Additional technical information (bump stop rates/lengths):
The 60mm OE front bump stops (~200 lb/in rate) touch after 20mm of wheel travel in compression. The rear 56mm bump stop touch after 40mm of wheel travel. It's clear the car was meant to corner on the front bump stops!
To optimize this situation for stock or lowering springs (especially for Stock class autocross), we consider the ratio of the motion ratios (0.89 / 0.65 front/rear). For reasonable ride and also better handling, we suggest keeping the rear length at 56mm, and using a shorter/softer density front stop. Theoretically, that would be ~41mm front and 56mm rear. We supply a 47mm strut front (100 lb/in) which is a legal length and there is 13mm of room to add additional bump stop spacers to adjust the car's balance. Especially if you decide to also add a larger rear sway bar, having additional front bump stop packers on hand is a good idea to further tune the car's balance.
For stock class, we suggest a 47mm front stop (~100 lb/in rate) and a 200 lb/in rear bump stop (our 58mm white). The rear stops need to be no longer than 56mm (what we measured as OE length) to maintain SCCA-legality with stock-length shocks. I suggest cutting 2-3mm from the thicker end of the bump stop, so the rear spring rate does not ramp too abruptly. The 'nose' of the bump stop helps make the engagement gentle and seamless. For the front bump stops, you may need to add the grey spacers shown in the image below if there is too much oversteer. The grey spacers are larger ID to accommodate a shaft vs. the shock-type black spacers for the rear.
With this combination of FCM bump stops and tuning flexibility with the front and rear spacers, your stock class Mini will have improved front grip and be very tunable while you take advantage of a larger, adjustable rear bar. The car's grip will improve as the suspension stays balanced through the compression travel range, inspiring further confidence which will also lead to faster lap times.
We are also happy to perform and FCM Elite revalve on Bilstein HD, Sport, or PSS suspensions for the Mini Cooper. Fill out an Elite consultation form if you're interested.
