309 Beam

[andyjstone 6]

What's the benefit of fitting a 309 rear beam instead of the standard 205 one?

[swordfish210 20]

More rear stability in the corners. Less fun though, takes away some of the 205-ness.

[andyjstone 6]

More rear stability in the corners.

 

Why is that, does it have a bigger torsion bar?

[swordfish210 20]

The wider track helps the stability. Stand up straight and slowly move your feet further apart, the wider apart they get the more stable you will feel, yes?

[welshpug 1,645]

just an extra bit of track, 36mm IIRC, hardly any extra spring rate from the larger torsion bars as they are longer.

[jimistdt 1]

Why is that, does it have a bigger torsion bar?

20mm bars as opposed to 18.9 on the 205.

[boombang 2]

Torsion bars are thicker, but certain spring rate calculations I have seen demonstrate this is negated by extra length.

 

The ARB is both thicker and comparatively uprated.

[Miles 331 1 Cars]

None, better off with a 205 one and wider rim's/tyres and larger ARB and all different Rear Arms from the ZX

[andyjstone 6]

None, better off with a 205 one and wider rim's/tyres and larger ARB and all different Rear Arms from the ZX

 

Surely that would give you the same effect as having a 309 one

[Alastairh 47]

Also they look better.

Edited September 24, 2009 by Alastairh

[andyjstone 6]

Also they look better.

 

Which look better???

[Anthony 1,002]

It's one of those personal things - some people prefer a 205 beam, and some a 309 beam.

 

I've run a 309 beam for the past 5 years or so, and I think it's great, suiting my driving style perfectly. You lose the degree of nervousness that you can get with a 205 width beam, replaced with a planted tail, but one that is still steerable on the throttle. I'd say that if anything it turns in better than a standard 205 beam thanks to the thicker bars, and feels better balanced to me when coupled with average lowering springs on the front. All IMO.

 

In the past couple of years, uprated torsion and anti-roll bars have become easily available and reasonably priced, which does negate some of the advantages of a 309 beam with its thicker TB and ARB as you can now build 205 beams with thicker bars - although it's significantly more money buying uprated bars as you'd expect.

 

Disadvantages are that because of the extra width you can't run anything wider than the standard 6" wheels with 195 width tyres without doing something with the arches. Not something that's ever bothered me personally though

 

For what it's worth, that I'm aware of, no one that I've ever supplied or fitted a 309 beam to has regretted the choice based on how the car drove - only person I know that wanted to revert to a 205 beam was Platty (his thread is on here somewhere) and that was because he couldn't run the SL434 wheels (6.75" wide) that he'd also bought. In his case I said that I'd build him a 205 width beam and swap at zero cost, and I'm happy to extend that offer to you - if you're not happy with the handling of the car with the new beam, I'll build you a 205 one instead at zero cost

[andyjstone 6]

In his case I said that I'd build him a 205 width beam and swap at zero cost, and I'm happy to extend that offer to you - if you're not happy with the handling of the car with the new beam, I'll build you a 205 one instead at zero cost

 

That sounds very fair, but I'm sure I'll be happy with it - not sure my driving style would be able to tell the difference anyway

[Anthony 1,002]

That sounds very fair, but I'm sure I'll be happy with it - not sure my driving style would be able to tell the difference anyway

You will notice a difference over your current beam if it's a standard 1.6 beam, I promise you that - hell, if you don't notice a night and day difference by the first roundabout you come to on the road, let alone on track, I'd be surprised

[andyjstone 6]

You will notice a difference over your current beam if it's a standard 1.6 beam, I promise you that - hell, if you don't notice a night and day difference by the first roundabout you come to on the road, let alone on track, I'd be surprised

 

I was meaning that I'm not sure I'd notice the difference between a 309 beam and a 205 one with uprated torsion/ARB - I too should hope I'll see a difference from what I have now, otherwise you can take it off again

[SurGie 54]

Having the 309 gti beam gives you more higher straight road speed stability, less twitchy than the 205 beam, iv read.

Edited September 24, 2009 by SurGie

[EdCherry 34 1 Cars]

I've heard using the bugatti veyrons rear beam improves stability ten fold. This is what I have on all my cars now including my ferrari enzo in 1:43, bloody hard to find bugatti donors in that size!

[andyjstone 6]

I've heard using the bugatti veyrons rear beam improves stability ten fold. This is what I have on all my cars now including my ferrari enzo in 1:43, bloody hard to find bugatti donors in that size!

 

What wheel arches do you use?

[EdCherry 34 1 Cars]

I use a mix of Metro 6r4 and standard metro bodywork, looks something like this with a 205 front end

 

[taylorspug 7]

Mm 5 door...

[Miles 331 1 Cars]

Thats Ace

[ravydavy 0]

Love it he he.

[andyjstone 6]

Mm 5 door...

 

Naaaa, despite the cut in the rear wing I'm sure those rear doors won't open - ITS A COUPE

[pablo 0]

10mm spacers on the rear would give much the same effect wouldnt it?

[andyjstone 6]

10mm spacers on the rear would give much the same effect wouldnt it?

 

That's what I've got at the moment - original 1.6 beam with 12mm spacers, but presumably this puts more strain on the beam and has some effect on the suspension.