While im happy with what everyone says (and i cant see anything leaking) the hiss that it makes sounds literally like an air line.....quite pronounced... unless its the design/hole layout of the disc thats making it do that..
My front pads hiss on the 1098. Sounds a bit like a good fry up. I assume it only hisses when on the move sofa? Above say, 15mph?
Usually when starting to brake reasonably hard....(and so the wind speed goes down then i can hear it) and then literally that second before you actually stop - it stops....its gotta be that...just really unnerving like somethings going to pop...
Sounds like you’re talking about the hiss you get from the sintered pad material making contact with the disc. Usually worse when new, it does lessen a bit. Be careful when slowing for horses as they bloody hate it.
Not sure what pads are on there.....they came with the m50's - theres a fair bit of wear left on there and i do know they cost a bit so theyre staying on!!
Probably sintered then. Little flakes of harder compound in the pad, which makes them brake harder for longer but creates the whizz/hiss noise when those harder flakes hit the disk.
My Guzzi Le Mans brakes used to 'hiss' really loudly - it was the pads (Ferodo race pads) passing over the holes in the disc. My SS did it with new pads (EBC sintered) until they had bedded in; but I could still hear them a bit after that. All quite normal IMO.
Caused by the smallest of interference fits between the pads and the discs. When you release the pressure at the master cylinder, the pistons in the caliper slightly retreat back into it. As the pad is free floating, it doesn’t neccessarily move back with the piston so is always just in contact with the disc. Our workshop applies a small amount of low strength spray adhesive to the back of the pad so it sticks to the pistons giving fractions of a millimetre more clearance between the pad and disc under “no load” and no hissing noise. Andy
Really useful question. I have had it on mine but never knew why. Like some of the theories/reasons put forward here
