I did some work on my fc on the beginning of the year:
rebuild of the 4 callipers
installation of braided brake lines
new suspension
silent bloc suspensions
etc...

I didn't noticed when i did the rebuild, but recently i had a bit of hard driving in the mountain and realised that my left rear brake was weird.
The disc is on only used on the outer half. It's like if the brake pad is not touching the inner half of the disc during braking.

I've ordered porterfield brake pads and all the little accessories (springs and coverplate) to complete my brake setup. i will have a look at the calliper when i will install the new brake pad.

Do you have any idea on what i should look for ? Is it a frequent problem (i have a friend that has a similar issue on his FD) ?

 

Your slide pins are probably froze up, just pull them out, if you can, and clean them up with fine sand paper. Then grease them up and put them back together, make sure there is plenty of grease in the part of the caliper they slide in too

 

now you said it, i think i've seen that one the sort of bushing covering those pins was damaged... I'll look out for this, thanks, very helpful