I can't speak for Vorshlag but all the Ohlins' we sell are valved for the spring rates the customer orders.
The car will handle better at the .75" drop due to suspension angles. With a 950 lb rear spring I would recommend the 275 rate over the 300 unless you have gone to a larger rear bar. PM or call us and we can discuss what you want to do with the car along with what mods you have already done to help with recommendations.
What ride height are you looking for? They designed the kit and the instructions for a 1" drop but you can run the car higher or lower.
Getting a .75" drop is not a problem with this kit.
No they don't make any noise or move.
You can use either the stock mount or spherical bearing mount like the one we are getting ready to release for sale.
No, they use either the stock front strut mount if ordered as a stock Ohlins' kit. If the customer selects custom spring rates they will come with our patented caster/camber plates designed for 2.5" springs.
I think it's mainly because most car guys seem to be more into engine and powertrain than suspension, so that's where the attention and the big money goes. That's just the path hotrodding / car modification has been following since the 1930's, at least in the USA. Want a faster car? Throw more engine power at it. Don't worry about the corners, win the drag race down the straight.
If you're referring to the "big springs" that Ford fits to the PP2, Ford would be choosing a free length appropriate to the chosen spring rate and desired ride height, given a fixed distance between the upper and lower spring seats. The springs are still under some amount of compression (preload) with the suspension at full droop, and there's a reason you need to use a spring compressor (or some similar approach) when working with big springs and struts or other limitations on droop travel. The only place I see 'preload' being involved is with coilovers, but even that isn't discussed in terms of 'preload' - it's cornerweighting and wheel loads, and the preloads are whatever they end up at when you've reached your crossweight target (and, I suppose, the car is level at least side to side).
I'm not quite sure what you're trying to calculate there, why you're adding 10 to the 19, or where you're going with that 587 lb result. I'm assuming that 90 is in N/mm (about 514 lb/in), which aren't the units most commonly used when dealing with US domestic cars. I am familiar with motion ratio math.
This thread is about the Ohlins solution . So I'm not sure why PP2 is relevant. Preload is the standard term to describe the difference between free length and compressed length of a spring before installing on the vehicle.
I found the Ohlins manual and it says the default preload is 10mm and after install the car takes a further 19mm sag. So the perceived weight at the spring is per my calculation. I need the leverage ratio observed at the shock mounting points to calculate the spring rate and preload amount to get -19mm moved up to -12'ish. Does a 110N/mm spring at 8mm preload work? I don't know. Or looked at another way, with the default 90N/mm spring, does preload of 15mm suffice? Does it need 20mm, 25? What is the shock valving range as it relates to spring rate? Generally speaking you can go up to 10-15% either side of the baseline and the valving can still cope or be within the adjustment range. More than that and it's time to re-shim.
Except I have the PP1 (not sure what I said to give the impression I had the PP2) and a bunch of hand-waving terms like "unique Stability Control, EPAS, and ABS Tuning" are meaningless. If they can't be quantified, then their contribution might as well be zero.
There's reasons for the the very high front wheel rate vs the rear that are more apparent now than they were. The rear motion ratio is 0.492 in the stock location (which these use), so to calculate wheel rate, you square that and multiply by the spring rate. The front motion ratio for any spring or coilover will be the same regardless of brand.
