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      01-03-2013, 09:33 PM   #29
Richard@M-World's Avatar

Drives: NASA TTA #92 M3
Join Date: May 2011
Location: TX/IL

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Originally Posted by BIU View Post
On the subject of KW and helper springs...

Does the V3s come with helper springs or are they only needed on setups with linear springs (ie. Clubsport)?

With progressive springs unseat themselves at full droop or is this only prone to linear springs?

Sorry if I have misunderstood some basic knowledge along the way
V3 for E9X M3 do not come with helper springs. They will stay seated at full droop.

The springs used for V3 are soft enough such that they compress sufficiently (from full droop to normal ride height) by the weight of the car to deliver proper ride heights.

For Clubsport, higher rate springs are used. Therefore, the springs may not compress sufficiently by the weight of the car to reach a reasonable ride height. To address this, the front axle lower spring perches have to be moved down to "lower the car" if you will. But this creates a gap between the spring and the spring perches. That's why helpers are added.

Looking at it using math:
(The numbers are made up)
  • Spring rate: 500 lb/in
  • Corner sprung weight: 1000 lb
  • Spring will compress 1000/500 = 2 in
But, we need suspension to compress 3 in to reach normal ride height.

Solution: move spring perch down by 1 in.

New problem: there is a 1 in gap between spring and perches at full droop.

New solution: add helper spring.

This may be a bit confusing so let me know if this makes sense.
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