No leaking on ultimate, but my rear caliper piston leaked on the rsc. I found my rsc to perform better, more than enough power, and lovely modulation, levers my favourite, with the bearings its super smooth, im back on zee's and levers feel really slow in comparison. maybe theres a problem with my ultimates, they are going back under warranty. I had sintered pads and the goldren sw33 carbon ceramic same or similar to trialtech pads, but its just not right.