On brake squeeling , might be loopy but I see it similar to a thin wine glass . Wet your finger and rub it around the rims edge and it will start ringing . I don't think it's the shoe vibrating but the cast iron drum . Only ever have seen one shoe shed its hook , this on many , many shoes . O rings in the grooves should damp out the effect . The spring around the drum lying in the fins seems a logical idea worth trying too . Sid .
Here`s where we improve Sids knowledge by at least 100%. In the
picture you can see the offending ( or rather can`t see) ear, and its roadside replacement, this was somewhere in France, it took about twenty minutes to get the brake plate off ! such was it jammed.
Interestingly Sids comparison with a wine glass gives a clue here as well. If you understand how wine glass resonance occurs, you will know that if the resonance is increased greatly, the glass will shatter. Consider that happening to the ear on the shoe.
I`ve had 3 ears break, all using AM4 linings, at the time I was experimenting with various styles of brake plate. AM4 I would consider to be a (now) thinking similar to the glass resonance, this caused by the slip/grip movement of the finger on the glass, press a little harder and you will not get any resonance, owing to the fact that you have compressed your fingerprints, and there`s nothing to give any slip/grip. AM4 with its impregnated material, I think, gives the same effect. So under heavy pressure the noise will disappear, which is probably why it was developed for racing, that being the major requirement, not for gentle braking, seen with road bikes.
Conclusions, I went off AM4 and had no more squeal.
Anyone know what the red braking material was, from way back ?