarrior205 0]

But wont it make the back end lighter causing that to push out?

 

The rear would have same grip as b4. all you doing is adjusting front track and camber making it turn in quicker increase out side front wheel foot print on hard corning. onlydown side is increased wear on inside edge of tyre but deferentially worth doing

[Baz 421]

onlydown side is increased wear on inside edge of tyre but deferentially worth doing

 

If anything it actually evens the tyre wear.

[Iain-gti 6]

Ok cheers only reason I wasn't going to run the rear beam is due to the clearance issues.

[jord294 89]

Ok cheers only reason I wasn't going to run the rear beam is due to the clearance issues.

 

only if the ride height has been set too low

[welshpug 1,646]

didn't seem to slow this car down at all, at brands, won the race

 

 

 

 

heard it runs AST dampers and proper size torsion bars and some camber.

[swordfish210 20]

I run my car like this and it's just fine. I wouldn't want a 309 beam as i think it would make the car understeer

[j_turnell 134 3 Cars]

309 beams dont make the car understeer atall in my experience, widening the rear helps reduce weight transfer and the 1mm increase increase in torsion bar and arb thickness also helps tighten up the rear end, making the car feel a lot more planted through fast twisties, although this is marginal in terms of increased stiffness due to the extra length of the bars it does make a noticeable difference. One of the best mods to a 205, and plus the stance looks so much better imo.

[boldy205 74]

Think that is a local car to bristol, as far as i know it runs 'std' 205 beam with v hard bars and wheel spacers.

[shalmaneser 26]

Widening the back end can't effect the handling significantly, but running stiffer springs on the front like many do will certainly increase understeer.

 

I'm running Eibachs and Gaz front dampers with a rebuilt 309 rear beam on Gaz dampers on the back and while I can get the back end out if I'm very aggressive the overall balance is certainly toward understeer, although I reckon this is because the front end is too stiff compaired to the back.

 

I'd like some slightly softer front springs ideally but as I'm not on coilovers my choice is limited and the Eibach springs seem to have the best overall reputation as a fast road spring. Hence I'm going to increase the rear ARB rate to hopefully balance things out a bit. Not an ideal solution but a good compromise given that I'm poor!

 

It's all about spring rates really, the 309 rear end is just a cheap and easy upgrade for most people hence they're popular.

[Baz 421]

I disagree with alot of that actually. A wider rear track will promote understeer and eibachs aren't that hard. Damping matters more than you realise too.

[swordfish210 20]

I disagree with alot of that actually. A wider rear track will promote understeer and eibachs aren't that hard. Damping matters more than you realise too.

 

I think the Eibachs are around 110lb iirc, hardly stiff at all. Having a soft rear end won't do the car any favors at all, it's just taking grip away from the front during cornering.

[Baz 421]

Of course, but increasing the rear track width doesn't help and arguably neither does the fact that a 309 beam has bigger bars etc...

[swordfish210 20]

Of course, but increasing the rear track width doesn't help and arguably neither does the fact that a 309 beam has bigger bars etc...

 

Don't the 309 bars work out to be the same lb as the 205 ones due to the extra length?

[Baz 421]

I'm not sure i'm allowed to say, but in some opinions yes!

Edited January 7, 2011 by Baz

[swordfish210 20]

I'm not sure i'm allowed to say, but in some opinions yes!

 

I'm sure it won't earn you any more warn

[Baz 421]

I wouldn't be so sure!!

 

[tomcolinjones 26]

I wouldn't be so sure!!

 

 

 

Come on lads, or this thread will end up getting deleted aswell. cant you just p.m someone your problems, instead of getting dirty laundry over the street?

[shalmaneser 26]

I disagree with alot of that actually. A wider rear track will promote understeer and eibachs aren't that hard. Damping matters more than you realise too.

 

I know you're a lot more experienced than me with this, but subjectively the back end of my car is a lot softer than the front.

 

We can argue all day about whether the spring rates of the 309 beam are more or less than that of the 205, but i had to adjust the spline a hell of a lot more with the 309 beam to get a 30mm drop than i needed to with my 205 beam. ergo, 309 bars must be harder.

 

How much harder is as i said undecided (although a 1mm increase in diameter from 205 to 309 bars is about a 10% increase in x-sectional area, which will directly affect spring rate, assuming the material is the same on both bars) and it's a small in length really, going on this picture:

 

 

I would suggest that 309 bars @ 103 cm are approximately 4 cm longer than 205 bars, which is 4% give or take, so the percentages add up to the 309 bar being stiffer as well.

 

 

However, this is neither here nor there really, what I'm suggesting is that a lot of people fit a 309 beam as a one stop 'stiffer back end' solution and it's not that much stiffer, really, given most people will be running front springs as stiff or stiffer than the Eibach setup, which suggests that a 309 bar is a step in the right direction, but not sufficient.

 

Looking at it again I think i probably need bigger rear bars to go with the 309 beam, but I don't really want to compromise the ride too much more on what is currently my daily driver.

 

Hence, I need softer fronts - the reason my car understeers is that it's not balanced, the 309 beam (or more accurately, the 40mm extra rear track) doesn't really matter one way or the other.

 

Or maybe it does, but I really don't see how it can. As far as damping goes I've done a lot of work regarding damping curves and stuff like that (albeit on a two wheeled application, not four) so I'm fairly happy with the damping levels F+R, but maybe I should have a go reducing the rebound on the fronts and increasing it on the backs to see if it makes any difference.

 

It's all good fun at the end of the day, if anyone has the perfect setup I suspect they're keeping it to themselves!

[Baz 421]

And you definitely have 309 GTi TB's and ARB in there?

[Baz 421]

It's all good fun at the end of the day, if anyone has the perfect setup I suspect they're keeping it to themselves!

 

Yes of course! The 'perfect setup' though is to a degree based upon personal preferences!

[swordfish210 20]

Yes of course! The 'perfect setup' though is to a degree based upon personal preferences!

 

Hence why i've made mine as stiff as a go-kart, just the way i likes it

[shalmaneser 26]

And you definitely have 309 GTi TB's and ARB in there?

 

Definitely. Measured with a digital vernier so you know it's good