I have just replaced my brake lines with Hel lines, & at the same time thought that i would replace the bleed nipples for stainless ones. Ordered some off tinternet, went with their guide stating that they are M8 x 1.25 thread, go to fit them on the bike & they are M7 x 1, get some replacements sent to me ( after sending back the M8 ones), fit fine on the front , b ut, the back caliper is M8, OBVIOUSLY I DIDN`T CHECK THIS BEFORE SENDING THEM BACK! What i need to know is, do you put anything on the thread before refitting, as the std ones i took out have some white stuff on them or is it o.k. to just bung in the new ones??
I'm not sure here but I think the white your seeing on the thread is corrosion from the alloy of the caliper.
I will try & stick a pic up when i have time, i am sure someone might have said ptfe tape, but i would hold my hands up if i am imagining it.
