I installed a 3mm thick, 167mm diameter brake disk. This is the kind of disk that comes from the factory on the citycoco. The brakes on this gx are not stock at all, but had to be modified to fit them. The disc itself on the motor fits without problems, except that the center hole is a little larger and therefore the brake disc is centered only with bolts.
I had to make an adapter plate under the caliper. I made it out of aluminum 5 mm thick. Also a little to improve the brake caliper itself, so that the disk of such thickness normally fit between the pads, I had to put two washers to slightly extend the caliper. As a result, everything turned out, the disk is even, overheat or bend it will be problematic, brakes super, remake satisfied.
The brakes are mechanical with a hall sensor in the handle. The regenerative force depends on how hard you push on the brake handle. Both wheels brake at the same time from pressing one handle. The rear MK is currently set up with 35 amp regen, the front one has 10 amp regen + mechanical brakes. The regen is enough to let the rear wheel skid. The brake caliper is automotive style, with a "floating" clamp that presses both pads down, unlike conventional bicycle/scooter pads.
Brake disk ordered here: https://aliexpress.ru/item/1005001880042605.html
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