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      11-15-2019, 05:29 PM   #23
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Drives: 328d Wagon, M2 Comp, i4 eD35
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Quote:
Originally Posted by Megator View Post
I meant 40mm of preload ie compressing the spring by 40mm from its resting position.

I did pick this value from the one being discussed as it seems like an easy mistake to make and to wrongly set the preload to 40mm. I was asking if doing so would lead to your bolded statement above and whether this might be the culprit for the poor ride and suggested this should be checked.

What seems to be missing from Ohlins instructions is what the rear preload should be.

If the car compresses the springs by 16mm due to its weight then as I understand it you only have 16mm of extension if the preload is set to 0. Further increasing the preload would lead to an extension of the shock for the same applied weight which reduces the available extension travel.

This would seem to lead to traction problems over bumps and potholes as the suspension can only decompress so little and compressing requires overcoming the "excess" preload.

To summarise it would seem that the spring rate might be too high (not enough compression due to the weight) or the preload is to high, which leads to not enough extension (rebound? not sure on the term if it is from rest out) travel.

Or? and thanks for your reply
I would imagine it'd be pretty difficult/nearly impossible to set 40mm of preload. If you set the height adjuster to have 40mm of pre load before installing it and the spring it'd be impossible to jack up the lower camber arm to align it into the subframe or knuckle (depending on which side you disconnect to take the OE spring out) since the car would raise before those points aligned. If you tried to set 40mm of preload after the spring was already installed using your typical cheap and narrow coilover wrenches you'd have to put a crazy amount of rotational force in there to get the perch to spin.

16mm of spring movement is like 27mm at the wheel.
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