i) Your rims are reet dirty and could do with a clean
ii) Or your pads aren't property aligned and are touching the rim all at once - though you'd normally get squealing throughout braking not just at the very end.
iii) Or they'll quickly wear in and the problem will just disappear (surface of pad could have been contaminated with something)
My thoughts are pretty similar to Object17's:
i) Your rims are reet dirty and could do with a clean
ii) Or your pads aren't property aligned and are touching the rim all at once - though you'd normally get squealing throughout braking not just at the very end.
iii) Or they'll quickly wear in and the problem will just disappear (surface of pad could have been contaminated with something)