I seriously doubt it's close to 300lb. I'd estimate less than 200lb, but I don't own any 700 series cars. I just know what 200lb, 250lb, and 325lb springs feel like on the rear of my 240, and it seems like 300 would be pretty stiff for a 7 series.

It might vary, though. 4cyl cars may have softer springs than the turbo diesel cars, given the additional weight of the engine. The V6, however, was not a heavy engine by comparison, so it probably didn't need a stiffer spring than the 4cyl.

You could calculate the spring rate if you knew the spring diameter, the coil wire diameter, and the number of active coils.
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