I recently acquired some Bilstein B8's with the intention of getting the Roadstersport springs on the next shipment to Australia. As I already had some eibach springs I thought I would at least fit them and give them a try at a recent track day. The factory front shock/Spring installed measurement was 260mm (top hat to bottom tip of Spring in lower shock retainer) and 238mm in the B8's (clearly more Spring preload). My hope was that this would be a sufficient set-up for the occasional track day and maybe save on buying the Roadstersport springs. My observation was that the additional preload was firmer on small road bumps but still similarly compliant on bigger bumps, however, there was little noticeable difference on the track as the additional preload isn't enough to overcome the lower Spring rate of the eibach's. Originally the eibach's dropped the car by 1/2" and with the B8's, dropped the height another 1/2" to 13 1/2" all round.
So my question is if the B8's are shorter than the Koni's and there is additional preload particularly on the 300 front springs will this be too much preload? By my calculation, if the B8 is 22mm shorter than the Koni, the front springs will have over 500lb initial preload? And is this a good or bad thing?