I have a JCW Roadster on order - expected to go into production next week. I added the sport suspension option ($500) but was large left wondering whether that was the right call. The miniusa site lists in the description of the JCW model that it includes a JCW tuned suspension. So my question is: what is the spec'd difference between the stock MCS suspension, the JCW suspension and the optional Sport suspension.

Thanks!

All R5x models come with base suspension regardless of trim level. The Sport suspension and JCW suspension are options. (aka the factory JCW does not come with upgraded suspension standard) The Sport suspension comes installed from the factory while the JCW version is a post-delivery dealer-installed option only.
The price of the JCW upgrade does not include the red springs (or labor). They have to be ordered separately, since there are different versions of the springs that are VIN-matched to the car depending on the vehicle weight/options. I have the JCW suspension and really love it.

There is no JCW dealer-installed suspension available for the Roadster. They took a long to time to make it available for the Coupe and decided not to do it for the Roadster. The factory sport suspension upgrades the shocks, springs, and anti-sway bars. The springs are keyed to the weight of the installed options for all trim levels.

The sport suspension is a neutral handling low-cost option when paired with decent non-runflat tires. I have it and like it for both the street and autocross. I'd put on Michelin Pilot Sport or Pilot Sport A/S 3 tires on the 17" wheels. If you end up wanting more than that and don't autocross in the street category, aftermarket coilovers would be your best option even if a JCW suspension was available.

BMW has refused to publish specs for the suspensions.

Thanks very much. Very helpful.