In any hydraulic system, pressure is equal throughout the system, regardless of line size.
So when you step on the brake, fluid is gonna move through tubes and push the shoes out. Until the shoes hit the drums, there's not much resistance and the pressure is low.
Once the shoes meet resistance, pressure goes up rapidly and remains equal throughout the system.
A smaller tube would introduce a *very* slight pressure drop during the initial take-up show movement, but that wouldn't matter since the shoes aren't touching yet.
Once the shoes touch, the amount of actual fluid flow is small, and so the very small pressure drop through the tube is not significant comapred to the severla hundred PSI operating pressure.
I'd use whatever tubes, etc fit the fittings.
Cheers!
George
