Originally Posted by
ardnet
My question is, can I use Tiagra 4700/4703 shifter with mechanical disc brakes?
I heard/read somewhere it is possible, but the mechanical disc brakes calliper must use the one that is specifically designed for mountain bike, is this true?
And if it is true, can I use that calliper onto the gravel/cyclocross frame?
A cable pull brake lever can be used with mechanical disc brakes. Its quite simple. Tiagra STI will work just fine with cable disc brakes.
As for the claim that an MTB brake caliper is needed, no that isnt the case. Cable brake levers can be used with common cable disc brake calipers like TRP Spyre, Avid BB5, Tektro Aries, etc etc.
The style of caliper mount on your frame(flat mount, post mount, etc) needs to match the disc brake caliper mounts. There are adapters available for some to work together.