Okay then, the latest news is that the near side caliper appears to have two sticking pots on the same side, and on closer inspection one of them has also formed a bit of rust, which i'm a bit surprised at because they are fully red rubber greased up whenever i clean them, which is about twice a year.
I ride 5 days a week, every week, and i'm wondering if it's just had water settling on those two pots when the bike's on the side-stand at work when it rains? Or maybe salt damage from gritters (just a thought)
Anyway, when i looked at the caliper the pots on one side were pushed out much more than i've ever seen before, but hardly at all on the other.
You can see in the photo that the pads are not central at all, so i'm 'guessing' that the disc was being pushed from one side only and not both sides, and that is what's causing the 'juddering' effect?
Luckily the discs weren't being pushed hard enough to touch the actual caliper body, otherwise that could have got messy.
I won't know without stripping them down but i can only imagine there to be a bit of rust on the pots that i can't see internally as well.
They've always cleaned up okay in the past and moved in and out freely before i've greased them up so i'm a bit disappointed this has happened to be honest.
I put the OEM discs back on, and cleaned up the pots as much as i could, before greasing them up again, and i treated the calipers to some new pad pins as well, but i can't see it lasting too long so i think i'll get another left caliper anyway.
The right caliper was functioning perfectly, and very evenly, but i cleaned that up as well while i was at it.
The pads were still in very good, clean and flat condition, they looked almost new.
I never got a chance to try it out today as i've had a very busy day off
, so i'll let you know the outcome tomorrow?Thanks for all your input and advice, it was very much appreciated!