HERMAN 33 Posted May 2, 2008 I think I might have to rebuild the rear beam on 205 is it worth looking for a 309 beam I am told they a slightly wider and improve handling ????? Cheers Neil Share this post Link to post Share on other sites
jonnie205 1 Posted May 2, 2008 try a search it has been covered many many times Share this post Link to post Share on other sites
Henry 1.9GTi 36 Posted May 2, 2008 wider rear track improves understeer, would need to modify other parts as well I reckon. Nothing wrong with a 205 beam btw does anyone know the grade of material is used for the torsion bars / arbs and whats the modulus of rigity (G) is? Always wondered whether the extra length of the 309 bars would compensate their extra diameter in torsion. Share this post Link to post Share on other sites
Rob Thomson 6 Posted May 2, 2008 Doesn't the wider rear track supposedly make the rear end less tail happy...? In other words it makes it understeer more. You don't need to know anything about the materials to determine relative spring rates, the material's the same on both beams. What does matter is that the spring rate is proportional to the fourth power of the bar's diameter and the inverse of it's length. Small difference in length makes bugger all difference. Small difference in diameter makes a lot of difference. Going back to the HERMAN's question, I think it depends how you define 'handling'. I haven't tried a 309 beam on a 205, but from what I've read it makes it less nervous. That sounds s*it to me because I love the fact that the back end doesn't always want to follow the front... Share this post Link to post Share on other sites
Henry 1.9GTi 36 Posted May 2, 2008 yes i see what you mean rob, both have same G roughly 80GPa for steel, twisted through same angle so only diameter and length affect the torque (N.m) or spring rate. I will work out some values of T to satisfy myself, sorry for thread hijack! will su now Share this post Link to post Share on other sites
Wurzel 16 Posted May 4, 2008 yes i see what you mean rob, both have same G roughly 80GPa for steel, twisted through same angle so only diameter and length affect the torque (N.m) or spring rate. I will work out some values of T to satisfy myself, sorry for thread hijack! will su now Those figures have been calculated before I believe. The 309 beam has a slightly thicker anti roll bar giving a better turn in (ie oversteer). The slightly extra track in theory gives better grip. It is a good relatively cheap modification that I found to improve the handling characteristics to my liking. LOO can still be promoted using this beam if required. For a smooth driver though, the car will corner better in my opinion. And to say this subject has been covered many times before is an understatement Share this post Link to post Share on other sites
