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      11-25-2010, 12:20 PM   #8

Drives: 335xi
Join Date: Nov 2010
Location: N/A

iTrader: (2)

t seems like the spring rates are being changed from stock ratio of 3/1 rear vs front to 2/1 rear vs front with the upgraded coilover package.
You need to look at the actual wheel rates, not the spring rates. It is not a linear relationship. Additionally, the higher the spring rates you run, the higher the ride frequency goes. The higher ride frequency the more you want to shift the bias to neutral or even front biased. It also depends on what sway bar set up you are running as this well affect the total load transfer and effective wheel rates. I don't have my worksheet, so I can't provide the actual ratios.

Ride comfort in relation to spring rate is a factor of damper construction and valving. You can run high springs rates with a properly setup damper with good ride comfort.
This is what I was getting at in regard to a proper spring/shock combo. With the adjustability of shock travel, compression/rebound in coilovers I think it is possible to get away with running higher spring rates.

It seems like the common "economy" trend to cure poor ride and/or body roll is to swap springs. This would only exacerbate the problem as the shocks seem to be underdamped from the factory. By adding shorter/stiffer springs you are further limiting the travel that the stock dampers can work in, as well as stiffening up the quick response characteristics of the ride. The end result? A rough ride that constantly bounces off the bumpstops. For economic performance upgrades, it may make sense to look at upgrading the shocks before springs.