hi sorry bout the delay, was busy welding up my turbo IC piping and was upto my neck with work.
anyway check my blog page 12 for full details of when i first fitted the BC coilover and page 32 for when i corner balanced it
http://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-12
first off i say its a superb quality piece of kit when its properly setup.
corner balancing it up is soo important after fitting it.
note that the lower the ride height, the less damper stroke you have available before hitting the bumpstops (or the wheel strikes the arch, whichever's more uncomfortable n damaging), in which to prevent, requires a higher spring rate and thus generally harsher response over street bumps as more bump force is transferred to the body, apart from very hard damper bump settings.
i first took out the springs and adjust the lower collar of the front strut and adjust the rear damper body height (keep settings equal left/right) till it only hits the bumpstop when the tyre is just about the touch the arch, thats what its for.
refit the springs and adjust the fronts upper preload collar & rear spring collar equally left/right till its generally at ur ideal height.
i set mine at -50mm cos any lower and i can't get my trolley jack under the rear wishbone mount, i'll risk hitting the speedbumps and i risk hitting the bumpstops or exhaust more often.
cos my front left was abit lighter thus higher, i weighed that corner down with ballast so the ride height, spring preload, and weight distribution are equally the same.
previously i had a Bilstein streetline kit which uses 35mm lowering apex progressive springs.
compared to stock, it reduced the boat-like bodyroll & pitching handling and over speedbumps the progressive coils provide a soft cusion but when cornering over rough tarmac i sense the rear dampers caused the back end to destabilise n move about abit.
on the track the bilstein was good but felt the springs n dampers were too soft as the back end perks up high under braking then the body rolls as it turns.
then i fitted the BC coilovers. initially the dampers are set near hard from factory so it was quite a shock when i was going down my street and boucing about. trying it at full hard was hilarious cos i never knew the street roads were this oscillating lol but gets annoying after awhile.
so then i turned it full soft and wow its soo smooth n well behaved. tis almost as soft as the old bilsteins but when i corner over the same bumpy road it feels soo much grippier n stabler which improves confidence.
the BC V1 comes with 4/3kg F/R springs. on track with full hard setting overall it feels so planted n consistant. i thought the fronts were abit soft so i upgraded to 6kg fronts to help the bodyroll under trail braking.
my back end is lighter cos of the removed spare tyre so take note the rear spring/damper might be abit harsh for rear passengers when driving over the rough London bumps.
I later found that the rear stock bumpstop/cover i was using was actually thicker than the short ones that came with the BC. so after fitting the correct ones in, the rear damper had alot more available travel rather than bouncing on the stock bumpstops, thus a less harsh back end.
if you have abs, the front struts don't have the sensor cable support bracket so mines ziptied on.
the pillowball top mount will need occasional cleaning oiling as mentioned before to prevent it binding when going full lock.
finally with such expensive kit exposed to the rough elements from the wheels I'd advise making some covers for the front/rear coilovers like mine to protect ur investment.