Quote:
Originally Posted by eeghie
+1
What struck me is that although the weight of the car is in perfect balance, the rear shocks are quite a bit stiffer R/F = 136%. This ratio is quite larger than fi the M3 shocks where front and rear shock compliance is largely equal (referring to E9X M3 ZCP shocks).
In service to OP's selection of upgraded shocks, I hope the more experienced shock-ers among us can also help all of us understand the 1M OEM setup better.
I would assume significant reasons could be to battle understeer (car will roll & pitch towards the outer corner front wheel) and to prevent excessive wheel torque jitter ???
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So first, I am fairly convinced that rebound and compression are mis-labeled on those graphs. I ran some simulation numbers and came out with rebound higher than compression (which is the norm), so I wouldn't want to read to much into these before that can be double checked.
Second, I'm not surprised the rear is overall stiffer than the front. Assuming the 1M's motion ratios are identical to the M3s (purely an assumption on my part based on what I've read about the M3 and 1M sharing parts) then the rear motion ratio is something like .56 vs a front of .96. This means the rear shocks would need to be much stiffer at the shock itself to have identical values at the wheel. Quick rough simulation suggested rear shocks almost 3x stiffer than the fronts would be about right- these are less than 2x, suggesting they may be softening up the rear (likely both springs and shocks?) to help put power down. Seems to make sense.
Could you post the M3 values you have as well? Any way to double check bounce if and rebound are labeled right?