I have seen adapters to convert some rear wheels to disc brake:How difficult is it to convert an early 90s v-brake MTB to a disk?
From some googling it would appear I dont' have the tabs on the forks for an optional caliper, but there are some tabs/holes/mounts there for something.
And how do you attach the disk to the wheel?
I have seen adapters to convert some rear wheels to disc brake:
ADEDS 6 Bolt Bicycle Freewheel Threaded Hubs Disk Bike Disc Brake Rotor Flange Adapter (44mm) https://www.amazon.com/dp/B01JREIQYG/ref=cm_sw_r_cp_apa_i_75ryEbJZV9NPA
And the frame adapter:
Fashion Life Adjustable Bike Disc Brake Bracket Mounting Holder New Bicycle MTB https://www.amazon.com/dp/B019OML8VE/ref=cm_sw_r_cp_apa_i_U1ryEb6MT919S
The frame adapter can work on a front standard fork, but not suspension fork. I have no idea of the quality and stability of the adapters. As far as I know you would have to get a new front wheel, with hub designed for disc brakes. Another option is to get hydraulic rim brakes, with dual compound - high speed shoes.
I have seen adapters to convert some rear wheels to disc brake:
Fashion Life Adjustable Bike Disc Brake Bracket Mounting Holder New Bicycle MTB https://www.amazon.com/dp/B019OML8VE/ref=cm_sw_r_cp_apa_i_U1ryEb6MT919S
Required? No. Smart about safety? Yes. Long distance road bike? No. Urban and mixed use trails? Yes. Single track trails? Yes. Can't count the number of times I come upon walkers who have an imaginary turn around point on the trail and do a 180 to return back to their start. It's taken some pretty hard braking a few times. And I much prefer disc brakes on both wheels, not just the one that can launch me over the handlebars!Are disc brakes required for a front hub conversion?