Yes, it is possible and you can use disc brakes on a BMX bike but it is not a cheaper setup and you have to convert many parts of your BMX bike to make bike wheels compatible with disc brakes. BMX hub is not compatible with disc brakes, you have to replace and interchange the BMX hub with the new disc brake compatible hub, and it is not a cheaper hub it almost costs up to 300$, new hub also has different flange hole sizes which also requires the new length of spokes to install within the rim holes, and it needs to re-build and re-dish the wheel thoroughly which also requires money, it shows that installing disc brakes on a BMX is not a cheaper step.
Brake Lever And cables:
Disc brake lever and BMX levers are not compatible with each other because of the shorter pull and longer pull issues and also the length of the cables are different between both of these brakes. you have to buy new brake cables which should be compatible with the disc brakes, or check the older BMX brake cables and measure the length of the front and rear brake cables, if the length is matching and fulfilling all the requirements of the dis brakes, then yes it is possible you can install the BMX brake cables with the disc brakes.
Levers of BMX brakes are not compatible with the dis brakes because the mounting bolts of the shifters and the bite angle of the levers are different for BMX and disc brake levers. and also the distance between the brake levers and grip of the handlebars would matter a lot for the riders, the fingers of the riders are trained for a specific pull force, smaller or greater pull force of the levers for disc and BMX brakes would affect the handling and griping of the bike on the terrains.
The size of the cables, levers, and hub would also matter for replacing BMX brakes with disc brakes, you have to buy an appropriate-sized brake part to make disc brakes compatible with the BMX wheelsets.
Calipers And rotors:
Calipers are also different but if BMX calipers are compatible with the disc brakes then you have to adjust and set the lining of the calipers for biting the edges of the rotors, if the lining is not accurate then the left and right side of the brake pads would start rubbing with the rotors and decreases the lifespan of the right or left side of the brake pads.
Rotors of the disc and BMX brakes are non-compatible with each other because different brands of rotors would need an accurate thickness and diameter for the brake calipers, BMX wheelsets have less than 100mm rotors but those rotors which are much thicker than the 100mm are non-compatible for BMX wheelsets, so rotor compatibility is must for interchanging and replacing BMX brakes with disc brakes.
BMX Frames For Disc Brakes:
BMX frames and forks are not compatible with mounting disc brakes, there are adapters which are called mounting brackets which are used to mount disc brakes with the BMX frames, these brackets are installed on the front and rear wheels but these brackets would distract the wheel lining and the wheel relocates from its actual position, you have to adjust and maintain the wheel lining after mounting of disc brakes with the brackets, it is time-consuming but in the end, your BMX frame would become compatible for mounting disc brakes.
BMX frames do not have mounting places for calipers, you have to install adapters and mounting brackets because it is a cheaper solution, otherwise, you have to buy a new compatible BMX disc brake for installation of disc brakes which is almost much expensive.
Adapters And Mounting Brackets:
There are adapters that are threaded within the dropouts of the rear frame, these adapters and brackets would prevent the bike frame from welding to new mounting places, you just have to buy the accurate sized threaded adapter so that it would accurately mount within the hub and axle of the BMX wheelsets, but if you won’t install these adapters and brackets then you have to weld new mounting places for the insertion of nut bolts of the disc brakes on both left and right side of the bike to make bike frame compatible for disc brakes.
How Disc Brakes Work With BMX Wheels:
The size of BMX wheels is smaller than road and mountain biking, and disc brakes have greater capacity of stopping power for wheelsets, smaller sized wheels would not work smoothly with the disc brakes, because when you pull the levers of disc brakes on a BMX bike, your wheels do not stop but wheels start skidding and slipping even a small pulling and squeezing of the levers by fingers of your hands. this difference is due to the wheel sizes, disc brakes are compatible for rod and mountain biking because their wheels have larger sizes as compared to smaller-sized BMX wheels.
Is It Possible To Use BMX Wheels For Disc Braking?
BMX wheels are not laced for disc brakes and the spokes and spoke nipples are not designed for enough tolerance of disc braking. if you use BMX wheels for disc braking then your wheels will start wobbling and untrue after some days of regular use of disc brake on these wheels, because disc brakes have enough power, and these are recommended for stronger wheelsets with a greater number of spokes. if you want to mount disc brake mounts on BMX wheels then you have re-dish or re-lace your wheelsets enough to hold the stopping power and dissipate the energy which is generated from the wheelsets.
BMX Disc Brake Kit:
You also need a new brake kit for converting and changing the brake setup on your BMX bike. because the previous BMX brake kit is not compatible with disc brakes, it also needs a lot of money to order a BMX kit from an online shop or any mechanic store.
Conclusion:
If you are thinking that mounting disc brakes on a BMX bike is an easier and reachable step, no it costs a lot of money, and new mountings for maintaining disc brakes, the better solution is that if you are willing to change your current BMX setup into disc brakes, then sell your bike frame or replace it with new modern disc compatible frames, nowadays almost everyone is using BMX bike with disc brakes installed on their rear wheels, and for front wheels, you have to swap your BMX fork with new disc compatible fork, so all of these things would cost a lot of money, you can simply replace your BMX with new compatible disc brake bike.