Caliper Dust seal/boot or internal piston seal ?
 

Which one allows the pot to retract ?

i ask because on my motorbike 6 pot calipers, 1 side (3 pots) the pots all retract a 0.5mm or so,so i have lever travel,trying to work out why they suck back into the caliper ??????

ive bled the system several times etc so i dont think its air in the system

cheers

Hi
Its the piston seal that retracts the pistons , I have have some calipers with the same problems before , a way round it is to remove the caliper , pump the pistons out slightly with the lever so the pistons are out too far to fit it back on the car / bike , and push the pistons in until you can get the caliper back on , obviously leave the pads in place , the caliper need to be a sug tight fit going back onto the disc
you should have a good pedal /lever then
Cheers Ian

cheers for the info

i did try/do do that quite often,ive done it about 3 times in as many mths, as you say,solid lever feel but as time goes by,they still slowly start to retract further into the caliper than they should

knackered seals then i guess ?

well,i stripped the calipers and cleaned the pots up

is it wise to smear red rubber grease over the piston before i re-fit it to stop any more corrosion to it ?