Std brake bias?
 

Is the S12 std setup meant to be rear biased?

Couple of times now I've had the back lock up on me under hard breaking.

Dunno if I just need to get my head around it but I feel as though I should be able to brake more than I am without locking, like the front brakes aren't doing much work.

I did change the front pads and discs a month or two back - could it just be the rear pads are better quality than the fronts?

(should also mention it's still auto so engine breaking not compounding things)