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Discussion Starter · #1 ·
Crawling through AutoDoc and have calculated the following spring rates for the F20/F21 M135i based on the specifications below with the assumption that the active coils is the same value as the number of coils.
Although this assumption may be incorrect.

I have seen the 93 spring rate mentioned on the forum before however I haven't seen the 106 spring rate.


Code: FF
Length [mm] : 294
Outer diameter [mm] : 159
Diameter [mm] : 12
Spring Design : Coil spring with constant wire diameter
Number of coils: 3.95
Active coils : 3.95 ?
Spring rate : 93.475 pound/inch ?


Code: FG
Length [mm] : 292
Outer diameter [mm] : 157
Diameter [mm] : 12.25
Spring Design : Coil spring with constant wire diameter
Number of coils: 3.95
Active coils : 3.95 ?
Spring rate : 106.317 pound/inch ?
 

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Discussion Starter · #2 ·
Another interesting observation is that the stiffer springs code FG don't appear for the pre-LCI F21 M135i (3-door) however do for the pre-LCI F20 M135i (5-door).

Stiffer springs code FG do appear though for the LCI F21 (3-door) and LCI F20 (5-door).

So if you drove a pre-LCI F21 M135i and then drove an LCI F21 M135i that had the stiffer springs you may notice an "improvement" in handling.

Perhaps this might explain why some reviews at the time of the LCI M135i launch commented on how the LCI F21 had better handling....
 
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