What's the point of the shoulder that fits in the fork? Is it just to line them up? Does it matter if they don't have the shoulder?
To space them out away from the disc. Do all radial brakes come with this shoulder to fit in the fork leg?
Not all radial brakes have them. I've removed them before to fit different callipers with no problems. They just pull out with a bit of force.
why not just use suitable spacers George? https://www.google.com/search?q=radial+caliper+spacers&safe=off&rlz=1C1KUBR_enGB784GB784&tbm=isch&source=iu&ictx=1&fir=tZfHFEG9j669kM%3A%2CXomKkXTJSezoPM%2C_&vet=1&usg=AI4_-kRTxwZF3F-NWepe2-FjVdoqp0gFQg&sa=X&ved=2ahUKEwikqpOP1cHiAhUAQRUIHQbOCpUQ9QEwAXoECAkQBg#imgrc=tZfHFEG9j669kM: https://www.google.com/search?q=rad...pUQ9QEwAXoECAkQBg#imgrc=mCp-VBuvaEOUkM:&vet=1
Are you putting larger diameter discs on? Ducati /Brembo radial brakes don’t have this feature. As above, probably to assist location and also to reduce shear applied to the bolt however there is unlikely a significant of shear load anyway.
As well a relieving sheer loads on the bolts. I would think they help to 'set' the calipers (Pistons/Pads) absolutely parallel with the discs? A bolt(s) alone wont do that...
the spacers don't have to have the protrusion, just stuck up as suggestions and preferable to modifying the calipers
On Ducati’s, one must lightly tighten the brake calliper bolts then squeeze the lever a few times and bounce the front end to line up the calipers with the discs. Then hold the brake on and do the bolts up to the final torque. This makes sure everything is lined up.
I just tried to find some without protrusions Andy but no luck, plus don't know sizes off top of head, this would be a stroll in the park for you of course.
Not seen Male/ no female or vice versa spacers, Chris If needed, I would file off spigots from calipers, if fork faces were flat.