Had a lazy sunday, washed the car and decided for a quickie shot with my Nokia N82. Had my 6 pot BBk for some time now and needed a rear one as there was far too much front bias that the back has just gone into hibernation. Fitted out the 4 potter yesterday and honestly, the I can for sure feel the back working now. The biggest difference, however, is the, weight savings or some of the more tech savvy would call, unsprung weight. Previously on WOT, the back squats and moves off. Now with the rear kit, the car is so much more balanced. On WOT, you dont get much of the squat anymore and you can feel a very trimmed pull on level with the front with the rear BBKs. I tried to carry the stock ones compared to the Alcon rear BBKs when they were installing it. The rears are really quite heavy. Like a big piece of chunk of metal. Since I was on my front for a long time, there was much I could feel in the way the car behaves especially from moving off and rolling WOT. BIGGEST difference. I still cant comment much on the rear brakes as yet as I am bedding it in. On the stock brakes with the Alcon 6 potter fronts, I could hardly feel the rears work since there was so much front bias. Now I can actually feel the back speed actually being erased when coming to a stop. This is great really as previously for North South Runs, you could feel all the braking biasing to the front when braking from ludicrous speeds. I would and am confident that the rear kit would definitely enhance the braking much more now than before.
All in all, I should have changed the back and front together. But Alcon only came out with the kit recently so no choice. And there is definitely a difference by adding the rear ones esp on high speed runs. A definite must. Most who have gone on full 6+4, be it Brembos or AP, would say the braking is phenomenal. Starting off from 6 pot front and subsequently, moving to 4 pot rears, is a big difference, at least to me. Well worth the dime...
Cheers!