My rear Koni shocks came from Paragon last week and eventually when the weather cools off a bit, I'll install them and while I have the car jacked up, I'll attend to the ride height adjustment as well. The car is a bit too low for my liking at the back and the speed bumps that are on my way to work. Not to mention the ramps on my lift.
Currently, the rear axle centre is 301.5 mm from the ground ("A") and the centre of the rear torsion bar cover is 267.5 mm from the ground ("B"). So the torsion bar centre is lower than the wheel centre by 34 mm. The Porsche spec is that the torsion bar should be higher by 12 mm, so in theory I need to adjust its height up by 34+12 mm = 46 mm. Not that I want to go that high. With reference to this figure, I am at -34 mm, not +12.
I see lots of measurements relating to fender heights (mine is 24.5 rear, 25.5 front in inches) but not references to the factory ride height measurement method. So let's say I want to raise my rear ride height to 25" rear (front would stay where it is at 25.5". The half inch higher front seems to be the way most people set these cars up. It means I have to raise my torsion bar centre height by half an inch (12.7 mm which is a lot less than 46 mm). Seems pretty straight forward. I'll just need to calculate what the new spring plate arm angle should be and then adjust away. There used to be a great calculator for this that I read years ago, but that bookmark is dead.
By the ER calculator (2400 lb, stock 23 mm torsion bar), the USA ride height gave a spring plate angle of 39.3 deg and the Euro ride height (whatever heights these were) gave 36.4 deg, which is close to the 36 deg Robert suggest setting it too. What were USA and Euro ride heights? I see confusing differences in various places.
I just wanted an ESR sanity check here because if I were to raise it 46 mm according to what I believe is the factory spec (i.e. a spring plate angle of 39.3 deg theoretically), then the rear fender height will go up 46/25.4 = 1.8" which takes it to 26.3". Which means the front would be something like 26.8" for factory spec. Were these cars really that high as delivered? I think I can believe that based on old magazine articles, but looking for validation here.
Ravi