Pts Build Manual Recommendations - 309 Tarmac

[Rich_p 23]

I have found a copy of the PTS rally build manual and it recommends a tarmac spec 309 should use 26mm torsion bars. (I have 25's so near enough)

 

I have had a search of google but cannot find any links where someone has used them for rallying and posted details.

 

What I need to know is a ball park figure for the front spring they use. I have 385lb and 400lb springs (I've not yet driven on them) and I want to know if I'm looking in roughly the right area.

 

(the car will be driven on 888's, Proper saloon car wets or depending on the day and venue old road tyres..)

 

Has anyone read anything anywhere that could help me?

[fast_eddie 0]

I ran 300lb spring on bilstein shocks on my road/track 309 with spax rear shocks and standard bars.

Seemed ok to me (with progressive under/oversteer) but was ready to go up all round in poundage before I took it off the road-I will watch this thread with interest.

[boombang 2]

If you are mainly doing trackdays, I would say you can beef up a bit over the old PTS specs. From everything read and gleaned from SBC years back, they ran relatively soft up front for rallying and then very stiff at rear to make it move about more on the throttle.

 

My old 309 genuinely was faster round a circuit and much more fun on smooth tarmac with a seized rear beam. Obviously was relying on a bit of give from the tyres, and over anything bumpy was downright dangerous!

[Alan_M 66 1 Cars]

Here.....about 4th post down there is a conversion table for TBs to wheelrate. Camerons post afterwards may be helpful too.

 

http://forum.205gtidrivers.com/index.php?s...888&hl=bars

Edited September 13, 2010 by Alan_M

[Anthony 1,002]

For what it's worth, the last 205 I did with 25mm torsion bars ran with 300lb springs, and that was very well balanced. That was running R888's

[allanallen 528 2 Cars]

I'd be interested to hear miles's thoughts on this as I believe he used to run 26mm TBs and a 28/30 arb on his/my 309, hopefully he'll spot the topic.

I've got a set of 25 bars and a 28 arb on there way, I currently only have a set of 300lb springs so that's what I'll be trying first. Al

[Baz 421]

To a degree it's also personal preference.

[Rich_p 23]

Miles actually gave me some info a while back on what he used

 

"240lb springs and 24mm rear bars with a 30mm rear ARB"

 

It's a lot softer at the front than I thought it would be.

[Baz 421]

Again, personal preference, i think you'd find it better like that if you dislike understeer.

 

I prefer a stiffer rear end...

[Miles 331 1 Cars]

The front needed to be stiffer which I never got around to as I only installed the 24mm bar's a race before the engine went up in smoke.

I would say at least 400 as it oversteered to the point of slowing you down

 

I've got 25mm bars on my 306 but the car weigh's more but the front is stiffer as well so again it's all trial and error

[Cameron 16]

Here.....about 4th post down there is a conversion table for TBs to wheelrate. Camerons post afterwards may be helpful too.

 

http://forum.205gtidrivers.com/index.php?s...888&hl=bars

 

The formula I gave in that post was wrong though, so make sure you go forwards a page or two to get the correct formula!

[Cameron 16]

To add to this, don't be persuaded into having an immensely stiff rear end, as Miles said you may well find that the excess oversteer slows you down. What you want is balance, oversteer is good if you have an LSD as it helps the car to go where it's being pointed, but you don't want to have so much oversteer that you're forced to hold back, or so that you kill the rear tyres too quickly. You want to be able to confidently keep the throttle applied; when you apply the throttle coming out of a corner, that's it, you don't take it off. If you have to take it off, you're going slower than you could be!

 

What front spring rates does the PTS manual mention out of interest?

[Rich_p 23]

What front spring rates does the PTS manual mention out of interest?

 

 

It doesn't hence my post

[Craigb 2]

It doesn't hence my post

 

orignially there were only 2 to choose from

 

10" 185 lb for gravel

9" 225 lb for tarmac .

 

these were fitted to both 205 and 309

[Cameron 16]

It doesn't hence my post

 

Duhhhhhh.. sorry!

 

225lb seems quite soft for 26mm rear bars though, I'm only running 24mm with 350lb fronts! I'd think with that sort of rear end stiffness you'd be looking at 400-450lb fronts. You want to be using at least top of the line semi-slicks (Yoko / Dunlop) for that though surely, preferably on slicks as road tyre sidewalls won't be stiff enough.

Edited September 16, 2010 by Cameron

[welshpug 1,655]

you have to remember that these are rally car specs, not race car, and are also chosen to work with the tyres of 20 years ago.

[Cameron 16]

Aha, figures really, having the rear that loose!

[welshpug 1,655]

indeed!

 

watch a few of the videos on youtube of the challenge and group A cars, Richard Burns in the 309 gti16 on the RAC, you'll see they are quite loose

 

 

Delacour in 1989

Edited September 16, 2010 by welshpug

[Rich_p 23]

After watching that I'm going with 150lb springs and a 38mm rear arb

[Craigb 2]

indeed!

 

watch a few of the videos on youtube of the challenge and group A cars, Richard Burns in the 309 gti16 on the RAC, you'll see they are quite loose

 

 

Robert Reids call of flat left through Wythops fresh air bends . Paterson notes have that corner as a caution . fantastic comittment