Hi Simon
WD 40 is a solvent, a bit of a penetrant, will prevent rust, and will displace water. It is not, however, any sort of a lubricant, in my view anyway. I am not the only one who thinks so
http://www.popularmechanics.com/cars/how-to/a6064/wd-40-vs-the-world-of-lubricants/
https://www.reddit.com/r/YouShouldKnow/comments/1wa9a6/ysk_wd40_is_a_solvent_not_a_lubricant_mistaking/
http://www.machinerylubrication.com/Read/28893/wd40-bearing-lubricant
even WD40 itself recognizes the limitations of the original WD40, and has brought out an extensive "Specialist" Product line to do the various things that the original WD 40 does not do, or does not do well.
http://wd40specialist.com/products
not trying to run down WD40, I just do not bother to use it. I do have some of the "Specialist" WD40 products, including the white lithium grease.
I have really liked using the Gibbs Brand the past couple of years, and am continuing to use it, just about to order another case of 12 spray cans from the Canadian distributor for $160 CAD plus shipping. Seems to be really effective in a variety of uses, with a much broader range of effectiveness than WD40. As I said earlier, everyone seems to have their personal favourite snake oil, not trying to convert anyone, and I would really like to know what is in the Gibbs Brand, the MSD didn't tell me much.
for brake discs, I have bead blasted and painted the three disc carriers, using VHT high gloss black brake caliper paint. I then baked them for two hours in the kitchen oven at 250 F to set the caliper paint. Couple of photos. I dropped the three discs and various fasteners and axle spacers off yesterday for yellow dichromate cadmium electroplating. I am hoping to have them back in a week or so.
Paul LeClair