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Well thanks for the reply. It both gives me a sense of relief in having some confirmation that these twist beam rear ends are in fact complex beasts, but also shows me that I'm way out of my depth when it comes to the proper engineering side of looking at it.
Perhaps I should give a bit of back ground as to why I'm looking at the rear end. The car I have is a vw polo 9n3 gti 1.8t. I use it in street registered class hillclimbs. Following mark Ortiz and dick shine advice on these rear ends I have lowered it as far as practical to get the COG and roll centre as low as possible. I have added a 20mm RARB set on hard to get the car to lift its inside rear - the reasoning being that this is just about the only way to get good traction out of the open diff front end when going up hills. Of course I still have problems getting the power down though. So I was wondering if my rear springs weren't too soft. Yes it will currently lift the inside rear but I think it is doing so because I have added the most 'retail' torsional stiffness to the twist beam that I can. But when it does this though, the whole rear is then supported on virtually a standard spring rate on the outside rear. I'm worried this will be inducing an outside rear 'squat' that will try to lift the inside front. So I want to run stiffer rear springs to try to help with the above scenario and also help with a bit of 'anti-squat' on launch and when powering up straight uphill sections - I can reduce the RARB stiffness to compensate on roll if I have too.
So I guess what I'm wondering is 1. is my reasoning in the ballpark/worth a shot 2. that's why I was asking about motion ratio's so that I can take a punt at a better rear spring rate.
MY front has 150lb springs and 22mm FARB on hardest of 2 settings, rears are 130lb springs with 20mm RARB on hardest of 3 settings. The car weighs 1100kg with a 65/35 f:r weight spilt in event trim.
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