If I understand this, you are saying that the
seal is expanded slightly by having less space ( axially) on the piston , due to the wire you’ve wound around it?
Regarding DOT 5 fluid, my one experience of using it made me question whether it was a good thing or not. The circumstances were that I had fitted Goodridge stainless braided brake lines to my one year old Yamaha XS1100. I refilled the brake system with DOT 5 , replacing the factory fluid. After a week or so, the front master cylinder piston became ‘sticky’ in its bore, not returning fully after brake application. I guess the seal must have swollen under influence of the DOT 5.
Has anybody else experienced this?