| We've tracked with a completely OEM suspension, H&R/Bilstein SP setup, Leda Single Adjustables, AST SA's, and KW V3's (custom). The coilovers have been BY FAR the fastest way around the track. You MUST invest in a proper cornerweighting after you set your ride height to optimize performance... Many people that install coilovers never have this done, and it's a critical step for optimum performance.
On the Cooper, we run TSW/AST's with Swift springs (342 lb/in or 60 kg/cm) all around, TSW camber plates, TSW rear control arms, TSW adjustable endlinks, TSW x-brace, 19mm H&R rear swaybar (set on full stiff). Alignment settings are -2.7 degrees of camber in the front, -1.5 degrees in the rear, zero (or "neutral") toe in the front and slight toe in for the rear (about 1/8" total toe IN). The TSW camber plates add a bit more postive caster, too. With this setup, we routinely see 1.2 G's sustained in corners on Hankook RS-2's and 1.45 G's with Toyo RA-1's. It's quite wicked in the corners!
The Cooper is cornerweighted (2650 lbs. with driver), perfect 50% cross weights, 58% front bias and 42% rear. Swaybars are neutral thanks to the adjustable endlinks - this made a major difference in fast transitions between corners AND we've seen endlinks snap at the track. It's stable on the straights, REALLY quick in fast sweepers, with very crisp turn-in and excellent lateral grip. In tight corners, it's got lots of grip and exits like lightning!
On the Cooper S, we're testing a new dual-adjustable KW Variant 3 setup with Swift springs (399 lb/in or 70 kg/cm) all around and all the same other bits on the Cooper with the exception of the swaybars - this car has both front and rear H-Sport bars. Since this car runs r-comps, we run -3 degrees of camber in the front and -1.75 in the rear, but the toe settings are the same. The S is also wicked fast on the track (about 2-3 seconds quicker than the Cooper) and behaves like the Cooper in all regards (except it puts down more power, obviously).
The Cooper has the Powerflex a-arm bushings, while the S has the Alta PSRS bits - we've noticed no difference between the two. We've also replaced the rear trailing arm bushings with new OEM units, as they have a tendency to wear out with lots of track and autocross use.
Hope this helps!  | 
