Thanks John_DGoing by the wear pattern on the pads your discs are just about worn out. When you do change them (I never let pads go below about 4mm friction material thickness) this time you really need to fit new discs at the same time as well.
Thanks pollyp,if the pad is 2-3mm thick and or the material has broken away, it needs replacing.
measure the discs thickness.
if the thinnest section is 17-18mm, it still has enough meat left. minimum is 16mm.
if the disc face has severe rippling scoring and the edge of the pads have left a radius lip, either have the disc remachined flat or replace the discs before fitting the new pads.
damn that piston boot has been obliterated. imo the caliper will require an overhaul. take out, clean & inspect the piston closely. if the chrome plated sealing surface is degraded in any way (chrome chipped off or rusted), replace the piston & seal.
while replacing the piston boot, you may as well get a full caliper service kit for £8-10 to replace all the rubber components/seals tbh.
clean & regrease the sliding guide pins only with non-petroleum lube like Red rubber grease so the rubber doesn't swell & seize.
if it's too much work, could get a new or used caliper.
All types of brake fluid up to and including DOT4 are hygroscopic (DOT 5 is silicon based and does not suffer with this), that is to say they absorb water from the air. This alters the 'feel' of the pedal, but more importantly reduces the boiling point of the fluid, such that under extreme braking conditions the fluid can boil and you lose the brakes due to the fluid in the caliper turning to vapour!I think brake fluid changes are majorly overlooked by car owners. On my bike I change it every year and the difference is noticeable, but then there's no servo on a bike so it's direct feel.
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